linux-toradex.git/net/ipv4/tcp_input.c, branch v3.0.71

tcp: fix double-counted receiver RTT when leaving receiver fast path

2013-03-20T19:58:54+00:00

[ Upstream commit aab2b4bf224ef8358d262f95b568b8ad0cecf0a0 ]

We should not update ts_recent and call tcp_rcv_rtt_measure_ts() both
before and after going to step5. That wastes CPU and double-counts the
receiver-side RTT sample.

Signed-off-by: Neal Cardwell 
Acked-by: Eric Dumazet 
Signed-off-by: David S. Miller 
Signed-off-by: Greg Kroah-Hartman

tcp: fix for zero packets_in_flight was too broad

2013-02-14T18:47:35+00:00

[ Upstream commit 6731d2095bd4aef18027c72ef845ab1087c3ba63 ]

There are transients during normal FRTO procedure during which
the packets_in_flight can go to zero between write_queue state
updates and firing the resulting segments out. As FRTO processing
occurs during that window the check must be more precise to
not match "spuriously" :-). More specificly, e.g., when
packets_in_flight is zero but FLAG_DATA_ACKED is true the problematic
branch that set cwnd into zero would not be taken and new segments
might be sent out later.

Signed-off-by: Ilpo Järvinen 
Tested-by: Eric Dumazet 
Acked-by: Neal Cardwell 
Signed-off-by: David S. Miller 
Signed-off-by: Greg Kroah-Hartman

tcp: frto should not set snd_cwnd to 0

2013-02-14T18:47:35+00:00

[ Upstream commit 2e5f421211ff76c17130b4597bc06df4eeead24f ]

Commit 9dc274151a548 (tcp: fix ABC in tcp_slow_start())
uncovered a bug in FRTO code :
tcp_process_frto() is setting snd_cwnd to 0 if the number
of in flight packets is 0.

As Neal pointed out, if no packet is in flight we lost our
chance to disambiguate whether a loss timeout was spurious.

We should assume it was a proper loss.

Reported-by: Pasi Kärkkäinen 
Signed-off-by: Neal Cardwell 
Signed-off-by: Eric Dumazet 
Cc: Ilpo Järvinen 
Cc: Yuchung Cheng 
Signed-off-by: David S. Miller 
Signed-off-by: Greg Kroah-Hartman

tcp: RFC 5961 5.2 Blind Data Injection Attack Mitigation

2013-01-11T17:03:48+00:00

[ Upstream commit 354e4aa391ed50a4d827ff6fc11e0667d0859b25 ]

RFC 5961 5.2 [Blind Data Injection Attack].[Mitigation]

  All TCP stacks MAY implement the following mitigation.  TCP stacks
  that implement this mitigation MUST add an additional input check to
  any incoming segment.  The ACK value is considered acceptable only if
  it is in the range of ((SND.UNA - MAX.SND.WND) <= SEG.ACK <=
  SND.NXT).  All incoming segments whose ACK value doesn't satisfy the
  above condition MUST be discarded and an ACK sent back.

Move tcp_send_challenge_ack() before tcp_ack() to avoid a forward
declaration.

Signed-off-by: Eric Dumazet 
Cc: Neal Cardwell 
Cc: Yuchung Cheng 
Cc: Jerry Chu 
Signed-off-by: David S. Miller 
Signed-off-by: Greg Kroah-Hartman

tcp: tcp_replace_ts_recent() should not be called from tcp_validate_incoming()

2013-01-11T17:03:48+00:00

[ Upstream commit bd090dfc634ddd711a5fbd0cadc6e0ab4977bcaf ]

We added support for RFC 5961 in latest kernels but TCP fails
to perform exhaustive check of ACK sequence.

We can update our view of peer tsval from a frame that is
later discarded by tcp_ack()

This makes timestamps enabled sessions vulnerable to injection of
a high tsval : peers start an ACK storm, since the victim
sends a dupack each time it receives an ACK from the other peer.

As tcp_validate_incoming() is called before tcp_ack(), we should
not peform tcp_replace_ts_recent() from it, and let callers do it
at the right time.

