Commit 28b346cb authored Aug 30, 2016 by Neal Cardwell Committed by David S. Miller Sep 01, 2016

tcp: fastopen: fix rcv_wup initialization for TFO server on SYN/data



Yuchung noticed that on the first TFO server data packet sent after
the (TFO) handshake, the server echoed the TCP timestamp value in the
SYN/data instead of the timestamp value in the final ACK of the
handshake. This problem did not happen on regular opens.

The tcp_replace_ts_recent() logic that decides whether to remember an
incoming TS value needs tp->rcv_wup to hold the latest receive
sequence number that we have ACKed (latest tp->rcv_nxt we have
ACKed). This commit fixes this issue by ensuring that a TFO server
properly updates tp->rcv_wup to match tp->rcv_nxt at the time it sends
a SYN/ACK for the SYN/data.

Reported-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
Fixes: 168a8f58 ("tcp: TCP Fast Open Server - main code path")
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 85a3d4a9

net/ipv4/tcp_fastopen.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -226,6 +226,7 @@ static struct sock tcp_fastopen_create_child(struct sock sk,
		tcp_fastopen_add_skb(child, skb);

		tcp_rsk(req)->rcv_nxt = tp->rcv_nxt;
		tp->rcv_wup = tp->rcv_nxt;
		/* tcp_conn_request() is sending the SYNACK,
		* and queues the child into listener accept queue.
		*/

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