1056599 - Firefox randomly using IPv6 via 6to4 relay on IPv4 connected client & servers

Status: RESOLVED INCOMPLETE

(Core :: Networking, defect, P3)

Description

[Simon]

User Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:34.0) Gecko/20100101 Firefox/34.0 (Beta/Release)
Build ID: 20140820030202

Steps to reproduce:

Browse a dual-stack connected website, any Google/Facebook property will do, with a client that has a native IPv4 connectivity only and 6to4 enabled (default in Windows, might need an ISP that runs a relay, though).
Observe in TCPView.


Actual results:

Firefox issues IPv4 and/or v6 connections for the different hosts involved, seemingly at random.


Expected results:

Firefox should prefer the faster, native v4 connection and only fall-back to 6to4 for hosts that are reachable exclusively via v6.

I haven't seen this before today's nightly and it's the first time I show up as logged in from a (2002: prefixed) v6 address on GMail, I'd suspect something to do with https://bugzilla.mozilla.org/show_bug.cgi?id=820391 ?

Comment 1

[Patrick McManus [:mcmanus]]

this is pretty interesting - thanks.

I don't know that I agree with you about the preference issues (I don't know that I disagree with you either :)), but the dns change certainly wasn't expected to have that impact.

Comment 2

[Firefox Bug Husbandry Bot]

Bulk change to priority: https://bugzilla.mozilla.org/show_bug.cgi?id=1399258

Comment 3

[Firefox Bug Husbandry Bot]

Bulk change to priority: https://bugzilla.mozilla.org/show_bug.cgi?id=1399258

Comment 5

[BugBot [:suhaib / :marco/ :calixte]]

Clear a needinfo that is pending on an inactive user.

Inactive users most likely will not respond; if the missing information is essential and cannot be collected another way, the bug maybe should be closed as INCOMPLETE.

For more information, please visit BugBot documentation.

Comment 6

[Lars Eggert [:lars]]

FWIW, on a dual-stacked host I still see Firefox retrieving objects using a seemingly random mix of IPv4 and IPv6 for dual-stacked servers. Chrome seems to always pick one address family for all retrievals.