Signed-off-by: Eric Dumazet 
Cc: Neal Cardwell 
Cc: Yuchung Cheng 
Cc: Nandita Dukkipati 
Cc: H.K. Jerry Chu 
Cc: Romain Francoise 
Signed-off-by: David S. Miller 
Signed-off-by: Greg Kroah-Hartman

tcp: refine SYN handling in tcp_validate_incoming

2013-01-11T17:03:48+00:00

[ Upstream commit e371589917011efe6ff8c7dfb4e9e81934ac5855 ]

Followup of commit 0c24604b68fc (tcp: implement RFC 5961 4.2)

As reported by Vijay Subramanian, we should send a challenge ACK
instead of a dup ack if a SYN flag is set on a packet received out of
window.

This permits the ratelimiting to work as intended, and to increase
correct SNMP counters.

Suggested-by: Vijay Subramanian 
Signed-off-by: Eric Dumazet 
Acked-by: Vijay Subramanian 
Cc: Kiran Kumar Kella 
Signed-off-by: David S. Miller 
Signed-off-by: Greg Kroah-Hartman

tcp: implement RFC 5961 4.2

2013-01-11T17:03:48+00:00

[ Upstream commit 0c24604b68fc7810d429d6c3657b6f148270e528 ]

Implement the RFC 5691 mitigation against Blind
Reset attack using SYN bit.

Section 4.2 of RFC 5961 advises to send a Challenge ACK and drop
incoming packet, instead of resetting the session.

Add a new SNMP counter to count number of challenge acks sent
in response to SYN packets.
(netstat -s | grep TCPSYNChallenge)

Remove obsolete TCPAbortOnSyn, since we no longer abort a TCP session
because of a SYN flag.

Signed-off-by: Eric Dumazet 
Cc: Kiran Kumar Kella 
Signed-off-by: David S. Miller 
Signed-off-by: Greg Kroah-Hartman

tcp: implement RFC 5961 3.2

2013-01-11T17:03:48+00:00

[ Upstream commit 282f23c6ee343126156dd41218b22ece96d747e3 ]

Implement the RFC 5691 mitigation against Blind
Reset attack using RST bit.

Idea is to validate incoming RST sequence,
to match RCV.NXT value, instead of previouly accepted
window : (RCV.NXT <= SEG.SEQ < RCV.NXT+RCV.WND)

If sequence is in window but not an exact match, send
a "challenge ACK", so that the other part can resend an
RST with the appropriate sequence.

Add a new sysctl, tcp_challenge_ack_limit, to limit
number of challenge ACK sent per second.

Add a new SNMP counter to count number of challenge acks sent.
(netstat -s | grep TCPChallengeACK)

Signed-off-by: Eric Dumazet 
Cc: Kiran Kumar Kella 
Signed-off-by: David S. Miller 
Signed-off-by: Greg Kroah-Hartman

tcp: perform DMA to userspace only if there is a task waiting for it

2012-08-09T15:27:52+00:00

[ Upstream commit 59ea33a68a9083ac98515e4861c00e71efdc49a1 ]

Back in 2006, commit 1a2449a87b ("[I/OAT]: TCP recv offload to I/OAT")
added support for receive offloading to IOAT dma engine if available.

The code in tcp_rcv_established() tries to perform early DMA copy if
applicable. It however does so without checking whether the userspace
task is actually expecting the data in the buffer.

This is not a problem under normal circumstances, but there is a corner
case where this doesn't work -- and that's when MSG_TRUNC flag to
recvmsg() is used.

If the IOAT dma engine is not used, the code properly checks whether
there is a valid ucopy.task and the socket is owned by userspace, but
misses the check in the dmaengine case.

This problem can be observed in real trivially -- for example 'tbench' is a
good reproducer, as it makes a heavy use of MSG_TRUNC. On systems utilizing
IOAT, you will soon find tbench waiting indefinitely in sk_wait_data(), as they
have been already early-copied in tcp_rcv_established() using dma engine.

This patch introduces the same check we are performing in the simple
iovec copy case to the IOAT case as well. It fixes the indefinite
recvmsg(MSG_TRUNC) hangs.

Signed-off-by: Jiri Kosina 
Signed-off-by: David S. Miller 
Signed-off-by: Greg Kroah-Hartman

tcp: drop SYN+FIN messages

2012-07-19T15:58:22+00:00

commit fdf5af0daf8019cec2396cdef8fb042d80fe71fa upstream.

Denys Fedoryshchenko reported that SYN+FIN attacks were bringing his
linux machines to their limits.

Dont call conn_request() if the TCP flags includes SYN flag

Reported-by: Denys Fedoryshchenko 
Signed-off-by: Eric Dumazet 
Signed-off-by: David S. Miller 
Cc: Ben Hutchings 
Signed-off-by: Greg Kroah-Hartman