| Message ID | 200908150339.12730.opurdila@ixiacom.com |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
On Saturday 15 August 2009 03:39:12 Octavian Purdila wrote: > NOTE: this issue has been found, fixed and tested on an ancient 2.6.7 > kernel. This patch is a blind port of that fix, since unfortunately there > is no easy way for me to reproduce the original issue with a newer kernel. > But the issue still seems to be there. Update: I was able to reproduce the issue on a 2.6.30 debian kernel with the attached test. It took me about 10 runs of 2-5 mins each to reproduce it (multiple runs to keep the capture file reasonable in terms of size). tavi
From: Octavian Purdila <opurdila@ixiacom.com> Date: Mon, 24 Aug 2009 23:47:05 +0300 > On Saturday 15 August 2009 03:39:12 Octavian Purdila wrote: > >> NOTE: this issue has been found, fixed and tested on an ancient 2.6.7 >> kernel. This patch is a blind port of that fix, since unfortunately there >> is no easy way for me to reproduce the original issue with a newer kernel. >> But the issue still seems to be there. > > Update: I was able to reproduce the issue on a 2.6.30 debian kernel with the > attached test. It took me about 10 runs of 2-5 mins each to reproduce it > (multiple runs to keep the capture file reasonable in terms of size). Thanks a lot for fixing this bug. I've applied your patch to net-next-2.6 -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/net/ipv4/inet_timewait_sock.c b/net/ipv4/inet_timewait_sock.c index 61283f9..13f0781 100644 --- a/net/ipv4/inet_timewait_sock.c +++ b/net/ipv4/inet_timewait_sock.c @@ -218,8 +218,8 @@ void inet_twdr_hangman(unsigned long data) /* We purged the entire slot, anything left? */ if (twdr->tw_count) need_timer = 1; + twdr->slot = ((twdr->slot + 1) & (INET_TWDR_TWKILL_SLOTS - 1)); } - twdr->slot = ((twdr->slot + 1) & (INET_TWDR_TWKILL_SLOTS - 1)); if (need_timer) mod_timer(&twdr->tw_timer, jiffies + twdr->period); out:
NOTE: this issue has been found, fixed and tested on an ancient 2.6.7 kernel. This patch is a blind port of that fix, since unfortunately there is no easy way for me to reproduce the original issue with a newer kernel. But the issue still seems to be there. tavi --- There is a race condition in the time-wait sockets code that can lead to premature termination of FIN_WAIT2 and, subsequently, to RST generation when the FIN,ACK from the peer finally arrives: Time TCP header 0.000000 30755 > http [SYN] Seq=0 Win=2920 Len=0 MSS=1460 TSV=282912 TSER=0 0.000008 http > 30755 aSYN, ACK] Seq=0 Ack=1 Win=2896 Len=0 MSS=1460 TSV=... 0.136899 HEAD /1b.html?n1Lg=v1 HTTP/1.0 [Packet size limited during capture] 0.136934 HTTP/1.0 200 OK [Packet size limited during capture] 0.136945 http > 30755 [FIN, ACK] Seq=187 Ack=207 Win=2690 Len=0 TSV=270521... 0.136974 30755 > http [ACK] Seq=207 Ack=187 Win=2734 Len=0 TSV=283049 TSER=... 0.177983 30755 > http [ACK] Seq=207 Ack=188 Win=2733 Len=0 TSV=283089 TSER=... 0.238618 30755 > http [FIN, ACK] Seq=207 Ack=188 Win=2733 Len=0 TSV=283151... 0.238625 http > 30755 [RST] Seq=188 Win=0 Len=0 Say twdr->slot = 1 and we are running inet_twdr_hangman and in this instance inet_twdr_do_twkill_work returns 1. At that point we will mark slot 1 and schedule inet_twdr_twkill_work. We will also make twdr->slot = 2. Next, a connection is closed and tcp_time_wait(TCP_FIN_WAIT2, timeo) is called which will create a new FIN_WAIT2 time-wait socket and will place it in the last to be reached slot, i.e. twdr->slot = 1. At this point say inet_twdr_twkill_work will run which will start destroying the time-wait sockets in slot 1, including the just added TCP_FIN_WAIT2 one. To avoid this issue we increment the slot only if all entries in the slot have been purged. This change may delay the slots cleanup by a time-wait death row period but only if the worker thread didn't had the time to run/purge the current slot in the next period (6 seconds with default sysctl settings). However, on such a busy system even without this change we would probably see delays... Signed-off-by: Octavian Purdila <opurdila@ixiacom.com> --- net/ipv4/inet_timewait_sock.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-)