From: Eric Dumazet <eric.duma...@gmail.com> Date: Thu, 24 Sep 2015 17:16:05 -0700
> From: Eric Dumazet <eduma...@google.com> > > We found that a TCP Fast Open passive connection was vulnerable > to reorders, as the exchange might look like > > [1] C -> S S <FO ...> <request> > [2] S -> C S. ack request <options> > [3] S -> C . <answer> > > packets [2] and [3] can be generated at almost the same time. > > If C receives the 3rd packet before the 2nd, it will drop it as > the socket is in SYN_SENT state and expects a SYNACK. > > S will have to retransmit the answer. > > Current OOO avoidance in linux is defeated because SYNACK > packets are attached to the LISTEN socket, while DATA packets > are attached to the children. They might be sent by different cpus, > and different TX queues might be selected. > > It turns out that for TFO, we created a child, which is a > full blown socket in TCP_SYN_RECV state, and we simply can attach > the SYNACK packet to this socket. > > This means that at the time tcp_sendmsg() pushes DATA packet, > skb->ooo_okay will be set iff the SYNACK packet had been sent > and TX completed. > > This removes the reorder source at the host level. > > We also removed the export of tcp_try_fastopen(), as it is no > longer called from IPv6. > > Signed-off-by: Eric Dumazet <eduma...@google.com> > Signed-off-by: Yuchung Cheng <ych...@google.com> Applied, thanks. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
