-.Pp
-Datagrams with a hoplimit of 1 are not forwarded beyond the local network.
-Multicast datagrams with a hoplimit of 0 will not be transmitted on any network,
-but may be delivered locally if the sending host belongs to the destination
-group and if multicast loopback has not been disabled on the sending socket
-(see below).
-Multicast datagrams with hoplimit greater than 1 may be forwarded
-to other networks if a multicast router is attached to the local network.
-.Pp
-For hosts with multiple interfaces, each multicast transmission is
-sent from the primary network interface.
-The
-.Dv IPV6_MULTICAST_IF
-option overrides the default for
-subsequent transmissions from a given socket:
-.Bd -literal -offset indent
-unsigned int outif;
-outif = if_nametoindex("ne0");
-setsockopt(s, IPPROTO_IPV6, IPV6_MULTICAST_IF, &outif, sizeof(outif));
-.Ed
-.Pp
-where "outif" is an interface index of the desired interface,
-or 0 to specify the default interface.
-.Pp
-If a multicast datagram is sent to a group to which the sending host itself
-belongs (on the outgoing interface), a copy of the datagram is, by default,
-looped back by the IPv6 layer for local delivery.
-The
-.Dv IPV6_MULTICAST_LOOP
-option gives the sender explicit control
-over whether or not subsequent datagrams are looped back:
-.Bd -literal -offset indent
-u_char loop; /* 0 = disable, 1 = enable (default) */
-setsockopt(s, IPPROTO_IPV6, IPV6_MULTICAST_LOOP, &loop, sizeof(loop));
-.Ed
-.Pp
-This option
-improves performance for applications that may have no more than one
-instance on a single host (such as a router daemon), by eliminating
-the overhead of receiving their own transmissions.
-It should generally not be used by applications for which there
-may be more than one instance on a single host (such as a conferencing
-program) or for which the sender does not belong to the destination
-group (such as a time querying program).
-.Pp
-A multicast datagram sent with an initial hoplimit greater than 1 may be delivered
-to the sending host on a different interface from that on which it was sent,
-if the host belongs to the destination group on that other interface.
-The loopback control option has no effect on such delivery.
-.Pp
+.Ss Options
+IPv6 allows header options on packets to manipulate the behavior of the
+protocol.
+These options and other control requests are accessed with the
+.Xr getsockopt 2
+and
+.Xr setsockopt 2
+system calls at level
+.Dv IPPROTO_IPV6
+and by using ancillary data in
+.Xr recvmsg 2
+and
+.Xr sendmsg 2 .
+They can be used to access most of the fields in the IPv6 header and
+extension headers.
+.Pp
+The following socket options are supported:
+.Bl -tag -width Ds
+.\" .It Dv IPV6_OPTIONS
+.It Dv IPV6_UNICAST_HOPS Fa "int *"
+Get or set the default hop limit header field for outgoing unicast
+datagrams sent on this socket.
+A value of \-1 resets to the default value.
+.\" .It Dv IPV6_RECVOPTS Fa "int *"
+.\" Get or set the status of whether all header options will be
+.\" delivered along with the datagram when it is received.
+.\" .It Dv IPV6_RECVRETOPTS Fa "int *"
+.\" Get or set the status of whether header options will be delivered
+.\" for reply.
+.\" .It Dv IPV6_RECVDSTADDR Fa "int *"
+.\" Get or set the status of whether datagrams are received with
+.\" destination addresses.
+.\" .It Dv IPV6_RETOPTS
+.\" Get or set IPv6 options.
+.It Dv IPV6_MULTICAST_IF Fa "u_int *"
+Get or set the interface from which multicast packets will be sent.
+For hosts with multiple interfaces, each multicast transmission is sent
+from the primary network interface.
+The interface is specified as its index as provided by
+.Xr if_nametoindex 3 .
+A value of zero specifies the default interface.
+.It Dv IPV6_MULTICAST_HOPS Fa "int *"
+Get or set the default hop limit header field for outgoing multicast
+datagrams sent on this socket.
+This option controls the scope of multicast datagram transmissions.
+.Pp
+Datagrams with a hop limit of 1 are not forwarded beyond the local
+network.
+Multicast datagrams with a hop limit of zero will not be transmitted on
+any network but may be delivered locally if the sending host belongs to
+the destination group and if multicast loopback (see below) has not been
+disabled on the sending socket.
+Multicast datagrams with a hop limit greater than 1 may be forwarded to
+the other networks if a multicast router (such as
+.Xr mrouted 8 )
+is attached to the local network.
+.It Dv IPV6_MULTICAST_LOOP Fa "u_int *"
+Get or set the status of whether multicast datagrams will be looped back
+for local delivery when a multicast datagram is sent to a group to which
+the sending host belongs.
+.Pp
+This option improves performance for applications that may have no more
+than one instance on a single host (such as a router daemon) by
+eliminating the overhead of receiving their own transmissions.
+It should generally not be used by applications for which there may be
+more than one instance on a single host (such as a conferencing program)
+or for which the sender does not belong to the destination group
+(such as a time-querying program).
+.Pp
+A multicast datagram sent with an initial hop limit greater than 1 may
+be delivered to the sending host on a different interface from that on
+which it was sent if the host belongs to the destination group on that
+other interface.
+The multicast loopback control option has no effect on such delivery.
+.It Dv IPV6_JOIN_GROUP Fa "struct ipv6_mreq *"
+Join a multicast group.
projects / apple / xnu.git / blobdiff