Google filtering ICMPv6 type 2?

[Mark Kamichoff]

Hi - 

I noticed today that HTTP requests to ipv6.google.com (and
www.google.com with Google-over-IPv6) seemed to be unusually laggy and
frequently timing out.  I looked a little deeper and saw that Google may
be inadvertently dropping ICMPv6 type 2 (packet too big) messages.  I'm
seeing things like this for TCP packets that are attempting to enter a
tunnel (MTU 1280) I have setup between me and a box of mine with native
IPv6 connectivity:

22:21:44.513137 IP6 2001:4860:800e::69.80 >
2001:48c8:1:105:219:d1ff:fe21:d70d.49530: . 1:1429(1428) ack 119 win 90
<nop,nop,timestamp 1528748730 1102342799>
22:21:44.513197 IP6 2001:48c8:1:2::2 > 2001:4860:800e::69: ICMP6, packet
too big, mtu 1280, length 1240
22:21:44.513263 IP6 2001:4860:800e::69.80 >
2001:48c8:1:105:219:d1ff:fe21:d70d.49530: . 1429:2857(1428) ack 119 win
90 <nop,nop,timestamp 1528748730 1102342799>
22:21:44.513298 IP6 2001:48c8:1:2::2 > 2001:4860:800e::69: ICMP6, packet
too big, mtu 1280, length 1240
22:21:44.513388 IP6 2001:4860:800e::69.80 >
2001:48c8:1:105:219:d1ff:fe21:d70d.49530: P 2857:4280(1423) ack 119 win
90 <nop,nop,timestamp 1528748730 1102342799>

Sorry if that's hard to read, the full packet capture is here:

http://www.prolixium.com/files/mynews/googleipv6.cap.txt

I've tested this from the above setup (in NYC) and from an HE tunnel to
Ashburn, VA.  Both experience similar issues.  However, I did another
test from a friend's box who has an HE tunnel to Chicago, IL, and didn't
see a problem.

Anyone else seeing this?  Perhaps Google put an erroneous filter on some
of their peering routers, but not others?

Hopefully it'll get yanked.  I'd hate to go back to IPv4 for searching
the web!

- Mark

-- 
Mark Kamichoff
prox at prolixium.com
http://www.prolixium.com/