[tor-bugs] #31851 [Core Tor/Tor]: Allow Tor to be compiled without support for relay mode

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#31851: Allow Tor to be compiled without support for relay mode
-------------------------------------------------+-------------------------
 Reporter:  teor                                 |          Owner:  teor
     Type:  task                                 |         Status:  new
 Priority:  Medium                               |      Milestone:  Tor:
                                                 |  0.4.3.x-final
Component:  Core Tor/Tor                         |        Version:
 Severity:  Normal                               |     Resolution:
 Keywords:  tor-design, network-team-roadmap-    |  Actual Points:  0.2
  october                                        |
Parent ID:                                       |         Points:  5
 Reviewer:  nickm                                |        Sponsor:
                                                 |  Sponsor31-can
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Comment (by nickm):

 Here's my attempt to list the parts of the relay code that could be
 modularized, in rough order of operation.  Within the phases, things could
 be done in any order.  I've tried to handle things on a roughly "top down"
 basis, removing each thing before removing the things that it depends on.

 PHASE 0.

 1. The relay_periodic.c entry point.
 2. The relay_sys.c entry point.

 PHASE 1.

 1. Acting as a directory cache.
 2. Responding to CREATE and EXTEND cells
 3. Responding to BEGIN cells
 4. Listening for OR connections
 5. Accounting
 6. Generating and uploading descriptors.
 7. Self-testing
 8. Responding to introduce/establish_intro/establish_rend cells.

 PHASE 2.

 1. Server-side DNS
 2. Key management.
 3. Statistics backend code.
 4. TLS responder code.

 PHASE 3.

 1. Whatever is left.

 At each stage, we should work to minimize layer-violations: there should
 generally not be calls from src/core/ into relay-specific code, and we
 should plan to refactor as needed to minimize them.  We can reduce layer
 violations in parallel with the above.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/31851#comment:10>
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