xnu-2782.30.5.tar.gz

[apple/xnu.git] / bsd / kern / uipc_mbuf2.c

diff --git a/bsd/kern/uipc_mbuf2.c b/bsd/kern/uipc_mbuf2.c
index 49727ff3ab70780479eb80dc0e0f28568c4cfa39..2d6f23f08e4b00de02082ffd88669319cd5e54ac 100644 (file)
--- a/bsd/kern/uipc_mbuf2.c
+++ b/bsd/kern/uipc_mbuf2.c
@@ -1,5 +1,5 @@
 /*
 /*

- * Copyright (c) 2000-2007 Apple Inc. All rights reserved.
+ * Copyright (c) 2000-2013 Apple Inc. All rights reserved.

  *
  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
  * 
  *
  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
  * 


@@ -105,11 +105,13 @@
 #include <sys/proc_internal.h>
 #include <sys/malloc.h>
 #include <sys/mbuf.h>
 #include <sys/proc_internal.h>
 #include <sys/malloc.h>
 #include <sys/mbuf.h>

-#if defined(PULLDOWN_STAT) && defined(INET6)
+#include <sys/mcache.h>

 #include <netinet/in.h>
 #include <netinet/in.h>

+#include <netinet/ip_var.h>
+#if INET6

 #include <netinet/ip6.h>
 #include <netinet6/ip6_var.h>
 #include <netinet/ip6.h>
 #include <netinet6/ip6_var.h>

-#endif
+#endif /* INET6 */

 
 #if CONFIG_MACF_NET
 #include <security/mac_framework.h>
 
 #if CONFIG_MACF_NET
 #include <security/mac_framework.h>


@@ -131,7 +133,7 @@ m_pulldown(struct mbuf *m, int off, int len, int *offp)
        struct mbuf *n, *o;
        int hlen, tlen, olen;
        int sharedcluster;
        struct mbuf *n, *o;
        int hlen, tlen, olen;
        int sharedcluster;

-#if defined(PULLDOWN_STAT) && defined(INET6)
+#if defined(PULLDOWN_STAT) && INET6

        static struct mbuf *prev = NULL;
        int prevlen = 0, prevmlen = 0;
 #endif
        static struct mbuf *prev = NULL;
        int prevlen = 0, prevmlen = 0;
 #endif


@@ -144,11 +146,11 @@ m_pulldown(struct mbuf *m, int off, int len, int *offp)
                return NULL;    /* impossible */
        }
 
                return NULL;    /* impossible */
        }
 

-#if defined(PULLDOWN_STAT) && defined(INET6)
+#if defined(PULLDOWN_STAT) && INET6

        ip6stat.ip6s_pulldown++;
 #endif
 
        ip6stat.ip6s_pulldown++;
 #endif
 

-#if defined(PULLDOWN_STAT) && defined(INET6)
+#if defined(PULLDOWN_STAT) && INET6

        /* statistics for m_pullup */
        ip6stat.ip6s_pullup++;
        if (off + len > MHLEN)
        /* statistics for m_pullup */
        ip6stat.ip6s_pullup++;
        if (off + len > MHLEN)


@@ -241,7 +243,7 @@ m_pulldown(struct mbuf *m, int off, int len, int *offp)
        if ((off == 0 || offp) && len <= n->m_len - off)
                goto ok;
 
        if ((off == 0 || offp) && len <= n->m_len - off)
                goto ok;
 

-#if defined(PULLDOWN_STAT) && defined(INET6)
+#if defined(PULLDOWN_STAT) && INET6

        ip6stat.ip6s_pulldown_copy++;
 #endif
 
        ip6stat.ip6s_pulldown_copy++;
 #endif
 


@@ -321,7 +323,7 @@ m_pulldown(struct mbuf *m, int off, int len, int *offp)
         * now, we need to do the hard way.  don't m_copy as there's no room
         * on both end.
         */
         * now, we need to do the hard way.  don't m_copy as there's no room
         * on both end.
         */

-#if defined(PULLDOWN_STAT) && defined(INET6)
+#if defined(PULLDOWN_STAT) && INET6

        ip6stat.ip6s_pulldown_alloc++;
 #endif
        MGET(o, M_DONTWAIT, m->m_type);
        ip6stat.ip6s_pulldown_alloc++;
 #endif
        MGET(o, M_DONTWAIT, m->m_type);


