On Mon, 2014-11-03 at 09:29 +0800, Chen Weilong wrote: > From: Weilong Chen <chenweil...@huawei.com> > > We got a problem like this:
> There was a wrong ack packet coming during TCP handshake. The socket's state > was TCP_SYN_RECV, its rcv_mss was not initialize yet. So > tcp_send_dupack -> tcp_enter_quickack_mode got a divide 0 error. > This patch add a state check before tcp_enter_quickack_mode. > > Signed-off-by: Weilong Chen <chenweil...@huawei.com> > --- > net/ipv4/tcp_input.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c > index 4e4617e..9eb56dc 100644 > --- a/net/ipv4/tcp_input.c > +++ b/net/ipv4/tcp_input.c > @@ -3986,7 +3986,8 @@ static void tcp_send_dupack(struct sock *sk, const > struct sk_buff *skb) > if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq && > before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { > NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKLOST); > - tcp_enter_quickack_mode(sk); > + if (sk->sk_state != TCP_SYN_RECV) > + tcp_enter_quickack_mode(sk); > > if (tcp_is_sack(tp) && sysctl_tcp_dsack) { > u32 end_seq = TCP_SKB_CB(skb)->end_seq; Sorry I do not think this is the right fix. We have to not simply avoid the divide, but fix this issue by understanding the missing steps. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/