Date: Sat, 16 Apr 2022 00:05:49 +0200 From: tuexen@freebsd.org To: Florian Smeets <flo@smeets.xyz> Cc: Gleb Smirnoff <glebius@freebsd.org>, current@freebsd.org Subject: Re: IPv6 TCP: first two SYN packets to local v6 unicast addresses ignored Message-ID: <46089B86-EF4C-4E4A-9240-51FEACE2BE3C@freebsd.org> In-Reply-To: <9679642b-5de6-28be-a64b-07375c3efeba@smeets.xyz> References: <131c363a-7b7d-a106-5b8a-6838e7a66567@smeets.xyz> <E0584477-0F2E-454D-871C-368F14A9AF1D@freebsd.org> <9679642b-5de6-28be-a64b-07375c3efeba@smeets.xyz>
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> On 15. Apr 2022, at 23:39, Florian Smeets <flo@smeets.xyz> wrote: >=20 > On 15.04.22 21:24, tuexen@freebsd.org wrote: >>> On 15. Apr 2022, at 20:20, Florian Smeets <flo@smeets.xyz> wrote: >>>=20 >>>=20 >>> Hi, >>>=20 >>> there seems to be an issue with local IPv6 TCP connections on main. = I have been seeing this for a couple of months at least. pkg upgr on my = webserver hosting the pkg repo is very slow, all other hosts can connect = to the pkg repo just fine. So IPv6 connections from external hosts are = not affected. >>>=20 >>> I thought I must have misconfigured something, as my setup is a bit = weird. Yesterday I noticed the same issue on a different host, turns out = all my 14.0 hosts seem to be affected, cognet@ could also reproduce it = on one of his systems. >>>=20 >>> The service/software used does not seem to matter, I tried with port = 22, 25, 80 and 443. >>>=20 >>> ICMP and UDP don't seem to be affected. ping6 gets replies = immediately. And UDP connections with nc -l -u / nc -u don't have any = delay, sent data is received immediately. >>>=20 >>> Testing local TCP connections show this: >>>=20 >>> flo@rp64:~ $ ifconfig dwc0|grep 2003 >>> inet6 2003:cf:df49:c97:4c59:ebff:fec1:463d prefixlen 64 autoconf >>> flo@rp64:~ $ nc -v 2003:cf:df49:c97:4c59:ebff:fec1:463d 22 >>> [3 second delay here] >>> Connection to 2003:cf:df49:c97:4c59:ebff:fec1:463d 22 port [tcp/ssh] = succeeded! >>> SSH-2.0-OpenSSH_8.9 FreeBSD-20220413 >>>=20 >=20 >>>=20 >>> I need help debugging this, I don't know how to analyze this = further. I will start bisecting this, but I thought maybe someone has an = idea. >> Hi Florian, >> I can reproduce this locally, will try to figure out what is going = on. If you can bisect it, it would be great. >=20 > Found the culprit 1817be481b8703ae86730b151a6f49cc3022930f. And indeed = toggling net.inet6.ip6.source_address_validation makes the issue go away = on latest main. Cool, thanks for providing the information. However, I don't understand = why results in dropping the first two SYN segments (this should not = happen) and why the third is accepted (they should all treated the same). Best regards Michael >=20 > Florian > <OpenPGP_0xEF5BA4DCD5A9F3C0.asc>
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