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Document the IP_RECVIF socket option.

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Submitted by:	 Bruce M Simpson
This commit is contained in:
mdodd 2003-04-29 08:37:52 +00:00
parent ac3f359209
commit 373ef8a1bd
1 changed files with 16 additions and 0 deletions
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16
share/man/man4/ip.4
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@ -164,6 +164,22 @@ control message from
can be used directly as a control message for
.Xr sendmsg 2 .
.Pp
If the
.Dv IP_RECVIF
option is enabled on a
.Dv SOCK_DGRAM
socket, the
.Xr recvmsg 2
call returns a struct sockaddr_dl corresponding to the interface on which the
packet was received. The msg_control field in the msghdr structure points
to a buffer that contains a cmsghdr structure followed by the
struct sockaddr_dl. The cmsghdr fields have the following values:
.Bd -literal
cmsg_len = sizeof(struct sockaddr_dl)
cmsg_level = IPPROTO_IP
cmsg_type = IP_RECVIF
.Ed
.Pp
.Dv IP_PORTRANGE
may be used to set the port range used for selecting a local port number
on a socket with an unspecified (zero) port number.