linux-stable.git/net/ipv4/tcp_timer.c, branch v5.6

tcp: export count for rehash attempts

2020-01-26T14:28:47+00:00

Using IPv6 flow-label to swiftly route around avoid congested or
disconnected network path can greatly improve TCP reliability.

This patch adds SNMP counters and a OPT_STATS counter to track both
host-level and connection-level statistics. Network administrators
can use these counters to evaluate the impact of this new ability better.

Export count for rehash attempts to
1) two SNMP counters: TcpTimeoutRehash (rehash due to timeouts),
   and TcpDuplicateDataRehash (rehash due to receiving duplicate
   packets)
2) Timestamping API SOF_TIMESTAMPING_OPT_STATS.

Signed-off-by: Abdul Kabbani 
Signed-off-by: Neal Cardwell 
Signed-off-by: Yuchung Cheng 
Signed-off-by: Kevin(Yudong) Yang 
Signed-off-by: Eric Dumazet 
Signed-off-by: David S. Miller

tcp: refactor tcp_retransmit_timer()

2019-12-03T19:52:38+00:00

It appears linux-4.14 stable needs a backport of commit
88f8598d0a30 ("tcp: exit if nothing to retransmit on RTO timeout")

Since tcp_rtx_queue_empty() is not in pre 4.15 kernels,
let's refactor tcp_retransmit_timer() to only use tcp_rtx_queue_head()

I will provide to stable teams the squashed patches.

Signed-off-by: Eric Dumazet 
Cc: Willem de Bruijn 
Cc: Greg Kroah-Hartman 
Acked-by: Soheil Hassas Yeganeh 
Signed-off-by: David S. Miller

tcp: add rcu protection around tp->fastopen_rsk

2019-10-13T17:13:08+00:00

Both tcp_v4_err() and tcp_v6_err() do the following operations
while they do not own the socket lock :

	fastopen = tp->fastopen_rsk;
 	snd_una = fastopen ? tcp_rsk(fastopen)->snt_isn : tp->snd_una;

The problem is that without appropriate barrier, the compiler
might reload tp->fastopen_rsk and trigger a NULL deref.

request sockets are protected by RCU, we can simply add
the missing annotations and barriers to solve the issue.

Fixes: 168a8f58059a ("tcp: TCP Fast Open Server - main code path")
Signed-off-by: Eric Dumazet 
Signed-off-by: David S. Miller

tcp: adjust rto_base in retransmits_timed_out()

2019-10-02T01:40:49+00:00

The cited commit exposed an old retransmits_timed_out() bug
which assumed it could call tcp_model_timeout() with
TCP_RTO_MIN as rto_base for all states.

But flows in SYN_SENT or SYN_RECV state uses a different
RTO base (1 sec instead of 200 ms, unless BPF choses
another value)

This caused a reduction of SYN retransmits from 6 to 4 with
the default /proc/sys/net/ipv4/tcp_syn_retries value.

Fixes: a41e8a88b06e ("tcp: better handle TCP_USER_TIMEOUT in SYN_SENT state")
Signed-off-by: Eric Dumazet 
Cc: Yuchung Cheng 
Cc: Marek Majkowski 
Signed-off-by: David S. Miller

tcp: better handle TCP_USER_TIMEOUT in SYN_SENT state

2019-09-27T18:42:24+00:00

Yuchung Cheng and Marek Majkowski independently reported a weird
behavior of TCP_USER_TIMEOUT option when used at connect() time.

When the TCP_USER_TIMEOUT is reached, tcp_write_timeout()
believes the flow should live, and the following condition
in tcp_clamp_rto_to_user_timeout() programs one jiffie timers :

    remaining = icsk->icsk_user_timeout - elapsed;
    if (remaining <= 0)
        return 1; /* user timeout has passed; fire ASAP */

This silly situation ends when the max syn rtx count is reached.

This patch makes sure we honor both TCP_SYNCNT and TCP_USER_TIMEOUT,
avoiding these spurious SYN packets.

