[src/trunk]: src/share/man/man4 Document alternative calling convention for I...

[dyoung <dyoung%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/1f44054c2570
branches:  trunk
changeset: 586271:1f44054c2570
user:      dyoung <dyoung%NetBSD.org@localhost>
date:      Mon Dec 12 07:20:38 2005 +0000

description:
Document alternative calling convention for IP_MULTICAST_IF.

diffstat:

 share/man/man4/ip.4 |  15 +++++++++++++--
 1 files changed, 13 insertions(+), 2 deletions(-)

diffs (29 lines):

diff -r 65e2984f273f -r 1f44054c2570 share/man/man4/ip.4
--- a/share/man/man4/ip.4       Mon Dec 12 04:51:55 2005 +0000
+++ b/share/man/man4/ip.4       Mon Dec 12 07:20:38 2005 +0000
@@ -1,4 +1,4 @@
-.\"    $NetBSD: ip.4,v 1.16 2003/09/07 16:22:28 wiz Exp $
+.\"    $NetBSD: ip.4,v 1.17 2005/12/12 07:20:38 dyoung Exp $
 .\"
 .\" Copyright (c) 1983, 1991, 1993
 .\"    The Regents of the University of California.  All rights reserved.
@@ -205,7 +205,18 @@
 and
 .Dv SIOCGIFFLAGS
 ioctls.
-Normal applications should not need to use this option.
+An application may also specify an alternative to the default network interface
+by index:
+.Bd -literal
+struct uint32_t idx = htonl(ifindex);
+setsockopt(s, IPPROTO_IP, IP_MULTICAST_IF, \*[Am]idx, sizeof(idx));
+.Ed
+.Pp
+where "ifindex" is an interface index as returned by
+.Xr if_nametoindex 4 .
+.Pp
+Normal applications should not need to use
+.Dv IP_MULTICAST_IF .
 .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,