@@ -365,6 +367,69 @@ ok:
        return n;
 }
 
        return n;
 }
 

+/*
+ * Create and return an m_tag, either by re-using space in a previous tag
+ * or by allocating a new mbuf/cluster
+ */
+struct m_tag *
+m_tag_create(u_int32_t id, u_int16_t type, int len, int wait, struct mbuf *buf)
+{
+       struct m_tag *t = NULL;
+       struct m_tag *p;
+
+       if (len < 0)
+               return (NULL);
+
+       if (len + sizeof (struct m_tag) + sizeof (struct m_taghdr) > MLEN)
+               return (m_tag_alloc(id, type, len, wait));
+
+       /*
+        * We've exhausted all external cases. Now, go through the m_tag
+        * chain and see if we can fit it in any of them.
+        * If not (t == NULL), call m_tag_alloc to store it in a new mbuf.
+        */
+       p = SLIST_FIRST(&buf->m_pkthdr.tags);
+       while(p != NULL) {
+               /* 2KCL m_tag */
+               if (M_TAG_ALIGN(p->m_tag_len) +
+                   sizeof (struct m_taghdr) > MLEN) {
+                       p = SLIST_NEXT(p, m_tag_link);
+                       continue;
+               }
+
+               VERIFY(p->m_tag_cookie == M_TAG_VALID_PATTERN);
+
+               struct mbuf *m = m_dtom(p);
+               struct m_taghdr *hdr = (struct m_taghdr *)(void *)m->m_data;
+
+               VERIFY(IS_P2ALIGNED(hdr + 1, sizeof (u_int64_t)));
+               VERIFY(m->m_flags & M_TAGHDR && !(m->m_flags & M_EXT));
+
+               /* The mbuf can store this m_tag */
+               if (M_TAG_ALIGN(len) <= MLEN - m->m_len) {
+                       t = (struct m_tag *)(void *)(m->m_data + m->m_len);
+                       VERIFY(IS_P2ALIGNED(t, sizeof (u_int64_t)));
+                       hdr->refcnt++;
+                       m->m_len += M_TAG_ALIGN(len);
+                       VERIFY(m->m_len <= MLEN);
+                       break;
+               }
+
+               p = SLIST_NEXT(p, m_tag_link);
+       }
+
+       if (t == NULL)
+               return (m_tag_alloc(id, type, len, wait));
+
+       t->m_tag_cookie = M_TAG_VALID_PATTERN;
+       t->m_tag_type = type;
+       t->m_tag_len = len;
+       t->m_tag_id = id;
+       if (len > 0)
+               bzero(t + 1, len);
+       return (t);
+}
+

 /* Get a packet tag structure along with specified data following. */
 struct m_tag *
 m_tag_alloc(u_int32_t id, u_int16_t type, int len, int wait)
 /* Get a packet tag structure along with specified data following. */
 struct m_tag *
 m_tag_alloc(u_int32_t id, u_int16_t type, int len, int wait)


@@ -372,26 +437,42 @@ m_tag_alloc(u_int32_t id, u_int16_t type, int len, int wait)
        struct m_tag *t;
 
        if (len < 0)
        struct m_tag *t;
 
        if (len < 0)

-               return NULL;
-#if CONFIG_MBUF_TAGS_MALLOC
-       t = _MALLOC(len + sizeof (struct m_tag), M_TEMP, wait);
-#else
-        if (len + sizeof(struct m_tag) <= MLEN) {
+               return (NULL);
+
+        if (M_TAG_ALIGN(len) + sizeof (struct m_taghdr) <= MLEN) {

                struct mbuf *m = m_get(wait, MT_TAG);
                struct mbuf *m = m_get(wait, MT_TAG);

+               struct m_taghdr *hdr;
+

                if (m == NULL)
                if (m == NULL)

-                       return NULL;
-               t = mtod(m, struct m_tag *);
-        } else if (len + sizeof(struct m_tag) <= MCLBYTES) {
-               t = (struct m_tag *) m_mclalloc(wait);
-        } else
+                       return (NULL);
+
+               m->m_flags |= M_TAGHDR;
+
+               hdr = (struct m_taghdr *)(void *)m->m_data;
+               VERIFY(IS_P2ALIGNED(hdr + 1, sizeof (u_int64_t)));
+               hdr->refcnt = 1;
+               m->m_len += sizeof (struct m_taghdr);
+               t = (struct m_tag *)(void *)(m->m_data + m->m_len);
+               VERIFY(IS_P2ALIGNED(t, sizeof (u_int64_t)));
+               m->m_len += M_TAG_ALIGN(len);
+               VERIFY(m->m_len <= MLEN);
+        } else if (len + sizeof (struct m_tag) <= MCLBYTES) {
+               t = (struct m_tag *)(void *)m_mclalloc(wait);
+        } else {

                 t = NULL;
                 t = NULL;

