Commit 78902dc8 authored May 30, 2015 by Eric Dumazet Committed by Zvikomborero Vincent Zvikaramba Jul 06, 2017

udp: fix behavior of wrong checksums



We have two problems in UDP stack related to bogus checksums :

1) We return -EAGAIN to application even if receive queue is not empty.
   This breaks applications using edge trigger epoll()

2) Under UDP flood, we can loop forever without yielding to other
   processes, potentially hanging the host, especially on non SMP.

This patch is an attempt to make things better.

We might in the future add extra support for rt applications
wanting to better control time spent doing a recv() in a hostile
environment. For example we could validate checksums before queuing
packets in socket receive queue.

Change-Id: Id97a6bf78f775b876a86afbd3a2442a39d63ca52
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent b1f18682

net/ipv4/udp.c

+2 −4

Original line number	Diff line number	Diff line
		@@ -1296,10 +1296,8 @@ csum_copy_err:
		}
		unlock_sock_fast(sk, slow);

		if (noblock)
		return -EAGAIN;

		/* starting over for a new packet */
		/* starting over for a new packet, but check if we need to yield */
		cond_resched();
		msg->msg_flags &= ~MSG_TRUNC;
		goto try_again;
		}

net/ipv6/udp.c

+2 −4

Original line number	Diff line number	Diff line
		@@ -497,10 +497,8 @@ csum_copy_err:
		}
		unlock_sock_fast(sk, slow);

		if (noblock)
		return -EAGAIN;

		/* starting over for a new packet */
		/* starting over for a new packet, but check if we need to yield */
		cond_resched();
		msg->msg_flags &= ~MSG_TRUNC;
		goto try_again;
		}