]> git.saurik.com Git - apple/xnu.git/blobdiff - bsd/net/route.c
xnu-1456.1.26.tar.gz
[apple/xnu.git] / bsd / net / route.c
index 7f4ec5ac694ebb5e74550c9a9d48ba412ac4763d..66082731e3f515d0475cb843a2fc0b799a17f687 100644 (file)
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000-2007 Apple Inc. All rights reserved.
+ * Copyright (c) 2000-2008 Apple Inc. All rights reserved.
  *
  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
  * 
@@ -76,7 +76,9 @@
 #include <net/route.h>
 
 #include <netinet/in.h>
+#include <netinet/in_var.h>
 #include <netinet/ip_mroute.h>
+#include <netinet/ip_var.h>
 
 #include <net/if_dl.h>
 
 
 #include <pexpert/pexpert.h>
 
+/*
+ * Synchronization notes:
+ *
+ * Routing entries fall under two locking domains: the global routing table
+ * lock (rnh_lock) and the per-entry lock (rt_lock); the latter is a mutex that
+ * resides (statically defined) in the rtentry structure.
+ *
+ * The locking domains for routing are defined as follows:
+ *
+ * The global routing lock is used to serialize all accesses to the radix
+ * trees defined by rt_tables[], as well as the tree of masks.  This includes
+ * lookups, insertions and removals of nodes to/from the respective tree.
+ * It is also used to protect certain fields in the route entry that aren't
+ * often modified and/or require global serialization (more details below.)
+ *
+ * The per-route entry lock is used to serialize accesses to several routing
+ * entry fields (more details below.)  Acquiring and releasing this lock is
+ * done via RT_LOCK() and RT_UNLOCK() routines.
+ *
+ * In cases where both rnh_lock and rt_lock must be held, the former must be
+ * acquired first in order to maintain lock ordering.  It is not a requirement
+ * that rnh_lock be acquired first before rt_lock, but in case both must be
+ * acquired in succession, the correct lock ordering must be followed.
+ *
+ * The fields of the rtentry structure are protected in the following way:
+ *
+ * rt_nodes[]
+ *
+ *     - Routing table lock (rnh_lock).
+ *
+ * rt_parent, rt_mask, rt_llinfo_free
+ *
+ *     - Set once during creation and never changes; no locks to read.
+ *
+ * rt_flags, rt_genmask, rt_llinfo, rt_rmx, rt_refcnt, rt_gwroute
+ *
+ *     - Routing entry lock (rt_lock) for read/write access.
+ *
+ *     - Some values of rt_flags are either set once at creation time,
+ *       or aren't currently used, and thus checking against them can
+ *       be done without rt_lock: RTF_GATEWAY, RTF_HOST, RTF_DYNAMIC,
+ *       RTF_DONE,  RTF_XRESOLVE, RTF_STATIC, RTF_BLACKHOLE, RTF_ANNOUNCE,
+ *       RTF_USETRAILERS, RTF_WASCLONED, RTF_PINNED, RTF_LOCAL,
+ *       RTF_BROADCAST, RTF_MULTICAST, RTF_IFSCOPE.
+ *
+ * rt_key, rt_gateway, rt_ifp, rt_ifa
+ *
+ *     - Always written/modified with both rnh_lock and rt_lock held.
+ *
+ *     - May be read freely with rnh_lock held, else must hold rt_lock
+ *       for read access; holding both locks for read is also okay.
+ *
+ *     - In the event rnh_lock is not acquired, or is not possible to be
+ *       acquired across the operation, setting RTF_CONDEMNED on a route
+ *       entry will prevent its rt_key, rt_gateway, rt_ifp and rt_ifa
+ *       from being modified.  This is typically done on a route that
+ *       has been chosen for a removal (from the tree) prior to dropping
+ *       the rt_lock, so that those values will remain the same until
+ *       the route is freed.
+ *
+ *       When rnh_lock is held rt_setgate(), rt_setif(), and rtsetifa() are
+ *       single-threaded, thus exclusive.  This flag will also prevent the
+ *       route from being looked up via rt_lookup().
+ *
+ * generation_id
+ *
+ *     - Assumes that 32-bit writes are atomic; no locks.
+ *
+ * rt_dlt, rt_output
+ *
+ *     - Currently unused; no locks.
+ *
+ * Operations on a route entry can be described as follows:
+ *
+ * CREATE an entry with reference count set to 0 as part of RTM_ADD/RESOLVE.
+ *
+ * INSERTION of an entry into the radix tree holds the rnh_lock, checks
+ * for duplicates and then adds the entry.  rtrequest returns the entry
+ * after bumping up the reference count to 1 (for the caller).
+ *
+ * LOOKUP of an entry holds the rnh_lock and bumps up the reference count
+ * before returning; it is valid to also bump up the reference count using
+ * RT_ADDREF after the lookup has returned an entry.
+ *
+ * REMOVAL of an entry from the radix tree holds the rnh_lock, removes the
+ * entry but does not decrement the reference count.  Removal happens when
+ * the route is explicitly deleted (RTM_DELETE) or when it is in the cached
+ * state and it expires.  The route is said to be "down" when it is no
+ * longer present in the tree.  Freeing the entry will happen on the last
+ * reference release of such a "down" route.
+ *
+ * RT_ADDREF/RT_REMREF operates on the routing entry which increments/
+ * decrements the reference count, rt_refcnt, atomically on the rtentry.
+ * rt_refcnt is modified only using this routine.  The general rule is to
+ * do RT_ADDREF in the function that is passing the entry as an argument,
+ * in order to prevent the entry from being freed by the callee.
+ */
+
 #define        equal(a1, a2) (bcmp((caddr_t)(a1), (caddr_t)(a2), (a1)->sa_len) == 0)
 #define        SA(p) ((struct sockaddr *)(p))
 
@@ -95,30 +195,38 @@ struct route_cb route_cb;
 __private_extern__ struct rtstat rtstat  = { 0, 0, 0, 0, 0 };
 struct radix_node_head *rt_tables[AF_MAX+1];
 
-lck_mtx_t      *rt_mtx;        /*### global routing tables mutex for now */
-lck_attr_t     *rt_mtx_attr;
-lck_grp_t      *rt_mtx_grp;
-lck_grp_attr_t         *rt_mtx_grp_attr;
+lck_mtx_t              *rnh_lock;      /* global routing tables mutex */
+static lck_attr_t      *rnh_lock_attr;
+static lck_grp_t       *rnh_lock_grp;
+static lck_grp_attr_t  *rnh_lock_grp_attr;
+
+/* Lock group and attribute for routing entry locks */
+static lck_attr_t      *rte_mtx_attr;
+static lck_grp_t       *rte_mtx_grp;
+static lck_grp_attr_t  *rte_mtx_grp_attr;
 
 lck_mtx_t      *route_domain_mtx;      /*### global routing tables mutex for now */
 int rttrash = 0;               /* routes not in table but not freed */
 
-static unsigned int rte_debug;
+unsigned int rte_debug;
 
 /* Possible flags for rte_debug */
 #define        RTD_DEBUG       0x1     /* enable or disable rtentry debug facility */
-#define        RTD_TRACE       0x2     /* trace alloc, free and refcnt */
+#define        RTD_TRACE       0x2     /* trace alloc, free, refcnt and lock */
 #define        RTD_NO_FREE     0x4     /* don't free (good to catch corruptions) */
 
+#define        RTE_NAME                "rtentry"       /* name for zone and rt_lock */
+
 static struct zone *rte_zone;                  /* special zone for rtentry */
 #define        RTE_ZONE_MAX            65536           /* maximum elements in zone */
-#define        RTE_ZONE_NAME           "rtentry"       /* name of rtentry zone */
+#define        RTE_ZONE_NAME           RTE_NAME        /* name of rtentry zone */
 
 #define        RTD_INUSE               0xFEEDFACE      /* entry is in use */
 #define        RTD_FREED               0xDEADBEEF      /* entry is freed */
 
-#define        RTD_TRSTACK_SIZE        8               /* depth of stack trace */
-#define        RTD_REFHIST_SIZE        4               /* refcnt history size */
+/* For gdb */
+__private_extern__ unsigned int ctrace_stack_size = CTRACE_STACK_SIZE;
+__private_extern__ unsigned int ctrace_hist_size = CTRACE_HIST_SIZE;
 
 /*
  * Debug variant of rtentry structure.
@@ -126,50 +234,334 @@ static struct zone *rte_zone;                    /* special zone for rtentry */
 struct rtentry_dbg {
        struct rtentry  rtd_entry;                      /* rtentry */
        struct rtentry  rtd_entry_saved;                /* saved rtentry */
-       u_int32_t       rtd_inuse;                      /* in use pattern */
-       u_int16_t       rtd_refhold_cnt;                /* # of rtref */
-       u_int16_t       rtd_refrele_cnt;                /* # of rtunref */
+       uint32_t        rtd_inuse;                      /* in use pattern */
+       uint16_t        rtd_refhold_cnt;                /* # of rtref */
+       uint16_t        rtd_refrele_cnt;                /* # of rtunref */
+       uint32_t        rtd_lock_cnt;                   /* # of locks */
+       uint32_t        rtd_unlock_cnt;                 /* # of unlocks */
        /*
-        * Thread and PC stack trace up to RTD_TRSTACK_SIZE
-        * deep during alloc and free.
+        * Alloc and free callers.
         */
-       struct thread   *rtd_alloc_thread;
-       void            *rtd_alloc_stk_pc[RTD_TRSTACK_SIZE];
-       struct thread   *rtd_free_thread;
-       void            *rtd_free_stk_pc[RTD_TRSTACK_SIZE];
+       ctrace_t        rtd_alloc;
+       ctrace_t        rtd_free;
        /*
         * Circular lists of rtref and rtunref callers.
         */
-       u_int16_t       rtd_refhold_next;
-       u_int16_t       rtd_refrele_next;
-       struct {
-               struct thread *th;
-               void *pc[RTD_TRSTACK_SIZE];
-       } rtd_refhold[RTD_REFHIST_SIZE];
-       struct {
-               struct thread *th;
-               void *pc[RTD_TRSTACK_SIZE];
-       } rtd_refrele[RTD_REFHIST_SIZE];
+       ctrace_t        rtd_refhold[CTRACE_HIST_SIZE];
+       ctrace_t        rtd_refrele[CTRACE_HIST_SIZE];
+       /*
+        * Circular lists of locks and unlocks.
+        */
+       ctrace_t        rtd_lock[CTRACE_HIST_SIZE];
+       ctrace_t        rtd_unlock[CTRACE_HIST_SIZE];
        /*
         * Trash list linkage
         */
        TAILQ_ENTRY(rtentry_dbg) rtd_trash_link;
 };
 
-/* List of trash route entries protected by rt_mtx */
+#define atomic_add_16_ov(a, n) \
+       ((uint16_t) OSAddAtomic16(n, (volatile SInt16 *)a))
+#define atomic_add_32_ov(a, n) \
+       ((uint32_t) OSAddAtomic(n, a))
+
+/* List of trash route entries protected by rnh_lock */
 static TAILQ_HEAD(, rtentry_dbg) rttrash_head;
 
+static void rte_lock_init(struct rtentry *);
+static void rte_lock_destroy(struct rtentry *);
 static inline struct rtentry *rte_alloc_debug(void);
 static inline void rte_free_debug(struct rtentry *);
+static inline void rte_lock_debug(struct rtentry_dbg *);
+static inline void rte_unlock_debug(struct rtentry_dbg *);
 static void rt_maskedcopy(struct sockaddr *,
            struct sockaddr *, struct sockaddr *);
 static void rtable_init(void **);
 static inline void rtref_audit(struct rtentry_dbg *);
 static inline void rtunref_audit(struct rtentry_dbg *);
+static struct rtentry *rtalloc1_common_locked(struct sockaddr *, int, uint32_t,
+    unsigned int);
+static int rtrequest_common_locked(int, struct sockaddr *,
+    struct sockaddr *, struct sockaddr *, int, struct rtentry **,
+    unsigned int);
+static void rtalloc_ign_common_locked(struct route *, uint32_t, unsigned int);
+static inline void sa_set_ifscope(struct sockaddr *, unsigned int);
+static struct sockaddr *sin_copy(struct sockaddr_in *, struct sockaddr_in *,
+    unsigned int);
+static struct sockaddr *mask_copy(struct sockaddr *, struct sockaddr_in *,
+    unsigned int);
+static struct sockaddr *sa_trim(struct sockaddr *, int);
+static struct radix_node *node_lookup(struct sockaddr *, struct sockaddr *,
+    unsigned int);
+static struct radix_node *node_lookup_default(void);
+static int rn_match_ifscope(struct radix_node *, void *);
+static struct ifaddr *ifa_ifwithroute_common_locked(int,
+    const struct sockaddr *, const struct sockaddr *, unsigned int);
+static struct rtentry *rte_alloc(void);
+static void rte_free(struct rtentry *);
+static void rtfree_common(struct rtentry *, boolean_t);
+
+uint32_t route_generation = 0;
+
+/*
+ * sockaddr_in with embedded interface scope; this is used internally
+ * to keep track of scoped route entries in the routing table.  The
+ * fact that such a scope is embedded in the structure is an artifact
+ * of the current implementation which could change in future.
+ */
+struct sockaddr_inifscope {
+       __uint8_t       sin_len;
+       sa_family_t     sin_family;
+       in_port_t       sin_port;
+       struct  in_addr sin_addr;
+       /*
+        * To avoid possible conflict with an overlaid sockaddr_inarp
+        * having sin_other set to SIN_PROXY, we use the first 4-bytes
+        * of sin_zero since sin_srcaddr is one of the unused fields
+        * in sockaddr_inarp.
+        */
+       union {
+               char    sin_zero[8];
+               struct {
+                       __uint32_t      ifscope;
+               } _in_index;
+       } un;
+#define        sin_ifscope     un._in_index.ifscope
+};
+
+#define        SIN(sa)         ((struct sockaddr_in *)(size_t)(sa))
+#define        SINIFSCOPE(sa)  ((struct sockaddr_inifscope *)(size_t)(sa))
+
+#define        ASSERT_SINIFSCOPE(sa) {                                         \
+       if ((sa)->sa_family != AF_INET ||                               \
+           (sa)->sa_len < sizeof (struct sockaddr_in))                 \
+               panic("%s: bad sockaddr_in %p\n", __func__, sa);        \
+}
+
+/*
+ * Argument to leaf-matching routine; at present it is scoped routing
+ * specific but can be expanded in future to include other search filters.
+ */
+struct matchleaf_arg {
+       unsigned int    ifscope;        /* interface scope */
+};
+
+/*
+ * For looking up the non-scoped default route (sockaddr instead
+ * of sockaddr_in for convenience).
+ */
+static struct sockaddr sin_def = {
+       sizeof (struct sockaddr_in), AF_INET, { 0, }
+};
+
+/*
+ * Interface index (scope) of the primary interface; determined at
+ * the time when the default, non-scoped route gets added, changed
+ * or deleted.  Protected by rnh_lock.
+ */
+static unsigned int primary_ifscope = IFSCOPE_NONE;
+
+#define        INET_DEFAULT(dst)       \
+       ((dst)->sa_family == AF_INET && SIN(dst)->sin_addr.s_addr == 0)
+
+#define        RT(r)           ((struct rtentry *)r)
+#define        RT_HOST(r)      (RT(r)->rt_flags & RTF_HOST)
+
+/*
+ * Given a route, determine whether or not it is the non-scoped default
+ * route; dst typically comes from rt_key(rt) but may be coming from
+ * a separate place when rt is in the process of being created.
+ */
+boolean_t
+rt_inet_default(struct rtentry *rt, struct sockaddr *dst)
+{
+       return (INET_DEFAULT(dst) && !(rt->rt_flags & RTF_IFSCOPE));
+}
+
+/*
+ * Set the ifscope of the primary interface; caller holds rnh_lock.
+ */
+void
+set_primary_ifscope(unsigned int ifscope)
+{
+       primary_ifscope = ifscope;
+}
+
+/*
+ * Return the ifscope of the primary interface; caller holds rnh_lock.
+ */
+unsigned int
+get_primary_ifscope(void)
+{
+       return (primary_ifscope);
+}
 
