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  1. 08 10月, 2008 1 次提交
    • I
      tcp: kill pointless urg_mode · 33f5f57e
      由 Ilpo Järvinen 提交于 
      It all started from me noticing that this urgent check in
tcp_clean_rtx_queue is unnecessarily inside the loop. Then
I took a longer look to it and found out that the users of
urg_mode can trivially do without, well almost, there was
one gotcha.

Bonus: those funny people who use urg with >= 2^31 write_seq -
snd_una could now rejoice too (that's the only purpose for the
between being there, otherwise a simple compare would have done
the thing). Not that I assume that the rest of the tcp code
happily lives with such mind-boggling numbers :-). Alas, it
turned out to be impossible to set wmem to such numbers anyway,
yes I really tried a big sendfile after setting some wmem but
nothing happened :-). ...Tcp_wmem is int and so is sk_sndbuf...
So I hacked a bit variable to long and found out that it seems
to work... :-)
Signed-off-by: NIlpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      33f5f57e
  3. 23 9月, 2008 1 次提交
  5. 22 9月, 2008 1 次提交
  7. 21 9月, 2008 8 次提交
  9. 09 9月, 2008 1 次提交
  11. 04 9月, 2008 1 次提交
  13. 23 8月, 2008 3 次提交
  15. 26 7月, 2008 1 次提交
  17. 24 7月, 2008 1 次提交
    • D
      tcp: Clear probes_out more aggressively in tcp_ack(). · 4b53fb67
      由 David S. Miller 提交于 
      This is based upon an excellent bug report from Eric Dumazet.

tcp_ack() should clear ->icsk_probes_out even if there are packets
outstanding.  Otherwise if we get a sequence of ACKs while we do have
packets outstanding over and over again, we'll never clear the
probes_out value and eventually think the connection is too sick and
we'll reset it.

This appears to be some "optimization" added to tcp_ack() in the 2.4.x
timeframe.  In 2.2.x, probes_out is pretty much always cleared by
tcp_ack().

Here is Eric's original report:

----------------------------------------
Apparently, we can in some situations reset TCP connections in a couple of seconds when some frames are lost.

In order to reproduce the problem, please try the following program on linux-2.6.25.*

Setup some iptables rules to allow two frames per second sent on loopback interface to tcp destination port 12000

iptables -N SLOWLO
iptables -A SLOWLO -m hashlimit --hashlimit 2 --hashlimit-burst 1 --hashlimit-mode dstip --hashlimit-name slow2 -j ACCEPT
iptables -A SLOWLO -j DROP

iptables -A OUTPUT -o lo -p tcp --dport 12000 -j SLOWLO

Then run the attached program and see the output :

# ./loop
State      Recv-Q Send-Q                                  Local Address:Port                                    Peer Address:Port
ESTAB      0      40                                          127.0.0.1:54455                                      127.0.0.1:12000  timer:(persist,200ms,1)
State      Recv-Q Send-Q                                  Local Address:Port                                    Peer Address:Port
ESTAB      0      40                                          127.0.0.1:54455                                      127.0.0.1:12000  timer:(persist,200ms,3)
State      Recv-Q Send-Q                                  Local Address:Port                                    Peer Address:Port
ESTAB      0      40                                          127.0.0.1:54455                                      127.0.0.1:12000  timer:(persist,200ms,5)
State      Recv-Q Send-Q                                  Local Address:Port                                    Peer Address:Port
ESTAB      0      40                                          127.0.0.1:54455                                      127.0.0.1:12000  timer:(persist,200ms,7)
State      Recv-Q Send-Q                                  Local Address:Port                                    Peer Address:Port
ESTAB      0      40                                          127.0.0.1:54455                                      127.0.0.1:12000  timer:(persist,200ms,9)
State      Recv-Q Send-Q                                  Local Address:Port                                    Peer Address:Port
ESTAB      0      40                                          127.0.0.1:54455                                      127.0.0.1:12000  timer:(persist,200ms,11)
State      Recv-Q Send-Q                                  Local Address:Port                                    Peer Address:Port
ESTAB      0      40                                          127.0.0.1:54455                                      127.0.0.1:12000  timer:(persist,201ms,13)
State      Recv-Q Send-Q                                  Local Address:Port                                    Peer Address:Port
ESTAB      0      40                                          127.0.0.1:54455                                      127.0.0.1:12000  timer:(persist,188ms,15)
write(): Connection timed out
wrote 890 bytes but was interrupted after 9 seconds
ESTAB      0      0                 127.0.0.1:12000            127.0.0.1:54455
Exiting read() because no data available (4000 ms timeout).
read 860 bytes

