@@ -2674,7 +2674,6 @@ static void tcp_enter_recovery(struct sock *sk, bool ece_ack)
*/
static void tcp_process_loss(struct sock *sk, int flag, bool is_dupack)
{
- struct inet_connection_sock *icsk = inet_csk(sk);
struct tcp_sock *tp = tcp_sk(sk);
bool recovered = !before(tp->snd_una, tp->high_seq);
@@ -2700,12 +2699,9 @@ static void tcp_process_loss(struct sock *sk, int flag, bool is_dupack)
if (recovered) {
/* F-RTO RFC5682 sec 3.1 step 2.a and 1st part of step 3.a */
- icsk->icsk_retransmits = 0;
tcp_try_undo_recovery(sk);
return;
}
- if (flag & FLAG_DATA_ACKED)
- icsk->icsk_retransmits = 0;
if (tcp_is_reno(tp)) {
/* A Reno DUPACK means new data in F-RTO step 2.b above are
* delivered. Lower inflight to clock out (re)tranmissions.
@@ -3394,8 +3390,10 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
icsk->icsk_pending == ICSK_TIME_LOSS_PROBE)
tcp_rearm_rto(sk);
- if (after(ack, prior_snd_una))
+ if (after(ack, prior_snd_una)) {
flag |= FLAG_SND_UNA_ADVANCED;
+ icsk->icsk_retransmits = 0;
+ }
prior_fackets = tp->fackets_out;
prior_in_flight = tcp_packets_in_flight(tp);
This is a note to let you know that I have just added a patch titled tcp: fix ssthresh and undo for consecutive short FRTO episodes to the linux-3.13.y-queue branch of the 3.13.y.z extended stable tree which can be found at: http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue This patch is scheduled to be released in version 3.13.11.11. If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.13.y.z tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Kamal ------ From 7e3f24de60f008c8eb2a362441fa4032928df818 Mon Sep 17 00:00:00 2001 From: Neal Cardwell <ncardwell@google.com> Date: Thu, 14 Aug 2014 16:13:07 -0400 Subject: tcp: fix ssthresh and undo for consecutive short FRTO episodes [ Upstream commit 0c9ab09223fe9922baeb22546c9a90d774a4bde6 ] Fix TCP FRTO logic so that it always notices when snd_una advances, indicating that any RTO after that point will be a new and distinct loss episode. Previously there was a very specific sequence that could cause FRTO to fail to notice a new loss episode had started: (1) RTO timer fires, enter FRTO and retransmit packet 1 in write queue (2) receiver ACKs packet 1 (3) FRTO sends 2 more packets (4) RTO timer fires again (should start a new loss episode) The problem was in step (3) above, where tcp_process_loss() returned early (in the spot marked "Step 2.b"), so that it never got to the logic to clear icsk_retransmits. Thus icsk_retransmits stayed non-zero. Thus in step (4) tcp_enter_loss() would see the non-zero icsk_retransmits, decide that this RTO is not a new episode, and decide not to cut ssthresh and remember the current cwnd and ssthresh for undo. There were two main consequences to the bug that we have observed. First, ssthresh was not decreased in step (4). Second, when there was a series of such FRTO (1-4) sequences that happened to be followed by an FRTO undo, we would restore the cwnd and ssthresh from before the entire series started (instead of the cwnd and ssthresh from before the most recent RTO). This could result in cwnd and ssthresh being restored to values much bigger than the proper values. Signed-off-by: Neal Cardwell <ncardwell@google.com> Signed-off-by: Yuchung Cheng <ycheng@google.com> Fixes: e33099f96d99c ("tcp: implement RFC5682 F-RTO") Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- net/ipv4/tcp_input.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) -- 1.9.1