IPv6-only clients fetch microdescriptors from a small number of IPv6 fallbacks

When an IPv6-only client bootstraps using microdescriptors (legacy/trac#19608 (moved)), it fetches the microdescriptor consensus from an IPv6 fallback, but the microdescriptor consensus has no IPv6 addresses.

So it falls back to the fallback directories, fetching ~7500/500 = 15 sets of descriptors from 15 of the 25 IPv6 fallbacks.

We should improve this behaviour somehow, to avoid overloading the fallbacks. One simple way of doing this is selecting 200 fallbacks for 0.2.9 in legacy/trac#18828 (moved).

It's worth noting that this extra load only happens on bootstrap, when there are no cached microdescriptors. If an IPv6-only client has any IPv6 microdescriptors that match the current consensus, it will use those relays instead.

changed milestone to %Tor: 0.3.3.x-final in legacy/trac

added component::core tor/tor in Legacy / Trac fallbacks in Legacy / Trac ipv6 in Legacy / Trac microdesc in Legacy / Trac milestone::Tor: 0.3.3.x-final in Legacy / Trac network-health in Legacy / Trac owner::teor in Legacy / Trac parent::23827 in Legacy / Trac points::1 in Legacy / Trac priority::medium in Legacy / Trac resolution::fixed in Legacy / Trac review-group-27 in Legacy / Trac severity::normal in Legacy / Trac status::closed in Legacy / Trac tor-client in Legacy / Trac type::defect in Legacy / Trac user-enumeration in Legacy / Trac version::tor 0.2.8.4-rc in Legacy / Trac labels

Trac:
Milestone: N/A to Tor: 0.3.0.x-final

One way of fixing this issue is to make IPv6-only clients use the regular consensus.

legacy/trac#19989 (moved) makes this worse is irrelevant - tor clients won't fetch microdescriptors from a single Exit as their EntryNode, but they work fine with two.

Triaged out on December 2016 from 030 to 031.

Trac:
Milestone: Tor: 0.3.0.x-final to Tor: 0.3.1.x-final
Keywords: N/A deleted, triage-out-030-201612 added

legacy/trac#19608 (moved) was fixed in 0.3.0.2-alpha, and we mitigated this issue by selecting 53 IPv6 fallbacks in legacy/trac#18828 (moved). We should continue to choose 200+ fallbacks, and encourage relay operators to enable their IPv6 ORPorts.

This will not be an issue until clients use IPv6 by default (legacy/trac#17217 (moved)).

Trac:
Parent: N/A to legacy/trac#17217 (moved)
Milestone: Tor: 0.3.1.x-final to Tor: unspecified

Trac:
Summary: IPv6-only clients fetch microdescriptors from 15/25 IPv6 fallbacks to IPv6-only clients fetch microdescriptors from a small number of IPv6 fallbacks

Trac:
Keywords: triage-out-030-201612 deleted, N/A added

Trac:
Keywords: N/A deleted, tor-client network-health user-enumeration added

This can be closed (and the IPv6-only bootstrasp workaround code removed) once the consensus method that adds IPv6 addresses to the microdesc consensus (legacy/trac#23826 (moved)) is supported by all directory authorities.

Trac:
Milestone: Tor: unspecified to Tor: 0.3.5.x-final

I think we should just close this when legacy/trac#20916 (moved) closes.

Trac:
Milestone: Tor: 0.3.5.x-final to Tor: 0.3.3.x-final
Parent: legacy/trac#17217 (moved) to legacy/trac#20916 (moved)

These are all mine

Trac:
Status: new to assigned
Owner: N/A to teor

Trac:
Status: assigned to new

legacy/trac#23827 (moved) has a branch which fixes this.

Trac:
Parent: legacy/trac#20916 (moved) to legacy/trac#23827 (moved)
Status: new to needs_review

Trac:
Keywords: tor-client network-health user-enumeration deleted, tor-client, user-enumeration, review-group-27, network-health added

This is part of legacy/trac#23827 (moved) - we need to make sure IPv6-only clients don't use fallbacks to fetch microdescs when consensus method 27 is in use. The relevant commit is 4ea838030a "Stop waiting for microdescs if the consensus supports IPv6 ORPorts".

Edit: be more specific about IPv6-only clients

Let's just call this implemented by the parent ticket.

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

closed

changed time estimate to 8h

moved from legacy/trac#19610 (moved)

added Bug label and removed 1 deleted label

added Client Fallback Directories IPv6 + 1 deleted label and removed 1 deleted label

added Network health label and removed 1 deleted label