[tor-bugs] #21642 [Core Tor/Tor]: Prop275: Eliminate "published" times from microdescriptor consensus

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#21642: Prop275: Eliminate "published" times from microdescriptor consensus
------------------------------------------------+--------------------------
 Reporter:  nickm                               |          Owner:  nickm
     Type:  enhancement                         |         Status:
                                                |  merge_ready
 Priority:  Medium                              |      Milestone:  Tor:
                                                |  0.3.1.x-final
Component:  Core Tor/Tor                        |        Version:
 Severity:  Normal                              |     Resolution:
 Keywords:  TorCoreTeam201703, review-group-17  |  Actual Points:  .5
Parent ID:                                      |         Points:  2
 Reviewer:                                      |        Sponsor:  Sponsor4
------------------------------------------------+--------------------------

Comment (by arma):

 Replying to [comment:16 arma]:
 > So if we do the next step, which would be setting the timestamp to 2037
 or whatever, we will disable this hack. Are we still using the hack much?

 It turns out we have a way to check -- when relays publish a new
 descriptor, they can include a header:
 {{{
     case DIR_PURPOSE_UPLOAD_DIR: {
       const char *why = router_get_descriptor_gen_reason();
 [...]
       if (why) {
         smartlist_add_asprintf(headers, "X-Desc-Gen-Reason: %s\r\n", why);
       }
 }}}

 So I instrumented moria1 like so:
 {{{
 diff --git a/src/or/directory.c b/src/or/directory.c
 index 67c28e1..4eb461f 100644
 --- a/src/or/directory.c
 +++ b/src/or/directory.c
 @@ -4462,6 +4462,12 @@ directory_handle_command_post,(dir_connection_t
 *conn, co
      const char *msg = "[None]";
      uint8_t purpose = authdir_mode_bridge(options) ?
                        ROUTER_PURPOSE_BRIDGE : ROUTER_PURPOSE_GENERAL;
 +    {
 +      char *genreason = http_get_header(headers, "X-Desc-Gen-Reason: ");
 +      log_info(LD_DIRSERV,
 +               "New descriptor post, because: %s",
 +               genreason ? genreason : "not specified");
 +    }
      was_router_added_t r = dirserv_add_multiple_descriptors(body,
 purpose,
                                               conn->base_.address, &msg);
      tor_assert(msg);
 }}}

 Over the course of about 15 minutes, I see:
 {{{
 $ grep "New descriptor post, because:" moria1-info|cut -d: -f5-|sort|uniq
 -c
      24  bandwidth has changed
       5  config change
      10  DirPort found reachable
      88  not listed in consensus
    9017  not specified
      20  ORPort found reachable
       9  rotated onion key
      79  time for new descriptor
      15  version listed in consensus is quite old
 }}}

 So, initial conclusion is "yes, it's still used".

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/21642#comment:22>
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