-__private_extern__ u_long route_generation = 0;
-extern int use_routegenid;
+/*
+ * Embed ifscope into a given a sockaddr_in.
+ */
+static inline void
+sa_set_ifscope(struct sockaddr *sa, unsigned int ifscope)
+{
+       /* Caller must pass in sockaddr_in */
+       ASSERT_SINIFSCOPE(sa);
 
+       SINIFSCOPE(sa)->sin_ifscope = ifscope;
+}
+
+/*
+ * Given a sockaddr_in, return the embedded ifscope to the caller.
+ */
+unsigned int
+sa_get_ifscope(struct sockaddr *sa)
+{
+       /* Caller must pass in sockaddr_in */
+       ASSERT_SINIFSCOPE(sa);
+
+       return (SINIFSCOPE(sa)->sin_ifscope);
+}
+
+/*
+ * Copy a sockaddr_in src to dst and embed ifscope into dst.
+ */
+static struct sockaddr *
+sin_copy(struct sockaddr_in *src, struct sockaddr_in *dst, unsigned int ifscope)
+{
+       *dst = *src;
+       sa_set_ifscope(SA(dst), ifscope);
+
+       return (SA(dst));
+}
+
+/*
+ * Copy a mask from src to a sockaddr_in dst and embed ifscope into dst.
+ */
+static struct sockaddr *
+mask_copy(struct sockaddr *src, struct sockaddr_in *dst, unsigned int ifscope)
+{
+       /* We know dst is at least the size of sockaddr{_in} */
+       bzero(dst, sizeof (*dst));
+       rt_maskedcopy(src, SA(dst), src);
+
+       /*
+        * The length of the mask sockaddr would need to be adjusted
+        * to cover the additional sin_ifscope field; when ifscope is
+        * IFSCOPE_NONE, we'd end up clearing the embedded ifscope on
+        * the destination mask in addition to extending the length
+        * of the sockaddr, as a side effect.  This is okay, as any
+        * trailing zeroes would be skipped by rn_addmask prior to
+        * inserting or looking up the mask in the mask tree.
+        */
+       SINIFSCOPE(dst)->sin_ifscope = ifscope;
+       SINIFSCOPE(dst)->sin_len =
+           offsetof(struct sockaddr_inifscope, sin_ifscope) +
+           sizeof (SINIFSCOPE(dst)->sin_ifscope);
+
+       return (SA(dst));
+}
+
+/*
+ * Trim trailing zeroes on a sockaddr and update its length.
+ */
+static struct sockaddr *
+sa_trim(struct sockaddr *sa, int skip)
+{
+       caddr_t cp, base = (caddr_t)sa + skip;
+
+       if (sa->sa_len <= skip)
+               return (sa);
+
+       for (cp = base + (sa->sa_len - skip); cp > base && cp[-1] == 0;)
+               cp--;
+
+       sa->sa_len = (cp - base) + skip;
+       if (sa->sa_len < skip) {
+               /* Must not happen, and if so, panic */
+               panic("%s: broken logic (sa_len %d < skip %d )", __func__,
+                   sa->sa_len, skip);
+               /* NOTREACHED */
+       } else if (sa->sa_len == skip) {
+               /* If we end up with all zeroes, then there's no mask */
+               sa->sa_len = 0;
+       }
+
+       return (sa);
+}
+
+/*
+ * Called by rtm_msg{1,2} routines to "scrub" the embedded interface scope
+ * away from the socket address structure, so that clients of the routing
+ * socket will not be confused by the presence of the embedded scope, or the
+ * side effect of the increased length due to that.  The source sockaddr is
+ * not modified; instead, the scrubbing happens on the destination sockaddr
+ * storage that is passed in by the caller.
+ */
+struct sockaddr *
+rtm_scrub_ifscope(int idx, struct sockaddr *hint, struct sockaddr *sa,
+    struct sockaddr_storage *ss)
+{
+       struct sockaddr *ret = sa;
+
+       switch (idx) {
+       case RTAX_DST:
+               /*
+                * If this is for an AF_INET destination address, call
+                * sin_copy() with IFSCOPE_NONE as it does what we need.
+                */
+               if (sa->sa_family == AF_INET &&
+                   SINIFSCOPE(sa)->sin_ifscope != IFSCOPE_NONE) {
+                       bzero(ss, sizeof (*ss));
+                       ret = sin_copy(SIN(sa), SIN(ss), IFSCOPE_NONE);
+               }
+               break;
+
+       case RTAX_NETMASK: {
+               /*
+                * If this is for a mask, we can't tell whether or not
+                * there is an embedded interface scope, as the span of
+                * bytes between sa_len and the beginning of the mask
+                * (offset of sin_addr in the case of AF_INET) may be
+                * filled with all-ones by rn_addmask(), and hence we
+                * cannot rely on sa_family.  Because of this, we use
+                * the sa_family of the hint sockaddr (RTAX_{DST,IFA})
+                * as indicator as to whether or not the mask is to be
+                * treated as one for AF_INET.  Clearing the embedded
+                * scope involves setting it to IFSCOPE_NONE followed
+                * by calling sa_trim() to trim trailing zeroes from
+                * the storage sockaddr, which reverses what was done
+                * earlier by mask_copy() on the source sockaddr.
+                */
+               int skip = offsetof(struct sockaddr_in, sin_addr);
+               if (sa->sa_len > skip && sa->sa_len <= sizeof (*ss) &&
+                   hint != NULL && hint->sa_family == AF_INET) {
+                       bzero(ss, sizeof (*ss));
+                       bcopy(sa, ss, sa->sa_len);
+                       SINIFSCOPE(ss)->sin_ifscope = IFSCOPE_NONE;
+                       ret = sa_trim(SA(ss), skip);
+               }
+               break;
+       }
+       default:
+               break;
+       }
+
+       return (ret);
+}
+
+/*
+ * Callback leaf-matching routine for rn_matchaddr_args used
+ * for looking up an exact match for a scoped route entry.
+ */
+static int
+rn_match_ifscope(struct radix_node *rn, void *arg)
+{
+       struct rtentry *rt = (struct rtentry *)rn;
+       struct matchleaf_arg *ma = arg;
+
+       if (!(rt->rt_flags & RTF_IFSCOPE) || rt_key(rt)->sa_family != AF_INET)
+               return (0);
+
+       return (SINIFSCOPE(rt_key(rt))->sin_ifscope == ma->ifscope);
+}
 
 static void
 rtable_init(void **table)
@@ -190,20 +582,22 @@ route_init(void)
        if (rte_debug != 0)
                rte_debug |= RTD_DEBUG;
 
-       rt_mtx_grp_attr = lck_grp_attr_alloc_init();
-
-       rt_mtx_grp = lck_grp_alloc_init("route", rt_mtx_grp_attr);
-
-       rt_mtx_attr = lck_attr_alloc_init();
-
-       if ((rt_mtx = lck_mtx_alloc_init(rt_mtx_grp, rt_mtx_attr)) == NULL) {
-               printf("route_init: can't alloc rt_mtx\n");
+       rnh_lock_grp_attr = lck_grp_attr_alloc_init();
+       rnh_lock_grp = lck_grp_alloc_init("route", rnh_lock_grp_attr);
+       rnh_lock_attr = lck_attr_alloc_init();
+       if ((rnh_lock = lck_mtx_alloc_init(rnh_lock_grp,
+           rnh_lock_attr)) == NULL) {
+               printf("route_init: can't alloc rnh_lock\n");
                return;
        }
 
-       lck_mtx_lock(rt_mtx);
+       rte_mtx_grp_attr = lck_grp_attr_alloc_init();
+       rte_mtx_grp = lck_grp_alloc_init(RTE_NAME, rte_mtx_grp_attr);
+       rte_mtx_attr = lck_attr_alloc_init();
+
+       lck_mtx_lock(rnh_lock);
        rn_init();      /* initialize all zeroes, all ones, mask table */
-       lck_mtx_unlock(rt_mtx);
+       lck_mtx_unlock(rnh_lock);
        rtable_init((void **)rt_tables);
        route_domain_mtx = routedomain.dom_mtx;
 
@@ -221,121 +615,197 @@ route_init(void)
        TAILQ_INIT(&rttrash_head);
 }
 
+/*
+ * Atomically increment route generation counter
+ */
+void
+routegenid_update(void)
+{
+       (void) atomic_add_32_ov(&route_generation, 1);
+}
+
 /*
  * Packet routing routines.
  */
 void
 rtalloc(struct route *ro)
 {
-       rtalloc_ign(ro, 0UL);
+       rtalloc_ign(ro, 0);
 }
 
 void
-rtalloc_ign_locked(struct route *ro, u_long ignore)
+rtalloc_ign_locked(struct route *ro, uint32_t ignore)
+{
+       return (rtalloc_ign_common_locked(ro, ignore, IFSCOPE_NONE));
+}
+
+void
+rtalloc_scoped_ign_locked(struct route *ro, uint32_t ignore,
+    unsigned int ifscope)
+{
+       return (rtalloc_ign_common_locked(ro, ignore, ifscope));
+}
+
+static void
+rtalloc_ign_common_locked(struct route *ro, uint32_t ignore,
+    unsigned int ifscope)
 {
        struct rtentry *rt;
 
        if ((rt = ro->ro_rt) != NULL) {
-               if (rt->rt_ifp != NULL && rt->rt_flags & RTF_UP)
+               RT_LOCK_SPIN(rt);
+               if (rt->rt_ifp != NULL && (rt->rt_flags & RTF_UP) &&
+                   rt->generation_id == route_generation) {
+                       RT_UNLOCK(rt);
                        return;
-               /* XXX - We are probably always at splnet here already. */
+               }
+               RT_UNLOCK(rt);
                rtfree_locked(rt);
                ro->ro_rt = NULL;
        }
-       ro->ro_rt = rtalloc1_locked(&ro->ro_dst, 1, ignore);
-       if (ro->ro_rt)
+       ro->ro_rt = rtalloc1_common_locked(&ro->ro_dst, 1, ignore, ifscope);
+       if (ro->ro_rt != NULL) {
                ro->ro_rt->generation_id = route_generation;
+               RT_LOCK_ASSERT_NOTHELD(ro->ro_rt);
+       }
 }
+
 void
-rtalloc_ign(struct route *ro, u_long ignore)
+rtalloc_ign(struct route *ro, uint32_t ignore)
 {
-       lck_mtx_assert(rt_mtx, LCK_MTX_ASSERT_NOTOWNED);
-       lck_mtx_lock(rt_mtx);
+       lck_mtx_assert(rnh_lock, LCK_MTX_ASSERT_NOTOWNED);
+       lck_mtx_lock(rnh_lock);
        rtalloc_ign_locked(ro, ignore);
-       lck_mtx_unlock(rt_mtx);
+       lck_mtx_unlock(rnh_lock);
+}
+
+void
+rtalloc_scoped_ign(struct route *ro, uint32_t ignore, unsigned int ifscope)
+{
+       lck_mtx_assert(rnh_lock, LCK_MTX_ASSERT_NOTOWNED);
+       lck_mtx_lock(rnh_lock);
+       rtalloc_scoped_ign_locked(ro, ignore, ifscope);
+       lck_mtx_unlock(rnh_lock);
+}
+
+struct rtentry *
+rtalloc1_locked(struct sockaddr *dst, int report, uint32_t ignflags)
+{
+       return (rtalloc1_common_locked(dst, report, ignflags, IFSCOPE_NONE));
+}
+
+struct rtentry *
+rtalloc1_scoped_locked(struct sockaddr *dst, int report, uint32_t ignflags,
+    unsigned int ifscope)
+{
+       return (rtalloc1_common_locked(dst, report, ignflags, ifscope));
 }
 
