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authorDamian Lukowski <damian@tvk.rwth-aachen.de>2010-02-10 21:04:08 -0500
committerDavid S. Miller <davem@davemloft.net>2010-02-10 21:04:08 -0500
commit598856407d4e20ebb4de01a91a93d89325924d43 (patch)
tree88df32f1dfad558dc652c6488032fb9c19f03958 /net/ipv4/tcp_input.c
parent044c18c9f51a2b92b310e28bb121e55451b088dd (diff)
tcp: fix ICMP-RTO war
Make sure, that TCP has a nonzero RTT estimation after three-way handshake. Currently, a listening TCP has a value of 0 for srtt, rttvar and rto right after the three-way handshake is completed with TCP timestamps disabled. This will lead to corrupt RTO recalculation and retransmission flood when RTO is recalculated on backoff reversion as introduced in "Revert RTO on ICMP destination unreachable" (f1ecd5d9e7366609d640ff4040304ea197fbc618). This behaviour can be provoked by connecting to a server which "responds first" (like SMTP) and rejecting every packet after the handshake with dest-unreachable, which will lead to softirq load on the server (up to 30% per socket in some tests). Thanks to Ilpo Jarvinen for providing debug patches and to Denys Fedoryshchenko for reporting and testing. Changes since v3: Removed bad characters in patchfile. Reported-by: Denys Fedoryshchenko <denys@visp.net.lb> Signed-off-by: Damian Lukowski <damian@tvk.rwth-aachen.de> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/tcp_input.c')
-rw-r--r--net/ipv4/tcp_input.c6
1 files changed, 2 insertions, 4 deletions
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 28e029632493..3fddc69ccccc 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -5783,11 +5783,9 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
5783 5783
5784 /* tcp_ack considers this ACK as duplicate 5784 /* tcp_ack considers this ACK as duplicate
5785 * and does not calculate rtt. 5785 * and does not calculate rtt.
5786 * Fix it at least with timestamps. 5786 * Force it here.
5787 */ 5787 */
5788 if (tp->rx_opt.saw_tstamp && 5788 tcp_ack_update_rtt(sk, 0, 0);
5789 tp->rx_opt.rcv_tsecr && !tp->srtt)
5790 tcp_ack_saw_tstamp(sk, 0);
5791 5789
5792 if (tp->rx_opt.tstamp_ok) 5790 if (tp->rx_opt.tstamp_ok)
5793 tp->advmss -= TCPOLEN_TSTAMP_ALIGNED; 5791 tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;