linux-toradex.git/net/ipv4, branch v2.6.25.7

tcp: Fix inconsistency source (CA_Open only when !tcp_left_out(tp))

2008-06-16T20:20:03+00:00

[ upstream commit: 8aca6cb1179ed9bef9351028c8d8af852903eae2 ]

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: Ilpo Järvinen 
Signed-off-by: David S. Miller 
Signed-off-by: Greg Kroah-Hartman

tcp FRTO: work-around inorder receivers

2008-06-16T20:20:00+00:00

[ upstream commit: 79d44516b4b178ffb6e2159c75584cfcfc097914 ]

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: Ilpo Järvinen 
Reported-by: Damon L. Chesser 
Tested-by: Damon L. Chesser 
Signed-off-by: David S. Miller 
Signed-off-by: Chris Wright

tcp FRTO: SACK variant is errorneously used with NewReno

2008-06-16T20:20:00+00:00

[ upstream commit: 62ab22278308a40bcb7f4079e9719ab8b7fe11b5 ]

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 
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: Ilpo Järvinen 
Signed-off-by: David S. Miller 
Signed-off-by: Chris Wright

tcp FRTO: Fix fallback to conventional recovery

2008-06-16T20:20:00+00:00

[ upstream commit: a1c1f281b84a751fdb5ff919da3b09df7297619f ]

It seems that commit 009a2e3e4ec ("[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: Ilpo Järvinen 
Reported-by: Damon L. Chesser 
Tested-by: Damon L. Chesser 
Tested-by: Sebastian Hyrwall 
Signed-off-by: David S. Miller 
Signed-off-by: Chris Wright

tcp: fix skb vs fack_count out-of-sync condition

2008-06-16T20:19:58+00:00

[ upstream commit: a6604471db5e7a33474a7f16c64d6b118fae3e74 ]

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 68f8353b48 ([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: Ilpo Järvinen 
Signed-off-by: David S. Miller 
Signed-off-by: Chris Wright

tcp: Limit cwnd growth when deferring for GSO

2008-06-16T20:19:57+00:00

[ upstream commit: 246eb2af060fc32650f07203c02bdc0456ad76c7 ]

This fixes inappropriately large cwnd growth on sender-limited flows
when GSO is enabled, limiting cwnd growth to 64k.

[ Backport to 2.6.25 by replacing sk->sk_gso_max_size with 65536 -DaveM ]

Signed-off-by: John Heffner 
Signed-off-by: David S. Miller 
Signed-off-by: Chris Wright

tcp: Allow send-limited cwnd to grow up to max_burst when gso disabled

2008-06-16T20:19:57+00:00

[ upstream commit: ce447eb91409225f8a488f6b7b2a1bdf7b2d884f ]

This changes the logic in tcp_is_cwnd_limited() so that cwnd may grow
up to tcp_max_burst() even when sk_can_gso() is false, or when
sysctl_tcp_tso_win_divisor != 0.

Signed-off-by: John Heffner 
Signed-off-by: David S. Miller 
Signed-off-by: Chris Wright

tcp: TCP connection times out if ICMP frag needed is delayed

2008-06-16T20:19:57+00:00

[ upstream commit: 7d227cd235c809c36c847d6a597956ad9e9d2bae ]

We are seeing an issue with TCP in handling an ICMP frag needed
message that is received after net.ipv4.tcp_retries1 retransmits.
The default value of retries1 is 3. So if the path mtu changes
and ICMP frag needed is lost for the first 3 retransmits or if
it gets delayed until 3 retransmits are done, TCP doesn't update
MSS correctly and continues to retransmit the orginal message
until it timesout after tcp_retries2 retransmits.

I am seeing this issue even with the latest 2.6.25.4 kernel.

In tcp_retransmit_timer(), when retransmits counter exceeds
tcp_retries1 value, the dst cache entry of the socket is reset.
At this time, if we receive an ICMP frag needed message, the
dst entry gets updated with the new MTU, but the TCP sockets
dst_cache entry remains NULL.

So the next time when we try to retransmit after the ICMP frag
needed is received, tcp_retransmit_skb() gets called. Here the
cur_mss value is calculated at the start of the routine with
a NULL sk_dst_cache. Instead we should call tcp_current_mss after
the rebuild_header that caches the dst entry with the updated mtu.
Also the rebuild_header should be called before tcp_fragment
so that skb is fragmented if the mss goes down.

Signed-off-by: Sridhar Samudrala 
Signed-off-by: David S. Miller 
Signed-off-by: Chris Wright

ipsec: Use the correct ip_local_out function

2008-06-16T20:19:55+00:00

[ upstream commit: 1ac06e0306d0192a7a4d9ea1c9e06d355ce7e7d3 ]

Because the IPsec output function xfrm_output_resume does its
own dst_output call it should always call __ip_local_output
instead of ip_local_output as the latter may invoke dst_output
directly.  Otherwise the return values from nf_hook and dst_output
may clash as they both use the value 1 but for different purposes.

When that clash occurs this can cause a packet to be used after
it has been freed which usually leads to a crash.  Because the
offending value is only returned from dst_output with qdiscs
such as HTB, this bug is normally not visible.

Thanks to Marco Berizzi for his perseverance in tracking this
down.

Signed-off-by: Herbert Xu 
Signed-off-by: David S. Miller 
Signed-off-by: Chris Wright

asn1: additional sanity checking during BER decoding (CVE-2008-1673)

2008-06-06T23:04:46+00:00

upstream commit: ddb2c43594f22843e9f3153da151deaba1a834c5

- Don't trust a length which is greater than the working buffer.
  An invalid length could cause overflow when calculating buffer size
  for decoding oid.

- An oid length of zero is invalid and allows for an off-by-one error when
  decoding oid because the first subid actually encodes first 2 subids.

- A primitive encoding may not have an indefinite length.

Thanks to Wei Wang from McAfee for report.

Cc: Steven French 
Cc: stable@kernel.org
Acked-by: Patrick McHardy 
Signed-off-by: Chris Wright 
Signed-off-by: Linus Torvalds