Merge branch 'tor-github/pr/1968'

36 files changed, 558 insertions, 331 deletions

diff --git a/src/core/crypto/onion_crypto.c b/src/core/crypto/onion_crypto.c
index 69b4dc40aa..1f34be1cc1 100644
--- a/src/core/crypto/onion_crypto.c
+++ b/src/core/crypto/onion_crypto.c
@@ -31,7 +31,7 @@
  **/
 
 #include "core/or/or.h"
-#include "core/or/circuitbuild.h"
+#include "core/or/extendinfo.h"
 #include "core/crypto/onion_crypto.h"
 #include "core/crypto/onion_fast.h"
 #include "core/crypto/onion_ntor.h"
diff --git a/src/core/or/channeltls.c b/src/core/or/channeltls.c
index f9937ce880..a51fbf1dd6 100644
--- a/src/core/or/channeltls.c
+++ b/src/core/or/channeltls.c
@@ -63,10 +63,10 @@
 #include "trunnel/channelpadding_negotiation.h"
 #include "trunnel/netinfo.h"
 #include "core/or/channelpadding.h"
+#include "core/or/extendinfo.h"
 
 #include "core/or/cell_st.h"
 #include "core/or/cell_queue_st.h"
-#include "core/or/extend_info_st.h"
 #include "core/or/or_connection_st.h"
 #include "core/or/or_handshake_certs_st.h"
 #include "core/or/or_handshake_state_st.h"
@@ -702,9 +702,9 @@ channel_tls_matches_extend_info_method(channel_t *chan,
     return 0;
   }
 
-  return (tor_addr_eq(&(extend_info->addr),
-                      &(TO_CONN(tlschan->conn)->addr)) &&
-         (extend_info->port == TO_CONN(tlschan->conn)->port));
+  return extend_info_has_orport(extend_info,
+                                &TO_CONN(tlschan->conn)->addr,
+                                TO_CONN(tlschan->conn)->port);
 }
 
 /**
diff --git a/src/core/or/circuitbuild.c b/src/core/or/circuitbuild.c
index e971fb0865..cef70e3e76 100644
--- a/src/core/or/circuitbuild.c
+++ b/src/core/or/circuitbuild.c
@@ -45,6 +45,7 @@
 #include "core/or/command.h"
 #include "core/or/connection_edge.h"
 #include "core/or/connection_or.h"
+#include "core/or/extendinfo.h"
 #include "core/or/onion.h"
 #include "core/or/ocirc_event.h"
 #include "core/or/policies.h"
@@ -78,9 +79,6 @@
 #include "feature/nodelist/node_st.h"
 #include "core/or/or_circuit_st.h"
 #include "core/or/origin_circuit_st.h"
-#include "feature/nodelist/microdesc_st.h"
-#include "feature/nodelist/routerinfo_st.h"
-#include "feature/nodelist/routerstatus_st.h"
 
 static int circuit_send_first_onion_skin(origin_circuit_t *circ);
 static int circuit_build_no_more_hops(origin_circuit_t *circ);
@@ -96,13 +94,17 @@ static const node_t *choose_good_middle_server(uint8_t purpose,
  * callbacks.
  */
 MOCK_IMPL(channel_t *,
-channel_connect_for_circuit,(const tor_addr_t *addr, uint16_t port,
-                             const char *id_digest,
-                             const struct ed25519_public_key_t *ed_id))
+channel_connect_for_circuit,(const extend_info_t *ei))
 {
   channel_t *chan;
 
-  chan = channel_connect(addr, port, id_digest, ed_id);
+  const tor_addr_port_t *orport = extend_info_pick_orport(ei);
+  if (!orport)
+    return NULL;
+  const char *id_digest = ei->identity_digest;
+  const ed25519_public_key_t *ed_id = &ei->ed_identity;
+
+  chan = channel_connect(&orport->addr, orport->port, id_digest, ed_id);
   if (chan) command_setup_channel(chan);
 
   return chan;
@@ -550,7 +552,7 @@ circuit_handle_first_hop(origin_circuit_t *circ)
    * - the address is internal, and
    * - we're not connecting to a configured bridge, and
    * - we're not configured to allow extends to private addresses. */
-  if (tor_addr_is_internal(&firsthop->extend_info->addr, 0) &&
+  if (extend_info_any_orport_addr_is_internal(firsthop->extend_info) &&
       !extend_info_is_a_configured_bridge(firsthop->extend_info) &&
       !options->ExtendAllowPrivateAddresses) {
     log_fn(LOG_PROTOCOL_WARN, LD_PROTOCOL,
@@ -559,19 +561,15 @@ circuit_handle_first_hop(origin_circuit_t *circ)
   }
 