While this tcp session makes progress (sending frames with 50 bytes of payload, every 500ms), linux tcp stack decides to reset it, when tcp_retries 2 is reached (default value : 15)

tcpdump :

15:30:28.856695 IP 127.0.0.1.56554 > 127.0.0.1.12000: S 33788768:33788768(0) win 32792 <mss 16396,nop,nop,sackOK,nop,wscale 7>
15:30:28.856711 IP 127.0.0.1.12000 > 127.0.0.1.56554: S 33899253:33899253(0) ack 33788769 win 32792 <mss 16396,nop,nop,sackOK,nop,wscale 7>
15:30:29.356947 IP 127.0.0.1.56554 > 127.0.0.1.12000: P 1:61(60) ack 1 win 257
15:30:29.356966 IP 127.0.0.1.12000 > 127.0.0.1.56554: . ack 61 win 257
15:30:29.866415 IP 127.0.0.1.56554 > 127.0.0.1.12000: P 61:111(50) ack 1 win 257
15:30:29.866427 IP 127.0.0.1.12000 > 127.0.0.1.56554: . ack 111 win 257
15:30:30.366516 IP 127.0.0.1.56554 > 127.0.0.1.12000: P 111:161(50) ack 1 win 257
15:30:30.366527 IP 127.0.0.1.12000 > 127.0.0.1.56554: . ack 161 win 257
15:30:30.876196 IP 127.0.0.1.56554 > 127.0.0.1.12000: P 161:211(50) ack 1 win 257
15:30:30.876207 IP 127.0.0.1.12000 > 127.0.0.1.56554: . ack 211 win 257
15:30:31.376282 IP 127.0.0.1.56554 > 127.0.0.1.12000: P 211:261(50) ack 1 win 257
15:30:31.376290 IP 127.0.0.1.12000 > 127.0.0.1.56554: . ack 261 win 257
15:30:31.885619 IP 127.0.0.1.56554 > 127.0.0.1.12000: P 261:311(50) ack 1 win 257
15:30:31.885631 IP 127.0.0.1.12000 > 127.0.0.1.56554: . ack 311 win 257
15:30:32.385705 IP 127.0.0.1.56554 > 127.0.0.1.12000: P 311:361(50) ack 1 win 257
15:30:32.385715 IP 127.0.0.1.12000 > 127.0.0.1.56554: . ack 361 win 257
15:30:32.895249 IP 127.0.0.1.56554 > 127.0.0.1.12000: P 361:411(50) ack 1 win 257
15:30:32.895266 IP 127.0.0.1.12000 > 127.0.0.1.56554: . ack 411 win 257
15:30:33.395341 IP 127.0.0.1.56554 > 127.0.0.1.12000: P 411:461(50) ack 1 win 257
15:30:33.395351 IP 127.0.0.1.12000 > 127.0.0.1.56554: . ack 461 win 257
15:30:33.918085 IP 127.0.0.1.56554 > 127.0.0.1.12000: P 461:511(50) ack 1 win 257
15:30:33.918096 IP 127.0.0.1.12000 > 127.0.0.1.56554: . ack 511 win 257
15:30:34.418163 IP 127.0.0.1.56554 > 127.0.0.1.12000: P 511:561(50) ack 1 win 257
15:30:34.418172 IP 127.0.0.1.12000 > 127.0.0.1.56554: . ack 561 win 257
15:30:34.927685 IP 127.0.0.1.56554 > 127.0.0.1.12000: P 561:611(50) ack 1 win 257
15:30:34.927698 IP 127.0.0.1.12000 > 127.0.0.1.56554: . ack 611 win 257
15:30:35.427757 IP 127.0.0.1.56554 > 127.0.0.1.12000: P 611:661(50) ack 1 win 257
15:30:35.427766 IP 127.0.0.1.12000 > 127.0.0.1.56554: . ack 661 win 257
15:30:35.937359 IP 127.0.0.1.56554 > 127.0.0.1.12000: P 661:711(50) ack 1 win 257
15:30:35.937376 IP 127.0.0.1.12000 > 127.0.0.1.56554: . ack 711 win 257
15:30:36.437451 IP 127.0.0.1.56554 > 127.0.0.1.12000: P 711:761(50) ack 1 win 257
15:30:36.437464 IP 127.0.0.1.12000 > 127.0.0.1.56554: . ack 761 win 257
15:30:36.947022 IP 127.0.0.1.56554 > 127.0.0.1.12000: P 761:811(50) ack 1 win 257
15:30:36.947039 IP 127.0.0.1.12000 > 127.0.0.1.56554: . ack 811 win 257
15:30:37.447135 IP 127.0.0.1.56554 > 127.0.0.1.12000: P 811:861(50) ack 1 win 257
15:30:37.447203 IP 127.0.0.1.12000 > 127.0.0.1.56554: . ack 861 win 257
15:30:41.448171 IP 127.0.0.1.12000 > 127.0.0.1.56554: F 1:1(0) ack 861 win 257
15:30:41.448189 IP 127.0.0.1.56554 > 127.0.0.1.12000: R 33789629:33789629(0) win 0

