[tor-bugs] #24404 [Core Tor/Tor]: Propose a relay protover that allows IPv6 extends

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#24404: Propose a relay protover that allows IPv6 extends
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 Reporter:  teor                             |          Owner:  (none)
     Type:  enhancement                      |         Status:  new
 Priority:  Medium                           |      Milestone:  Tor:
                                             |  0.3.3.x-final
Component:  Core Tor/Tor                     |        Version:
 Severity:  Normal                           |     Resolution:
 Keywords:  needs-proposal, ipv6, tor-relay  |  Actual Points:
Parent ID:  #24403                           |         Points:  1
 Reviewer:                                   |        Sponsor:  SponsorV-
                                             |  can
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Comment (by teor):

 Replying to [comment:5 teor]:
 > relays with the latest protover respond to NETINFO cells on existing
 connections by sending a NETINFO cell, at most every N minutes per
 connection (N < 20 minutes, the current reachability warning threshold)
 >
 > Then the fallback becomes:
 > * if there are no relays with the right protover or all relays with the
 right protover have an existing connection to this relay, try these steps
 in order
 >   1. Elicit a NETINFO cell by sending a relay with the right protover a
 NETINFO cell, where this relay is the server side of an existing TLS
 connection over the desired IP version

 These won't work, they don't get a NETINFO for the ORPort address:

 >   2. ~~Elicit a NETINFO cell by sending a relay with the right protover
 a NETINFO cell, where this relay is the client side of an existing TLS
 connection over the desired IP version~~
 >   3. ~~Open a connection to a relay to elicit a NETINFO cell over the
 desired IP version~~

 Instead, we should:
 2. expire 10% of our oldest connections, and optionally 10% of our least-
 used connections (don't do this on authorities)
 3. Retry step 1
 4. If we keep on failing, we are not getting any inbound connections, so
 we're an anomaly: a busy relay that can only make outbound connections.
 (This situation fixes itself: if we give up and drop out of the consensus,
 we're no longer a busy relay, and our reachability checks should work.)

 There will need to be limits so that we publish immediately if a minimum
 number of relays supporting the protover aren't in the consensus.
 And we should make sure we expire a minimum number of connections.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/24404#comment:6>
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