 /*
  * Look up the route that matches the address given
  * Or, at least try.. Create a cloned route if needed.
  */
-struct rtentry *
-rtalloc1_locked(struct sockaddr *dst, int report, u_long ignflags)
+static struct rtentry *
+rtalloc1_common_locked(struct sockaddr *dst, int report, uint32_t ignflags,
+    unsigned int ifscope)
 {
        struct radix_node_head *rnh = rt_tables[dst->sa_family];
-       struct rtentry *rt;
-       struct radix_node *rn;
-       struct rtentry *newrt = 0;
+       struct rtentry *rt, *newrt = NULL;
        struct rt_addrinfo info;
-       u_long nflags;
+       uint32_t nflags;
        int  err = 0, msgtype = RTM_MISS;
+
+       if (rnh == NULL)
+               goto unreachable;
+
        /*
-        * Look up the address in the table for that Address Family
+        * Find the longest prefix or exact (in the scoped case) address match;
+        * callee adds a reference to entry and checks for root node as well
         */
-       if (rnh && (rn = rnh->rnh_matchaddr((caddr_t)dst, rnh)) &&
-           ((rn->rn_flags & RNF_ROOT) == 0)) {
+       rt = rt_lookup(FALSE, dst, NULL, rnh, ifscope);
+       if (rt == NULL)
+               goto unreachable;
+
+       RT_LOCK_SPIN(rt);
+       newrt = rt;
+       nflags = rt->rt_flags & ~ignflags;
+       RT_UNLOCK(rt);
+       if (report && (nflags & (RTF_CLONING | RTF_PRCLONING))) {
                /*
-                * If we find it and it's not the root node, then
-                * get a refernce on the rtentry associated.
+                * We are apparently adding (report = 0 in delete).
+                * If it requires that it be cloned, do so.
+                * (This implies it wasn't a HOST route.)
                 */
-               newrt = rt = (struct rtentry *)rn;
-               nflags = rt->rt_flags & ~ignflags;
-               if (report && (nflags & (RTF_CLONING | RTF_PRCLONING))) {
+               err = rtrequest_locked(RTM_RESOLVE, dst, NULL, NULL, 0, &newrt);
+               if (err) {
                        /*
-                        * We are apparently adding (report = 0 in delete).
-                        * If it requires that it be cloned, do so.
-                        * (This implies it wasn't a HOST route.)
+                        * If the cloning didn't succeed, maybe what we
+                        * have from lookup above will do.  Return that;
+                        * no need to hold another reference since it's
+                        * already done.
                         */
-                       err = rtrequest_locked(RTM_RESOLVE, dst, SA(0),
-                                             SA(0), 0, &newrt);
-                       if (err) {
-                               /*
-                                * If the cloning didn't succeed, maybe
-                                * what we have will do. Return that.
-                                */
-                               newrt = rt;
-                               rtref(rt);
-                               goto miss;
-                       }
-                       if ((rt = newrt) && (rt->rt_flags & RTF_XRESOLVE)) {
-                               /*
-                                * If the new route specifies it be
-                                * externally resolved, then go do that.
-                                */
-                               msgtype = RTM_RESOLVE;
-                               goto miss;
-                       }
-               } else
-                       rtref(rt);
-       } else {
+                       newrt = rt;
+                       goto miss;
+               }
+
                /*
-                * Either we hit the root or couldn't find any match,
-                * Which basically means
-                * "caint get there frm here"
+                * We cloned it; drop the original route found during lookup.
+                * The resulted cloned route (newrt) would now have an extra
+                * reference held during rtrequest.
                 */
-               rtstat.rts_unreach++;
-       miss:   if (report) {
+               rtfree_locked(rt);
+               if ((rt = newrt) && (rt->rt_flags & RTF_XRESOLVE)) {
                        /*
-                        * If required, report the failure to the supervising
-                        * Authorities.
-                        * For a delete, this is not an error. (report == 0)
+                        * If the new route specifies it be
+                        * externally resolved, then go do that.
                         */
-                       bzero((caddr_t)&info, sizeof(info));
-                       info.rti_info[RTAX_DST] = dst;
-                       rt_missmsg(msgtype, &info, 0, err);
+                       msgtype = RTM_RESOLVE;
+                       goto miss;
                }
        }
+       goto done;
+
+unreachable:
+       /*
+        * Either we hit the root or couldn't find any match,
+        * Which basically means "cant get there from here"
+        */
+       rtstat.rts_unreach++;
+miss:
+       if (report) {
+               /*
+                * If required, report the failure to the supervising
+                * Authorities.
+                * For a delete, this is not an error. (report == 0)
+                */
+               bzero((caddr_t)&info, sizeof(info));
+               info.rti_info[RTAX_DST] = dst;
+               rt_missmsg(msgtype, &info, 0, err);
+       }
+done:
        return (newrt);
 }
 
 struct rtentry *
-rtalloc1(struct sockaddr *dst, int report, u_long ignflags)
+rtalloc1(struct sockaddr *dst, int report, uint32_t ignflags)
 {
        struct rtentry * entry;
-       lck_mtx_assert(rt_mtx, LCK_MTX_ASSERT_NOTOWNED);
-       lck_mtx_lock(rt_mtx);
+       lck_mtx_assert(rnh_lock, LCK_MTX_ASSERT_NOTOWNED);
+       lck_mtx_lock(rnh_lock);
        entry = rtalloc1_locked(dst, report, ignflags);
-       lck_mtx_unlock(rt_mtx);
+       lck_mtx_unlock(rnh_lock);
+       return (entry);
+}
+
+struct rtentry *
+rtalloc1_scoped(struct sockaddr *dst, int report, uint32_t ignflags,
+    unsigned int ifscope)
+{
+       struct rtentry * entry;
+       lck_mtx_assert(rnh_lock, LCK_MTX_ASSERT_NOTOWNED);
+       lck_mtx_lock(rnh_lock);
+       entry = rtalloc1_scoped_locked(dst, report, ignflags, ifscope);
+       lck_mtx_unlock(rnh_lock);
        return (entry);
 }
 
@@ -346,34 +816,70 @@ rtalloc1(struct sockaddr *dst, int report, u_long ignflags)
 void
 rtfree_locked(struct rtentry *rt)
 {
-       /*
-        * find the tree for that address family
-        * Note: in the case of igmp packets, there might not be an rnh
-        */
-       struct radix_node_head *rnh;
+       rtfree_common(rt, TRUE);
+}
 
-       lck_mtx_assert(rt_mtx, LCK_MTX_ASSERT_OWNED);
+static void
+rtfree_common(struct rtentry *rt, boolean_t locked)
+{
+       struct radix_node_head *rnh;
 
-       /* See 3582620 - We hit this during the transition from funnels to locks */
-       if (rt == 0) {
-               printf("rtfree - rt is NULL\n");
+       /*
+        * Atomically decrement the reference count and if it reaches 0,
+        * and there is a close function defined, call the close function.
+        */
+       RT_LOCK_SPIN(rt);
+       if (rtunref(rt) > 0) {
+               RT_UNLOCK(rt);
                return;
        }
-       
-       rnh = rt_tables[rt_key(rt)->sa_family];
 
        /*
-        * decrement the reference count by one and if it reaches 0,
-        * and there is a close function defined, call the close function
+        * To avoid violating lock ordering, we must drop rt_lock before
+        * trying to acquire the global rnh_lock.  If we are called with
+        * rnh_lock held, then we already have exclusive access; otherwise
+        * we do the lock dance.
         */
-       rtunref(rt);
-       if (rt->rt_refcnt > 0)
-               return;
+       if (!locked) {
+               /*
+               * Note that we check it again below after grabbing rnh_lock,
+               * since it is possible that another thread doing a lookup wins
+               * the race, grabs the rnh_lock first, and bumps up the reference
+               * count in which case the route should be left alone as it is
+               * still in use.  It's also possible that another thread frees
+               * the route after we drop rt_lock; to prevent the route from
+               * being freed, we hold an extra reference.
+               */
+               RT_ADDREF_LOCKED(rt);
+               RT_UNLOCK(rt);
+               lck_mtx_lock(rnh_lock);
+               RT_LOCK_SPIN(rt);
+               RT_REMREF_LOCKED(rt);
+               if (rt->rt_refcnt > 0) {
+                       /* We've lost the race, so abort */
+                       RT_UNLOCK(rt);
+                       goto done;
+               }
+       }
+
+       /*
+        * We may be blocked on other lock(s) as part of freeing
+        * the entry below, so convert from spin to full mutex.
+        */
+       RT_CONVERT_LOCK(rt);
+
+       lck_mtx_assert(rnh_lock, LCK_MTX_ASSERT_OWNED);
+
+       /* Negative refcnt must never happen */
+       if (rt->rt_refcnt != 0)
+               panic("rt %p invalid refcnt %d", rt, rt->rt_refcnt);
+
+       /*
+        * find the tree for that address family
+        * Note: in the case of igmp packets, there might not be an rnh
+        */
+       rnh = rt_tables[rt_key(rt)->sa_family];
 
-       if ((rt->rt_flags & RTF_TRACKREFS) != 0)
-               printf("%s rt(%p)->rt_refcnt(%d), caller=%p\n", __FUNCTION__,
-                       rt, rt->rt_refcnt, __builtin_return_address(0));
-       
        /*
         * On last reference give the "close method" a chance to cleanup
         * private state.  This also permits (for IPv4 and IPv6) a chance
@@ -382,49 +888,59 @@ rtfree_locked(struct rtentry *rt)
         * close routine typically issues RTM_DELETE which clears the RTF_UP
         * flag on the entry so that the code below reclaims the storage.
         */
-       if (rnh && rnh->rnh_close && rt->rt_refcnt == 0)
+       if (rnh != NULL && rnh->rnh_close != NULL)
                rnh->rnh_close((struct radix_node *)rt, rnh);
 
        /*
-        * If we are no longer "up" (and ref == 0)
-        * then we can free the resources associated
-        * with the route.
+        * If we are no longer "up" (and ref == 0) then we can free the
+        * resources associated with the route.
         */
        if (!(rt->rt_flags & RTF_UP)) {
                if (rt->rt_nodes->rn_flags & (RNF_ACTIVE | RNF_ROOT))
-                       panic ("rtfree 2");
+                       panic("rt %p freed while in radix tree\n", rt);
                /*
                 * the rtentry must have been removed from the routing table
-                * so it is represented in rttrash.. remove that now.
+                * so it is represented in rttrash; remove that now.
                 */
-               (void) OSDecrementAtomic((SInt32 *)&rttrash);
+               (void) OSDecrementAtomic(&rttrash);
                if (rte_debug & RTD_DEBUG) {
                        TAILQ_REMOVE(&rttrash_head, (struct rtentry_dbg *)rt,
                            rtd_trash_link);
                }
 
-#ifdef DIAGNOSTIC
-               if (rt->rt_refcnt < 0) {
-                       printf("rtfree: %p not freed (neg refs) cnt=%d\n",
-                           rt, rt->rt_refcnt);
-                       return;
-               }
-#endif
+               /*
+               * Route is no longer in the tree and refcnt is 0;
+               * we have exclusive access, so destroy it.
+               */
+               RT_UNLOCK(rt);
 
                /*
                 * release references on items we hold them on..
                 * e.g other routes and ifaddrs.
                 */
-               if (rt->rt_parent)
+               if (rt->rt_parent != NULL) {
                        rtfree_locked(rt->rt_parent);
+                       rt->rt_parent = NULL;
+               }
 
-               if(rt->rt_ifa) {
+               if (rt->rt_ifa != NULL) {
                        ifafree(rt->rt_ifa);
                        rt->rt_ifa = NULL;
                }
 
                /*
-                * The key is separatly alloc'd so free it (see rt_setgate()).
+                * Now free any attached link-layer info.
+                */
+               if (rt->rt_llinfo != NULL) {
+                       if (rt->rt_llinfo_free != NULL)
+                               (*rt->rt_llinfo_free)(rt->rt_llinfo);
+                       else
+                               R_Free(rt->rt_llinfo);
+                       rt->rt_llinfo = NULL;
+               }
+
+               /*
+                * The key is separately alloc'd so free it (see rt_setgate()).
                 * This also frees the gateway, as they are always malloc'd
                 * together.
                 */
@@ -433,17 +949,25 @@ rtfree_locked(struct rtentry *rt)
                /*
                 * and the rtentry itself of course
                 */
+               rte_lock_destroy(rt);
                rte_free(rt);
+       } else {
+               /*
+                * The "close method" has been called, but the route is
+                * still in the radix tree with zero refcnt, i.e. "up"
+                * and in the cached state.
+                */
+               RT_UNLOCK(rt);
        }
+done:
+       if (!locked)
+               lck_mtx_unlock(rnh_lock);
 }
 
 void
 rtfree(struct rtentry *rt)
 {
-       lck_mtx_assert(rt_mtx, LCK_MTX_ASSERT_NOTOWNED);
-       lck_mtx_lock(rt_mtx);   
-       rtfree_locked(rt);
-       lck_mtx_unlock(rt_mtx);
+       rtfree_common(rt, FALSE);
 }
 