Source of program :

/*
 * small producer/consumer program.
 * setup a listener on 127.0.0.1:12000
 * Forks a child
 *   child connect to 127.0.0.1, and sends 10 bytes on this tcp socket every 100 ms
 * Father accepts connection, and read all data
 */
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <unistd.h>
#include <stdio.h>
#include <time.h>
#include <sys/poll.h>

int port = 12000;
char buffer[4096];
int main(int argc, char *argv[])
{
        int lfd = socket(AF_INET, SOCK_STREAM, 0);
        struct sockaddr_in socket_address;
        time_t t0, t1;
        int on = 1, sfd, res;
        unsigned long total = 0;
        socklen_t alen = sizeof(socket_address);
        pid_t pid;

        time(&t0);
        socket_address.sin_family = AF_INET;
        socket_address.sin_port = htons(port);
        socket_address.sin_addr.s_addr = htonl(INADDR_LOOPBACK);

        if (lfd == -1) {
                perror("socket()");
                return 1;
        }
        setsockopt(lfd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(int));
        if (bind(lfd, (struct sockaddr *)&socket_address, sizeof(socket_address)) == -1) {
                perror("bind");
                close(lfd);
                return 1;
        }
        if (listen(lfd, 1) == -1) {
                perror("listen()");
                close(lfd);
                return 1;
        }
        pid = fork();
        if (pid == 0) {
                int i, cfd = socket(AF_INET, SOCK_STREAM, 0);
                close(lfd);
                if (connect(cfd, (struct sockaddr *)&socket_address, sizeof(socket_address)) == -1) {
                        perror("connect()");
                        return 1;
                        }
                for (i = 0 ; ;) {
                        res = write(cfd, "blablabla\n", 10);
                        if (res > 0) total += res;
                        else if (res == -1) {
                                perror("write()");
                                break;
                        } else break;
                        usleep(100000);
                        if (++i == 10) {
                                system("ss -on dst 127.0.0.1:12000");
                                i = 0;
                        }
                }
                time(&t1);
                fprintf(stderr, "wrote %lu bytes but was interrupted after %g seconds\n", total, difftime(t1, t0));
                system("ss -on | grep 127.0.0.1:12000");
                close(cfd);
                return 0;
        }
        sfd = accept(lfd, (struct sockaddr *)&socket_address, &alen);
        if (sfd == -1) {
                perror("accept");
                return 1;
        }
        close(lfd);
        while (1) {
                struct pollfd pfd[1];
                pfd[0].fd = sfd;
                pfd[0].events = POLLIN;
                if (poll(pfd, 1, 4000) == 0) {
                        fprintf(stderr, "Exiting read() because no data available (4000 ms timeout).\n");
                        break;
                }
                res = read(sfd, buffer, sizeof(buffer));
                if (res > 0) total += res;
                else if (res == 0) break;
                else perror("read()");
        }
        fprintf(stderr, "read %lu bytes\n", total);
        close(sfd);
        return 0;
}
----------------------------------------
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      4b53fb67
  19. 19 7月, 2008 2 次提交
  21. 17 7月, 2008 3 次提交
  23. 03 7月, 2008 1 次提交
    • P
      tcp: de-bloat a bit with factoring NET_INC_STATS_BH out · 40b215e5
      由 Pavel Emelyanov 提交于 
      There are some places in TCP that select one MIB index to
bump snmp statistics like this:

	if (<something>)
		NET_INC_STATS_BH(<some_id>);
	else if (<something_else>)
		NET_INC_STATS_BH(<some_other_id>);
	...
	else
		NET_INC_STATS_BH(<default_id>);

or in a more tricky but still similar way.

On the other hand, this NET_INC_STATS_BH is a camouflaged
increment of percpu variable, which is not that small.

Factoring those cases out de-bloats 235 bytes on non-preemptible
i386 config and drives parts of the code into 80 columns.

add/remove: 0/0 grow/shrink: 0/7 up/down: 0/-235 (-235)
function                                     old     new   delta
tcp_fastretrans_alert                       1437    1424     -13
tcp_dsack_set                                137     124     -13
tcp_xmit_retransmit_queue                    690     676     -14
tcp_try_undo_recovery                        283     265     -18
tcp_sacktag_write_queue                     1550    1515     -35
tcp_update_reordering                        162     106     -56
tcp_retransmit_timer                         990     904     -86
Signed-off-by: NPavel Emelyanov <xemul@openvz.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      40b215e5
  25. 13 6月, 2008 1 次提交
    • D
      tcp: Revert 'process defer accept as established' changes. · ec0a1966
      由 David S. Miller 提交于 
      This reverts two changesets, ec3c0982
("[TCP]: TCP_DEFER_ACCEPT updates - process as established") and
the follow-on bug fix 9ae27e0a
("tcp: Fix slab corruption with ipv6 and tcp6fuzz").

This change causes several problems, first reported by Ingo Molnar
as a distcc-over-loopback regression where connections were getting
stuck.

Ilpo Järvinen first spotted the locking problems.  The new function
added by this code, tcp_defer_accept_check(), only has the
child socket locked, yet it is modifying state of the parent
listening socket.

Fixing that is non-trivial at best, because we can't simply just grab
the parent listening socket lock at this point, because it would
create an ABBA deadlock.  The normal ordering is parent listening
socket --> child socket, but this code path would require the
reverse lock ordering.

Next is a problem noticed by Vitaliy Gusev, he noted:

----------------------------------------
>--- a/net/ipv4/tcp_timer.c
>+++ b/net/ipv4/tcp_timer.c
>@@ -481,6 +481,11 @@ static void tcp_keepalive_timer (unsigned long data)
> 		goto death;
> 	}
>
>+	if (tp->defer_tcp_accept.request && sk->sk_state == TCP_ESTABLISHED) {
>+		tcp_send_active_reset(sk, GFP_ATOMIC);
>+		goto death;

Here socket sk is not attached to listening socket's request queue. tcp_done()
will not call inet_csk_destroy_sock() (and tcp_v4_destroy_sock() which should
release this sk) as socket is not DEAD. Therefore socket sk will be lost for
freeing.
----------------------------------------

Finally, Alexey Kuznetsov argues that there might not even be any
real value or advantage to these new semantics even if we fix all
of the bugs:

----------------------------------------
Hiding from accept() sockets with only out-of-order data only
is the only thing which is impossible with old approach. Is this really
so valuable? My opinion: no, this is nothing but a new loophole
to consume memory without control.
----------------------------------------

So revert this thing for now.
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      ec0a1966
  27. 12 6月, 2008 2 次提交
  29. 05 6月, 2008 2 次提交
    • I
      tcp: fix skb vs fack_count out-of-sync condition · a6604471
      由 Ilpo Järvinen 提交于 
      This bug is able to corrupt fackets_out in very rare cases.
In order for this to cause corruption:
  1) DSACK in the middle of previous SACK block must be generated.
  2) In order to take that particular branch, part or all of the
     DSACKed segment must already be SACKed so that we have that
     in cache in the first place.
  3) The new info must be top enough so that fackets_out will be
     updated on this iteration.
...then fack_count is updated while skb wasn't, then we walk again
that particular segment thus updating fack_count twice for
a single skb and finally that value is assigned to fackets_out
by tcp_sacktag_one.

