Remove support for now-obsolete consensus methods before 28.

Closes ticket 32695.

changes/ticket32695

@@ -0,0 +1,6 @@
+  o Removed features:
+    - We no longer support consensus methods before method 28; these
+      methods were only used by authorities running versions of Tor that
+      are now at end-of-life. In effect, this means that clients and
+      relays, and authorities now assume that authorities will be
+      running version 0.3.5.x or later. Closes ticket 32695.

src/feature/dirauth/dirvote.c

@@ -1540,14 +1540,11 @@ networkstatus_compute_consensus(smartlist_t *votes,
     consensus_method = MAX_SUPPORTED_CONSENSUS_METHOD;
   }
 
-  if (consensus_method >= MIN_METHOD_FOR_INIT_BW_WEIGHTS_ONE) {
+  {
     /* It's smarter to initialize these weights to 1, so that later on,
      * we can't accidentally divide by zero. */
     G = M = E = D = 1;
     T = 4;
-  } else {
-    /* ...but originally, they were set to zero. */
-    G = M = E = D = T = 0;
   }
 
   /* Compute medians of time-related things, and figure out how many
@@ -2268,8 +2265,7 @@ networkstatus_compute_consensus(smartlist_t *votes,
         smartlist_add_strdup(chunks, chosen_version);
       }
       smartlist_add_strdup(chunks, "\n");
-      if (chosen_protocol_list &&
-          consensus_method >= MIN_METHOD_FOR_RS_PROTOCOLS) {
+      if (chosen_protocol_list) {
         smartlist_add_asprintf(chunks, "pr %s\n", chosen_protocol_list);
       }
       /*     Now the weight line. */
@@ -3805,13 +3801,6 @@ dirvote_create_microdescriptor(const routerinfo_t *ri, int consensus_method)
     smartlist_add_asprintf(chunks, "ntor-onion-key %s", kbuf);
   }
 
-  /* We originally put a lines in the micrdescriptors, but then we worked out
-   * that we needed them in the microdesc consensus. See #20916. */
-  if (consensus_method < MIN_METHOD_FOR_NO_A_LINES_IN_MICRODESC &&
-      !tor_addr_is_null(&ri->ipv6_addr) && ri->ipv6_orport)
-    smartlist_add_asprintf(chunks, "a %s\n",
-                           fmt_addrport(&ri->ipv6_addr, ri->ipv6_orport));
-
   if (family) {
     if (consensus_method < MIN_METHOD_FOR_CANONICAL_FAMILIES_IN_MICRODESCS) {
       smartlist_add_asprintf(chunks, "family %s\n", family);
@@ -3917,8 +3906,7 @@ static const struct consensus_method_range_t {
   int low;
   int high;
 } microdesc_consensus_methods[] = {
-  {MIN_SUPPORTED_CONSENSUS_METHOD, MIN_METHOD_FOR_NO_A_LINES_IN_MICRODESC - 1},
-  {MIN_METHOD_FOR_NO_A_LINES_IN_MICRODESC,
+  {MIN_SUPPORTED_CONSENSUS_METHOD,
    MIN_METHOD_FOR_CANONICAL_FAMILIES_IN_MICRODESCS - 1},
   {MIN_METHOD_FOR_CANONICAL_FAMILIES_IN_MICRODESCS,
    MAX_SUPPORTED_CONSENSUS_METHOD},

src/feature/dirauth/dirvote.h

@@ -54,31 +54,11 @@
 #define ROUTERSTATUS_FORMAT_NO_CONSENSUS_METHOD 0
 
 /** The lowest consensus method that we currently support. */
-#define MIN_SUPPORTED_CONSENSUS_METHOD 25
+#define MIN_SUPPORTED_CONSENSUS_METHOD 28
 
 /** The highest consensus method that we currently support. */
 #define MAX_SUPPORTED_CONSENSUS_METHOD 29
 
-/** Lowest consensus method where authorities vote on required/recommended
- * protocols. */
-#define MIN_METHOD_FOR_RECOMMENDED_PROTOCOLS 25
-
-/** Lowest consensus method where authorities add protocols to routerstatus
- * entries. */
-#define MIN_METHOD_FOR_RS_PROTOCOLS 25
-
-/** Lowest consensus method where authorities initialize bandwidth weights to 1
- * instead of 0. See #14881 */
-#define MIN_METHOD_FOR_INIT_BW_WEIGHTS_ONE 26
-
-/** Lowest consensus method where the microdesc consensus contains relay IPv6
- * addresses. See #23826 and #20916. */
-#define MIN_METHOD_FOR_A_LINES_IN_MICRODESC_CONSENSUS 27
-
-/** Lowest consensus method where microdescriptors do not contain relay IPv6
- * addresses. See #23828 and #20916. */
-#define MIN_METHOD_FOR_NO_A_LINES_IN_MICRODESC 28
-
 /**
  * Lowest consensus method where microdescriptor lines are put in canonical
  * form for improved compressibility and ease of storage. See proposal 298.

