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udp: fix behavior of wrong checksums 

[ Upstream commit beb39db59d ]

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.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Eric Dumazet 2015-05-30 09:16:53 -07:00 committed by Greg Kroah-Hartman
parent 4d97213d4f
commit 542744f265
2 changed files with 4 additions and 8 deletions
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6
net/ipv4/udp.c
View File

@ -1317,10 +1317,8 @@ 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;
}

6
net/ipv6/udp.c
View File

@ -515,10 +515,8 @@ 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;
}