-#endif
+       }
+

        if (t == NULL)
        if (t == NULL)

-               return NULL;
+               return (NULL);
+
+       VERIFY(IS_P2ALIGNED(t, sizeof (u_int64_t)));
+       t->m_tag_cookie = M_TAG_VALID_PATTERN;

        t->m_tag_type = type;
        t->m_tag_len = len;
        t->m_tag_id = id;
        t->m_tag_type = type;
        t->m_tag_len = len;
        t->m_tag_id = id;

-       return t;
+       if (len > 0)
+               bzero(t + 1, len);
+       return (t);

 }
 
 
 }
 
 


@@ -405,25 +486,42 @@ m_tag_free(struct m_tag *t)
            t->m_tag_type == KERNEL_TAG_TYPE_MACLABEL)
                mac_mbuf_tag_destroy(t);
 #endif
            t->m_tag_type == KERNEL_TAG_TYPE_MACLABEL)
                mac_mbuf_tag_destroy(t);
 #endif

-#if CONFIG_MBUF_TAGS_MALLOC
-       _FREE(t, M_TEMP);
-#else

        if (t == NULL)
                return;
        if (t == NULL)
                return;

-       if (t->m_tag_len + sizeof(struct m_tag) <= MLEN) {
+
+       VERIFY(t->m_tag_cookie == M_TAG_VALID_PATTERN);
+
+       if (M_TAG_ALIGN(t->m_tag_len) + sizeof (struct m_taghdr) <= MLEN) {

                struct mbuf * m = m_dtom(t);
                struct mbuf * m = m_dtom(t);

-               m_free(m);
+               VERIFY(m->m_flags & M_TAGHDR);
+               struct m_taghdr *hdr = (struct m_taghdr *)(void *)m->m_data;
+
+               VERIFY(IS_P2ALIGNED(hdr + 1, sizeof (u_int64_t)));
+
+               /* No other tags in this mbuf */
+               if(--hdr->refcnt == 0) {
+                       m_free(m);
+                       return;
+               }
+
+               /* Pattern-fill the header */
+               u_int64_t *fill_ptr = (u_int64_t *)t;
+               u_int64_t *end_ptr = (u_int64_t *)(t + 1);
+               while (fill_ptr < end_ptr) {
+                       *fill_ptr = M_TAG_FREE_PATTERN;
+                       fill_ptr++;
+               }

        } else {
        } else {

-               MCLFREE((caddr_t)t);
+               m_mclfree((caddr_t)t);

        }
        }

-#endif

 }
 
 /* Prepend a packet tag. */
 void
 m_tag_prepend(struct mbuf *m, struct m_tag *t)
 {
 }
 
 /* Prepend a packet tag. */
 void
 m_tag_prepend(struct mbuf *m, struct m_tag *t)
 {

-       KASSERT(m && t, ("m_tag_prepend: null argument, m %p t %p", m, t));
+       VERIFY(m != NULL && t != NULL);
+

        SLIST_INSERT_HEAD(&m->m_pkthdr.tags, t, m_tag_link);
 }
 
        SLIST_INSERT_HEAD(&m->m_pkthdr.tags, t, m_tag_link);
 }
 


@@ -431,7 +529,9 @@ m_tag_prepend(struct mbuf *m, struct m_tag *t)
 void
 m_tag_unlink(struct mbuf *m, struct m_tag *t)
 {
 void
 m_tag_unlink(struct mbuf *m, struct m_tag *t)
 {

-       KASSERT(m && t, ("m_tag_unlink: null argument, m %p t %p", m, t));
+       VERIFY(m->m_flags & M_PKTHDR);
+       VERIFY(t != NULL && t->m_tag_cookie == M_TAG_VALID_PATTERN);
+

