IPv6-only clients can't fetch microdescriptors on 0.2.8.5-rc

There's a lovely catch-22 when IPv6-only clients try to fetch microdescriptors:

• some fallback directories are on IPv6, and deliver the microdescriptor consensus
• but the microdescriptor consensus doesn't contain any IPv6 addresses
• but it's a consensus, so IPv6-only clients try to use it to find an IPv6 relay, and fail

A solution is to teach IPv6-only clients to get (at least some of) their descriptors from the fallback directories, at least until they have some IPv6 microdescriptors. Perhaps this should happen automatically when the entire consensus fails, but for some reason it doesn't.

I have no idea how we didn't catch this during testing - perhaps there were always cached descriptors? Perhaps we broke falling back to the fallbacks for descriptors?

changed milestone to %Tor: 0.2.8.x-final

added actualpoints::0.5 component::core tor/tor fallbacks ipv6 microdesc milestone::Tor: 0.2.8.x-final parent::20996 points::0.5 priority::high regression resolution::fixed severity::major status::closed type::defect version::tor 0.2.8.2-alpha labels

Please see my branch bug19608 on https://github.com/teor2345/tor.git

It fixes this issue by checking routerstatus reachability based only on the addresses in the routerstatus. (We were checking the node, but this causes issues when there is no node, and it's inaccurate anyway, as the connection address is taken from the routerstatus, not the node.)

I've tested this on an IPv6-only BSD box, and it works with and without bridges, with and without microdescriptors.

This could end up overloading the IPv6 fallbacks if we have lots of IPv6-only clients. I split that issue off into #19610 (moved), and stuck it into 0.3.0.

Trac:
Actualpoints: N/A to 0.5
Keywords: N/A deleted, microdesc, fallbacks added
Status: new to needs_review
Version: N/A to Tor: 0.2.8.2-alpha

I've merged it onto 0.2.8.

Trac:
Resolution: N/A to fixed
Status: needs_review to closed

I just tested 0.2.8.7 and master, and ClientUseIPv4 0 only bootstraps with UseMicrodescriptors 0.

I wonder what went wrong?

Trac:
Status: closed to reopened
Resolution: fixed to N/A
Keywords: N/A deleted, regression added

I can confirm.

Trac:
Priority: Medium to High

At the very least, we should fix this by updating the man page and listing the UseMicrodescriptors 0 workaround. But it would be nice to fix the bug itself.

Closing this in favour of #20996 (moved).

Trac:
Resolution: N/A to duplicate
Status: reopened to closed

This will be fixed when #20996 (moved) is fixed.

Trac:
Parent: N/A to #20996 (moved)
Resolution: duplicate to N/A
Status: closed to reopened

Trac:
Status: reopened to closed
Resolution: N/A to fixed

closed

changed time estimate to 4h

added 4h of time spent

mentioned in issue #19610 (moved)

mentioned in issue #19989 (moved)

mentioned in issue #19991 (moved)

mentioned in issue #20069 (moved)

mentioned in issue #20996 (moved)

moved to tpo/core/tor#19608 (closed)