   /* now see if we're already connected to the first OR in 'route' */
-  log_debug(LD_CIRC,"Looking for firsthop '%s'",
-            fmt_addrport(&firsthop->extend_info->addr,
-                         firsthop->extend_info->port));
-
-  /* We'll cleanup this code in #33220, when we add an IPv6 address to
-   * extend_info_t. */
-  const bool addr_is_ipv4 =
-    (tor_addr_family(&firsthop->extend_info->addr) == AF_INET);
+  const tor_addr_port_t *orport4 =
+    extend_info_get_orport(firsthop->extend_info, AF_INET);
+  const tor_addr_port_t *orport6 =
+    extend_info_get_orport(firsthop->extend_info, AF_INET6);
   n_chan = channel_get_for_extend(
                           firsthop->extend_info->identity_digest,
                           &firsthop->extend_info->ed_identity,
-                          addr_is_ipv4 ? &firsthop->extend_info->addr : NULL,
-                          addr_is_ipv4 ? NULL : &firsthop->extend_info->addr,
+                          orport4 ? &orport4->addr : NULL,
+                          orport6 ? &orport6->addr : NULL,
                           &msg,
                           &should_launch);
 
@@ -583,11 +581,7 @@ circuit_handle_first_hop(origin_circuit_t *circ)
     circ->base_.n_hop = extend_info_dup(firsthop->extend_info);
 
     if (should_launch) {
-      n_chan = channel_connect_for_circuit(
-          &firsthop->extend_info->addr,
-          firsthop->extend_info->port,
-          firsthop->extend_info->identity_digest,
-          &firsthop->extend_info->ed_identity);
+      n_chan = channel_connect_for_circuit(firsthop->extend_info);
       if (!n_chan) { /* connect failed, forget the whole thing */
         log_info(LD_CIRC,"connect to firsthop failed. Closing.");
         return -END_CIRC_REASON_CONNECTFAILED;
@@ -605,7 +599,8 @@ circuit_handle_first_hop(origin_circuit_t *circ)
     tor_assert(!circ->base_.n_hop);
     circ->base_.n_chan = n_chan;
     circuit_chan_publish(circ, n_chan);
-    log_debug(LD_CIRC,"Conn open. Delivering first onion skin.");
+    log_debug(LD_CIRC,"Conn open for %s. Delivering first onion skin.",
+              safe_str_client(extend_info_describe(firsthop->extend_info)));
     if ((err_reason = circuit_send_next_onion_skin(circ)) < 0) {
       log_info(LD_CIRC,"circuit_send_next_onion_skin failed.");
       circ->base_.n_chan = NULL;
@@ -1078,42 +1073,40 @@ circuit_send_intermediate_onion_skin(origin_circuit_t *circ,
                                      crypt_path_t *hop)
 {
   int len;
-  int family = tor_addr_family(&hop->extend_info->addr);
   extend_cell_t ec;
+  /* Relays and bridges can send IPv6 extends. But for clients, it's an
+   * obvious version distinguisher. */
+  const bool include_ipv6 = server_mode(get_options());
   memset(&ec, 0, sizeof(ec));
+  tor_addr_make_unspec(&ec.orport_ipv4.addr);
+  tor_addr_make_unspec(&ec.orport_ipv6.addr);
 
   log_debug(LD_CIRC,"starting to send subsequent skin.");
 
-  /* Relays and bridges can send IPv6 extends. But for clients, it's an
-   * obvious version distinguisher. */
-  if (server_mode(get_options())) {
-    if (family != AF_INET && family != AF_INET6) {
-      log_warn(LD_BUG, "Server trying to extend to an invalid address "
-               "family.");
-      return - END_CIRC_REASON_INTERNAL;
-    }
-  } else {
-    if (family != AF_INET) {
-      log_warn(LD_BUG, "Client trying to extend to a non-IPv4 address.");
-      return - END_CIRC_REASON_INTERNAL;
-    }
-  }
-
   circuit_pick_extend_handshake(&ec.cell_type,
                                 &ec.create_cell.cell_type,
                                 &ec.create_cell.handshake_type,
                                 hop->extend_info);
 
-  /* At the moment, extend_info only has one ORPort address. We'll add a
-   * second address in #34069, to support dual-stack extend cells. */
-  if (family == AF_INET) {
-    tor_addr_copy(&ec.orport_ipv4.addr, &hop->extend_info->addr);
-    ec.orport_ipv4.port = hop->extend_info->port;
-    tor_addr_make_unspec(&ec.orport_ipv6.addr);
-  } else {
-    tor_addr_copy(&ec.orport_ipv6.addr, &hop->extend_info->addr);
-    ec.orport_ipv6.port = hop->extend_info->port;
-    tor_addr_make_unspec(&ec.orport_ipv4.addr);
+  const tor_addr_port_t *orport4 =
+    extend_info_get_orport(hop->extend_info, AF_INET);
+  const tor_addr_port_t *orport6 =
+    extend_info_get_orport(hop->extend_info, AF_INET6);
+  int n_addrs_set = 0;
+  if (orport4) {
+    tor_addr_copy(&ec.orport_ipv4.addr, &orport4->addr);
+    ec.orport_ipv4.port = orport4->port;
+    ++n_addrs_set;
+  }
+  if (orport6 && include_ipv6) {
+    tor_addr_copy(&ec.orport_ipv6.addr, &orport6->addr);
+    ec.orport_ipv6.port = orport6->port;
+    ++n_addrs_set;
+  }
+
+  if (n_addrs_set == 0) {
+    log_warn(LD_BUG, "No supported address family found in extend_info.");
+    return - END_CIRC_REASON_INTERNAL;
   }
   memcpy(ec.node_id, hop->extend_info->identity_digest, DIGEST_LEN);
   /* Set the ED25519 identity too -- it will only get included
@@ -2462,143 +2455,6 @@ onion_extend_cpath(origin_circuit_t *circ)
   return 0;
 }
 