        SLIST_REMOVE(&m->m_pkthdr.tags, t, m_tag, m_tag_link);
 }
 
        SLIST_REMOVE(&m->m_pkthdr.tags, t, m_tag, m_tag_link);
 }
 


@@ -439,7 +539,6 @@ m_tag_unlink(struct mbuf *m, struct m_tag *t)
 void
 m_tag_delete(struct mbuf *m, struct m_tag *t)
 {
 void
 m_tag_delete(struct mbuf *m, struct m_tag *t)
 {

-       KASSERT(m && t, ("m_tag_delete: null argument, m %p t %p", m, t));

        m_tag_unlink(m, t);
        m_tag_free(t);
 }
        m_tag_unlink(m, t);
        m_tag_free(t);
 }


@@ -450,15 +549,21 @@ m_tag_delete_chain(struct mbuf *m, struct m_tag *t)
 {
        struct m_tag *p, *q;
 
 {
        struct m_tag *p, *q;
 

-       KASSERT(m, ("m_tag_delete_chain: null mbuf"));
-       if (t != NULL)
+       VERIFY(m->m_flags & M_PKTHDR);
+
+       if (t != NULL) {

                p = t;
                p = t;

-       else
+       } else {

                p = SLIST_FIRST(&m->m_pkthdr.tags);
                p = SLIST_FIRST(&m->m_pkthdr.tags);

+       }

        if (p == NULL)
                return;
        if (p == NULL)
                return;

-       while ((q = SLIST_NEXT(p, m_tag_link)) != NULL)
+
+       VERIFY(p->m_tag_cookie == M_TAG_VALID_PATTERN);
+       while ((q = SLIST_NEXT(p, m_tag_link)) != NULL) {
+               VERIFY(q->m_tag_cookie == M_TAG_VALID_PATTERN);

                m_tag_delete(m, q);
                m_tag_delete(m, q);

+       }

        m_tag_delete(m, p);
 }
 
        m_tag_delete(m, p);
 }
 


@@ -468,17 +573,21 @@ m_tag_locate(struct mbuf *m, u_int32_t id, u_int16_t type, struct m_tag *t)
 {
        struct m_tag *p;
 
 {
        struct m_tag *p;
 

-       KASSERT(m, ("m_tag_find: null mbuf"));
-       if (t == NULL)
+       VERIFY(m->m_flags & M_PKTHDR);
+
+       if (t == NULL) {

                p = SLIST_FIRST(&m->m_pkthdr.tags);
                p = SLIST_FIRST(&m->m_pkthdr.tags);

-       else
+       } else {
+               VERIFY(t->m_tag_cookie == M_TAG_VALID_PATTERN);

                p = SLIST_NEXT(t, m_tag_link);
                p = SLIST_NEXT(t, m_tag_link);

+       }

        while (p != NULL) {
        while (p != NULL) {

+               VERIFY(p->m_tag_cookie == M_TAG_VALID_PATTERN);

                if (p->m_tag_id == id && p->m_tag_type == type)
                if (p->m_tag_id == id && p->m_tag_type == type)

-                       return p;
+                       return (p);

                p = SLIST_NEXT(p, m_tag_link);
        }
                p = SLIST_NEXT(p, m_tag_link);
        }

-       return NULL;
+       return (NULL);

 }
 
 /* Copy a single tag. */
 }
 
 /* Copy a single tag. */


@@ -487,7 +596,8 @@ m_tag_copy(struct m_tag *t, int how)
 {
        struct m_tag *p;
 
 {
        struct m_tag *p;
 

-       KASSERT(t, ("m_tag_copy: null tag"));
+       VERIFY(t != NULL);
+

        p = m_tag_alloc(t->m_tag_id, t->m_tag_type, t->m_tag_len, how);
        if (p == NULL)
                return (NULL);
        p = m_tag_alloc(t->m_tag_id, t->m_tag_type, t->m_tag_len, how);
        if (p == NULL)
                return (NULL);


@@ -508,7 +618,7 @@ m_tag_copy(struct m_tag *t, int how)
        } else
 #endif
        bcopy(t + 1, p + 1, t->m_tag_len); /* Copy the data */
        } else
 #endif
        bcopy(t + 1, p + 1, t->m_tag_len); /* Copy the data */

-       return p;
+       return (p);

 }
 
 /*
 }
 
 /*


@@ -522,45 +632,236 @@ m_tag_copy_chain(struct mbuf *to, struct mbuf *from, int how)
 {
        struct m_tag *p, *t, *tprev = NULL;
 
