Have directory authorities vote on IPv6 OR ports according to the spec

Define new new consensus method 14 adding "a" lines to vote and
consensus documents.

From proposal 186:

  As with other data in the vote derived from the descriptor, the
  consensus will include whichever set of "a" lines are given by the
  most authorities who voted for the descriptor digest that will be
  used for the router.

This patch implements this.

1 files changed, 63 insertions, 3 deletions

diff --git a/src/or/dirvote.c b/src/or/dirvote.c
index b3de90b5c..9056cf592 100644
--- a/src/or/dirvote.c
+++ b/src/or/dirvote.c
@@ -54,7 +54,7 @@ static int dirvote_publish_consensus(void);
 static char *make_consensus_method_list(int low, int high, const char *sep);
 
 /** The highest consensus method that we currently support. */
-#define MAX_SUPPORTED_CONSENSUS_METHOD 13
+#define MAX_SUPPORTED_CONSENSUS_METHOD 14
 
 /** Lowest consensus method that contains a 'directory-footer' marker */
 #define MIN_METHOD_FOR_FOOTER 9
@@ -76,6 +76,9 @@ static char *make_consensus_method_list(int low, int high, const char *sep);
  * with no microdesc. */
 #define MIN_METHOD_FOR_MANDATORY_MICRODESC 13
 
+/** Lowest consensus method that contains "a" lines. */
+#define MIN_METHOD_FOR_A_LINES 14
+
 /* =====
  * Voting
  * =====*/
@@ -430,6 +433,21 @@ _compare_vote_rs(const void **_a, const void **_b)
   return compare_vote_rs(a,b);
 }
 
+/** Helper for sorting OR ports. */
+static int
+_compare_orports(const void **_a, const void **_b)
+{
+  const tor_addr_port_t *a = *_a, *b = *_b;
+  int r;
+
+  if ((r = tor_addr_compare(&a->addr, &b->addr, CMP_EXACT)))
+    return r;
+  if ((r = (((int) b->port) - ((int) a->port))))
+    return r;
+
+  return 0;
+}
+
 /** Given a list of vote_routerstatus_t, all for the same router identity,
  * return whichever is most frequent, breaking ties in favor of more
  * recently published vote_routerstatus_t and in case of ties there,
@@ -437,7 +455,8 @@ _compare_vote_rs(const void **_a, const void **_b)
  */
 static vote_routerstatus_t *
 compute_routerstatus_consensus(smartlist_t *votes, int consensus_method,
-                               char *microdesc_digest256_out)
+                               char *microdesc_digest256_out,
+                               tor_addr_port_t *best_alt_orport_out)
 {
   vote_routerstatus_t *most = NULL, *cur = NULL;
   int most_n = 0, cur_n = 0;
@@ -473,6 +492,42 @@ compute_routerstatus_consensus(smartlist_t *votes, int consensus_method,
 
   tor_assert(most);
 
+  /* If we're producing "a" lines, vote on potential alternative (sets
+   * of) OR port(s) in the winning routerstatuses.
+   *
+   * XXX prop186 There's at most one alternative OR port (_the_ IPv6
+   * port) for now. */
+  if (consensus_method >= MIN_METHOD_FOR_A_LINES && best_alt_orport_out) {
+    smartlist_t *alt_orports = smartlist_new();
+    const tor_addr_port_t *most_alt_orport = NULL;
+
+    SMARTLIST_FOREACH_BEGIN(votes, vote_routerstatus_t *, rs) {
+      if (compare_vote_rs(most, rs) == 0 &&
+          !tor_addr_is_null(&rs->status.ipv6_addr)
+          && rs->status.ipv6_orport) {
+        smartlist_add(alt_orports, tor_addr_port_alloc(&rs->status.ipv6_addr,
+                                                       rs->status.ipv6_orport));
+        log_debug(LD_DIR, "picking %s:%d (%s) for voting on \"a\" lines", /* FIXME: remove */
+                  fmt_and_decorate_addr(&rs->status.ipv6_addr), rs->status.ipv6_orport,
+                  rs->status.nickname);
+      }
+    } SMARTLIST_FOREACH_END(rs);
+
+    smartlist_sort(alt_orports, _compare_orports);
+    most_alt_orport = smartlist_get_most_frequent(alt_orports, _compare_orports);
+    if (most_alt_orport) {
+      memcpy(best_alt_orport_out, most_alt_orport, sizeof(tor_addr_port_t));
+
+      log_debug(LD_DIR, "\"a\" line winner for %s is %s:%d",
+                most->status.nickname,
+                fmt_and_decorate_addr(&most_alt_orport->addr),
+                most_alt_orport->port);
+    }
+
+    SMARTLIST_FOREACH(alt_orports, tor_addr_port_t *, ap, tor_free(ap));
+    smartlist_free(alt_orports);
+  }
+
   if (consensus_method >= MIN_METHOD_FOR_MICRODESC &&
       microdesc_digest256_out) {
     smartlist_t *digests = smartlist_new();
@@ -1685,6 +1740,7 @@ networkstatus_compute_consensus(smartlist_t *votes,
       int n_listing = 0;
       int i;
       char microdesc_digest[DIGEST256_LEN];
+      tor_addr_port_t alt_orport = {TOR_ADDR_NULL, 0};
 
       /* Of the next-to-be-considered digest in each voter, which is first? */
       SMARTLIST_FOREACH(votes, networkstatus_t *, v, {
@@ -1754,7 +1810,7 @@ networkstatus_compute_consensus(smartlist_t *votes,
        * routerinfo and its contents are. */
       memset(microdesc_digest, 0, sizeof(microdesc_digest));
       rs = compute_routerstatus_consensus(matching_descs, consensus_method,
-                                          microdesc_digest);
+                                          microdesc_digest, &alt_orport);
       /* Copy bits of that into rs_out. */
       memset(&rs_out, 0, sizeof(rs_out));
       tor_assert(fast_memeq(lowest_id, rs->status.identity_digest,DIGEST_LEN));
@@ -1765,6 +1821,10 @@ networkstatus_compute_consensus(smartlist_t *votes,
       rs_out.published_on = rs->status.published_on;
       rs_out.dir_port = rs->status.dir_port;
       rs_out.or_port = rs->status.or_port;
+      if (consensus_method >= MIN_METHOD_FOR_A_LINES) {
+        tor_addr_copy(&rs_out.ipv6_addr, &alt_orport.addr);
+        rs_out.ipv6_orport = alt_orport.port;
+      }
       rs_out.has_bandwidth = 0;
       rs_out.has_exitsummary = 0;