-/** Allocate a new extend_info object based on the various arguments. */
-extend_info_t *
-extend_info_new(const char *nickname,
-                const char *rsa_id_digest,
-                const ed25519_public_key_t *ed_id,
-                crypto_pk_t *onion_key,
-                const curve25519_public_key_t *ntor_key,
-                const tor_addr_t *addr, uint16_t port)
-{
-  extend_info_t *info = tor_malloc_zero(sizeof(extend_info_t));
-  memcpy(info->identity_digest, rsa_id_digest, DIGEST_LEN);
-  if (ed_id && !ed25519_public_key_is_zero(ed_id))
-    memcpy(&info->ed_identity, ed_id, sizeof(ed25519_public_key_t));
-  if (nickname)
-    strlcpy(info->nickname, nickname, sizeof(info->nickname));
-  if (onion_key)
-    info->onion_key = crypto_pk_dup_key(onion_key);
-  if (ntor_key)
-    memcpy(&info->curve25519_onion_key, ntor_key,
-           sizeof(curve25519_public_key_t));
-  tor_addr_copy(&info->addr, addr);
-  info->port = port;
-  return info;
-}
-
-/** Allocate and return a new extend_info that can be used to build a
- * circuit to or through the node <b>node</b>. Use the primary address
- * of the node (i.e. its IPv4 address) unless
- * <b>for_direct_connect</b> is true, in which case the preferred
- * address is used instead. May return NULL if there is not enough
- * info about <b>node</b> to extend to it--for example, if the preferred
- * routerinfo_t or microdesc_t is missing, or if for_direct_connect is
- * true and none of the node's addresses is allowed by tor's firewall
- * and IP version config.
- **/
-extend_info_t *
-extend_info_from_node(const node_t *node, int for_direct_connect)
-{
-  crypto_pk_t *rsa_pubkey = NULL;
-  extend_info_t *info = NULL;
-  tor_addr_port_t ap;
-  int valid_addr = 0;
-
-  if (!node_has_preferred_descriptor(node, for_direct_connect)) {
-    return NULL;
-  }
-
-  /* Choose a preferred address first, but fall back to an allowed address. */
-  if (for_direct_connect)
-    fascist_firewall_choose_address_node(node, FIREWALL_OR_CONNECTION, 0, &ap);
-  else {
-    node_get_prim_orport(node, &ap);
-  }
-  valid_addr = tor_addr_port_is_valid_ap(&ap, 0);
-
-  if (valid_addr)
-    log_debug(LD_CIRC, "using %s for %s",
-              fmt_addrport(&ap.addr, ap.port),
-              node->ri ? node->ri->nickname : node->rs->nickname);
-  else
-    log_warn(LD_CIRC, "Could not choose valid address for %s",
-              node->ri ? node->ri->nickname : node->rs->nickname);
-
-  /* Every node we connect or extend to must support ntor */
-  if (!node_has_curve25519_onion_key(node)) {
-    log_fn(LOG_PROTOCOL_WARN, LD_CIRC,
-           "Attempted to create extend_info for a node that does not support "
-           "ntor: %s", node_describe(node));
-    return NULL;
-  }
-
-  const ed25519_public_key_t *ed_pubkey = NULL;
-
-  /* Don't send the ed25519 pubkey unless the target node actually supports
-   * authenticating with it. */
-  if (node_supports_ed25519_link_authentication(node, 0)) {
-    log_info(LD_CIRC, "Including Ed25519 ID for %s", node_describe(node));
-    ed_pubkey = node_get_ed25519_id(node);
-  } else if (node_get_ed25519_id(node)) {
-    log_info(LD_CIRC, "Not including the ed25519 ID for %s, since it won't "
-             "be able to authenticate it.",
-             node_describe(node));
-  }
-
-  /* Retrieve the curve25519 pubkey. */
-  const curve25519_public_key_t *curve_pubkey =
-    node_get_curve25519_onion_key(node);
-  rsa_pubkey = node_get_rsa_onion_key(node);
-
-  if (valid_addr && node->ri) {
-    info = extend_info_new(node->ri->nickname,
-                           node->identity,
-                           ed_pubkey,
-                           rsa_pubkey,
-                           curve_pubkey,
-                           &ap.addr,
-                           ap.port);
-  } else if (valid_addr && node->rs && node->md) {
-    info = extend_info_new(node->rs->nickname,
-                           node->identity,
-                           ed_pubkey,
-                           rsa_pubkey,
-                           curve_pubkey,
-                           &ap.addr,
-                           ap.port);
-  }
-
-  crypto_pk_free(rsa_pubkey);
-  return info;
-}
-
-/** Release storage held by an extend_info_t struct. */
-void
-extend_info_free_(extend_info_t *info)
-{
-  if (!info)
-    return;
-  crypto_pk_free(info->onion_key);
-  tor_free(info);
-}
-
-/** Allocate and return a new extend_info_t with the same contents as
- * <b>info</b>. */
-extend_info_t *
-extend_info_dup(extend_info_t *info)
-{
-  extend_info_t *newinfo;
-  tor_assert(info);
-  newinfo = tor_malloc(sizeof(extend_info_t));
-  memcpy(newinfo, info, sizeof(extend_info_t));
-  if (info->onion_key)
-    newinfo->onion_key = crypto_pk_dup_key(info->onion_key);
-  else
-    newinfo->onion_key = NULL;
-  return newinfo;
-}
-
 /** Return the node_t for the chosen exit router in <b>state</b>.
  * If there is no chosen exit, or if we don't know the node_t for
  * the chosen exit, return NULL.
@@ -2634,43 +2490,6 @@ build_state_get_exit_nickname(cpath_build_state_t *state)
   return state->chosen_exit->nickname;
 }
 
