netdev - Re: Unexpected tcpv6 connection resets since linux 4.4

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Date:	Mon, 7 Mar 2016 15:58:47 -0800
From:	Cong Wang <xiyou.wangcong@...il.com>
To:	Andreas Messer <andi@...telmap.de>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: Unexpected tcpv6 connection resets since linux 4.4

Cc'ing netdev

On Sun, Mar 6, 2016 at 7:10 AM, Andreas Messer <andi@...telmap.de> wrote:
> Hi there,
>
> i have updated two of my machines in the last weeks to linux 4.4.1 and linux
> 4.4.3. It seems that since then i get unexpected TCPv6 connection resets when
> connecting to these machines remotely. The issue occurs with sshd and with a
> http service. /etc/hosts.deny and /etc/hosts.allow are empty on both server
> machines. I'm not so in IPv6 and have no idea whats going on. Please find
> attached a network trace from one of the machines when connecting with ssh (on
> port 23 for debugging).

Sounds like the problem fixed by the following commit:

commit 9cf7490360bf2c46a16b7525f899e4970c5fc144
Author: Eric Dumazet <edumazet@...gle.com>
Date:   Tue Feb 2 19:31:12 2016 -0800

    tcp: do not drop syn_recv on all icmp reports


Thanks.


>
> Redirects should be accepted according to settings:
>
> root@...ana:/proc/sys/net/ipv6# cat conf/wlan0/forwarding
> 0
> root@...ana:/proc/sys/net/ipv6# cat conf/wlan0/accept_redirects
> 1
> root@...ana:/proc/sys/net/ipv6# uname -a
> Linux banana 4.4.1-banana #3 SMP Wed Feb 17 23:03:38 CET 2016 x86_64 GNU/Linux
>
> Is there some new network settings or features? My network consists of an
> ethernet/wlan router where subnet of wlan and ethernet are identical.  (forced
> by the router, but was never a problem before). The problem occurs when
> connecting from ethernet machine to wlan machine and when connecting from wlan
> machine to wlan machine. At the moment its not possible to establish a
> connection with these machines using IPv6.
>
> Thanks for help!
>
> Cheers
> Andreas