hs-v3: Attempt descriptor refetch when dirinfo changes

When the directory information changes, callback to the HS client subsystem so
it can check if any pending SOCKS connections are waiting for a descriptor. If
yes, attempt a refetch for those.

Fixes #23762

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

4 files changed, 66 insertions, 5 deletions

diff --git a/src/or/connection_edge.c b/src/or/connection_edge.c
index 77dac62b09..b9d8eeaff6 100644
--- a/src/or/connection_edge.c
+++ b/src/or/connection_edge.c
@@ -1571,10 +1571,10 @@ connection_ap_handle_onion(entry_connection_t *conn,
       int ret = hs_client_refetch_hsdesc(&edge_conn->hs_ident->identity_pk);
       switch (ret) {
       case HS_CLIENT_FETCH_MISSING_INFO:
-        /* By going to the end, the connection is put in waiting for a circuit
-         * state which means that it will be retried and consider as a pending
-         * connection. */
-        goto end;
+        /* Keeping the connection in descriptor wait state is fine because
+         * once we get enough dirinfo or a new live consensus, the HS client
+         * subsystem is notified and every connection in that state will
+         * trigger a fetch for the service key. */
       case HS_CLIENT_FETCH_LAUNCHED:
       case HS_CLIENT_FETCH_PENDING:
       case HS_CLIENT_FETCH_HAVE_DESC:
@@ -1591,7 +1591,6 @@ connection_ap_handle_onion(entry_connection_t *conn,
   /* We have the descriptor!  So launch a connection to the HS. */
   log_info(LD_REND, "Descriptor is here. Great.");
 
- end:
   base_conn->state = AP_CONN_STATE_CIRCUIT_WAIT;
   /* We'll try to attach it at the next event loop, or whenever
    * we call connection_ap_attach_pending() */
diff --git a/src/or/hs_client.c b/src/or/hs_client.c
index d66e563528..18b76e8b38 100644
--- a/src/or/hs_client.c
+++ b/src/or/hs_client.c
@@ -233,6 +233,55 @@ close_all_socks_conns_waiting_for_desc(const ed25519_public_key_t *identity_pk,
   smartlist_free(conns);
 }
 
+/* Find all pending SOCKS connection waiting for a descriptor and retry them
+ * all. This is called when the directory information changed. */
+static void
+retry_all_socks_conn_waiting_for_desc(void)
+{
+  smartlist_t *conns =
+    connection_list_by_type_state(CONN_TYPE_AP, AP_CONN_STATE_RENDDESC_WAIT);
+
+  SMARTLIST_FOREACH_BEGIN(conns, connection_t *, base_conn) {
+    hs_client_fetch_status_t status;
+    const edge_connection_t *edge_conn =
+      ENTRY_TO_EDGE_CONN(TO_ENTRY_CONN(base_conn));
+
+    /* Ignore non HS or non v3 connection. */
+    if (edge_conn->hs_ident == NULL) {
+      continue;
+    }
+    /* In this loop, we will possibly try to fetch a descriptor for the
+     * pending connections because we just got more directory information.
+     * However, the refetch process can cleanup all SOCKS request so the same
+     * service if an internal error happens. Thus, we can end up with closed
+     * connections in our list. */
+    if (base_conn->marked_for_close) {
+      continue;
+    }
+
+    /* XXX: There is an optimization we could do which is that for a service
+     * key, we could check if we can fetch and remember that decision. */
+
+    /* Order a refetch in case it works this time. */
+    status = hs_client_refetch_hsdesc(&edge_conn->hs_ident->identity_pk);
+    if (BUG(status == HS_CLIENT_FETCH_HAVE_DESC)) {
+      /* This case is unique because it can NOT happen in theory. Once we get
+       * a new descriptor, the HS client subsystem is notified immediately and
+       * the connections waiting for it are handled which means the state will
+       * change from renddesc wait state. Log this and continue to next
+       * connection. */
+      continue;
+    }
+    /* In the case of an error, either all SOCKS connections have been
+     * closed or we are still missing directory information. Leave the
+     * connection in renddesc wait state so when we get more info, we'll be
+     * able to try it again. */
+  } SMARTLIST_FOREACH_END(base_conn);
+
+  /* We don't have ownership of those objects. */
+  smartlist_free(conns);
+}
+
 /* A v3 HS circuit successfully connected to the hidden service. Update the
  * stream state at <b>hs_conn_ident</b> appropriately. */
 static void
@@ -1529,3 +1578,13 @@ hs_client_purge_state(void)
   log_info(LD_REND, "Hidden service client state has been purged.");
 }
 
+/* Called when our directory information has changed. */
+void
+hs_client_dir_info_changed(void)
+{
+  /* We have possibly reached the minimum directory information or new
+   * consensus so retry all pending SOCKS connection in
+   * AP_CONN_STATE_RENDDESC_WAIT state in order to fetch the descriptor. */
+  retry_all_socks_conn_waiting_for_desc();
+}
+
diff --git a/src/or/hs_client.h b/src/or/hs_client.h
index 164accc0e6..2523568ad1 100644
--- a/src/or/hs_client.h
+++ b/src/or/hs_client.h
@@ -41,6 +41,7 @@ int hs_client_decode_descriptor(
 int hs_client_any_intro_points_usable(const ed25519_public_key_t *service_pk,
                                       const hs_descriptor_t *desc);
 int hs_client_refetch_hsdesc(const ed25519_public_key_t *identity_pk);
+void hs_client_dir_info_changed(void);
 
 int hs_client_send_introduce1(origin_circuit_t *intro_circ,
                               origin_circuit_t *rend_circ);
diff --git a/src/or/nodelist.c b/src/or/nodelist.c
index eae74e18b5..fd5a8f0c0d 100644
--- a/src/or/nodelist.c
+++ b/src/or/nodelist.c
@@ -48,6 +48,7 @@
 #include "entrynodes.h"
 #include "geoip.h"
 #include "hs_common.h"
+#include "hs_client.h"
 #include "main.h"
 #include "microdesc.h"
 #include "networkstatus.h"
@@ -1973,6 +1974,7 @@ router_dir_info_changed(void)
   need_to_update_have_min_dir_info = 1;
   rend_hsdir_routers_changed();
   hs_service_dir_info_changed();
+  hs_client_dir_info_changed();
 }
 
 /** Return a string describing what we're missing before we have enough