-/** Return true iff the given address can be used to extend to. */
-int
-extend_info_addr_is_allowed(const tor_addr_t *addr)
-{
-  tor_assert(addr);
-
-  /* Check if we have a private address and if we can extend to it. */
-  if ((tor_addr_is_internal(addr, 0) || tor_addr_is_multicast(addr)) &&
-      !get_options()->ExtendAllowPrivateAddresses) {
-    goto disallow;
-  }
-  /* Allowed! */
-  return 1;
- disallow:
-  return 0;
-}
-
-/* Does ei have a valid TAP key? */
-int
-extend_info_supports_tap(const extend_info_t* ei)
-{
-  tor_assert(ei);
-  /* Valid TAP keys are not NULL */
-  return ei->onion_key != NULL;
-}
-
-/* Does ei have a valid ntor key? */
-int
-extend_info_supports_ntor(const extend_info_t* ei)
-{
-  tor_assert(ei);
-  /* Valid ntor keys have at least one non-zero byte */
-  return !fast_mem_is_zero(
-                          (const char*)ei->curve25519_onion_key.public_key,
-                          CURVE25519_PUBKEY_LEN);
-}
-
 /* Is circuit purpose allowed to use the deprecated TAP encryption protocol?
  * The hidden service protocol still uses TAP for some connections, because
  * ntor onion keys aren't included in HS descriptors or INTRODUCE cells. */
@@ -2705,15 +2524,6 @@ circuit_has_usable_onion_key(const origin_circuit_t *circ)
           circuit_can_use_tap(circ));
 }
 
-/* Does ei have an onion key which it would prefer to use?
- * Currently, we prefer ntor keys*/
-int
-extend_info_has_preferred_onion_key(const extend_info_t* ei)
-{
-  tor_assert(ei);
-  return extend_info_supports_ntor(ei);
-}
-
 /** Find the circuits that are waiting to find out whether their guards are
  * usable, and if any are ready to become usable, mark them open and try
  * attaching streams as appropriate. */
diff --git a/src/core/or/circuitbuild.h b/src/core/or/circuitbuild.h
index 565be09975..0cd1eb4f45 100644
--- a/src/core/or/circuitbuild.h
+++ b/src/core/or/circuitbuild.h
@@ -42,23 +42,8 @@ MOCK_DECL(int, circuit_all_predicted_ports_handled, (time_t now,
 
 int circuit_append_new_exit(origin_circuit_t *circ, extend_info_t *info);
 int circuit_extend_to_new_exit(origin_circuit_t *circ, extend_info_t *info);
-extend_info_t *extend_info_new(const char *nickname,
-                               const char *rsa_id_digest,
-                               const struct ed25519_public_key_t *ed_id,
-                               crypto_pk_t *onion_key,
-                               const struct curve25519_public_key_t *ntor_key,
-                               const tor_addr_t *addr, uint16_t port);
-extend_info_t *extend_info_from_node(const node_t *r, int for_direct_connect);
-extend_info_t *extend_info_dup(extend_info_t *info);
-void extend_info_free_(extend_info_t *info);
-#define extend_info_free(info) \
-  FREE_AND_NULL(extend_info_t, extend_info_free_, (info))
-int extend_info_addr_is_allowed(const tor_addr_t *addr);
-int extend_info_supports_tap(const extend_info_t* ei);
-int extend_info_supports_ntor(const extend_info_t* ei);
 int circuit_can_use_tap(const origin_circuit_t *circ);
 int circuit_has_usable_onion_key(const origin_circuit_t *circ);
-int extend_info_has_preferred_onion_key(const extend_info_t* ei);
 const uint8_t *build_state_get_exit_rsa_id(cpath_build_state_t *state);
 MOCK_DECL(const node_t *,
           build_state_get_exit_node,(cpath_build_state_t *state));
@@ -71,13 +56,7 @@ const node_t *choose_good_entry_server(uint8_t purpose,
                            struct circuit_guard_state_t **guard_state_out);
 void circuit_upgrade_circuits_from_guard_wait(void);
 
