Re: kern/52554: IPv6 connections not routing to default gateway

[Roy Bixler <rcbixler%nyx.net@localhost>]

On Thu, Sep 28, 2017 at 09:55:01PM +0000, Ryota Ozaki wrote:
>  Oh sorry, I suppose to see packets of telnet by tcpdump on br0 and eth0
>  of Linux. I suspected that a SYN packet is broken and filtered out on the
>  interfaces for some reasons. And also we may see a SYNACK packet on
>  the interfaces if a SYN packet reaches the server.

I wasn't thinking the same way, since I have had success with IPv6 on
guests running different operating systems, like NetBSD 7.1.  I also
have success with IPv6 on NetBSD 8 when connecting to other hosts on
the same LAN.  That only changes when I try to connect outside the
LAN.

I decided to try something different, which is an "ssh" connection
with IPv6 to a host outside of the LAN.  I run tcpdump locally and on
the remote host.  What appears to happen is that the NetBSD 8 host
sends its SYN packets, the remote host receives them and tries to
reply, but NetBSD 8 never sees the replies.

Here's the trace from NetBSD 8 (times in UTC):

13:27:00.789450 IP6 2620:105:c000:3:58a4:a8c:71ce:44f9.65532 >
2620:105:c002:2:5054:ff:feaa:dbd1.ssh: Flags [S], seq 4071621244, win
32768, options [mss 1440,nop,wscale 3,sackOK,TS val 1 ecr 0], length 0
13:27:06.788199 IP6 2620:105:c000:3:58a4:a8c:71ce:44f9.65532 >
2620:105:c002:2:5054:ff:feaa:dbd1.ssh: Flags [S], seq 4071621244, win
32768, options [mss 1440,nop,wscale 3,sackOK,TS val 13 ecr 0], length
0
13:27:18.794959 IP6 2620:105:c000:3:58a4:a8c:71ce:44f9.65532 >
2620:105:c002:2:5054:ff:feaa:dbd1.ssh: Flags [S], seq 4071621244, win
32768, options [mss 1440,nop,wscale 3,sackOK,TS val 37 ecr 0], length
0
13:27:42.808871 IP6 2620:105:c000:3:58a4:a8c:71ce:44f9.65532 >
2620:105:c002:2:5054:ff:feaa:dbd1.ssh: Flags [S], seq 4071621244, win
32768, options [mss 1440,nop,wscale 3,sackOK,TS val 85 ecr 0], length
0

and from the remote host (times local ~ 4 sec. fast):

08:27:04.693607 IP6 2620:105:c000:3:58a4:a8c:71ce:44f9.65532 >
2620:105:c002:2:5054:ff:feaa:dbd1.ssh: Flags [S], seq 4071621244, win
32768, options [mss 1440,nop,wscale 3,sackOK,TS val 1 ecr 0], length 0
08:27:04.693706 IP6 2620:105:c002:2:5054:ff:feaa:dbd1.ssh >
2620:105:c000:3:58a4:a8c:71ce:44f9.65532: Flags [S.], seq 3269583768,
ack 4071621245, win 28560, options [mss 1440,sackOK,TS val 577917728
ecr 1,nop,wscale 7], length 0
08:27:05.692834 IP6 2620:105:c002:2:5054:ff:feaa:dbd1.ssh >
2620:105:c000:3:58a4:a8c:71ce:44f9.65532: Flags [S.], seq 3269583768,
ack 4071621245, win 28560, options [mss 1440,sackOK,TS val 577918728
ecr 1,nop,wscale 7], length 0
08:27:07.692864 IP6 2620:105:c002:2:5054:ff:feaa:dbd1.ssh >
2620:105:c000:3:58a4:a8c:71ce:44f9.65532: Flags [S.], seq 3269583768,
ack 4071621245, win 28560, options [mss 1440,sackOK,TS val 577920728
ecr 1,nop,wscale 7], length 0
08:27:10.692697 IP6 2620:105:c000:3:58a4:a8c:71ce:44f9.65532 >
2620:105:c002:2:5054:ff:feaa:dbd1.ssh: Flags [S], seq 4071621244, win
32768, options [mss 1440,nop,wscale 3,sackOK,TS val 13 ecr 0], length
0
08:27:10.692760 IP6 2620:105:c002:2:5054:ff:feaa:dbd1.ssh >
2620:105:c000:3:58a4:a8c:71ce:44f9.65532: Flags [S.], seq 3269583768,
ack 4071621245, win 28560, options [mss 1440,sackOK,TS val 577923727
ecr 1,nop,wscale 7], length 0
08:27:14.692847 IP6 2620:105:c002:2:5054:ff:feaa:dbd1.ssh >
2620:105:c000:3:58a4:a8c:71ce:44f9.65532: Flags [S.], seq 3269583768,
ack 4071621245, win 28560, options [mss 1440,sackOK,TS val 577927728
ecr 1,nop,wscale 7], length 0
08:27:22.692861 IP6 2620:105:c002:2:5054:ff:feaa:dbd1.ssh >
2620:105:c000:3:58a4:a8c:71ce:44f9.65532: Flags [S.], seq 3269583768,
ack 4071621245, win 28560, options [mss 1440,sackOK,TS val 577935728
ecr 1,nop,wscale 7], length 0
08:27:22.700595 IP6 2620:105:c000:3:58a4:a8c:71ce:44f9.65532 >
2620:105:c002:2:5054:ff:feaa:dbd1.ssh: Flags [S], seq 4071621244, win
32768, options [mss 1440,nop,wscale 3,sackOK,TS val 37 ecr 0], length
0
08:27:22.700638 IP6 2620:105:c002:2:5054:ff:feaa:dbd1.ssh >
2620:105:c000:3:58a4:a8c:71ce:44f9.65532: Flags [S.], seq 3269583768,
ack 4071621245, win 28560, options [mss 1440,sackOK,TS val 577935735
ecr 1,nop,wscale 7], length 0
08:27:38.699848 IP6 2620:105:c002:2:5054:ff:feaa:dbd1.ssh >
2620:105:c000:3:58a4:a8c:71ce:44f9.65532: Flags [S.], seq 3269583768,
ack 4071621245, win 28560, options [mss 1440,sackOK,TS val 577951735
ecr 1,nop,wscale 7], length 0
08:27:46.716395 IP6 2620:105:c000:3:58a4:a8c:71ce:44f9.65532 >
2620:105:c002:2:5054:ff:feaa:dbd1.ssh: Flags [S], seq 4071621244, win
32768, options [mss 1440,nop,wscale 3,sackOK,TS val 85 ecr 0], length
0
08:27:46.716437 IP6 2620:105:c002:2:5054:ff:feaa:dbd1.ssh >
2620:105:c000:3:58a4:a8c:71ce:44f9.65532: Flags [S.], seq 3269583768,
ack 4071621245, win 28560, options [mss 1440,sackOK,TS val 577959751
ecr 1,nop,wscale 7], length 0


-- 
Roy Bixler <rcbixler%nyx.net@localhost>
"The fundamental principle of science, the definition almost, is this: the
sole test of the validity of any idea is experiment."
-- Richard P. Feynman