[tor-bugs] #33817 [Core Tor/Tor]: Perform all IPv4 and IPv6 extend checks in one place

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#33817: Perform all IPv4 and IPv6 extend checks in one place
-------------------------------------------------+-------------------------
 Reporter:  teor                                 |          Owner:  teor
     Type:  task                                 |         Status:
                                                 |  needs_revision
 Priority:  Medium                               |      Milestone:  Tor:
                                                 |  0.4.4.x-final
Component:  Core Tor/Tor                         |        Version:
 Severity:  Normal                               |     Resolution:
 Keywords:  ipv6, prop311, technical-debt-       |  Actual Points:
  partial                                        |
Parent ID:  #33220                               |         Points:  1
 Reviewer:                                       |        Sponsor:
                                                 |  Sponsor55-must
-------------------------------------------------+-------------------------

Comment (by teor):

 Replying to [ticket:33817 teor]:
 > Currently, tor checks that extend cells have IPv4 addresses in:
 > [ ] some functions in circuitbuild_relay.c (a new file introduced by
 #33633)

 I am most of the way through this change:
 * tor considers IPv6-only extend requests valid
 * tor checks IPv4 and IPv6 addresses before extending
 * tor re-uses existing IPv4 and IPv6 connections for extends

 I still need to initiate new IPv6 connections in response to extend
 requests.

 Here is the draft PR, with #33899, #33901, and #33917:
 * don't merge: ​https://github.com/torproject/tor/pull/1864

 The PR also has #33918, but the next push will drop that commit - we can
 review and merge it separately.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/33817#comment:7>
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