-struct ed25519_public_key_t;
-
-MOCK_DECL(channel_t *,
-channel_connect_for_circuit,(const tor_addr_t *addr,
-                             uint16_t port,
-                             const char *id_digest,
-                             const struct ed25519_public_key_t *ed_id));
+MOCK_DECL(channel_t *, channel_connect_for_circuit,(const extend_info_t *ei));
 
 struct create_cell_t;
 MOCK_DECL(int,
diff --git a/src/core/or/circuitlist.c b/src/core/or/circuitlist.c
index a69b7cbbe5..f4d6cd3c12 100644
--- a/src/core/or/circuitlist.c
+++ b/src/core/or/circuitlist.c
@@ -64,6 +64,7 @@
 #include "core/or/circuitstats.h"
 #include "core/or/circuitpadding.h"
 #include "core/or/crypt_path.h"
+#include "core/or/extendinfo.h"
 #include "core/mainloop/connection.h"
 #include "app/config/config.h"
 #include "core/or/connection_edge.h"
diff --git a/src/core/or/circuituse.c b/src/core/or/circuituse.c
index f4cd4ced43..6ff308dae2 100644
--- a/src/core/or/circuituse.c
+++ b/src/core/or/circuituse.c
@@ -37,6 +37,7 @@
 #include "core/or/circuituse.h"
 #include "core/or/circuitpadding.h"
 #include "core/or/connection_edge.h"
+#include "core/or/extendinfo.h"
 #include "core/or/policies.h"
 #include "feature/client/addressmap.h"
 #include "feature/client/bridges.h"
@@ -202,8 +203,8 @@ circuit_is_acceptable(const origin_circuit_t *origin_circ,
           const int family = tor_addr_parse(&addr,
                                             conn->socks_request->address);
           if (family < 0 ||
-              !tor_addr_eq(&build_state->chosen_exit->addr, &addr) ||
-              build_state->chosen_exit->port != conn->socks_request->port)
+              !extend_info_has_orport(build_state->chosen_exit, &addr,
+                                      conn->socks_request->port))
             return 0;
         }
       }
diff --git a/src/core/or/connection_edge.c b/src/core/or/connection_edge.c
index fc77db8334..2826a99249 100644
--- a/src/core/or/connection_edge.c
+++ b/src/core/or/connection_edge.c
@@ -70,6 +70,7 @@
 #include "core/or/circuitpadding.h"
 #include "core/or/connection_edge.h"
 #include "core/or/connection_or.h"
+#include "core/or/extendinfo.h"
 #include "core/or/policies.h"
 #include "core/or/reasons.h"
 #include "core/or/relay.h"
@@ -1444,8 +1445,8 @@ connection_ap_fail_onehop(const char *failed_digest,
         continue;
       }
       if (tor_addr_parse(&addr, entry_conn->socks_request->address)<0 ||
-          !tor_addr_eq(&build_state->chosen_exit->addr, &addr) ||
-          build_state->chosen_exit->port != entry_conn->socks_request->port)
+          !extend_info_has_orport(build_state->chosen_exit, &addr,
+                                  entry_conn->socks_request->port))
         continue;
     }
     log_info(LD_APP, "Closing one-hop stream to '%s/%s' because the OR conn "
diff --git a/src/core/or/crypt_path.c b/src/core/or/crypt_path.c
index 8f41540848..e1bbd81251 100644
--- a/src/core/or/crypt_path.c
+++ b/src/core/or/crypt_path.c
@@ -30,6 +30,7 @@
 #include "core/crypto/onion_crypto.h"
 #include "core/or/circuitbuild.h"
 #include "core/or/circuitlist.h"
+#include "core/or/extendinfo.h"
 
 #include "lib/crypt_ops/crypto_dh.h"
 #include "lib/crypt_ops/crypto_util.h"
@@ -259,4 +260,3 @@ cpath_get_n_hops(crypt_path_t **head_ptr)
 }
 
 #endif /* defined(TOR_UNIT_TESTS) */
-
diff --git a/src/core/or/extend_info_st.h b/src/core/or/extend_info_st.h
index a66ce24cfa..757c6a1771 100644
--- a/src/core/or/extend_info_st.h
+++ b/src/core/or/extend_info_st.h
@@ -15,9 +15,14 @@
 #include "lib/crypt_ops/crypto_curve25519.h"
 #include "lib/crypt_ops/crypto_ed25519.h"
 
+/** Largest number of addresses we handle in an extend_info.
+ *
+ * More are permitted in an EXTEND cell, but we won't handle them. */
+#define EXTEND_INFO_MAX_ADDRS 2
+
 /** Information on router used when extending a circuit. We don't need a
  * full routerinfo_t to extend: we only need addr:port:keyid to build an OR
- * connection, and onion_key to create the onionskin. Note that for onehop
+ * connection, and onion_key to create the onionskin. Note that for one-hop
  * general-purpose tunnels, the onion_key is NULL. */
 struct extend_info_t {
   char nickname[MAX_HEX_NICKNAME_LEN+1]; /**< This router's nickname for
@@ -26,9 +31,12 @@ struct extend_info_t {
   char identity_digest[DIGEST_LEN];
   /** Ed25519 identity for this router, if any. */
   ed25519_public_key_t ed_identity;
-  uint16_t port; /**< OR port. */
-  tor_addr_t addr; /**< IP address. */
-  crypto_pk_t *onion_key; /**< Current onionskin key. */
+  /** IP/Port values for this hop's ORPort(s).  Any unused values are set
+   * to a null address. */
+  tor_addr_port_t orports[EXTEND_INFO_MAX_ADDRS];
+  /** TAP onion key for this hop. */
+  crypto_pk_t *onion_key;
+  /** Ntor onion key for this hop. */
   curve25519_public_key_t curve25519_onion_key;
 };
 
