tree 4b1825f2432916f117f9104153b9c37cf58458ae
parent cdf49c283e2e105da86ca575ad35b453f5ff24ea
author Eric Dumazet <eric.dumazet@gmail.com> 1329866695 +0000
committer David S. Miller <davem@davemloft.net> 1329940022 -0500

af_unix: MSG_TRUNC support for dgram sockets

Piergiorgio Beruto expressed the need to fetch size of first datagram in
queue for AF_UNIX sockets and suggested a patch against SIOCINQ ioctl.

I suggested instead to implement MSG_TRUNC support as a recv() input
flag, as already done for RAW, UDP & NETLINK sockets.

len = recv(fd, &byte, 1, MSG_PEEK | MSG_TRUNC);

MSG_TRUNC asks recv() to return the real length of the packet, even when
is was longer than the passed buffer.

There is risk that a userland application used MSG_TRUNC by accident
(since it had no effect on af_unix sockets) and this might break after
this patch.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Tested-by: Piergiorgio Beruto <piergiorgio.beruto@gmail.com>
CC: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>