Recreate nodelist before use if it's outdated.

We currently only do the check when we are about to use the HSDir indices.

src/or/hs_common.c

@@ -1340,6 +1340,9 @@ hs_get_responsible_hsdirs(const ed25519_public_key_t *blinded_pk,
       goto done;
   }
 
+  /* Ensure the nodelist is fresh, since it contains the HSDir indices. */
+  nodelist_ensure_freshness(c);
+
   /* Add every node_t that support HSDir v3 for which we do have a valid
    * hsdir_index already computed for them for this consensus. */
   {

src/or/nodelist.c

@@ -113,6 +113,11 @@ typedef struct nodelist_t {
 
   /* Set of addresses that belong to nodes we believe in. */
   address_set_t *node_addrs;
+
+  /* The valid-after time of the last live consensus that initialized the
+   * nodelist.  We use this to detect outdated nodelists that need to be
+   * rebuilt using a newer consensus. */
+  time_t live_consensus_valid_after;
 } nodelist_t;
 
 static inline unsigned int
@@ -630,6 +635,12 @@ nodelist_set_consensus(networkstatus_t *ns)
       }
     } SMARTLIST_FOREACH_END(node);
   }
+
+  /* If the consensus is live, note down the consensus valid-after that formed
+   * the nodelist. */
+  if (networkstatus_is_live(ns, approx_time())) {
+    the_nodelist->live_consensus_valid_after = ns->valid_after;
+  }
 }
 
 /** Helper: return true iff a node has a usable amount of information*/
@@ -854,6 +865,25 @@ nodelist_assert_ok(void)
   digestmap_free(dm, NULL);
 }
 
+/** Ensure that the nodelist has been created with the most recent consensus.
+ *  If that's not the case, make it so.  */
+void
+nodelist_ensure_freshness(networkstatus_t *ns)
+{
+  tor_assert(ns);
+
+  /* We don't even have a nodelist: this is a NOP. */
+  if (!the_nodelist) {
+    return;
+  }
+
+  if (the_nodelist->live_consensus_valid_after != ns->valid_after) {
+    log_info(LD_GENERAL, "Nodelist was not fresh: rebuilding. (%d / %d)",
+             (int) the_nodelist->live_consensus_valid_after,
+             (int) ns->valid_after);
+    nodelist_set_consensus(ns);
+  }
+}
 /** Return a list of a node_t * for every node we know about.  The caller
  * MUST NOT modify the list. (You can set and clear flags in the nodes if
  * you must, but you must not add or remove nodes.) */

src/or/nodelist.h

@@ -29,6 +29,7 @@ const node_t *node_get_by_hex_id(const char *identity_digest,
 node_t *nodelist_set_routerinfo(routerinfo_t *ri, routerinfo_t **ri_old_out);
 node_t *nodelist_add_microdesc(microdesc_t *md);
 void nodelist_set_consensus(networkstatus_t *ns);
+void nodelist_ensure_freshness(networkstatus_t *ns);
 int nodelist_probably_contains_address(const tor_addr_t *addr);
 
 void nodelist_remove_microdesc(const char *identity_digest, microdesc_t *md);