 /*
@@ -451,38 +975,34 @@ rtfree(struct rtentry *rt)
  * the refcount reaches zero. Unless you have really good reason,
  * use rtfree not rtunref.
  */
-void
+int
 rtunref(struct rtentry *p)
 {
-       lck_mtx_assert(rt_mtx, LCK_MTX_ASSERT_OWNED);
+       RT_LOCK_ASSERT_HELD(p);
+
+       if (p->rt_refcnt == 0)
+               panic("%s(%p) bad refcnt\n", __func__, p);
 
-       if (p->rt_refcnt <= 0)
-               panic("rtunref: bad refcnt %d for rt=%p\n", p->rt_refcnt, p);
+       --p->rt_refcnt;
 
        if (rte_debug & RTD_DEBUG)
                rtunref_audit((struct rtentry_dbg *)p);
 
-       p->rt_refcnt--;
+       /* Return new value */
+       return (p->rt_refcnt);
 }
 
 static inline void
 rtunref_audit(struct rtentry_dbg *rte)
 {
+       uint16_t idx;
+
        if (rte->rtd_inuse != RTD_INUSE)
                panic("rtunref: on freed rte=%p\n", rte);
 
-       rte->rtd_refrele_cnt++;
-
-       if (rte_debug & RTD_TRACE) {
-               rte->rtd_refrele[rte->rtd_refrele_next].th = current_thread();
-               bzero(rte->rtd_refrele[rte->rtd_refrele_next].pc,
-                   sizeof (rte->rtd_refrele[rte->rtd_refrele_next].pc));
-               (void) OSBacktrace(rte->rtd_refrele[rte->rtd_refrele_next].pc,
-                   RTD_TRSTACK_SIZE);
-
-               rte->rtd_refrele_next =
-                   (rte->rtd_refrele_next + 1) % RTD_REFHIST_SIZE;
-       }
+       idx = atomic_add_16_ov(&rte->rtd_refrele_cnt, 1) % CTRACE_HIST_SIZE;
+       if (rte_debug & RTD_TRACE)
+               ctrace_record(&rte->rtd_refrele[idx]);
 }
 
 /*
@@ -491,46 +1011,34 @@ rtunref_audit(struct rtentry_dbg *rte)
 void
 rtref(struct rtentry *p)
 {
-       lck_mtx_assert(rt_mtx, LCK_MTX_ASSERT_OWNED);
+       RT_LOCK_ASSERT_HELD(p);
 
-       if (p->rt_refcnt < 0)
-               panic("rtref: bad refcnt %d for rt=%p\n", p->rt_refcnt, p);
+       if (++p->rt_refcnt == 0)
+               panic("%s(%p) bad refcnt\n", __func__, p);
 
        if (rte_debug & RTD_DEBUG)
                rtref_audit((struct rtentry_dbg *)p);
-
-       p->rt_refcnt++;
-       
-       if ((p->rt_flags & RTF_TRACKREFS) != 0)
-               printf("%s rt(%p)->rt_refcnt(%d), caller=%p\n", __FUNCTION__,
-                       p, p->rt_refcnt, __builtin_return_address(0));
 }
 
 static inline void
 rtref_audit(struct rtentry_dbg *rte)
 {
+       uint16_t idx;
+
        if (rte->rtd_inuse != RTD_INUSE)
                panic("rtref_audit: on freed rte=%p\n", rte);
 
-       rte->rtd_refhold_cnt++;
-
-       if (rte_debug & RTD_TRACE) {
-               rte->rtd_refhold[rte->rtd_refhold_next].th = current_thread();
-               bzero(rte->rtd_refhold[rte->rtd_refhold_next].pc,
-                   sizeof (rte->rtd_refhold[rte->rtd_refhold_next].pc));
-               (void) OSBacktrace(rte->rtd_refhold[rte->rtd_refhold_next].pc,
-                   RTD_TRSTACK_SIZE);
-
-               rte->rtd_refhold_next =
-                   (rte->rtd_refhold_next + 1) % RTD_REFHIST_SIZE;
-       }
+       idx = atomic_add_16_ov(&rte->rtd_refhold_cnt, 1) % CTRACE_HIST_SIZE;
+       if (rte_debug & RTD_TRACE)
+               ctrace_record(&rte->rtd_refhold[idx]);
 }
 
 void
 rtsetifa(struct rtentry *rt, struct ifaddr* ifa)
 {
-       if (rt == NULL)
-               panic("rtsetifa");
+       lck_mtx_assert(rnh_lock, LCK_MTX_ASSERT_OWNED);
+
+       RT_LOCK_ASSERT_HELD(rt);
 
        if (rt->rt_ifa == ifa)
                return;
@@ -547,71 +1055,54 @@ rtsetifa(struct rtentry *rt, struct ifaddr* ifa)
                ifaref(rt->rt_ifa);
 }
 
-void
-ifafree(struct ifaddr *ifa)
-{
-       int oldval;
-
-       if (ifa == NULL)
-               panic("ifafree");
-
-       oldval = OSAddAtomic(-1, (SInt32 *)&ifa->ifa_refcnt);
-
-       if (oldval == 0) {
-               if  ((ifa->ifa_debug & IFA_ATTACHED) != 0) {
-                       panic("ifa attached to ifp is being freed\n");
-               }
-               FREE(ifa, M_IFADDR);
-       }
-}
-
-void
-ifaref(struct ifaddr *ifa)
-{
-       if (ifa == NULL)
-               panic("ifaref");
-
-       if (OSAddAtomic(1, (SInt32 *)&ifa->ifa_refcnt) == 0xffffffff)
-               panic("ifaref - reference count rolled over!");
-}
-
 /*
  * Force a routing table entry to the specified
  * destination to go through the given gateway.
  * Normally called as a result of a routing redirect
  * message from the network layer.
- *
- * N.B.: must be called at splnet
- *
  */
 void
-rtredirect(struct sockaddr *dst, struct sockaddr *gateway,
-          struct sockaddr *netmask, int flags, struct sockaddr *src,
-          struct rtentry **rtp)
+rtredirect(struct ifnet *ifp, struct sockaddr *dst, struct sockaddr *gateway,
+   struct sockaddr *netmask, int flags, struct sockaddr *src,
+   struct rtentry **rtp)
 {
-       struct rtentry *rt;
+       struct rtentry *rt = NULL;
        int error = 0;
        short *stat = 0;
        struct rt_addrinfo info;
        struct ifaddr *ifa = NULL;
+       unsigned int ifscope = (ifp != NULL) ? ifp->if_index : IFSCOPE_NONE;
+       struct sockaddr_in sin;
 
-       lck_mtx_assert(rt_mtx, LCK_MTX_ASSERT_NOTOWNED);
-       lck_mtx_lock(rt_mtx);
+       lck_mtx_assert(rnh_lock, LCK_MTX_ASSERT_NOTOWNED);
+       lck_mtx_lock(rnh_lock);
 
-       /* verify the gateway is directly reachable */
-       if ((ifa = ifa_ifwithnet(gateway)) == 0) {
+       /*
+        * Verify the gateway is directly reachable; if scoped routing
+        * is enabled, verify that it is reachable from the interface
+        * where the ICMP redirect arrived on.
+        */
+       if ((ifa = ifa_ifwithnet_scoped(gateway, ifscope)) == NULL) {
                error = ENETUNREACH;
                goto out;
        }
 
-       rt = rtalloc1_locked(dst, 0, RTF_CLONING | RTF_PRCLONING);
+       /* Lookup route to the destination (from the original IP header) */
+       rt = rtalloc1_scoped_locked(dst, 0, RTF_CLONING|RTF_PRCLONING, ifscope);
+       if (rt != NULL)
+               RT_LOCK(rt);
+
+       /* Embed scope in src for comparison against rt_gateway below */
+       if (ip_doscopedroute && src->sa_family == AF_INET)
+               src = sin_copy(SIN(src), &sin, ifscope);
+
        /*
         * If the redirect isn't from our current router for this dst,
         * it's either old or wrong.  If it redirects us to ourselves,
         * we have a routing loop, perhaps as a result of an interface
         * going down recently.
         */
-       if (!(flags & RTF_DONE) && rt &&
+       if (!(flags & RTF_DONE) && rt != NULL &&
             (!equal(src, rt->rt_gateway) || !equal(rt->rt_ifa->ifa_addr,
             ifa->ifa_addr))) {
                error = EINVAL;
@@ -623,37 +1114,45 @@ rtredirect(struct sockaddr *dst, struct sockaddr *gateway,
                        error = EHOSTUNREACH;
                }
        }
-       
+
        if (ifa) {
                ifafree(ifa);
                ifa = NULL;
        }
-       
-       if (error)
+
+       if (error) {
+               if (rt != NULL)
+                       RT_UNLOCK(rt);
                goto done;
+       }
+
        /*
         * Create a new entry if we just got back a wildcard entry
         * or the the lookup failed.  This is necessary for hosts
         * which use routing redirects generated by smart gateways
         * to dynamically build the routing tables.
         */
-       if ((rt == 0) || (rt_mask(rt) && rt_mask(rt)->sa_len < 2))
+       if ((rt == NULL) || (rt_mask(rt) != NULL && rt_mask(rt)->sa_len < 2))
                goto create;
        /*
         * Don't listen to the redirect if it's
         * for a route to an interface.
         */
+       RT_LOCK_ASSERT_HELD(rt);
        if (rt->rt_flags & RTF_GATEWAY) {
                if (((rt->rt_flags & RTF_HOST) == 0) && (flags & RTF_HOST)) {
                        /*
                         * Changing from route to net => route to host.
-                        * Create new route, rather than smashing route to net.
+                        * Create new route, rather than smashing route
+                        * to net; similar to cloned routes, the newly
+                        * created host route is scoped as well.
                         */
-               create:
+create:
+                       if (rt != NULL)
+                               RT_UNLOCK(rt);
                        flags |=  RTF_GATEWAY | RTF_DYNAMIC;
-                       error = rtrequest_locked((int)RTM_ADD, dst, gateway,
-                                   netmask, flags,
-                                   (struct rtentry **)0);
+                       error = rtrequest_scoped_locked(RTM_ADD, dst,
+                           gateway, netmask, flags, NULL, ifscope);
                        stat = &rtstat.rts_dynamic;
                } else {
                        /*
@@ -666,36 +1165,44 @@ rtredirect(struct sockaddr *dst, struct sockaddr *gateway,
                        /*
                         * add the key and gateway (in one malloc'd chunk).
                         */
-                       rt_setgate(rt, rt_key(rt), gateway);
+                       error = rt_setgate(rt, rt_key(rt), gateway);
+                       RT_UNLOCK(rt);
                }
-       } else
+       } else {
+               RT_UNLOCK(rt);
                error = EHOSTUNREACH;
+       }
 done:
-       if (rt) {
+       if (rt != NULL) {
+               RT_LOCK_ASSERT_NOTHELD(rt);
                if (rtp && !error)
                        *rtp = rt;
                else
                        rtfree_locked(rt);
        }
 out:
-       if (error)
+       if (error) {
                rtstat.rts_badredirect++;
-       else if (stat != NULL)
-               (*stat)++;
+       } else {
+               if (stat != NULL)
+                       (*stat)++;
+               if (use_routegenid)
+                       routegenid_update();
+       }
+       lck_mtx_unlock(rnh_lock);
        bzero((caddr_t)&info, sizeof(info));
        info.rti_info[RTAX_DST] = dst;
        info.rti_info[RTAX_GATEWAY] = gateway;
        info.rti_info[RTAX_NETMASK] = netmask;
        info.rti_info[RTAX_AUTHOR] = src;
        rt_missmsg(RTM_REDIRECT, &info, flags, error);
-       lck_mtx_unlock(rt_mtx);
 }
 
 /*
 * Routing table ioctl interface.
 */
 int
-rtioctl(int req, caddr_t data, struct proc *p)
+rtioctl(unsigned long req, caddr_t data, struct proc *p)
 {
 #pragma unused(p)
 #if INET && MROUTING
@@ -713,23 +1220,54 @@ ifa_ifwithroute(
 {
        struct ifaddr *ifa;
 
-       lck_mtx_lock(rt_mtx);
+       lck_mtx_lock(rnh_lock);
        ifa = ifa_ifwithroute_locked(flags, dst, gateway);
-       lck_mtx_unlock(rt_mtx);
+       lck_mtx_unlock(rnh_lock);
 
        return (ifa);
 }
 
 struct ifaddr *
-ifa_ifwithroute_locked(
-       int flags,
-       const struct sockaddr *dst,
-       const struct sockaddr *gateway)
+ifa_ifwithroute_locked(int flags, const struct sockaddr *dst,
+    const struct sockaddr *gateway)
+{
+       return (ifa_ifwithroute_common_locked((flags & ~RTF_IFSCOPE), dst,
+           gateway, IFSCOPE_NONE));
+}
+
+struct ifaddr *
+ifa_ifwithroute_scoped_locked(int flags, const struct sockaddr *dst,
+    const struct sockaddr *gateway, unsigned int ifscope)
+{
+       if (ifscope != IFSCOPE_NONE)
+               flags |= RTF_IFSCOPE;
+       else
+               flags &= ~RTF_IFSCOPE;
+
+       return (ifa_ifwithroute_common_locked(flags, dst, gateway, ifscope));
+}
+
+static struct ifaddr *
+ifa_ifwithroute_common_locked(int flags, const struct sockaddr *dst,
+    const struct sockaddr *gateway, unsigned int ifscope)
 {
        struct ifaddr *ifa = NULL;
        struct rtentry *rt = NULL;
+       struct sockaddr_in dst_in, gw_in;
 