It is safe to call tcp_sacktag_one just once for a segment (at
DSACK), no need to call again for plain SACK.

Potential problem of the miscount are limited to premature entry
to recovery and to inflated reordering metric (which could even
cancel each other out in the most the luckiest scenarios :-)).
Both are quite insignificant in worst case too and there exists
also code to reset them (fackets_out once sacked_out becomes zero
and reordering metric on RTO).

This has been reported by a number of people, because it occurred
quite rarely, it has been very evasive. Andy Furniss was able to
get it to occur couple of times so that a bit more info was
collected about the problem using a debug patch, though it still
required lot of checking around. Thanks also to others who have
tried to help here.

This is listed as Bugzilla #10346. The bug was introduced by
me in commit 68f8353b ([TCP]: Rewrite SACK block processing & 
sack_recv_cache use), I probably thought back then that there's
need to scan that entry twice or didn't dare to make it go
through it just once there. Going through twice would have
required restoring fack_count after the walk but as noted above,
I chose to drop the additional walk step altogether here.
Signed-off-by: NIlpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      a6604471
    • I
      tcp: Fix inconsistency source (CA_Open only when !tcp_left_out(tp)) · 8aca6cb1
      由 Ilpo Järvinen 提交于 
      It is possible that this skip path causes TCP to end up into an
invalid state where ca_state was left to CA_Open while some
segments already came into sacked_out. If next valid ACK doesn't
contain new SACK information TCP fails to enter into
tcp_fastretrans_alert(). Thus at least high_seq is set
incorrectly to a too high seqno because some new data segments
could be sent in between (and also, limited transmit is not
being correctly invoked there). Reordering in both directions
can easily cause this situation to occur.

I guess we would want to use tcp_moderate_cwnd(tp) there as well
as it may be possible to use this to trigger oversized burst to
network by sending an old ACK with huge amount of SACK info, but
I'm a bit unsure about its effects (mainly to FlightSize), so to
be on the safe side I just currently fixed it minimally to keep
TCP's state consistent (obviously, such nasty ACKs have been
possible this far). Though it seems that FlightSize is already
underestimated by some amount, so probably on the long term we
might want to trigger recovery there too, if appropriate, to make
FlightSize calculation to resemble reality at the time when the
losses where discovered (but such change scares me too much now
and requires some more thinking anyway how to do that as it
likely involves some code shuffling).

This bug was found by Brian Vowell while running my TCP debug
patch to find cause of another TCP issue (fackets_out
miscount).
Signed-off-by: NIlpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      8aca6cb1
  31. 13 5月, 2008 2 次提交
    • I
      tcp FRTO: work-around inorder receivers · 79d44516
      由 Ilpo Järvinen 提交于 
      If receiver consumes segments successfully only in-order, FRTO
fallback to conventional recovery produces RTO loop because
FRTO's forward transmissions will always get dropped and need to
be resent, yet by default they're not marked as lost (which are
the only segments we will retransmit in CA_Loss).

Price to pay about this is occassionally unnecessarily
retransmitting the forward transmission(s). SACK blocks help
a bit to avoid this, so it's mainly a concern for NewReno case
though SACK is not fully immune either.

This change has a side-effect of fixing SACKFRTO problem where
it didn't have snd_nxt of the RTO time available anymore when
fallback become necessary (this problem would have only occured
when RTO would occur for two or more segments and ECE arrives
in step 3; no need to figure out how to fix that unless the
TODO item of selective behavior is considered in future).
Signed-off-by: NIlpo Järvinen <ilpo.jarvinen@helsinki.fi>
Reported-by: NDamon L. Chesser <damon@damtek.com>
Tested-by: NDamon L. Chesser <damon@damtek.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      79d44516
    • I
      tcp FRTO: Fix fallback to conventional recovery · a1c1f281
      由 Ilpo Järvinen 提交于 
      It seems that commit 009a2e3e ("[TCP] FRTO: Improve
interoperability with other undo_marker users") run into
another land-mine which caused fallback to conventional
recovery to break:

1. Cumulative ACK arrives after FRTO retransmission
2. tcp_try_to_open sees zero retrans_out, clears retrans_stamp
   which should be kept like in CA_Loss state it would be
3. undo_marker change allowed tcp_packet_delayed to return
   true because of the cleared retrans_stamp once FRTO is
   terminated causing LossUndo to occur, which means all loss
   markings FRTO made are reverted.

