Commit beb39db5 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller

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.
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Cc: Willem de Bruijn <willemb@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 9eb0a5d1
...@@ -1345,10 +1345,8 @@ int udp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int noblock, ...@@ -1345,10 +1345,8 @@ int udp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int noblock,
} }
unlock_sock_fast(sk, slow); unlock_sock_fast(sk, slow);
if (noblock) /* starting over for a new packet, but check if we need to yield */
return -EAGAIN; cond_resched();
/* starting over for a new packet */
msg->msg_flags &= ~MSG_TRUNC; msg->msg_flags &= ~MSG_TRUNC;
goto try_again; goto try_again;
} }
......
...@@ -525,10 +525,8 @@ int udpv6_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, ...@@ -525,10 +525,8 @@ int udpv6_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
} }
unlock_sock_fast(sk, slow); unlock_sock_fast(sk, slow);
if (noblock) /* starting over for a new packet, but check if we need to yield */
return -EAGAIN; cond_resched();
/* starting over for a new packet */
msg->msg_flags &= ~MSG_TRUNC; msg->msg_flags &= ~MSG_TRUNC;
goto try_again; goto try_again;
} }
......
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