Commit 96f1e69f authored by Nick Mathewson's avatar Nick Mathewson 🥔
Browse files

Implement proposal 275: don't put "published" times in md consensus 

When a new consensus method is negotiated, these values will all get
replaced with "2038-01-01 00:00:00".

This change should be safe because:

  * As of 0.2.9.11 / 0.3.0.7 / 0.3.1.1-alpha, Tor takes no action
    about published_on times in the future.

  * The only remaining parties relying on published_on values are (we
    believe) relays running 0.3.5.x, which rely on the values in a NS
    consensus to see whether their descriptors are out of date.  But
    this patch only changes microdesc consensuses.

  * The latest Tor no longer looks at this field in consensuses.

Why make this change?  In experiments, replacing these values with a
fixed value made the size of compressed consensus diffs much much
smaller.  (Like, by over 50%!)

Implements proposal 275; Implements #40130.
parent 1d2c918d

changes/prop275

0 → 100644
+12 −0
Original line number Diff line number Diff line 
  o Minor features (directory authority):

    - Add a new consensus method in which the "published" times on router

      entries in a microdesc consensus are all set to a meaningless fixed

      date.  Doing this will make the download size for compressed microdesc

      consensus diffs much smaller.

      Part of ticket 40130; implements proposal 275.



  o Minor features (network documents):

    - Clients and relays no longer track the "published on" time declared

      for relays in any consensus documents.  When reporting this time on

      the control port, they instead report a fixed date in the future.

      Part of ticket 40130.

src/feature/dirauth/dirvote.c

+15 −1
Original line number Diff line number Diff line
@@ -2048,7 +2048,6 @@ networkstatus_compute_consensus(smartlist_t *votes, 
      memcpy(rs_out.descriptor_digest, rs->status.descriptor_digest,

             DIGEST_LEN);

      tor_addr_copy(&rs_out.ipv4_addr, &rs->status.ipv4_addr);

      time_t published_on = rs->published_on;

      rs_out.ipv4_dirport = rs->status.ipv4_dirport;

      rs_out.ipv4_orport = rs->status.ipv4_orport;

      tor_addr_copy(&rs_out.ipv6_addr, &alt_orport.addr);
@@ -2056,6 +2055,21 @@ networkstatus_compute_consensus(smartlist_t *votes, 
      rs_out.has_bandwidth = 0;

      rs_out.has_exitsummary = 0;



      time_t published_on = rs->published_on;



      /* Starting with this consensus method, we no longer include a

         meaningful published_on time for microdescriptor consensuses.  This

         makes their diffs smaller and more compressible.



         We need to keep including a meaningful published_on time for NS

         consensuses, however, until 035 relays are all obsolete. (They use

         it for a purpose similar to the current StaleDesc flag.)

      */

      if (consensus_method >= MIN_METHOD_TO_SUPPRESS_MD_PUBLISHED &&

          flavor == FLAV_MICRODESC) {

        published_on = -1;

      }



      if (chosen_name && !naming_conflict) {

        strlcpy(rs_out.nickname, chosen_name, sizeof(rs_out.nickname));

      } else {

src/feature/dirauth/dirvote.h

+7 −1
Original line number Diff line number Diff line
@@ -53,7 +53,7 @@ 
#define MIN_SUPPORTED_CONSENSUS_METHOD 28



/** The highest consensus method that we currently support. */

#define MAX_SUPPORTED_CONSENSUS_METHOD 32

#define MAX_SUPPORTED_CONSENSUS_METHOD 33



/**

 * Lowest consensus method where microdescriptor lines are put in canonical
@@ -74,6 +74,12 @@ 
 */

#define MIN_METHOD_FOR_MIDDLEONLY 32



/**

 * Lowest consensus method for which we suppress the published time in

 * microdescriptor consensuses.

 */

#define MIN_METHOD_TO_SUPPRESS_MD_PUBLISHED 33



/** Default bandwidth to clip unmeasured bandwidths to using method >=

 * MIN_METHOD_TO_CLIP_UNMEASURED_BW.  (This is not a consensus method; do not

 * get confused with the above macros.) */

src/feature/nodelist/fmt_routerstatus.c

+1 −1
Original line number Diff line number Diff line
@@ -58,7 +58,7 @@ routerstatus_format_entry(const routerstatus_t *rs, const char *version, 
  char digest64[BASE64_DIGEST_LEN+1];

  smartlist_t *chunks = smartlist_new();



  if (declared_publish_time != -1) {

  if (declared_publish_time >= 0) {

    format_iso_time(published, declared_publish_time);

  } else if (vrs) {

    format_iso_time(published, vrs->published_on);