 {
        struct m_tag *p, *t, *tprev = NULL;
 

-       KASSERT(to && from,
-               ("m_tag_copy: null argument, to %p from %p", to, from));
+       VERIFY((to->m_flags & M_PKTHDR) && (from->m_flags & M_PKTHDR));
+

        m_tag_delete_chain(to, NULL);
        SLIST_FOREACH(p, &from->m_pkthdr.tags, m_tag_link) {
        m_tag_delete_chain(to, NULL);
        SLIST_FOREACH(p, &from->m_pkthdr.tags, m_tag_link) {

+               VERIFY(p->m_tag_cookie == M_TAG_VALID_PATTERN);

                t = m_tag_copy(p, how);
                if (t == NULL) {
                        m_tag_delete_chain(to, NULL);
                t = m_tag_copy(p, how);
                if (t == NULL) {
                        m_tag_delete_chain(to, NULL);

-                       return 0;
+                       return (0);

                }
                }

-               if (tprev == NULL)
+               if (tprev == NULL) {

                        SLIST_INSERT_HEAD(&to->m_pkthdr.tags, t, m_tag_link);
                        SLIST_INSERT_HEAD(&to->m_pkthdr.tags, t, m_tag_link);

-               else {
+               } else {

                        SLIST_INSERT_AFTER(tprev, t, m_tag_link);
                        tprev = t;
                }
        }
                        SLIST_INSERT_AFTER(tprev, t, m_tag_link);
                        tprev = t;
                }
        }

-       return 1;
+       return (1);

 }
 
 }
 

-/* Initialize tags on an mbuf. */
+/* Initialize dynamic and static tags on an mbuf. */

 void
 void

-m_tag_init(struct mbuf *m)
+m_tag_init(struct mbuf *m, int all)

 {
 {

+       VERIFY(m->m_flags & M_PKTHDR);
+

        SLIST_INIT(&m->m_pkthdr.tags);
        SLIST_INIT(&m->m_pkthdr.tags);

-#if PF_PKTHDR
-       bzero(&m->m_pkthdr.pf_mtag, sizeof (m->m_pkthdr.pf_mtag));
-#endif
+       /*
+        * If the caller wants to preserve static mbuf tags
+        * (e.g. m_dup_pkthdr), don't zero them out.
+        */
+       if (all) {
+               bzero(&m->m_pkthdr.pf_mtag, sizeof (m->m_pkthdr.pf_mtag));
+               bzero(&m->m_pkthdr.proto_mtag, sizeof (m->m_pkthdr.proto_mtag));
+               bzero(&m->m_pkthdr.necp_mtag, sizeof (m->m_pkthdr.necp_mtag));
+       }

 }
 
 /* Get first tag in chain. */
 struct m_tag *
 m_tag_first(struct mbuf *m)
 {
 }
 
 /* Get first tag in chain. */
 struct m_tag *
 m_tag_first(struct mbuf *m)
 {

-       return SLIST_FIRST(&m->m_pkthdr.tags);
+       VERIFY(m->m_flags & M_PKTHDR);
+
+       return (SLIST_FIRST(&m->m_pkthdr.tags));

