relay/circuitbuild: Consider IPv6-only extends valid

Allow extend cells with IPv6-only link specifiers.
Warn and fail if both IPv4 and IPv6 are invalid.

Also warn if the IPv4 or IPv6 addresses are unexpectedly internal,
but continue with the valid address.

Part of 33817.

1 files changed, 38 insertions, 12 deletions

diff --git a/src/feature/relay/circuitbuild_relay.c b/src/feature/relay/circuitbuild_relay.c
index 05146f1b67..080781f719 100644
--- a/src/feature/relay/circuitbuild_relay.c
+++ b/src/feature/relay/circuitbuild_relay.c
@@ -123,11 +123,14 @@ circuit_extend_add_ed25519_helper(struct extend_cell_t *ec)
  * and are allowed by the current ExtendAllowPrivateAddresses config.
  *
  * If they are valid, return 0.
- * Otherwise, if they are invalid, log a warning at <b>log_level</b>,
- * and return -1.
+ * Otherwise, if they are invalid, return -1.
+ * If <b>log_zero_addrs</b> is true, log warnings about zero addresses at
+ * <b>log_level</b>. If <b>log_internal_addrs</b> is true, log warnings about
+ * internal addresses at <b>log_level</b>.
  */
 static int
 circuit_extend_addr_port_helper(const struct tor_addr_port_t *ap,
+                                bool log_zero_addrs, bool log_internal_addrs,
                                 int log_level)
 {
   /* It's safe to print the family. But we don't want to print the address,
@@ -135,19 +138,23 @@ circuit_extend_addr_port_helper(const struct tor_addr_port_t *ap,
    * But some internal addresses might be.)*/
 
   if (!tor_addr_port_is_valid_ap(ap, 0)) {
-    log_fn(log_level, LD_PROTOCOL,
-           "Client asked me to extend to a zero destination port or "
-           "%s address '%s'.",
-           fmt_addr_family(&ap->addr), safe_str(fmt_addrport_ap(ap)));
+    if (log_zero_addrs) {
+      log_fn(log_level, LD_PROTOCOL,
+             "Client asked me to extend to a zero destination port or "
+             "%s address '%s'.",
+             fmt_addr_family(&ap->addr), safe_str(fmt_addrport_ap(ap)));
+    }
     return -1;
   }
 
   if (tor_addr_is_internal(&ap->addr, 0) &&
       !get_options()->ExtendAllowPrivateAddresses) {
-    log_fn(log_level, LD_PROTOCOL,
-           "Client asked me to extend to a private %s address '%s'.",
-           fmt_addr_family(&ap->addr),
-           safe_str(fmt_and_decorate_addr(&ap->addr)));
+    if (log_internal_addrs) {
+      log_fn(log_level, LD_PROTOCOL,
+             "Client asked me to extend to a private %s address '%s'.",
+             fmt_addr_family(&ap->addr),
+             safe_str(fmt_and_decorate_addr(&ap->addr)));
+    }
     return -1;
   }
 
@@ -174,9 +181,28 @@ circuit_extend_lspec_valid_helper(const struct extend_cell_t *ec,
     return -1;
   }
 
-  if (circuit_extend_addr_port_helper(&ec->orport_ipv4,
-                                      LOG_PROTOCOL_WARN) < 0) {
+  /* Check the addresses, without logging */
+  const int ipv4_valid =
+    (circuit_extend_addr_port_helper(&ec->orport_ipv4, false, false, 0) == 0);
+  const int ipv6_valid =
+    (circuit_extend_addr_port_helper(&ec->orport_ipv6, false, false, 0) == 0);
+  /* We need at least one valid address */
+  if (!ipv4_valid && !ipv6_valid) {
+    /* Now, log the invalid addresses at protocol warning level */
+    circuit_extend_addr_port_helper(&ec->orport_ipv4, true, true,
+                                    LOG_PROTOCOL_WARN);
+    circuit_extend_addr_port_helper(&ec->orport_ipv6, true, true,
+                                    LOG_PROTOCOL_WARN);
+    /* And fail */
     return -1;
+  } else if (!ipv4_valid) {
+    /* Always log unexpected internal addresses, but go on to use the other
+     * valid address */
+    circuit_extend_addr_port_helper(&ec->orport_ipv4, false, true,
+                                    LOG_PROTOCOL_WARN);
+  } else if (!ipv6_valid) {
+    circuit_extend_addr_port_helper(&ec->orport_ipv6, false, true,
+                                    LOG_PROTOCOL_WARN);
   }
 
   IF_BUG_ONCE(circ->magic != OR_CIRCUIT_MAGIC) {