-       lck_mtx_assert(rt_mtx, LCK_MTX_ASSERT_OWNED);
+       lck_mtx_assert(rnh_lock, LCK_MTX_ASSERT_OWNED);
+
+       if (ip_doscopedroute) {
+               /*
+                * Just in case the sockaddr passed in by the caller
+                * contains embedded scope, make sure to clear it since
+                * IPv4 interface addresses aren't scoped.
+                */
+               if (dst != NULL && dst->sa_family == AF_INET)
+                       dst = sin_copy(SIN(dst), &dst_in, IFSCOPE_NONE);
+               if (gateway != NULL && gateway->sa_family == AF_INET)
+                       gateway = sin_copy(SIN(gateway), &gw_in, IFSCOPE_NONE);
+       }
 
        if (!(flags & RTF_GATEWAY)) {
                /*
@@ -743,7 +1281,7 @@ ifa_ifwithroute_locked(
                        ifa = ifa_ifwithdstaddr(dst);
                }
                if (ifa == NULL)
-                       ifa = ifa_ifwithaddr(gateway);
+                       ifa = ifa_ifwithaddr_scoped(gateway, ifscope);
        } else {
                /*
                 * If we are adding a route to a remote net
@@ -753,15 +1291,18 @@ ifa_ifwithroute_locked(
                ifa = ifa_ifwithdstaddr(gateway);
        }
        if (ifa == NULL)
-               ifa = ifa_ifwithnet(gateway);
+               ifa = ifa_ifwithnet_scoped(gateway, ifscope);
        if (ifa == NULL) {
                /* Workaround to avoid gcc warning regarding const variable */
-               rt = rtalloc1_locked((struct sockaddr *)(size_t)dst, 0, 0UL);
+               rt = rtalloc1_scoped_locked((struct sockaddr *)(size_t)dst,
+                   0, 0, ifscope);
                if (rt != NULL) {
+                       RT_LOCK_SPIN(rt);
                        ifa = rt->rt_ifa;
                        if (ifa != NULL)
                                ifaref(ifa);
-                       rtunref(rt);
+                       RT_REMREF_LOCKED(rt);
+                       RT_UNLOCK(rt);
                        rt = NULL;
                }
        }
@@ -784,50 +1325,91 @@ ifa_ifwithroute_locked(
         */
        if ((ifa == NULL ||
            !equal(ifa->ifa_addr, (struct sockaddr *)(size_t)gateway)) &&
-           (rt = rtalloc1_locked((struct sockaddr *)(size_t)gateway,
-           0, 0UL)) != NULL) {
+           (rt = rtalloc1_scoped_locked((struct sockaddr *)(size_t)gateway,
+           0, 0, ifscope)) != NULL) {
                if (ifa != NULL)
                        ifafree(ifa);
+               RT_LOCK_SPIN(rt);
                ifa = rt->rt_ifa;
                if (ifa != NULL)
                        ifaref(ifa);
-               rtunref(rt);
+               RT_REMREF_LOCKED(rt);
+               RT_UNLOCK(rt);
+       }
+       /*
+        * If an interface scope was specified, the interface index of
+        * the found ifaddr must be equivalent to that of the scope;
+        * otherwise there is no match.
+        */
+       if ((flags & RTF_IFSCOPE) &&
+           ifa != NULL && ifa->ifa_ifp->if_index != ifscope) {
+               ifafree(ifa);
+               ifa = NULL;
        }
+
        return (ifa);
 }
 
-#define ROUNDUP(a) (a>0 ? (1 + (((a) - 1) | (sizeof(long) - 1))) : sizeof(long))
+static int rt_fixdelete(struct radix_node *, void *);
+static int rt_fixchange(struct radix_node *, void *);
 
-static int rt_fixdelete __P((struct radix_node *, void *));
-static int rt_fixchange __P((struct radix_node *, void *));
+struct rtfc_arg {
+       struct rtentry *rt0;
+       struct radix_node_head *rnh;
+};
+
+int
+rtrequest_locked(int req, struct sockaddr *dst, struct sockaddr *gateway,
+    struct sockaddr *netmask, int flags, struct rtentry **ret_nrt)
+{
+       return (rtrequest_common_locked(req, dst, gateway, netmask,
+           (flags & ~RTF_IFSCOPE), ret_nrt, IFSCOPE_NONE));
+}
+
+int
+rtrequest_scoped_locked(int req, struct sockaddr *dst,
+    struct sockaddr *gateway, struct sockaddr *netmask, int flags,
+    struct rtentry **ret_nrt, unsigned int ifscope)
+{
+       if (ifscope != IFSCOPE_NONE)
+               flags |= RTF_IFSCOPE;
+       else
+               flags &= ~RTF_IFSCOPE;
 
-struct rtfc_arg {
-       struct rtentry *rt0;
-       struct radix_node_head *rnh;
-};
+       return (rtrequest_common_locked(req, dst, gateway, netmask,
+           flags, ret_nrt, ifscope));
+}
 
 /*
- * Do appropriate manipulations of a routing tree given
- * all the bits of info needed
+ * Do appropriate manipulations of a routing tree given all the bits of
+ * info needed.
+ *
+ * Embedding the scope in the radix key is an internal job that should be
+ * left to routines in this module.  Callers should specify the scope value
+ * to the "scoped" variants of route routines instead of manipulating the
+ * key itself.  This is typically done when creating a scoped route, e.g.
+ * rtrequest(RTM_ADD).  Once such a route is created and marked with the
+ * RTF_IFSCOPE flag, callers can simply use its rt_key(rt) to clone it
+ * (RTM_RESOLVE) or to remove it (RTM_DELETE).  An exception to this is
+ * during certain routing socket operations where the search key might be
+ * derived from the routing message itself, in which case the caller must
+ * specify the destination address and scope value for RTM_ADD/RTM_DELETE.
  */
-int
-rtrequest_locked(
-       int req,
-       struct sockaddr *dst,
-       struct sockaddr *gateway,
-       struct sockaddr *netmask,
-       int flags,
-       struct rtentry **ret_nrt)
+static int
+rtrequest_common_locked(int req, struct sockaddr *dst0,
+    struct sockaddr *gateway, struct sockaddr *netmask, int flags,
+    struct rtentry **ret_nrt, unsigned int ifscope)
 {
        int error = 0;
        struct rtentry *rt;
        struct radix_node *rn;
        struct radix_node_head *rnh;
        struct ifaddr *ifa = NULL;
-       struct sockaddr *ndst;
+       struct sockaddr *ndst, *dst = dst0;
+       struct sockaddr_in sin, mask;
 #define senderr(x) { error = x ; goto bad; }
 
-       lck_mtx_assert(rt_mtx, LCK_MTX_ASSERT_OWNED);
+       lck_mtx_assert(rnh_lock, LCK_MTX_ASSERT_OWNED);
        /*
         * Find the correct routing tree to use for this Address Family
         */
@@ -839,6 +1421,37 @@ rtrequest_locked(
         */
        if (flags & RTF_HOST)
                netmask = 0;
+
+       /*
+        * If RTF_IFSCOPE is specified, use a local copy of the destination
+        * address to embed the scope into.  This logic is repeated below
+        * in the RTM_RESOLVE handler since the caller does not normally
+        * specify such a flag during a resolve; instead it passes in the
+        * route used for cloning for which the scope info is derived from.
+        * Note also that in the case of RTM_DELETE, the address passed in
+        * by the caller might already contain the embedded scope info when
+        * it is the key itself, thus making RTF_IFSCOPE unnecessary; one
+        * instance where it is explicitly set is inside route_output()
+        * as part of handling a routing socket request.
+        */
+       if (req != RTM_RESOLVE && (flags & RTF_IFSCOPE)) {
+               /* Scoped routing is for AF_INET only */
+               if (dst->sa_family != AF_INET ||
+                   (req == RTM_ADD && !ip_doscopedroute))
+                       senderr(EINVAL);
+
+               if (ifscope == IFSCOPE_NONE) {
+                       flags &= ~RTF_IFSCOPE;
+               } else {
+                       /* Embed ifscope into the key (local copy) */
+                       dst = sin_copy(SIN(dst), &sin, ifscope);
+
+                       /* Embed ifscope into netmask (local copy) */
+                       if (netmask != NULL)
+                               netmask = mask_copy(netmask, &mask, ifscope);
+               }
+       }
+
        switch (req) {
        case RTM_DELETE:
                /*
@@ -860,17 +1473,25 @@ rtrequest_locked(
                 * will decrement the reference via rtfree_locked() and then
                 * possibly deallocate it.
                 */
-               rtref(rt);
+               RT_LOCK(rt);
+               RT_ADDREF_LOCKED(rt);
                rt->rt_flags &= ~RTF_UP;
 
+               /*
+                * For consistency, in case the caller didn't set the flag.
+                */
+               rt->rt_flags |= RTF_CONDEMNED;
+
                /*
                 * Now search what's left of the subtree for any cloned
                 * routes which might have been formed from this node.
                 */
                if ((rt->rt_flags & (RTF_CLONING | RTF_PRCLONING)) &&
                    rt_mask(rt)) {
+                       RT_UNLOCK(rt);
                        rnh->rnh_walktree_from(rnh, dst, rt_mask(rt),
                                               rt_fixdelete, rt);
+                       RT_LOCK(rt);
                }
 
                /*
@@ -878,10 +1499,9 @@ rtrequest_locked(
                 * This might result in another rtentry being freed if
                 * we held its last reference.
                 */
-               if (rt->rt_gwroute) {
-                       rt = rt->rt_gwroute;
-                       rtfree_locked(rt);
-                       (rt = (struct rtentry *)rn)->rt_gwroute = 0;
+               if (rt->rt_gwroute != NULL) {
+                       rtfree_locked(rt->rt_gwroute);
+                       rt->rt_gwroute = NULL;
                }
 
                /*
@@ -895,12 +1515,21 @@ rtrequest_locked(
                 * one more rtentry floating around that is not
                 * linked to the routing table.
                 */
-               (void) OSIncrementAtomic((SInt32 *)&rttrash);
+               (void) OSIncrementAtomic(&rttrash);
                if (rte_debug & RTD_DEBUG) {
                        TAILQ_INSERT_TAIL(&rttrash_head,
                            (struct rtentry_dbg *)rt, rtd_trash_link);
                }
 
+               /*
+                * If this is the (non-scoped) default route, clear
+                * the interface index used for the primary ifscope.
+                */
+               if (rt_inet_default(rt, rt_key(rt)))
+                       set_primary_ifscope(IFSCOPE_NONE);
+
+               RT_UNLOCK(rt);
+
                /*
                 * If the caller wants it, then it can have it,
                 * but it's up to it to free the rtentry as we won't be
@@ -918,6 +1547,16 @@ rtrequest_locked(
        case RTM_RESOLVE:
                if (ret_nrt == 0 || (rt = *ret_nrt) == 0)
                        senderr(EINVAL);
+               /*
+                * If cloning, we have the parent route given by the caller
+                * and will use its rt_gateway, rt_rmx as part of the cloning
+                * process below.  Since rnh_lock is held at this point, the
+                * parent's rt_ifa and rt_gateway will not change, and its
+                * relevant rt_flags will not change as well.  The only thing
+                * that could change are the metrics, and thus we hold the
+                * parent route's rt_lock later on during the actual copying
+                * of rt_rmx.
+                */
                ifa = rt->rt_ifa;
                ifaref(ifa);
                flags = rt->rt_flags &
@@ -926,25 +1565,63 @@ rtrequest_locked(
                gateway = rt->rt_gateway;
                if ((netmask = rt->rt_genmask) == 0)
                        flags |= RTF_HOST;
+
+               if (!ip_doscopedroute || dst->sa_family != AF_INET)
+                       goto makeroute;
+               /*
+                * When scoped routing is enabled, cloned entries are
+                * always scoped according to the interface portion of
+                * the parent route.  The exception to this are IPv4
+                * link local addresses.
+                */
+               if (!IN_LINKLOCAL(ntohl(SIN(dst)->sin_addr.s_addr))) {
+                       if (flags & RTF_IFSCOPE) {
+                               ifscope = sa_get_ifscope(rt_key(rt));
+                       } else {
+                               ifscope = rt->rt_ifp->if_index;
+                               flags |= RTF_IFSCOPE;
+                       }
+               } else {
+                       ifscope = IFSCOPE_NONE;
+                       flags &= ~RTF_IFSCOPE;
+               }
+
+               /* Embed or clear ifscope into/from the key (local copy) */
+               dst = sin_copy(SIN(dst), &sin, ifscope);
+
+               /* Embed or clear ifscope into/from netmask (local copy) */
+               if (netmask != NULL)
+                       netmask = mask_copy(netmask, &mask, ifscope);
+
                goto makeroute;
 
        case RTM_ADD:
                if ((flags & RTF_GATEWAY) && !gateway)
-                       panic("rtrequest: GATEWAY but no gateway");
+                       panic("rtrequest: RTF_GATEWAY but no gateway");
 
-               if ((ifa = ifa_ifwithroute_locked(flags, dst, gateway)) == 0)
+               if (flags & RTF_IFSCOPE) {
+                       ifa = ifa_ifwithroute_scoped_locked(flags, dst0,
+                           gateway, ifscope);
+               } else {
+                       ifa = ifa_ifwithroute_locked(flags, dst0, gateway);
+               }
+               if (ifa == NULL)
                        senderr(ENETUNREACH);
-
-       makeroute:
+makeroute:
                if ((rt = rte_alloc()) == NULL)
                        senderr(ENOBUFS);
                Bzero(rt, sizeof(*rt));
+               rte_lock_init(rt);
+               RT_LOCK(rt);
                rt->rt_flags = RTF_UP | flags;
+
                /*
                 * Add the gateway. Possibly re-malloc-ing the storage for it
                 * also add the rt_gwroute if possible.
                 */
                if ((error = rt_setgate(rt, dst, gateway)) != 0) {
+                       RT_UNLOCK(rt);
+                       rte_lock_destroy(rt);
                        rte_free(rt);
                        senderr(error);
                }
@@ -957,9 +1634,9 @@ rtrequest_locked(
                /*
                 * make sure it contains the value we want (masked if needed).
                 */
-               if (netmask) {
+               if (netmask)
                        rt_maskedcopy(dst, ndst, netmask);
-               else
+               else
                        Bcopy(dst, ndst, dst->sa_len);
 
