#25295 closed defect (wontfix)

Torsocks only accepts IPv4 replies but Tor prefers IPv6Automap by default

Reported by: fuzzyTew Owned by: dgoulet
Priority: Medium Milestone: Tor: 0.3.4.x-final
Component: Core Tor/Tor Version: Tor:
Severity: Major Keywords: tor torsocks ipv6 fast-fix
Cc: Actual Points:
Parent ID: Points:
Reviewer: mikeperry Sponsor:


At the moment, MapAddress .exit entries won't resolve through torsocks for me, because tor gives an IPv6 reply, and torsocks is only designed for IPv4 replies.

Torsocks gives the characteristic error [socks5] Resolve destination buffer too small (in socks5_recv_resolve_reply() at socks5.c:681) when tor replies with an IPv6 address, which it does every single time for mapaddress .exit entries for me.

Child Tickets

Attachments (1)

nopreferipv6automap.patch (2.9 KB) - added by fuzzyTew 22 months ago.
Patch to Change IPv6Automap Defaults for Compatibility with Torsocks

Download all attachments as: .zip

Change History (7)

Changed 22 months ago by fuzzyTew

Attachment: nopreferipv6automap.patch added

Patch to Change IPv6Automap Defaults for Compatibility with Torsocks

comment:1 Changed 20 months ago by dgoulet

Component: Core Tor/TorsocksCore Tor/Tor
Keywords: fast-fix added
Milestone: Tor: 0.3.4.x-final
Status: newneeds_review

comment:2 Changed 20 months ago by dgoulet

Reviewer: mikeperry

comment:3 Changed 20 months ago by mikeperry

This looks sane to me as far as code goes. It also seems odd that Tor chose different defaults for PreferIPv6 and this option. It seems like we should be turning on PreferIPv6 because it does not introduce compatibility issues, where as this option does.. yet we chose the reverse...

I would like dgoulet to confirm that fixing this torsocks compatibility issue by changing this default in Tor makes sense. After that, is merge_ready IMO.

comment:4 Changed 20 months ago by mikeperry

Status: needs_reviewneeds_information

I guess I'll set this to needs_information for dgoulet's input.

comment:5 Changed 19 months ago by nickm

IPv6 automap is indeed much safer than IPv4: even with 24 bits of IPv4 automap space (eg, mapping into 10/8 or 127/8), it's still IMO too easy for a webpage to try guessing a bunch of addresses in the automapped range to see whether any of them are already mapped.

I'd rather not make this change in Tor.

comment:6 Changed 19 months ago by dgoulet

Resolution: wontfix
Status: needs_informationclosed


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