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Date:      Fri, 27 Jul 2012 00:10:30 +0100
From:      Matthew Seaman <m.seaman@infracaninophile.co.uk>
To:        freebsd-stable@freebsd.org
Subject:   Re: Regression with jails/IPv6/pf
Message-ID:  <5011CE66.4080509@infracaninophile.co.uk>
In-Reply-To: <5011ADE6.7010602@bit0.com>
References:  <5011902C.1070600@infracaninophile.co.uk> <5011ADE6.7010602@bit0.com>

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On 26/07/2012 21:51, Mike Andrews wrote:
> Sounds like what I hit and filed kern/170070 on -- basically a host not=

> being able to talk to itself on IPv6, except on the ::1 address.
>=20
> Workaround: ifconfig lo0 -txcsum6 -rxcsum6
>=20
> or in /etc/rc.conf:
>=20
> ifconfig_lo0=3D"inet 127.0.0.1/8 -txcsum6 -rxcsum6"

Unfortunately that doesn't help.  It's not that traffic is not getting
anywhere: I'm seeing SSH packets going in both directions when trying to
log in, but the handshaking fails because of bad checksums on the
response packets.

If it's not obvious, I'm trying to ssh from seedling to xenophobe, and
this is what the package exchange looks like:

seedling:~:% sudo tcpdump -vvi en1 host xenophobe
tcpdump: listening on en1, link-type EN10MB (Ethernet), capture size
65535 bytes
00:06:14.814804 IP6 (hlim 64, next-header TCP (6) payload length: 44)
seedling.black-earth.co.uk.61608 > xenophobe.infracaninophile.co.uk.ssh:
Flags [S], cksum 0xcc56 (correct), seq 1949604450, win 65535, options
[mss 1440,nop,wscale 2,nop,nop,TS val 648835584 ecr 0,sackOK,eol], length=
 0
00:06:15.814223 IP6 (hlim 64, next-header TCP (6) payload length: 44)
seedling.black-earth.co.uk.61608 > xenophobe.infracaninophile.co.uk.ssh:
Flags [S], cksum 0xcc4d (correct), seq 1949604450, win 65535, options
[mss 1440,nop,wscale 2,nop,nop,TS val 648835593 ecr 0,sackOK,eol], length=
 0
00:06:16.341018 IP6 (flowlabel 0xf3c22, hlim 64, next-header TCP (6)
payload length: 40) xenophobe.infracaninophile.co.uk.ssh >
seedling.black-earth.co.uk.61608: Flags [S.], cksum 0xee83 (incorrect ->
0x7237), seq 2817652559, ack 1949604451, win 65535, options [mss
1440,nop,wscale 9,sackOK,TS val 1898338980 ecr 648835584], length 0
00:06:16.359176 IP6 (flowlabel 0xf3c22, hlim 64, next-header TCP (6)
payload length: 40) xenophobe.infracaninophile.co.uk.ssh >
seedling.black-earth.co.uk.61608: Flags [S.], cksum 0xee7a (incorrect ->
0x722e), seq 2817652559, ack 1949604451, win 65535, options [mss
1440,nop,wscale 9,sackOK,TS val 1898338980 ecr 648835593], length 0
00:06:16.815012 IP6 (hlim 64, next-header TCP (6) payload length: 44)
seedling.black-earth.co.uk.61608 > xenophobe.infracaninophile.co.uk.ssh:
Flags [S], cksum 0xcc43 (correct), seq 1949604450, win 65535, options
[mss 1440,nop,wscale 2,nop,nop,TS val 648835603 ecr 0,sackOK,eol], length=
 0
00:06:17.815463 IP6 (hlim 64, next-header TCP (6) payload length: 44)
seedling.black-earth.co.uk.61608 > xenophobe.infracaninophile.co.uk.ssh:
Flags [S], cksum 0xcc39 (correct), seq 1949604450, win 65535, options
[mss 1440,nop,wscale 2,nop,nop,TS val 648835613 ecr 0,sackOK,eol], length=
 0
00:06:17.826830 IP6 (flowlabel 0xf3c22, hlim 64, next-header TCP (6)
payload length: 40) xenophobe.infracaninophile.co.uk.ssh >
seedling.black-earth.co.uk.61608: Flags [S.], cksum 0xee70 (incorrect ->
0x7224), seq 2817652559, ack 1949604451, win 65535, options [mss
1440,nop,wscale 9,sackOK,TS val 1898338980 ecr 648835603], length 0
00:06:17.827062 IP6 (flowlabel 0xf3c22, hlim 64, next-header TCP (6)
payload length: 40) xenophobe.infracaninophile.co.uk.ssh >
seedling.black-earth.co.uk.61608: Flags [S.], cksum 0xee66 (incorrect ->
0x721a), seq 2817652559, ack 1949604451, win 65535, options [mss
1440,nop,wscale 9,sackOK,TS val 1898338980 ecr 648835613], length 0
00:06:18.816761 IP6 (hlim 64, next-header TCP (6) payload length: 44)
seedling.black-earth.co.uk.61608 > xenophobe.infracaninophile.co.uk.ssh:
Flags [S], cksum 0xcc2f (correct), seq 1949604450, win 65535, options
[mss 1440,nop,wscale 2,nop,nop,TS val 648835623 ecr 0,sackOK,eol], length=
 0
00:06:19.362251 IP6 (hlim 255, next-header ICMPv6 (58) payload length:
32) seedling.black-earth.co.uk > xenophobe.infracaninophile.co.uk:
[icmp6 sum ok] ICMP6, neighbor solicitation, length 32, who has
xenophobe.infracaninophile.co.uk
	  source link-address option (1), length 8 (1): f8:1e:df:da:c0:bb
	    0x0000:  f81e dfda c0bb
00:06:19.526659 IP6 (class 0x06, flowlabel 0xf3c22, hlim 64, next-header
TCP (6) payload length: 40) xenophobe.infracaninophile.co.uk.ssh >
seedling.black-earth.co.uk.61608: Flags [S.], cksum 0xee5c (incorrect ->
0x7210), seq 2817652559, ack 1949604451, win 65535, options [mss
1440,nop,wscale 9,sackOK,TS val 1898338980 ecr 648835623], length 0
00:06:19.817464 IP6 (hlim 64, next-header TCP (6) payload length: 44)
seedling.black-earth.co.uk.61608 > xenophobe.infracaninophile.co.uk.ssh:
Flags [S], cksum 0xcc25 (correct), seq 1949604450, win 65535, options
[mss 1440,nop,wscale 2,nop,nop,TS val 648835633 ecr 0,sackOK,eol], length=
 0

Looks like the checksumming is a bit toast there.

	Cheers,

	Matthew

--=20
Dr Matthew J Seaman MA, D.Phil.                   7 Priory Courtyard
                                                  Flat 3
PGP: http://www.infracaninophile.co.uk/pgpkey     Ramsgate
JID: matthew@infracaninophile.co.uk               Kent, CT11 9PW


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