                /*
@@ -983,13 +1660,21 @@ rtrequest_locked(
                         * mechanism, then we just blow it away and retry
                         * the insertion of the new one.
                         */
-                       rt2 = rtalloc1_locked(dst, 0,
-                           RTF_CLONING | RTF_PRCLONING);
+                       if (flags & RTF_IFSCOPE) {
+                               rt2 = rtalloc1_scoped_locked(dst0, 0,
+                                   RTF_CLONING | RTF_PRCLONING, ifscope);
+                       } else {
+                               rt2 = rtalloc1_locked(dst, 0,
+                                   RTF_CLONING | RTF_PRCLONING);
+                       }
                        if (rt2 && rt2->rt_parent) {
-                               rtrequest_locked(RTM_DELETE,
-                                         (struct sockaddr *)rt_key(rt2),
-                                         rt2->rt_gateway,
-                                         rt_mask(rt2), rt2->rt_flags, 0);
+                               /*
+                                * rnh_lock is held here, so rt_key and
+                                * rt_gateway of rt2 will not change.
+                                */
+                               (void) rtrequest_locked(RTM_DELETE, rt_key(rt2),
+                                   rt2->rt_gateway, rt_mask(rt2),
+                                   rt2->rt_flags, 0);
                                rtfree_locked(rt2);
                                rn = rnh->rnh_addaddr((caddr_t)ndst,
                                                      (caddr_t)netmask,
@@ -1005,12 +1690,17 @@ rtrequest_locked(
                 * then un-make it (this should be a function)
                 */
                if (rn == 0) {
-                       if (rt->rt_gwroute)
+                       if (rt->rt_gwroute) {
                                rtfree_locked(rt->rt_gwroute);
+                               rt->rt_gwroute = NULL;
+                       }
                        if (rt->rt_ifa) {
                                ifafree(rt->rt_ifa);
+                               rt->rt_ifa = NULL;
                        }
                        R_Free(rt_key(rt));
+                       RT_UNLOCK(rt);
+                       rte_lock_destroy(rt);
                        rte_free(rt);
                        senderr(EEXIST);
                }
@@ -1018,16 +1708,22 @@ rtrequest_locked(
                rt->rt_parent = 0;
 
                /*
-                * If we got here from RESOLVE, then we are cloning
-                * so clone the rest, and note that we
-                * are a clone (and increment the parent's references)
+                * If we got here from RESOLVE, then we are cloning so clone
+                * the rest, and note that we are a clone (and increment the
+                * parent's references).  rnh_lock is still held, which prevents
+                * a lookup from returning the newly-created route.  Hence
+                * holding and releasing the parent's rt_lock while still
+                * holding the route's rt_lock is safe since the new route
+                * is not yet externally visible.
                 */
                if (req == RTM_RESOLVE) {
+                       RT_LOCK_SPIN(*ret_nrt);
                        rt->rt_rmx = (*ret_nrt)->rt_rmx; /* copy metrics */
                        if ((*ret_nrt)->rt_flags & (RTF_CLONING | RTF_PRCLONING)) {
                                rt->rt_parent = (*ret_nrt);
-                               rtref(*ret_nrt);
+                               RT_ADDREF_LOCKED(*ret_nrt);
                        }
+                       RT_UNLOCK(*ret_nrt);
                }
 
                /*
@@ -1039,6 +1735,22 @@ rtrequest_locked(
                ifafree(ifa);
                ifa = 0;
 
+               /*
+                * If this is the (non-scoped) default route, record
+                * the interface index used for the primary ifscope.
+                */
+               if (rt_inet_default(rt, rt_key(rt)))
+                       set_primary_ifscope(rt->rt_ifp->if_index);
+
+               /*
+                * actually return a resultant rtentry and
+                * give the caller a single reference.
+                */
+               if (ret_nrt) {
+                       *ret_nrt = rt;
+                       RT_ADDREF_LOCKED(rt);
+               }
+
                /*
                 * We repeat the same procedure from rt_setgate() here because
                 * it doesn't fire when we call it there because the node
@@ -1048,17 +1760,11 @@ rtrequest_locked(
                        struct rtfc_arg arg;
                        arg.rnh = rnh;
                        arg.rt0 = rt;
+                       RT_UNLOCK(rt);
                        rnh->rnh_walktree_from(rnh, rt_key(rt), rt_mask(rt),
                                               rt_fixchange, &arg);
-               }
-
-               /*
-                * actually return a resultant rtentry and
-                * give the caller a single reference.
-                */
-               if (ret_nrt) {
-                       *ret_nrt = rt;
-                       rtref(rt);
+               } else {
+                       RT_UNLOCK(rt);
                }
                break;
        }
@@ -1078,10 +1784,10 @@ rtrequest(
        struct rtentry **ret_nrt)
 {
        int error;
-       lck_mtx_assert(rt_mtx, LCK_MTX_ASSERT_NOTOWNED);
-       lck_mtx_lock(rt_mtx);
+       lck_mtx_assert(rnh_lock, LCK_MTX_ASSERT_NOTOWNED);
+       lck_mtx_lock(rnh_lock);
        error = rtrequest_locked(req, dst, gateway, netmask, flags, ret_nrt);
-       lck_mtx_unlock(rt_mtx);
+       lck_mtx_unlock(rnh_lock);
        return (error);
 }
 /*
@@ -1097,14 +1803,21 @@ rt_fixdelete(struct radix_node *rn, void *vp)
        struct rtentry *rt = (struct rtentry *)rn;
        struct rtentry *rt0 = vp;
 
-       lck_mtx_assert(rt_mtx, LCK_MTX_ASSERT_OWNED);
+       lck_mtx_assert(rnh_lock, LCK_MTX_ASSERT_OWNED);
 
+       RT_LOCK(rt);
        if (rt->rt_parent == rt0 &&
            !(rt->rt_flags & (RTF_PINNED | RTF_CLONING | RTF_PRCLONING))) {
-               return rtrequest_locked(RTM_DELETE, rt_key(rt),
-                                (struct sockaddr *)0, rt_mask(rt),
-                                rt->rt_flags, (struct rtentry **)0);
+               /*
+                * Safe to drop rt_lock and use rt_key, since holding
+                * rnh_lock here prevents another thread from calling
+                * rt_setgate() on this route.
+                */
+               RT_UNLOCK(rt);
+               return (rtrequest_locked(RTM_DELETE, rt_key(rt), NULL,
+                   rt_mask(rt), rt->rt_flags, NULL));
        }
+       RT_UNLOCK(rt);
        return 0;
 }
 
@@ -1121,10 +1834,6 @@ rt_fixdelete(struct radix_node *rn, void *vp)
  * routine just for adds.  I'm not sure why I thought it was necessary to do
  * changes this way.
  */
-#ifdef DEBUG
-static int rtfcdebug = 0;
-#endif
-
 static int
 rt_fixchange(struct radix_node *rn, void *vp)
 {
@@ -1135,36 +1844,24 @@ rt_fixchange(struct radix_node *rn, void *vp)
        u_char *xk1, *xm1, *xk2, *xmp;
        int i, len, mlen;
 
-#ifdef DEBUG
-       if (rtfcdebug)
-               printf("rt_fixchange: rt %p, rt0 %p\n", rt, rt0);
-#endif
+       lck_mtx_assert(rnh_lock, LCK_MTX_ASSERT_OWNED);
 
-       lck_mtx_assert(rt_mtx, LCK_MTX_ASSERT_OWNED);
+       RT_LOCK(rt);
 
        if (!rt->rt_parent ||
            (rt->rt_flags & (RTF_PINNED | RTF_CLONING | RTF_PRCLONING))) {
-#ifdef DEBUG
-               if(rtfcdebug) printf("no parent or pinned\n");
-#endif
-               return 0;
+               RT_UNLOCK(rt);
+               return (0);
        }
 
-       if (rt->rt_parent == rt0) {
-#ifdef DEBUG
-               if(rtfcdebug) printf("parent match\n");
-#endif
-               return rtrequest_locked(RTM_DELETE, rt_key(rt),
-                                (struct sockaddr *)0, rt_mask(rt),
-                                rt->rt_flags, (struct rtentry **)0);
-       }
+       if (rt->rt_parent == rt0)
+               goto delete_rt;
 
        /*
         * There probably is a function somewhere which does this...
         * if not, there should be.
         */
-       len = imin(((struct sockaddr *)rt_key(rt0))->sa_len,
-                  ((struct sockaddr *)rt_key(rt))->sa_len);
+       len = imin(rt_key(rt0)->sa_len, rt_key(rt)->sa_len);
 
        xk1 = (u_char *)rt_key(rt0);
        xm1 = (u_char *)rt_mask(rt0);
@@ -1172,32 +1869,23 @@ rt_fixchange(struct radix_node *rn, void *vp)
 
        /* avoid applying a less specific route */
        xmp = (u_char *)rt_mask(rt->rt_parent);
-       mlen = ((struct sockaddr *)rt_key(rt->rt_parent))->sa_len;
-       if (mlen > ((struct sockaddr *)rt_key(rt0))->sa_len) {
-#if DEBUG
-               if (rtfcdebug)
-                       printf("rt_fixchange: inserting a less "
-                              "specific route\n");
-#endif
-               return 0;
+       mlen = rt_key(rt->rt_parent)->sa_len;
+       if (mlen > rt_key(rt0)->sa_len) {
+               RT_UNLOCK(rt);
+               return (0);
        }
+
        for (i = rnh->rnh_treetop->rn_offset; i < mlen; i++) {
                if ((xmp[i] & ~(xmp[i] ^ xm1[i])) != xmp[i]) {
-#if DEBUG
-                       if (rtfcdebug)
-                               printf("rt_fixchange: inserting a less "
-                                      "specific route\n");
-#endif
-                       return 0;
+                       RT_UNLOCK(rt);
+                       return (0);
                }
        }
 
        for (i = rnh->rnh_treetop->rn_offset; i < len; i++) {
                if ((xk2[i] & xm1[i]) != xk1[i]) {
-#ifdef DEBUG
-                       if(rtfcdebug) printf("no match\n");
-#endif
-                       return 0;
+                       RT_UNLOCK(rt);
+                       return (0);
                }
        }
 
@@ -1205,107 +1893,218 @@ rt_fixchange(struct radix_node *rn, void *vp)
         * OK, this node is a clone, and matches the node currently being
         * changed/added under the node's mask.  So, get rid of it.
         */
-#ifdef DEBUG
-       if(rtfcdebug) printf("deleting\n");
-#endif
-       return rtrequest_locked(RTM_DELETE, rt_key(rt), (struct sockaddr *)0,
-                        rt_mask(rt), rt->rt_flags, (struct rtentry **)0);
+delete_rt:
+       /*
+        * Safe to drop rt_lock and use rt_key, since holding rnh_lock here
+        * prevents another thread from calling rt_setgate() on this route.
+        */
+       RT_UNLOCK(rt);
+       return (rtrequest_locked(RTM_DELETE, rt_key(rt), NULL,
+           rt_mask(rt), rt->rt_flags, NULL));
 }
 
+/*
+ * Round up sockaddr len to multiples of 32-bytes.  This will reduce
+ * or even eliminate the need to re-allocate the chunk of memory used
+ * for rt_key and rt_gateway in the event the gateway portion changes.
+ * Certain code paths (e.g. IPSec) are notorious for caching the address
+ * of rt_gateway; this rounding-up would help ensure that the gateway
+ * portion never gets deallocated (though it may change contents) and
+ * thus greatly simplifies things.
+ */
+#define        SA_SIZE(x) (-(-((uintptr_t)(x)) & -(32)))
+
+/*
+ * Sets the gateway and/or gateway route portion of a route; may be
+ * called on an existing route to modify the gateway portion.  Both
+ * rt_key and rt_gateway are allocated out of the same memory chunk.
+ * Route entry lock must be held by caller; this routine will return
+ * with the lock held.
+ */
 int
-rt_setgate(struct rtentry *rt0, struct sockaddr *dst, struct sockaddr *gate)
+rt_setgate(struct rtentry *rt, struct sockaddr *dst, struct sockaddr *gate)
 {
-       caddr_t new, old;
-       int dlen = ROUNDUP(dst->sa_len), glen = ROUNDUP(gate->sa_len);
-       struct rtentry *rt = rt0;
+       int dlen = SA_SIZE(dst->sa_len), glen = SA_SIZE(gate->sa_len);
        struct radix_node_head *rnh = rt_tables[dst->sa_family];
+
+       lck_mtx_assert(rnh_lock, LCK_MTX_ASSERT_OWNED);
+       RT_LOCK_ASSERT_HELD(rt);
+
+       /*
+        * If this is for a route that is on its way of being removed,
+        * or is temporarily frozen, reject the modification request.
+        */
+       if (rt->rt_flags & RTF_CONDEMNED)
+               return (EBUSY);
+
+       /* Add an extra ref for ourselves */
+       RT_ADDREF_LOCKED(rt);
+
        /*
         * A host route with the destination equal to the gateway
         * will interfere with keeping LLINFO in the routing
         * table, so disallow it.
         */
-       
-       lck_mtx_assert(rt_mtx, LCK_MTX_ASSERT_OWNED);
-
-       if (((rt0->rt_flags & (RTF_HOST|RTF_GATEWAY|RTF_LLINFO)) ==
-                                       (RTF_HOST|RTF_GATEWAY)) &&
-           (dst->sa_len == gate->sa_len) &&
+       if (((rt->rt_flags & (RTF_HOST|RTF_GATEWAY|RTF_LLINFO)) ==
+           (RTF_HOST|RTF_GATEWAY)) && (dst->sa_len == gate->sa_len) &&
            (bcmp(dst, gate, dst->sa_len) == 0)) {
                /*
                 * The route might already exist if this is an RTM_CHANGE
                 * or a routing redirect, so try to delete it.
                 */
-               if (rt_key(rt0))
-                       rtrequest_locked(RTM_DELETE, (struct sockaddr *)rt_key(rt0),
-                           rt0->rt_gateway, rt_mask(rt0), rt0->rt_flags, 0);
-               return EADDRNOTAVAIL;
+               if (rt_key(rt) != NULL) {
+                       /*
+                        * Safe to drop rt_lock and use rt_key, rt_gateway,
+                        * since holding rnh_lock here prevents another thread
+                        * from calling rt_setgate() on this route.
+                        */
+                       RT_UNLOCK(rt);
+                       (void) rtrequest_locked(RTM_DELETE, rt_key(rt),
+                           rt->rt_gateway, rt_mask(rt), rt->rt_flags, NULL);
+                       RT_LOCK(rt);
+               }
+               /* Release extra ref */
+               RT_REMREF_LOCKED(rt);
+               return (EADDRNOTAVAIL);
        }
 