 }
 
 /* Get next tag in chain. */
 struct m_tag *
 }
 
 /* Get next tag in chain. */
 struct m_tag *

-m_tag_next(__unused struct mbuf *m, struct m_tag *t)
+m_tag_next(struct mbuf *m, struct m_tag *t)
+{
+#pragma unused(m)
+       VERIFY(t != NULL);
+       VERIFY(t->m_tag_cookie == M_TAG_VALID_PATTERN);
+
+       return (SLIST_NEXT(t, m_tag_link));
+}
+
+int
+m_set_traffic_class(struct mbuf *m, mbuf_traffic_class_t tc)
+{
+       u_int32_t val = MBUF_TC2SCVAL(tc);      /* just the val portion */
+
+       return (m_set_service_class(m, m_service_class_from_val(val)));
+}
+
+mbuf_traffic_class_t
+m_get_traffic_class(struct mbuf *m)
+{
+       return (MBUF_SC2TC(m_get_service_class(m)));
+}
+
+int
+m_set_service_class(struct mbuf *m, mbuf_svc_class_t sc)
+{
+       int error = 0;
+
+       VERIFY(m->m_flags & M_PKTHDR);
+
+       if (MBUF_VALID_SC(sc))
+               m->m_pkthdr.pkt_svc = sc;
+       else
+               error = EINVAL;
+
+       return (error);
+}
+
+mbuf_svc_class_t
+m_get_service_class(struct mbuf *m)
+{
+       mbuf_svc_class_t sc;
+
+       VERIFY(m->m_flags & M_PKTHDR);
+
+       if (MBUF_VALID_SC(m->m_pkthdr.pkt_svc))
+               sc = m->m_pkthdr.pkt_svc;
+       else
+               sc = MBUF_SC_BE;
+
+       return (sc);
+}
+
+mbuf_svc_class_t
+m_service_class_from_idx(u_int32_t i)
+{
+       mbuf_svc_class_t sc = MBUF_SC_BE;
+
+       switch (i) {
+       case SCIDX_BK_SYS:
+               return (MBUF_SC_BK_SYS);
+
+       case SCIDX_BK:
+               return (MBUF_SC_BK);
+
+       case SCIDX_BE:
+               return (MBUF_SC_BE);
+
+       case SCIDX_RD:
+               return (MBUF_SC_RD);
+
+       case SCIDX_OAM:
+               return (MBUF_SC_OAM);
+
+       case SCIDX_AV:
+               return (MBUF_SC_AV);
+
+       case SCIDX_RV:
+               return (MBUF_SC_RV);
+
+       case SCIDX_VI:
+               return (MBUF_SC_VI);
+
+       case SCIDX_VO:
+               return (MBUF_SC_VO);
+
+       case SCIDX_CTL:
+               return (MBUF_SC_CTL);
+
+       default:
+               break;
+       }
+
+       VERIFY(0);
+       /* NOTREACHED */
+       return (sc);
+}
+
+mbuf_svc_class_t
+m_service_class_from_val(u_int32_t v)
+{
+       mbuf_svc_class_t sc = MBUF_SC_BE;
+
+       switch (v) {
+       case SCVAL_BK_SYS:
+               return (MBUF_SC_BK_SYS);
+
+       case SCVAL_BK:
+               return (MBUF_SC_BK);
+
+       case SCVAL_BE:
+               return (MBUF_SC_BE);
+
+       case SCVAL_RD:
+               return (MBUF_SC_RD);
+
+       case SCVAL_OAM:
+               return (MBUF_SC_OAM);
+
+       case SCVAL_AV:
+               return (MBUF_SC_AV);
+
+       case SCVAL_RV:
+               return (MBUF_SC_RV);
+
+       case SCVAL_VI:
+               return (MBUF_SC_VI);
+
+       case SCVAL_VO:
+               return (MBUF_SC_VO);
+
+       case SCVAL_CTL:
+               return (MBUF_SC_CTL);
+
+       default:
+               break;
+       }
+
+       VERIFY(0);
+       /* NOTREACHED */
+       return (sc);
+}
+
+uint16_t
+m_adj_sum16(struct mbuf *m, uint32_t start, uint32_t ulpoff, uint32_t sum)
+{
+       int len = (ulpoff - start);
+
+       if (len > 0) {
+               uint32_t adj = m_sum16(m, start, len);
+               if (adj >= sum)
+                       sum = ~(adj - sum) & 0xffff;
+               else
+                       sum -= adj;
+       } else if (len < 0) {
+               sum += m_sum16(m, ulpoff, -len);
+       }
+
+       ADDCARRY(sum);
+
+       return (sum);
+}
+
+extern int cpu_in_cksum(struct mbuf *m, int len, int off, uint32_t initial_sum);
+
+uint16_t
+m_sum16(struct mbuf *m, uint32_t off, uint32_t len)

 {
 {

-       return SLIST_NEXT(t, m_tag_link);
+       int mlen;
+
+       /*
+        * Sanity check
+        *
+        * Use m_length2() instead of m_length(), as we cannot rely on
+        * the caller setting m_pkthdr.len correctly, if the mbuf is
+        * a M_PKTHDR one.
+        */
+       if ((mlen = m_length2(m, NULL)) < (off + len)) {
+               panic("%s: mbuf len (%d) < off+len (%d+%d)\n", __func__,
+                   mlen, off, len);
+       }
+
+       return (~cpu_in_cksum(m, len, off, 0) & 0xffff);

 }
 }