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udp/recvmsg: Clear MSG_TRUNC flag when starting over for a new packet

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Consider this scenario: When the size of the first received udp packet
is bigger than the receive buffer, MSG_TRUNC bit is set in msg->msg_flags.
However, if checksum error happens and this is a blocking socket, it will
goto try_again loop to receive the next packet.  But if the size of the
next udp packet is smaller than receive buffer, MSG_TRUNC flag should not
be set, but because MSG_TRUNC bit is not cleared in msg->msg_flags before
receive the next packet, MSG_TRUNC is still set, which is wrong.

Fix this problem by clearing MSG_TRUNC flag when starting over for a
new packet.

Signed-off-by: Xufeng Zhang <xufeng.zhang@windriver.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Xufeng Zhang 2011-06-21 10:43:40 +00:00 committed by David S. Miller
parent 32c90254ed
commit 9cfaa8def1
2 changed files with 6 additions and 0 deletions
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3
net/ipv4/udp.c
View file

@ -1249,6 +1249,9 @@ int udp_recvmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
if (noblock)
return -EAGAIN;
/* starting over for a new packet */
msg->msg_flags &= ~MSG_TRUNC;
goto try_again;
}

3
net/ipv6/udp.c
View file

@ -455,6 +455,9 @@ int udpv6_recvmsg(struct kiocb *iocb, struct sock *sk,
if (noblock)
return -EAGAIN;
/* starting over for a new packet */
msg->msg_flags &= ~MSG_TRUNC;
goto try_again;
}