diff --git a/src/core/or/extendinfo.c b/src/core/or/extendinfo.c
new file mode 100644
index 0000000000..bcdb57d5a0
--- /dev/null
+++ b/src/core/or/extendinfo.c
@@ -0,0 +1,305 @@
+/* Copyright (c) 2001 Matej Pfajfar.
+ * Copyright (c) 2001-2004, Roger Dingledine.
+ * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
+ * Copyright (c) 2007-2020, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+/**
+ * @file extendinfo.c
+ * @brief Functions for creating and using extend_info_t objects.
+ *
+ * An extend_info_t is the information we hold about a relay in order to
+ * extend a circuit to it.
+ **/
+
+#include "core/or/or.h"
+#include "core/or/extendinfo.h"
+
+#include "app/config/config.h"
+#include "core/or/policies.h"
+#include "feature/nodelist/describe.h"
+#include "feature/nodelist/nodelist.h"
+
+#include "core/or/extend_info_st.h"
+#include "feature/nodelist/node_st.h"
+#include "feature/nodelist/routerinfo_st.h"
+#include "feature/nodelist/routerstatus_st.h"
+
+/** Allocate a new extend_info object based on the various arguments. */
+extend_info_t *
+extend_info_new(const char *nickname,
+                const char *rsa_id_digest,
+                const ed25519_public_key_t *ed_id,
+                crypto_pk_t *onion_key,
+                const curve25519_public_key_t *ntor_key,
+                const tor_addr_t *addr, uint16_t port)
+{
+  extend_info_t *info = tor_malloc_zero(sizeof(extend_info_t));
+  if (rsa_id_digest)
+    memcpy(info->identity_digest, rsa_id_digest, DIGEST_LEN);
+  if (ed_id && !ed25519_public_key_is_zero(ed_id))
+    memcpy(&info->ed_identity, ed_id, sizeof(ed25519_public_key_t));
+  if (nickname)
+    strlcpy(info->nickname, nickname, sizeof(info->nickname));
+  if (onion_key)
+    info->onion_key = crypto_pk_dup_key(onion_key);
+  if (ntor_key)
+    memcpy(&info->curve25519_onion_key, ntor_key,
+           sizeof(curve25519_public_key_t));
+  for (int i = 0; i < EXTEND_INFO_MAX_ADDRS; ++i) {
+    tor_addr_make_unspec(&info->orports[i].addr);
+  }
+
+  if (addr) {
+    extend_info_add_orport(info, addr, port);
+  }
+  return info;
+}
+
+/**
+ * Add another address:port pair to a given extend_info_t, if there is
+ * room.  Return 0 on success, -1 on failure.
+ **/
+int
+extend_info_add_orport(extend_info_t *ei,
+                       const tor_addr_t *addr,
+                       uint16_t port)
+{
+  for (int i = 0; i < EXTEND_INFO_MAX_ADDRS; ++i) {
+    if (tor_addr_is_unspec(&ei->orports[i].addr)) {
+      tor_addr_copy(&ei->orports[i].addr, addr);
+      ei->orports[i].port = port;
+      return 0;
+    }
+  }
+  return -1;
+}
+
+/** Allocate and return a new extend_info that can be used to build a
+ * circuit to or through the node <b>node</b>. Use the primary address
+ * of the node (i.e. its IPv4 address) unless
+ * <b>for_direct_connect</b> is true, in which case the preferred
+ * address is used instead. May return NULL if there is not enough
+ * info about <b>node</b> to extend to it--for example, if the preferred
+ * routerinfo_t or microdesc_t is missing, or if for_direct_connect is
+ * true and none of the node's addresses is allowed by tor's firewall
+ * and IP version config.
+ **/
+extend_info_t *
+extend_info_from_node(const node_t *node, int for_direct_connect)
+{
+  crypto_pk_t *rsa_pubkey = NULL;
+  extend_info_t *info = NULL;
+  tor_addr_port_t ap;
+  int valid_addr = 0;
+
+  if (!node_has_preferred_descriptor(node, for_direct_connect)) {
+    return NULL;
+  }
+
+  /* Choose a preferred address first, but fall back to an allowed address. */
+  if (for_direct_connect)
+    fascist_firewall_choose_address_node(node, FIREWALL_OR_CONNECTION, 0, &ap);
+  else {
+    node_get_prim_orport(node, &ap);
+  }
+  valid_addr = tor_addr_port_is_valid_ap(&ap, 0);
+
+  if (valid_addr)
+    log_debug(LD_CIRC, "using %s for %s",
+              fmt_addrport(&ap.addr, ap.port),
+              node->ri ? node->ri->nickname : node->rs->nickname);
+  else
+    log_warn(LD_CIRC, "Could not choose valid address for %s",
+              node->ri ? node->ri->nickname : node->rs->nickname);
+
+  /* Every node we connect or extend to must support ntor */
+  if (!node_has_curve25519_onion_key(node)) {
+    log_fn(LOG_PROTOCOL_WARN, LD_CIRC,
