Add networkstatus_consensus_has_ipv6() and unit tests

networkstatus_consensus_has_ipv6() tells us whether the consensus method of
our current consensus supports IPv6 ORPorts in the consensus.

Part of #23827.

1 files changed, 26 insertions, 0 deletions

diff --git a/src/or/networkstatus.c b/src/or/networkstatus.c
index 2843d06262..61cca1b9b6 100644
--- a/src/or/networkstatus.c
+++ b/src/or/networkstatus.c
@@ -1507,6 +1507,32 @@ networkstatus_consensus_is_already_downloading(const char *resource)
   return answer;
 }
 
+/* Does the current, reasonably live consensus have IPv6 addresses?
+ * Returns 1 if there is a reasonably live consensus and its consensus method
+ * includes IPv6 addresses in the consensus.
+ * Otherwise, if there is no consensus, or the method does not include IPv6
+ * addresses, returns 0. */
+int
+networkstatus_consensus_has_ipv6(const or_options_t* options)
+{
+  const networkstatus_t *cons = networkstatus_get_reasonably_live_consensus(
+                                                    approx_time(),
+                                                    usable_consensus_flavor());
+
+  /* If we have no consensus, we have no IPv6 in it */
+  if (!cons) {
+    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 cons->consensus_method >= MIN_METHOD_FOR_A_LINES;
+  }
+}
+
 /** Given two router status entries for the same router identity, return 1 if
  * if the contents have changed between them. Otherwise, return 0. */
 static int