This means that the conventional recovery basically recovered
one loss per RTT, which is not that efficient. It was quite
unobvious that the undo_marker change broken something like
this, I had a quite long session to track it down because of
the non-intuitiviness of the bug (luckily I had a trivial
reproducer at hand and I was also able to learn to use kprobes
in the process as well :-)).

This together with the NewReno+FRTO fix and FRTO in-order
workaround this fixes Damon's problems, this and the first
mentioned are enough to fix Bugzilla #10063.
Signed-off-by: NIlpo Järvinen <ilpo.jarvinen@helsinki.fi>
Reported-by: NDamon L. Chesser <damon@damtek.com>
Tested-by: NDamon L. Chesser <damon@damtek.com>
Tested-by: NSebastian Hyrwall <zibbe@cisko.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      a1c1f281
  33. 08 5月, 2008 1 次提交
    • I
      tcp FRTO: SACK variant is errorneously used with NewReno · 62ab2227
      由 Ilpo Järvinen 提交于 
      Note: there's actually another bug in FRTO's SACK variant, which
is the causing failure in NewReno case because of the error
that's fixed here. I'll fix the SACK case separately (it's
a separate bug really, though related, but in order to fix that
I need to audit tp->snd_nxt usage a bit).

There were two places where SACK variant of FRTO is getting
incorrectly used even if SACK wasn't negotiated by the TCP flow.
This leads to incorrect setting of frto_highmark with NewReno
if a previous recovery was interrupted by another RTO.

An eventual fallback to conventional recovery then incorrectly
considers one or couple of segments as forward transmissions
though they weren't, which then are not LOST marked during
fallback making them "non-retransmittable" until the next RTO.
In a bad case, those segments are really lost and are the only
one left in the window. Thus TCP needs another RTO to continue.
The next FRTO, however, could again repeat the same events
making the progress of the TCP flow extremely slow.

In order for these events to occur at all, FRTO must occur
again in FRTOs step 3 while the key segments must be lost as
well, which is not too likely in practice. It seems to most
frequently with some small devices such as network printers
that *seem* to accept TCP segments only in-order. In cases
were key segments weren't lost, things get automatically
resolved because those wrongly marked segments don't need to be
retransmitted in order to continue.

I found a reproducer after digging up relevant reports (few
reports in total, none at netdev or lkml I know of), some
cases seemed to indicate middlebox issues which seems now
to be a false assumption some people had made. Bugzilla
#10063 _might_ be related. Damon L. Chesser <damon@damtek.com>
had a reproducable case and was kind enough to tcpdump it
for me. With the tcpdump log it was quite trivial to figure
out.
Signed-off-by: NIlpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      62ab2227
  35. 05 5月, 2008 1 次提交
  37. 03 5月, 2008 1 次提交
  39. 28 4月, 2008 1 次提交
    • E
      tcp: Fix slab corruption with ipv6 and tcp6fuzz · 9ae27e0a
      由 Evgeniy Polyakov 提交于 
      From: Evgeniy Polyakov <johnpol@2ka.mipt.ru>

This fixes a regression added by ec3c0982
("[TCP]: TCP_DEFER_ACCEPT updates - process as established")

tcp_v6_do_rcv()->tcp_rcv_established(), the latter goes to step5, where
eventually skb can be freed via tcp_data_queue() (drop: label), then if
check for tcp_defer_accept_check() returns true and thus
tcp_rcv_established() returns -1, which forces tcp_v6_do_rcv() to jump
to reset: label, which in turn will pass through discard: label and free
the same skb again.

Tested by Eric Sesterhenn.
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
Acked-By: NPatrick McManus <mcmanus@ducksong.com>
      9ae27e0a
  41. 22 4月, 2008 1 次提交
  43. 16 4月, 2008 1 次提交
  45. 15 4月, 2008 1 次提交
  47. 14 4月, 2008 2 次提交