        /*
-        * Both dst and gateway are stored in the same malloc'd chunk
-        * (If I ever get my hands on....)
-        * if we need to malloc a new chunk, then keep the old one around
-        * till we don't need it any more.
+        * The destination is not directly reachable.  Get a route
+        * to the next-hop gateway and store it in rt_gwroute.
         */
-       if (rt->rt_gateway == 0 || glen > ROUNDUP(rt->rt_gateway->sa_len)) {
-               old = (caddr_t)rt_key(rt);
-               R_Malloc(new, caddr_t, dlen + glen);
-               if (new == 0)
-                       return ENOBUFS;
-               rt->rt_nodes->rn_key = new;
-       } else {
+       if (rt->rt_flags & RTF_GATEWAY) {
+               struct rtentry *gwrt;
+               unsigned int ifscope;
+
+               ifscope = (dst->sa_family == AF_INET) ?
+                   sa_get_ifscope(dst) : IFSCOPE_NONE;
+
+               RT_UNLOCK(rt);
+               gwrt = rtalloc1_scoped_locked(gate, 1, RTF_PRCLONING, ifscope);
+               if (gwrt != NULL)
+                       RT_LOCK_ASSERT_NOTHELD(gwrt);
+               RT_LOCK(rt);
+
+               /*
+                * Cloning loop avoidance:
+                *
+                * In the presence of protocol-cloning and bad configuration,
+                * it is possible to get stuck in bottomless mutual recursion
+                * (rtrequest rt_setgate rtalloc1).  We avoid this by not
+                * allowing protocol-cloning to operate for gateways (which
+                * is probably the correct choice anyway), and avoid the
+                * resulting reference loops by disallowing any route to run
+                * through itself as a gateway.  This is obviously mandatory
+                * when we get rt->rt_output().  It implies that a route to
+                * the gateway must already be present in the system in order
+                * for the gateway to be referred to by another route.
+                */
+               if (gwrt == rt) {
+                       RT_REMREF_LOCKED(gwrt);
+                       /* Release extra ref */
+                       RT_REMREF_LOCKED(rt);
+                       return (EADDRINUSE); /* failure */
+               }
+
+               /*
+                * If scoped, the gateway route must use the same interface;
+                * we're holding rnh_lock now, so rt_gateway and rt_ifp of gwrt
+                * should not change and are freely accessible.
+                */
+               if (ifscope != IFSCOPE_NONE && (rt->rt_flags & RTF_IFSCOPE) &&
+                   gwrt != NULL && gwrt->rt_ifp != NULL &&
+                   gwrt->rt_ifp->if_index != ifscope) {
+                       rtfree_locked(gwrt);    /* rt != gwrt, no deadlock */
+                       /* Release extra ref */
+                       RT_REMREF_LOCKED(rt);
+                       return ((rt->rt_flags & RTF_HOST) ?
+                           EHOSTUNREACH : ENETUNREACH);
+               }
+
+               /* Check again since we dropped the lock above */
+               if (rt->rt_flags & RTF_CONDEMNED) {
+                       if (gwrt != NULL)
+                               rtfree_locked(gwrt);
+                       /* Release extra ref */
+                       RT_REMREF_LOCKED(rt);
+                       return (EBUSY);
+               }
+
+               if (rt->rt_gwroute != NULL)
+                       rtfree_locked(rt->rt_gwroute);
+               rt->rt_gwroute = gwrt;
+
+               /*
+                * In case the (non-scoped) default route gets modified via
+                * an ICMP redirect, record the interface index used for the
+                * primary ifscope.  Also done in rt_setif() to take care
+                * of the non-redirect cases.
+                */
+               if (rt_inet_default(rt, dst) && rt->rt_ifp != NULL)
+                       set_primary_ifscope(rt->rt_ifp->if_index);
+
                /*
-                * otherwise just overwrite the old one
+                * Tell the kernel debugger about the new default gateway
+                * if the gateway route uses the primary interface, or
+                * if we are in a transient state before the non-scoped
+                * default gateway is installed (similar to how the system
+                * was behaving in the past).  In future, it would be good
+                * to do all this only when KDP is enabled.
                 */
-               new = rt->rt_nodes->rn_key;
-               old = 0;
+               if ((dst->sa_family == AF_INET) &&
+                   gwrt != NULL && gwrt->rt_gateway->sa_family == AF_LINK &&
+                   (gwrt->rt_ifp->if_index == get_primary_ifscope() ||
+                   get_primary_ifscope() == IFSCOPE_NONE))
+                       kdp_set_gateway_mac(SDL(gwrt->rt_gateway)->sdl_data);
        }
 
        /*
-        * copy the new gateway value into the memory chunk
+        * Prepare to store the gateway in rt_gateway.  Both dst and gateway
+        * are stored one after the other in the same malloc'd chunk.  If we
+        * have room, reuse the old buffer since rt_gateway already points
+        * to the right place.  Otherwise, malloc a new block and update
+        * the 'dst' address and point rt_gateway to the right place.
         */
-       Bcopy(gate, (rt->rt_gateway = (struct sockaddr *)(new + dlen)), glen);
+       if (rt->rt_gateway == NULL || glen > SA_SIZE(rt->rt_gateway->sa_len)) {
+               caddr_t new;
 
-       /*
-        * if we are replacing the chunk (or it's new) we need to
-        * replace the dst as well
-        */
-       if (old) {
-               Bcopy(dst, new, dlen);
-               R_Free(old);
+               /* The underlying allocation is done with M_WAITOK set */
+               R_Malloc(new, caddr_t, dlen + glen);
+               if (new == NULL) {
+                       if (rt->rt_gwroute != NULL)
+                               rtfree_locked(rt->rt_gwroute);
+                       rt->rt_gwroute = NULL;
+                       /* Release extra ref */
+                       RT_REMREF_LOCKED(rt);
+                       return (ENOBUFS);
+               }
+
+               /*
+                * Copy from 'dst' and not rt_key(rt) because we can get
+                * here to initialize a newly allocated route entry, in
+                * which case rt_key(rt) is NULL (and so does rt_gateway).
+                */
+               bzero(new, dlen + glen);
+               Bcopy(dst, new, dst->sa_len);
+               R_Free(rt_key(rt));     /* free old block; NULL is okay */
+               rt->rt_nodes->rn_key = new;
+               rt->rt_gateway = (struct sockaddr *)(new + dlen);
        }
 
        /*
-        * If there is already a gwroute, it's now almost definitly wrong
-        * so drop it.
+        * Copy the new gateway value into the memory chunk.
         */
-       if (rt->rt_gwroute) {
-               rt = rt->rt_gwroute; rtfree_locked(rt);
-               rt = rt0; rt->rt_gwroute = 0;
-       }
+       Bcopy(gate, rt->rt_gateway, gate->sa_len);
+
        /*
-        * Cloning loop avoidance:
-        * In the presence of protocol-cloning and bad configuration,
-        * it is possible to get stuck in bottomless mutual recursion
-        * (rtrequest rt_setgate rtalloc1).  We avoid this by not allowing
-        * protocol-cloning to operate for gateways (which is probably the
-        * correct choice anyway), and avoid the resulting reference loops
-        * by disallowing any route to run through itself as a gateway.
-        * This is obviously mandatory when we get rt->rt_output().
+        * For consistency between rt_gateway and rt_key(gwrt).
         */
-       if (rt->rt_flags & RTF_GATEWAY) {
-               rt->rt_gwroute = rtalloc1_locked(gate, 1, RTF_PRCLONING);
-               if (rt->rt_gwroute == rt) {
-                       rtfree_locked(rt->rt_gwroute);
-                       rt->rt_gwroute = 0;
-                       return EDQUOT; /* failure */
-               }
-               /* Tell the kernel debugger about the new default gateway */
-               if ((AF_INET == rt->rt_gateway->sa_family) && 
-                   rt->rt_gwroute && rt->rt_gwroute->rt_gateway && 
-                   (AF_LINK == rt->rt_gwroute->rt_gateway->sa_family)) {
-                 kdp_set_gateway_mac(((struct sockaddr_dl *)rt0->rt_gwroute->rt_gateway)->sdl_data);
-               }
+       if ((rt->rt_flags & RTF_GATEWAY) && rt->rt_gwroute != NULL &&
+           (rt->rt_gwroute->rt_flags & RTF_IFSCOPE) &&
+           rt->rt_gateway->sa_family == AF_INET &&
+           rt_key(rt->rt_gwroute)->sa_family == AF_INET) {
+               sa_set_ifscope(rt->rt_gateway,
+                   sa_get_ifscope(rt_key(rt->rt_gwroute)));
        }
 
        /*
@@ -1317,13 +2116,19 @@ rt_setgate(struct rtentry *rt0, struct sockaddr *dst, struct sockaddr *gate)
                struct rtfc_arg arg;
                arg.rnh = rnh;
                arg.rt0 = rt;
+               RT_UNLOCK(rt);
                rnh->rnh_walktree_from(rnh, rt_key(rt), rt_mask(rt),
-                                      rt_fixchange, &arg);
+                   rt_fixchange, &arg);
+               RT_LOCK(rt);
        }
 
-       return 0;
+       /* Release extra ref */
+       RT_REMREF_LOCKED(rt);
+       return (0);
 }
 
+#undef SA_SIZE
+
 static void
 rt_maskedcopy(struct sockaddr *src, struct sockaddr *dst,
              struct sockaddr *netmask)
@@ -1344,6 +2149,232 @@ rt_maskedcopy(struct sockaddr *src, struct sockaddr *dst,
                bzero((caddr_t)cp2, (unsigned)(cplim2 - cp2));
 }
 
