socket.7: Document SO_MARK socket option

Commit 4a19ec5800fc3bb64e2d87c4d9fdd9e636086fe0 in Jan 2008 added
the new SO_MARK socket option.

This patch is based on text from the commit message.

See https://bugzilla.kernel.org/show_bug.cgi?id=16461.

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

diff --git a/man7/socket.7 b/man7/socket.7
index a0e186a2a28b2cd56a0b27b97e282b0a42438a3c..88a4fda5395024cd72ff394d2db5593f7bc85b01 100644 (file)
--- a/man7/socket.7
+++ b/man7/socket.7
@@ -19,11 +19,10 @@
 .\" The following are not yet documented:
 .\"    SO_PEERNAME
 .\"    SO_TIMESTAMPNS
-.\"    SO_MARK (see https://bugzilla.kernel.org/show_bug.cgi?id=16461)
 .\"    SO_TIMESTAMPING (2.6.30)
 .\"    SO_RXQ_OVFL (2.6.33)
 .\"
-.TH SOCKET 7 2012-04-23 Linux "Linux Programmer's Manual"
+.TH SOCKET 7 2012-07-07 Linux "Linux Programmer's Manual"
 .SH NAME
 socket \- Linux socket interface
 .SH SYNOPSIS
@@ -320,6 +319,17 @@ When the socket is closed as part of
 .BR exit (2),
 it always lingers in the background.
 .TP
+.BR SO_MARK " (since Linux 2.6.25)"
+.\" commit 4a19ec5800fc3bb64e2d87c4d9fdd9e636086fe0
+.\" and    914a9ab386a288d0f22252fc268ecbc048cdcbd5
+Set the mark for each packet sent through this socket
+(similar to the netfilter MARK target but socket-based).
+Changing the mark can be used for mark-based
+routing without netfilter or for packet filtering.
+Setting this option requires the
+.B CAP_NET_ADMIN
+capability.
+.TP
 .B SO_OOBINLINE
 If this option is enabled,
 out-of-band data is directly placed into the receive data stream.