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Document conditions for IP_SENDSRCADDR socket option.

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Obtained from:	r167342 commit message
This commit is contained in:
Gleb Smirnoff 2012-09-12 10:09:34 +00:00
parent be81cc14ab
commit f99a2a0c2b
1 changed files with 18 additions and 4 deletions
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22
share/man/man4/ip.4
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@ -32,7 +32,7 @@
.\" @(#)ip.4 8.2 (Berkeley) 11/30/93
.\" $FreeBSD$
.\"
.Dd June 15, 2012
.Dd September 12, 2012
.Dt IP 4
.Os
.Sh NAME
@ -172,9 +172,7 @@ cmsg_type = IP_RECVDSTADDR
.Pp
The source address to be used for outgoing
.Tn UDP
datagrams on a socket that is not bound to a specific
.Tn IP
address can be specified as ancillary data with a type code of
datagrams on a socket can be specified as ancillary data with a type code of
.Dv IP_SENDSRCADDR .
The msg_control field in the msghdr structure should point to a buffer
that contains a
@ -189,6 +187,22 @@ cmsg_level = IPPROTO_IP
cmsg_type = IP_SENDSRCADDR
.Ed
.Pp
The socket should be bound to a local port.
The socket may be bound or not bound to a local address.
In the former case address supplied with
.Dv IP_SENDSRCADDR
overrides bound address.
If the socket is bound to a local address and the address supplied with
.Dv IP_SENDSRCADDR
is
.Dv INADDR_ANY ,
then bound address is overriden via generic source address selection logic,
which would choose IP address of interface closest to destination.
If the socket is not bound to a local address, then address supplied with
.Dv IP_SENDSRCADDR
can't be
.Dv INADDR_ANY .
.Pp
For convenience,
.Dv IP_SENDSRCADDR
is defined to have the same value as