+/*
+ * Lookup an AF_INET scoped or non-scoped route depending on the ifscope
+ * value passed in by the caller (IFSCOPE_NONE implies non-scoped).
+ */
+static struct radix_node *
+node_lookup(struct sockaddr *dst, struct sockaddr *netmask,
+    unsigned int ifscope)
+{
+       struct radix_node_head *rnh = rt_tables[AF_INET];
+       struct radix_node *rn;
+       struct sockaddr_in sin, mask;
+       struct matchleaf_arg ma = { ifscope };
+       rn_matchf_t *f = rn_match_ifscope;
+       void *w = &ma;
+
+       if (dst->sa_family != AF_INET)
+               return (NULL);
+
+       /*
+        * Embed ifscope into the search key; for a non-scoped
+        * search this will clear out any embedded scope value.
+        */
+       dst = sin_copy(SIN(dst), &sin, ifscope);
+
+       /* Embed (or clear) ifscope into netmask */
+       if (netmask != NULL)
+               netmask = mask_copy(netmask, &mask, ifscope);
+
+       if (ifscope == IFSCOPE_NONE)
+               f = w = NULL;
+
+       rn = rnh->rnh_lookup_args(dst, netmask, rnh, f, w);
+       if (rn != NULL && (rn->rn_flags & RNF_ROOT))
+               rn = NULL;
+
+       return (rn);
+}
+
+/*
+ * Lookup the AF_INET non-scoped default route.
+ */
+static struct radix_node *
+node_lookup_default(void)
+{
+       struct radix_node_head *rnh = rt_tables[AF_INET];
+       return (rnh->rnh_lookup(&sin_def, NULL, rnh));
+}
+
+/*
+ * Common routine to lookup/match a route.  It invokes the lookup/matchaddr
+ * callback which could be address family-specific.  The main difference
+ * between the two (at least for AF_INET/AF_INET6) is that a lookup does
+ * not alter the expiring state of a route, whereas a match would unexpire
+ * or revalidate the route.
+ *
+ * The optional scope or interface index property of a route allows for a
+ * per-interface route instance.  This permits multiple route entries having
+ * the same destination (but not necessarily the same gateway) to exist in
+ * the routing table; each of these entries is specific to the corresponding
+ * interface.  This is made possible by embedding the scope value into the
+ * radix key, thus making each route entry unique.  These scoped entries
+ * exist along with the regular, non-scoped entries in the same radix tree
+ * for a given address family (currently AF_INET only); the scope logically
+ * partitions it into multiple per-interface sub-trees.
+ *
+ * When a scoped route lookup is performed, the routing table is searched for
+ * the best match that would result in a route using the same interface as the
+ * one associated with the scope (the exception to this are routes that point
+ * to the loopback interface).  The search rule follows the longest matching
+ * prefix with the additional interface constraint.
+ */
+struct rtentry *
+rt_lookup(boolean_t lookup_only, struct sockaddr *dst, struct sockaddr *netmask,
+    struct radix_node_head *rnh, unsigned int ifscope)
+{
+       struct radix_node *rn0, *rn;
+       boolean_t dontcare = (ifscope == IFSCOPE_NONE);
+
+       lck_mtx_assert(rnh_lock, LCK_MTX_ASSERT_OWNED);
+
+       if (!lookup_only)
+               netmask = NULL;
+
+       /*
+        * Non-scoped route lookup.
+        */
+       if (!ip_doscopedroute || dst->sa_family != AF_INET) {
+               if (lookup_only)
+                       rn = rnh->rnh_lookup(dst, netmask, rnh);
+               else
+                       rn = rnh->rnh_matchaddr(dst, rnh);
+
+               /*
+                * Don't return a root node; also, rnh_matchaddr callback
+                * would have done the necessary work to clear RTPRF_OURS
+                * for certain protocol families.
+                */
+               if (rn != NULL && (rn->rn_flags & RNF_ROOT))
+                       rn = NULL;
+               if (rn != NULL) {
+                       RT_LOCK_SPIN(RT(rn));
+                       if (!(RT(rn)->rt_flags & RTF_CONDEMNED)) {
+                               RT_ADDREF_LOCKED(RT(rn));
+                               RT_UNLOCK(RT(rn));
+                       } else {
+                               RT_UNLOCK(RT(rn));
+                               rn = NULL;
+                       }
+               }
+               return (RT(rn));
+       }
+
+       /*
+        * Scoped route lookup:
+        *
+        * We first perform a non-scoped lookup for the original result.
+        * Afterwards, depending on whether or not the caller has specified
+        * a scope, we perform a more specific scoped search and fallback
+        * to this original result upon failure.
+        */
+       rn0 = rn = node_lookup(dst, netmask, IFSCOPE_NONE);
+
+       /*
+        * If the caller did not specify a scope, use the primary scope
+        * derived from the system's non-scoped default route.  If, for
+        * any reason, there is no primary interface, return what we have.
+        */
+       if (dontcare && (ifscope = get_primary_ifscope()) == IFSCOPE_NONE)
+               goto done;
+
+       /*
+        * Keep the original result if either of the following is true:
+        *
+        *   1) The interface portion of the route has the same interface
+        *      index as the scope value and it is marked with RTF_IFSCOPE.
+        *   2) The route uses the loopback interface, in which case the
+        *      destination (host/net) is local/loopback.
+        *
+        * Otherwise, do a more specified search using the scope;
+        * we're holding rnh_lock now, so rt_ifp should not change.
+        */
+       if (rn != NULL) {
+               struct rtentry *rt = RT(rn);
+               if (rt->rt_ifp != lo_ifp) {
+                       if (rt->rt_ifp->if_index != ifscope) {
+                               /*
+                                * Wrong interface; keep the original result
+                                * only if the caller did not specify a scope,
+                                * and do a more specific scoped search using
+                                * the scope of the found route.  Otherwise,
+                                * start again from scratch.
+                                */
+                               rn = NULL;
+                               if (dontcare)
+                                       ifscope = rt->rt_ifp->if_index;
+                               else
+                                       rn0 = NULL;
+                       } else if (!(rt->rt_flags & RTF_IFSCOPE)) {
+                               /*
+                                * Right interface, except that this route
+                                * isn't marked with RTF_IFSCOPE.  Do a more
+                                * specific scoped search.  Keep the original
+                                * result and return it it in case the scoped
+                                * search fails.
+                                */
+                               rn = NULL;
+                       }
+               }
+       }
+
+       /*
+        * Scoped search.  Find the most specific entry having the same
+        * interface scope as the one requested.  The following will result
+        * in searching for the longest prefix scoped match.
+        */
+       if (rn == NULL)
+               rn = node_lookup(dst, netmask, ifscope);
+
+       /*
+        * Use the original result if either of the following is true:
+        *
+        *   1) The scoped search did not yield any result.
+        *   2) The result from the scoped search is a scoped default route,
+        *      and the original (non-scoped) result is not a default route,
+        *      i.e. the original result is a more specific host/net route.
+        *   3) The scoped search yielded a net route but the original
+        *      result is a host route, i.e. the original result is treated
+        *      as a more specific route.
+        */
+       if (rn == NULL || (rn0 != NULL &&
+           ((INET_DEFAULT(rt_key(RT(rn))) && !INET_DEFAULT(rt_key(RT(rn0)))) ||
+           (!RT_HOST(rn) && RT_HOST(rn0)))))
+               rn = rn0;
+
+       /*
+        * If we still don't have a route, use the non-scoped default
+        * route as long as the interface portion satistifes the scope.
+        */
+       if (rn == NULL && (rn = node_lookup_default()) != NULL &&
+           RT(rn)->rt_ifp->if_index != ifscope)
+               rn = NULL;
+
+done:
+       if (rn != NULL) {
+               /*
+                * Manually clear RTPRF_OURS using in_validate() and
+                * bump up the reference count after, and not before;
+                * we only get here for AF_INET.  node_lookup() has
+                * done the check against RNF_ROOT, so we can be sure
+                * that we're not returning a root node here.
+                */
+               RT_LOCK_SPIN(RT(rn));
+               if (!(RT(rn)->rt_flags & RTF_CONDEMNED)) {
+                       if (!lookup_only)
+                               (void) in_validate(rn);
+                       RT_ADDREF_LOCKED(RT(rn));
+                       RT_UNLOCK(RT(rn));
+               } else {
+                       RT_UNLOCK(RT(rn));
+                       rn = NULL;
+               }
+       }
+
+       return (RT(rn));
+}
+
 /*
  * Set up a routing table entry, normally
  * for an interface.
@@ -1352,10 +2383,10 @@ int
 rtinit(struct ifaddr *ifa, int cmd, int flags)
 {
        int error;
-       lck_mtx_assert(rt_mtx, LCK_MTX_ASSERT_NOTOWNED);
-       lck_mtx_lock(rt_mtx);
+       lck_mtx_assert(rnh_lock, LCK_MTX_ASSERT_NOTOWNED);
+       lck_mtx_lock(rnh_lock);
        error = rtinit_locked(ifa, cmd, flags);
-       lck_mtx_unlock(rt_mtx);
+       lck_mtx_unlock(rnh_lock);
        return (error);
 }
 
@@ -1396,15 +2427,17 @@ rtinit_locked(struct ifaddr *ifa, int cmd, int flags)
                 * We set "report" to FALSE so that if it doesn't exist,
                 * it doesn't report an error or clone a route, etc. etc.
                 */
-               rt = rtalloc1_locked(dst, 0, 0UL);
+               rt = rtalloc1_locked(dst, 0, 0);
                if (rt) {
                        /*
                         * Ok so we found the rtentry. it has an extra reference
                         * for us at this stage. we won't need that so
                         * lop that off now.
                         */
-                       rtunref(rt);
+                       RT_LOCK_SPIN(rt);
                        if (rt->rt_ifa != ifa) {
+                               RT_REMREF_LOCKED(rt);
+                               RT_UNLOCK(rt);
                                /*
                                 * If the interface in the rtentry doesn't match
                                 * the interface we are using, then we don't
@@ -1416,6 +2449,9 @@ rtinit_locked(struct ifaddr *ifa, int cmd, int flags)
                                        (void) m_free(m);
                                return (flags & RTF_HOST ? EHOSTUNREACH
                                                        : ENETUNREACH);
+                       } else {
+                               RT_REMREF_LOCKED(rt);
+                               RT_UNLOCK(rt);
                        }
                }
                /* XXX */
@@ -1426,7 +2462,7 @@ rtinit_locked(struct ifaddr *ifa, int cmd, int flags)
                         * it doesn't exist, we could just return at this point
                         * with an "ELSE" clause, but apparently not..
                         */
-                       lck_mtx_unlock(rt_mtx);
+                       lck_mtx_unlock(rnh_lock);
                        return (flags & RTF_HOST ? EHOSTUNREACH
                                                        : ENETUNREACH);
                }
@@ -1445,11 +2481,13 @@ rtinit_locked(struct ifaddr *ifa, int cmd, int flags)
         */
        if (cmd == RTM_DELETE && error == 0 && (rt = nrt)) {
                /*
-                * notify any listenning routing agents of the change
+                * notify any listening routing agents of the change
                 */
+               RT_LOCK(rt);
                rt_newaddrmsg(cmd, ifa, error, nrt);
                if (use_routegenid)
-                       route_generation++;
+                       routegenid_update();
+               RT_UNLOCK(rt);
                rtfree_locked(rt);
        }
 
@@ -1458,6 +2496,7 @@ rtinit_locked(struct ifaddr *ifa, int cmd, int flags)
         * We need to sanity check the result.
         */
        if (cmd == RTM_ADD && error == 0 && (rt = nrt)) {
+               RT_LOCK(rt);
                /*
                 * If it came back with an unexpected interface, then it must
                 * have already existed or something. (XXX)
@@ -1496,7 +2535,7 @@ rtinit_locked(struct ifaddr *ifa, int cmd, int flags)
                 */
                rt_newaddrmsg(cmd, ifa, error, nrt);
                if (use_routegenid)
-                       route_generation++;
+                       routegenid_update();
                /*
                 * We just wanted to add it; we don't actually need a
                 * reference.  This will result in a route that's added
@@ -1504,12 +2543,68 @@ rtinit_locked(struct ifaddr *ifa, int cmd, int flags)
                 * RTM_DELETE code will do the necessary step to adjust
                 * the reference count at deletion time.
                 */
-               rtunref(rt);
+               RT_REMREF_LOCKED(rt);
+               RT_UNLOCK(rt);
        }
        return (error);
 }
 
-struct rtentry *
+static void
+rte_lock_init(struct rtentry *rt)
+{
+       lck_mtx_init(&rt->rt_lock, rte_mtx_grp, rte_mtx_attr);
+}
+
+static void
+rte_lock_destroy(struct rtentry *rt)
+{
+       RT_LOCK_ASSERT_NOTHELD(rt);
+       lck_mtx_destroy(&rt->rt_lock, rte_mtx_grp);
+}
+
+void
+rt_lock(struct rtentry *rt, boolean_t spin)
+{
+       RT_LOCK_ASSERT_NOTHELD(rt);
+       if (spin)
+               lck_mtx_lock_spin(&rt->rt_lock);
+       else
+               lck_mtx_lock(&rt->rt_lock);
+       if (rte_debug & RTD_DEBUG)
+               rte_lock_debug((struct rtentry_dbg *)rt);
+}
+
+void
+rt_unlock(struct rtentry *rt)
+{
+       RT_LOCK_ASSERT_HELD(rt);
+       if (rte_debug & RTD_DEBUG)
+               rte_unlock_debug((struct rtentry_dbg *)rt);
+       lck_mtx_unlock(&rt->rt_lock);
+
+}
+
+static inline void
+rte_lock_debug(struct rtentry_dbg *rte)
+{
+       uint32_t idx;
+
+       idx = atomic_add_32_ov(&rte->rtd_lock_cnt, 1) % CTRACE_HIST_SIZE;
+       if (rte_debug & RTD_TRACE)
+               ctrace_record(&rte->rtd_lock[idx]);
+}
+
+static inline void
+rte_unlock_debug(struct rtentry_dbg *rte)
+{
+       uint32_t idx;
+
+       idx = atomic_add_32_ov(&rte->rtd_unlock_cnt, 1) % CTRACE_HIST_SIZE;
+       if (rte_debug & RTD_TRACE)
+               ctrace_record(&rte->rtd_unlock[idx]);
+}
+
+static struct rtentry *
 rte_alloc(void)
 {
        if (rte_debug & RTD_DEBUG)
@@ -1518,7 +2613,7 @@ rte_alloc(void)
        return ((struct rtentry *)zalloc(rte_zone));
 }
 
-void
+static void
 rte_free(struct rtentry *p)
 {
        if (rte_debug & RTD_DEBUG) {
@@ -1540,11 +2635,8 @@ rte_alloc_debug(void)
        rte = ((struct rtentry_dbg *)zalloc(rte_zone));
        if (rte != NULL) {
                bzero(rte, sizeof (*rte));
-               if (rte_debug & RTD_TRACE) {
-                       rte->rtd_alloc_thread = current_thread();
-                       (void) OSBacktrace(rte->rtd_alloc_stk_pc,
-                           RTD_TRSTACK_SIZE);
-               }
+               if (rte_debug & RTD_TRACE)
+                       ctrace_record(&rte->rtd_alloc);
                rte->rtd_inuse = RTD_INUSE;
        }
        return ((struct rtentry *)rte);
@@ -1564,15 +2656,22 @@ rte_free_debug(struct rtentry *p)
                panic("rte_free: corrupted rte=%p\n", rte);
 
        bcopy((caddr_t)p, (caddr_t)&rte->rtd_entry_saved, sizeof (*p));
-       bzero((caddr_t)p, sizeof (*p));
+       /* Preserve rt_lock to help catch use-after-free cases */
+       bzero((caddr_t)p, offsetof(struct rtentry, rt_lock));
 
        rte->rtd_inuse = RTD_FREED;
 
-       if (rte_debug & RTD_TRACE) {
-               rte->rtd_free_thread = current_thread();
-               (void) OSBacktrace(rte->rtd_free_stk_pc, RTD_TRSTACK_SIZE);
-       }
+       if (rte_debug & RTD_TRACE)
+               ctrace_record(&rte->rtd_free);
 
        if (!(rte_debug & RTD_NO_FREE))
                zfree(rte_zone, p);
 }
+
+void
+ctrace_record(ctrace_t *tr)
+{
+       tr->th = current_thread();
+       bzero(tr->pc, sizeof (tr->pc));
+       (void) OSBacktrace(tr->pc, CTRACE_STACK_SIZE);
+}