src/feature/nodelist/fmt_routerstatus.c

@@ -50,6 +50,8 @@ routerstatus_format_entry(const routerstatus_t *rs, const char *version,
                           int consensus_method,
                           const vote_routerstatus_t *vrs)
 {
+  (void) consensus_method;
+
   char *summary;
   char *result = NULL;
 
@@ -78,12 +80,6 @@ routerstatus_format_entry(const routerstatus_t *rs, const char *version,
    * networkstatus_type_t values, with an additional control port value
    * added -MP */
 
-  /* V3 microdesc consensuses only have "a" lines in later consensus methods
-   */
-  if (format == NS_V3_CONSENSUS_MICRODESC &&
-      consensus_method < MIN_METHOD_FOR_A_LINES_IN_MICRODESC_CONSENSUS)
-    goto done;
-
   /* Possible "a" line. At most one for now. */
   if (!tor_addr_is_null(&rs->ipv6_addr)) {
     smartlist_add_asprintf(chunks, "a %s\n",

src/feature/nodelist/networkstatus.c

@@ -1585,6 +1585,7 @@ networkstatus_consensus_is_already_downloading(const char *resource)
 int
 networkstatus_consensus_has_ipv6(const or_options_t* options)
 {
+  (void) options;
   const networkstatus_t *cons = networkstatus_get_reasonably_live_consensus(
                                                     approx_time(),
                                                     usable_consensus_flavor());
@@ -1594,13 +1595,8 @@ networkstatus_consensus_has_ipv6(const or_options_t* options)
     return 0;
   }
 
-  /* Different flavours of consensus gained IPv6 at different times */
-  if (we_use_microdescriptors_for_circuits(options)) {
-    return
-       cons->consensus_method >= MIN_METHOD_FOR_A_LINES_IN_MICRODESC_CONSENSUS;
-  } else {
-    return 1;
-  }
+  /* All supported consensus methods have IPv6 addresses. */
+  return 1;
 }
 
 /** Given two router status entries for the same router identity, return 1 if

src/test/test_dir.c

@@ -7108,7 +7108,7 @@ test_dir_networkstatus_consensus_has_ipv6(void *arg)
   mock_options->UseMicrodescriptors = 1;
 
   mock_networkstatus->consensus_method =
-      MIN_METHOD_FOR_A_LINES_IN_MICRODESC_CONSENSUS;
+    MIN_SUPPORTED_CONSENSUS_METHOD;
   has_ipv6 = networkstatus_consensus_has_ipv6(get_options());
   tt_assert(has_ipv6);
 
@@ -7117,24 +7117,19 @@ test_dir_networkstatus_consensus_has_ipv6(void *arg)
   tt_assert(has_ipv6);
 
   mock_networkstatus->consensus_method =
-      MIN_METHOD_FOR_A_LINES_IN_MICRODESC_CONSENSUS + 1;
+    MIN_SUPPORTED_CONSENSUS_METHOD + 1;
   has_ipv6 = networkstatus_consensus_has_ipv6(get_options());
   tt_assert(has_ipv6);
 
   mock_networkstatus->consensus_method =
-      MIN_METHOD_FOR_A_LINES_IN_MICRODESC_CONSENSUS + 20;
+    MIN_SUPPORTED_CONSENSUS_METHOD + 20;
   has_ipv6 = networkstatus_consensus_has_ipv6(get_options());
   tt_assert(has_ipv6);
 
-  mock_networkstatus->consensus_method =
-      MIN_METHOD_FOR_A_LINES_IN_MICRODESC_CONSENSUS - 1;
-  has_ipv6 = networkstatus_consensus_has_ipv6(get_options());
-  tt_assert(!has_ipv6);
-
   /* Test the edge cases */
   mock_options->UseMicrodescriptors = 1;
   mock_networkstatus->consensus_method =
-      MIN_METHOD_FOR_A_LINES_IN_MICRODESC_CONSENSUS;
+    MIN_SUPPORTED_CONSENSUS_METHOD;
 
   /* Reasonably live */
   mock_networkstatus->valid_until = approx_time() - 60;