prop224: Build hsdir index for node_t

This hsdir index value is used to give an index value to all node_t (relays)
that supports HSDir v3. An index value is then computed using the blinded key
to know where to fetch/upload the service descriptor from/to.

To avoid computing that index value everytime the client/service needs it, we
do that everytime we get a new consensus which then doesn't change until the
next one. The downside is that we need to sort them once we need to compute
the set of responsible HSDir.

Finally, the "hs_index" function is also added but not used. It will be used
in later commits to compute which node_t is a responsible HSDir for the
service we want to fetch/upload the descriptor.

Signed-off-by: David Goulet <dgoulet@torproject.org>

1 files changed, 78 insertions, 0 deletions

diff --git a/src/or/nodelist.c b/src/or/nodelist.c
index dafeb9f12d..117598cf1b 100644
--- a/src/or/nodelist.c
+++ b/src/or/nodelist.c
@@ -45,6 +45,7 @@
 #include "dirserv.h"
 #include "entrynodes.h"
 #include "geoip.h"
+#include "hs_common.h"
 #include "main.h"
 #include "microdesc.h"
 #include "networkstatus.h"
@@ -164,12 +165,71 @@ node_get_or_create(const char *identity_digest)
 
   smartlist_add(the_nodelist->nodes, node);
   node->nodelist_idx = smartlist_len(the_nodelist->nodes) - 1;
+  node->hsdir_index = tor_malloc_zero(sizeof(hsdir_index_t));
 
   node->country = -1;
 
   return node;
 }
 
+/* For a given <b>node</b> for the consensus <b>ns</b>, set the hsdir index
+ * for the node, both current and next if possible. This can only fails if the
+ * node_t ed25519 identity key can't be found which would be a bug. */
+static void
+node_set_hsdir_index(node_t *node, const networkstatus_t *ns)
+{
+  time_t now = time(NULL);
+  const ed25519_public_key_t *node_identity_pk;
+  uint8_t *next_hsdir_index_srv = NULL, *current_hsdir_index_srv = NULL;
+  uint64_t next_time_period_num, current_time_period_num;
+
+  tor_assert(node);
+  tor_assert(ns);
+
+  node_identity_pk = node_get_ed25519_id(node);
+  if (node_identity_pk == NULL) {
+    log_warn(LD_BUG, "ed25519 identity public key not found when "
+                     "trying to build the hsdir indexes for node %s",
+             node_describe(node));
+    goto done;
+  }
+
+  /* Get the current and next time period number, we might use them both. */
+  current_time_period_num = hs_get_time_period_num(now);
+  next_time_period_num = hs_get_next_time_period_num(now);
+
+  /* If NOT in overlap mode, we only need to compute the current hsdir index
+   * for the ongoing time period and thus the current SRV. If it can't be
+   * found, the disaster one is returned. */
+  current_hsdir_index_srv = hs_get_current_srv(current_time_period_num);
+
+  if (hs_overlap_mode_is_active(ns, now)) {
+    /* We are in overlap mode, this means that our consensus has just cycled
+     * from current SRV to previous SRV so for the _next_ upcoming time
+     * period, we have to use the current SRV and use the previous SRV for the
+     * current time period. If the current or previous SRV can't be found, the
+     * disaster one is returned. */
+    next_hsdir_index_srv = hs_get_current_srv(next_time_period_num);
+    /* The following can be confusing so again, in overlap mode, we use our
+     * previous SRV for our _current_ hsdir index. */
+    current_hsdir_index_srv = hs_get_previous_srv(current_time_period_num);
+  }
+
+  /* Build the current hsdir index. */
+  hs_build_hsdir_index(node_identity_pk, current_hsdir_index_srv,
+                       current_time_period_num, node->hsdir_index->current);
+  if (next_hsdir_index_srv) {
+    /* Build the next hsdir index if we have a next SRV that we can use. */
+    hs_build_hsdir_index(node_identity_pk, next_hsdir_index_srv,
+                         next_time_period_num, node->hsdir_index->next);
+  }
+
+ done:
+  tor_free(current_hsdir_index_srv);
+  tor_free(next_hsdir_index_srv);
+  return;
+}
+
 /** Called when a node's address changes. */
 static void
 node_addrs_changed(node_t *node)
@@ -216,6 +276,14 @@ nodelist_set_routerinfo(routerinfo_t *ri, routerinfo_t **ri_old_out)
     dirserv_set_node_flags_from_authoritative_status(node, status);
   }
 
+  /* Setting the HSDir index requires the ed25519 identity key which can
+   * only be found either in the ri or md. This is why this is called here.
+   * Only nodes supporting HSDir=2 protocol version needs this index. */
+  if (node->rs && node->rs->supports_v3_hsdir) {
+    node_set_hsdir_index(node,
+                         networkstatus_get_latest_consensus());
+  }
+
   return node;
 }
 
@@ -246,6 +314,12 @@ nodelist_add_microdesc(microdesc_t *md)
       node->md->held_by_nodes--;
     node->md = md;
     md->held_by_nodes++;
+    /* Setting the HSDir index requires the ed25519 identity key which can
+     * only be found either in the ri or md. This is why this is called here.
+     * Only nodes supporting HSDir=2 protocol version needs this index. */
+    if (rs->supports_v3_hsdir) {
+      node_set_hsdir_index(node, ns);
+    }
   }
   return node;
 }
@@ -283,6 +357,9 @@ nodelist_set_consensus(networkstatus_t *ns)
       }
     }
 
+    if (rs->supports_v3_hsdir) {
+      node_set_hsdir_index(node, ns);
+    }
     node_set_country(node);
 
     /* If we're not an authdir, believe others. */
@@ -410,6 +487,7 @@ node_free(node_t *node)
   if (node->md)
     node->md->held_by_nodes--;
   tor_assert(node->nodelist_idx == -1);
+  tor_free(node->hsdir_index);
   tor_free(node);
 }