+           "Attempted to create extend_info for a node that does not support "
+           "ntor: %s", node_describe(node));
+    return NULL;
+  }
+
+  const ed25519_public_key_t *ed_pubkey = NULL;
+
+  /* Don't send the ed25519 pubkey unless the target node actually supports
+   * authenticating with it. */
+  if (node_supports_ed25519_link_authentication(node, 0)) {
+    log_info(LD_CIRC, "Including Ed25519 ID for %s", node_describe(node));
+    ed_pubkey = node_get_ed25519_id(node);
+  } else if (node_get_ed25519_id(node)) {
+    log_info(LD_CIRC, "Not including the ed25519 ID for %s, since it won't "
+             "be able to authenticate it.",
+             node_describe(node));
+  }
+
+  /* Retrieve the curve25519 pubkey. */
+  const curve25519_public_key_t *curve_pubkey =
+    node_get_curve25519_onion_key(node);
+  rsa_pubkey = node_get_rsa_onion_key(node);
+
+  if (valid_addr && node->ri) {
+    info = extend_info_new(node->ri->nickname,
+                           node->identity,
+                           ed_pubkey,
+                           rsa_pubkey,
+                           curve_pubkey,
+                           &ap.addr,
+                           ap.port);
+  } else if (valid_addr && node->rs && node->md) {
+    info = extend_info_new(node->rs->nickname,
+                           node->identity,
+                           ed_pubkey,
+                           rsa_pubkey,
+                           curve_pubkey,
+                           &ap.addr,
+                           ap.port);
+  }
+
+  crypto_pk_free(rsa_pubkey);
+  return info;
+}
+
+/** Release storage held by an extend_info_t struct. */
+void
+extend_info_free_(extend_info_t *info)
+{
+  if (!info)
+    return;
+  crypto_pk_free(info->onion_key);
+  tor_free(info);
+}
+
+/** Allocate and return a new extend_info_t with the same contents as
+ * <b>info</b>. */
+extend_info_t *
+extend_info_dup(extend_info_t *info)
+{
+  extend_info_t *newinfo;
+  tor_assert(info);
+  newinfo = tor_malloc(sizeof(extend_info_t));
+  memcpy(newinfo, info, sizeof(extend_info_t));
+  if (info->onion_key)
+    newinfo->onion_key = crypto_pk_dup_key(info->onion_key);
+  else
+    newinfo->onion_key = NULL;
+  return newinfo;
+}
+
+/* Does ei have a valid TAP key? */
+int
+extend_info_supports_tap(const extend_info_t* ei)
+{
+  tor_assert(ei);
+  /* Valid TAP keys are not NULL */
+  return ei->onion_key != NULL;
+}
+
+/* Does ei have a valid ntor key? */
+int
+extend_info_supports_ntor(const extend_info_t* ei)
+{
+  tor_assert(ei);
+  /* Valid ntor keys have at least one non-zero byte */
+  return !fast_mem_is_zero(
+                          (const char*)ei->curve25519_onion_key.public_key,
+                          CURVE25519_PUBKEY_LEN);
+}
+
+/* Does ei have an onion key which it would prefer to use?
+ * Currently, we prefer ntor keys*/
+int
+extend_info_has_preferred_onion_key(const extend_info_t* ei)
+{
+  tor_assert(ei);
+  return extend_info_supports_ntor(ei);
+}
+
+/** Return true iff the given address can be used to extend to. */
+int
+extend_info_addr_is_allowed(const tor_addr_t *addr)
+{
+  tor_assert(addr);
+
+  /* Check if we have a private address and if we can extend to it. */
+  if ((tor_addr_is_internal(addr, 0) || tor_addr_is_multicast(addr)) &&
+      !get_options()->ExtendAllowPrivateAddresses) {
+    goto disallow;
+  }
+  /* Allowed! */
+  return 1;
+ disallow:
+  return 0;
+}
+
+/**
+ * Return true if @a addr : @a port is a listed ORPort in @a ei.
+ **/
+bool
+extend_info_has_orport(const extend_info_t *ei,
+                       const tor_addr_t *addr, uint16_t port)
+{
+  IF_BUG_ONCE(ei == NULL) {
+    return false;
+  }
+
+  for (int i = 0; i < EXTEND_INFO_MAX_ADDRS; ++i) {
+    const tor_addr_port_t *ei_ap = &ei->orports[i];
+    if (tor_addr_eq(&ei_ap->addr, addr) && ei_ap->port == port)
+      return true;
+  }
+  return false;
+}
+
+/**
+ * If the extend_info @a ei has an orport of the chosen family, then return
+ * that orport.  Otherwise, return NULL.
+ **/
+const tor_addr_port_t *
+extend_info_get_orport(const extend_info_t *ei, int family)
+{
+  for (int i = 0; i < EXTEND_INFO_MAX_ADDRS; ++i) {
+    if (tor_addr_is_unspec(&ei->orports[i].addr))
+      continue;
