netdev - Re: Fw: [Bug 194723] connect() to localhost stalls after 4.9 -> 4.10 upgrade

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Date:   Wed, 15 Mar 2017 14:40:34 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Stephen Hemminger <stephen@...workplumber.org>
Cc:     netdev@...r.kernel.org
Subject: Re: Fw: [Bug 194723] connect() to localhost stalls after 4.9 ->
 4.10 upgrade

On Wed, 2017-03-15 at 13:36 -0700, Stephen Hemminger wrote:
> 
> Begin forwarded message:
> 
> Date: Wed, 15 Mar 2017 19:41:59 +0000
> From: bugzilla-daemon@...zilla.kernel.org
> To: stephen@...workplumber.org
> Subject: [Bug 194723] connect() to localhost stalls after 4.9 -> 4.10 upgrade
> 
> 
> https://bugzilla.kernel.org/show_bug.cgi?id=194723
> 
> --- Comment #15 from Lutz Vieweg (lvml@....de) ---
> At last, bisecting converged:
> 
> git bisect start
> # bad: [c470abd4fde40ea6a0846a2beab642a578c0b8cd] Linux 4.10
> git bisect bad c470abd4fde40ea6a0846a2beab642a578c0b8cd
> # good: [69973b830859bc6529a7a0468ba0d80ee5117826] Linux 4.9
> git bisect good 69973b830859bc6529a7a0468ba0d80ee5117826
> # bad: [f4000cd99750065d5177555c0a805c97174d1b9f] Merge tag 'arm64-upstream' of
> git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux
> git bisect bad f4000cd99750065d5177555c0a805c97174d1b9f
> # bad: [7079efc9d3e7f1f7cdd34082ec58209026315057] Merge tag 'fbdev-4.10' of
> git://git.kernel.org/pub/scm/linux/kernel/git/tomba/linux
> git bisect bad 7079efc9d3e7f1f7cdd34082ec58209026315057
> # bad: [669bb4c58c3091cd54650e37c5f4e345dd12c564] Merge branch 'for-linus' of
> git://git.kernel.org/pub/scm/linux/kernel/git/egtvedt/linux-avr32
> git bisect bad 669bb4c58c3091cd54650e37c5f4e345dd12c564
> # good: [7a8bca043cf1bb0433aa43d008b6c4de6c07d6a2] Merge branch 'sfc-tso-v2'
> git bisect good 7a8bca043cf1bb0433aa43d008b6c4de6c07d6a2
> # bad: [4f4f907a6729ae9e132810711c3a05e48311a948] Merge branch 'mvneta-64bit'
> git bisect bad 4f4f907a6729ae9e132810711c3a05e48311a948
> # good: [33f8a0458b2ce4546b681c5fae04427e3077a543] Merge tag
> 'wireless-drivers-next-for-davem-2016-11-25' of
> git://git.kernel.org/pub/scm/linux/kernel/git/kvalo/wireless-drivers-next
> git bisect good 33f8a0458b2ce4546b681c5fae04427e3077a543
> # good: [80439a1704e811697ee01fd09dd95dd10790bc93] qede: Remove 'num_tc'.
> git bisect good 80439a1704e811697ee01fd09dd95dd10790bc93
> # good: [5067b6020770ef7c8102f47079c9e577d175ef2c] net/mlx5e: Remove flow encap
> entry in the correct place
> git bisect good 5067b6020770ef7c8102f47079c9e577d175ef2c
> # bad: [7091d8c7055d7310339435ae3af2fb490a92524d] net/sched: cls_flower: Add
> offload support using egress Hardware device
> git bisect bad 7091d8c7055d7310339435ae3af2fb490a92524d
> # good: [b14945ac3efdf5217182a344b037f96d6b0afae1] net: atarilance: use %8ph
> for printing hex string
> git bisect good b14945ac3efdf5217182a344b037f96d6b0afae1
> # bad: [25429d7b7dca01dc4f17205de023a30ca09390d0] tcp: allow to turn tcp
> timestamp randomization off
> git bisect bad 25429d7b7dca01dc4f17205de023a30ca09390d0
> # good: [1d6cff4fca4366d0529dbce170e0f33cfe213790] qed: Add iSCSI out of order
> packet handling.
> git bisect good 1d6cff4fca4366d0529dbce170e0f33cfe213790
> # bad: [95a22caee396cef0bb2ca8fafdd82966a49367bb] tcp: randomize tcp timestamp
> offsets for each connection
> git bisect bad 95a22caee396cef0bb2ca8fafdd82966a49367bb
> 
> 
> So the culprit seems to be this change: 
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=95a22caee396cef0bb2ca8fafdd82966a49367bb
> 
> "tcp: randomize tcp timestamp offsets for each connection
> jiffies based timestamps allow for easy inference of number of devices
> behind NAT translators and also makes tracking of hosts simpler.
> 
> commit ceaa1fef65a7c2e ("tcp: adding a per-socket timestamp offset")
> added the main infrastructure that is needed for per-connection ts
> randomization, in particular writing/reading the on-wire tcp header
> format takes the offset into account so rest of stack can use normal
> tcp_time_stamp (jiffies).
> 
> So only two items are left:
>  - add a tsoffset for request sockets
>  - extend the tcp isn generator to also return another 32bit number
>    in addition to the ISN.
> 
> Re-use of ISN generator also means timestamps are still monotonically
> increasing for same connection quadruple, i.e. PAWS will still work.
> 
> Includes fixes from Eric Dumazet.
> 
> Signed-off-by: Florian Westphal <fw@...len.de>
> Acked-by: Eric Dumazet <edumazet@...gle.com>
> Acked-by: Yuchung Cheng <ycheng@...gle.com>
> Signed-off-by: David S. Miller <davem@...emloft.net>
> "
> 
> I will try to attract some attention from above mentioned people.
> 

Finally time to get rid of buggy tw_recycle, that apparently some
distros set to one.