Fixes: b701a99e431d ("tcp: Add tcp_clamp_rto_to_user_timeout() helper to improve accuracy")
Signed-off-by: Eric Dumazet 
Reported-by: Yuchung Cheng 
Reported-by: Marek Majkowski 
Cc: Jon Maxwell 
Link: https://marc.info/?l=linux-netdev&m=156940118307949&w=2
Acked-by: Jon Maxwell 
Tested-by: Marek Majkowski 
Signed-off-by: Marek Majkowski 
Acked-by: Yuchung Cheng 
Signed-off-by: David S. Miller

tcp: add new tcp_mtu_probe_floor sysctl

2019-08-09T20:03:30+00:00

The current implementation of TCP MTU probing can considerably
underestimate the MTU on lossy connections allowing the MSS to get down to
48. We have found that in almost all of these cases on our networks these
paths can handle much larger MTUs meaning the connections are being
artificially limited. Even though TCP MTU probing can raise the MSS back up
we have seen this not to be the case causing connections to be "stuck" with
an MSS of 48 when heavy loss is present.

Prior to pushing out this change we could not keep TCP MTU probing enabled
b/c of the above reasons. Now with a reasonble floor set we've had it
enabled for the past 6 months.

The new sysctl will still default to TCP_MIN_SND_MSS (48), but gives
administrators the ability to control the floor of MSS probing.

Signed-off-by: Josh Hunt 
Signed-off-by: Eric Dumazet 
Acked-by: Neal Cardwell 
Signed-off-by: David S. Miller

tcp: enforce tcp_min_snd_mss in tcp_mtu_probing()

2019-06-16T01:47:31+00:00

If mtu probing is enabled tcp_mtu_probing() could very well end up
with a too small MSS.

Use the new sysctl tcp_min_snd_mss to make sure MSS search
is performed in an acceptable range.

CVE-2019-11479 -- tcp mss hardcoded to 48

Signed-off-by: Eric Dumazet 
Reported-by: Jonathan Lemon 
Cc: Jonathan Looney 
Acked-by: Neal Cardwell 
Cc: Yuchung Cheng 
Cc: Tyler Hicks 
Cc: Bruce Curtis 
Signed-off-by: David S. Miller

treewide: Add SPDX license identifier for missed files

2019-05-21T08:50:45+00:00

Add SPDX license identifiers to all files which:

 - Have no license information of any form

 - Have EXPORT_.*_SYMBOL_GPL inside which was used in the
   initial scan/conversion to ignore the file

These files fall under the project license, GPL v2 only. The resulting SPDX
license identifier is:

  GPL-2.0-only

Signed-off-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman

tcp: lower congestion window on Fast Open SYNACK timeout

2019-05-01T15:47:54+00:00

TCP sender would use congestion window of 1 packet on the second SYN
and SYNACK timeout except passive TCP Fast Open. This makes passive
TFO too aggressive and unfair during congestion at handshake. This
patch fixes this issue so TCP (fast open or not, passive or active)
always conforms to the RFC6298.

Note that tcp_enter_loss() is called only once during recurring
timeouts.  This is because during handshake, high_seq and snd_una
are the same so tcp_enter_loss() would incorrect set the undo state
variables multiple times.

Signed-off-by: Yuchung Cheng 
Signed-off-by: Neal Cardwell 
Signed-off-by: Eric Dumazet 
Signed-off-by: David S. Miller

tcp: Refactor pingpong code

2019-01-27T21:29:43+00:00

Instead of using pingpong as a single bit information, we refactor the
code to treat it as a counter. When interactive session is detected,
we set pingpong count to TCP_PINGPONG_THRESH. And when pingpong count
is >= TCP_PINGPONG_THRESH, we consider the session in pingpong mode.

This patch is a pure refactor and sets foundation for the next patch.
This patch itself does not change any pingpong logic.

Signed-off-by: Wei Wang 
Signed-off-by: Yuchung Cheng 
Signed-off-by: Eric Dumazet 
Signed-off-by: David S. Miller