+    if (tor_addr_family(&ei->orports[i].addr) == family)
+      return &ei->orports[i];
+  }
+  return NULL;
+}
+
+/**
+ * Chose an addr_port_t within @a ei to connect to.
+ **/
+const tor_addr_port_t *
+extend_info_pick_orport(const extend_info_t *ei)
+{
+  // XXXX S55 -- for now, we just pick the first.  We'll work on
+  // XXXX more choices as we move forward.
+  IF_BUG_ONCE(!ei) {
+    return NULL;
+  }
+
+  if (tor_addr_is_unspec(&ei->orports[0].addr)) {
+    return NULL;
+  }
+  return &ei->orports[0];
+}
+
+/**
+ * Return true if any orport address in @a ei is an internal address.
+ **/
+bool
+extend_info_any_orport_addr_is_internal(const extend_info_t *ei)
+{
+  IF_BUG_ONCE(ei == NULL) {
+    return false;
+  }
+
+  for (int i = 0; i < EXTEND_INFO_MAX_ADDRS; ++i) {
+    if (! tor_addr_is_unspec(&ei->orports[i].addr) &&
+        tor_addr_is_internal(&ei->orports[i].addr, 0))
+      return true;
+  }
+  return false;
+}
diff --git a/src/core/or/extendinfo.h b/src/core/or/extendinfo.h
new file mode 100644
index 0000000000..0049dd0189
--- /dev/null
+++ b/src/core/or/extendinfo.h
@@ -0,0 +1,40 @@
+/* Copyright (c) 2001 Matej Pfajfar.
+ * Copyright (c) 2001-2004, Roger Dingledine.
+ * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
+ * Copyright (c) 2007-2020, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+/**
+ * @file extendinfo.h
+ * @brief Header for core/or/extendinfo.c
+ **/
+
+#ifndef TOR_CORE_OR_EXTENDINFO_H
+#define TOR_CORE_OR_EXTENDINFO_H
+
+extend_info_t *extend_info_new(const char *nickname,
+                               const char *rsa_id_digest,
+                               const struct ed25519_public_key_t *ed_id,
+                               crypto_pk_t *onion_key,
+                               const struct curve25519_public_key_t *ntor_key,
+                               const tor_addr_t *addr, uint16_t port);
+extend_info_t *extend_info_from_node(const node_t *r, int for_direct_connect);
+extend_info_t *extend_info_dup(extend_info_t *info);
+void extend_info_free_(extend_info_t *info);
+#define extend_info_free(info) \
+  FREE_AND_NULL(extend_info_t, extend_info_free_, (info))
+int extend_info_addr_is_allowed(const tor_addr_t *addr);
+int extend_info_supports_tap(const extend_info_t* ei);
+int extend_info_supports_ntor(const extend_info_t* ei);
+int extend_info_has_preferred_onion_key(const extend_info_t* ei);
+bool extend_info_has_orport(const extend_info_t *ei,
+                            const tor_addr_t *addr, uint16_t port);
+int extend_info_add_orport(extend_info_t *ei,
+                           const tor_addr_t *addr,
+                           uint16_t port);
+const tor_addr_port_t *extend_info_get_orport(const extend_info_t *ei,
+                                              int family);
+const tor_addr_port_t *extend_info_pick_orport(const extend_info_t *ei);
+bool extend_info_any_orport_addr_is_internal(const extend_info_t *ei);
+
+#endif /* !defined(TOR_CORE_OR_EXTENDINFO_H) */
diff --git a/src/core/or/include.am b/src/core/or/include.am
index 3626e76bed..af7c5a6f51 100644
--- a/src/core/or/include.am
+++ b/src/core/or/include.am
@@ -18,6 +18,7 @@ LIBTOR_APP_A_SOURCES += 				\
 	src/core/or/connection_edge.c		\
 	src/core/or/connection_or.c		\
 	src/core/or/dos.c			\
+	src/core/or/extendinfo.c			\
 	src/core/or/onion.c			\
 	src/core/or/ocirc_event.c		\
 	src/core/or/or_periodic.c		\
@@ -64,6 +65,7 @@ noinst_HEADERS +=					\
 	src/core/or/destroy_cell_queue_st.h		\
 	src/core/or/dos.h				\
 	src/core/or/edge_connection_st.h		\
+	src/core/or/extendinfo.h			\
 	src/core/or/half_edge_st.h			\
 	src/core/or/entry_connection_st.h		\
 	src/core/or/entry_port_cfg_st.h			\
diff --git a/src/core/or/onion.h b/src/core/or/onion.h
index 256f0a3f31..600e67c3cd 100644
--- a/src/core/or/onion.h
+++ b/src/core/or/onion.h
@@ -48,8 +48,7 @@ typedef struct extend_cell_t {
   uint8_t cell_type;
   /** An IPv4 address and port for the node we're connecting to. */
   tor_addr_port_t orport_ipv4;
-  /** An IPv6 address and port for the node we're connecting to. Not currently
-   * used. */
+  /** An IPv6 address and port for the node we're connecting to. */
   tor_addr_port_t orport_ipv6;
   /** Identity fingerprint of the node we're conecting to.*/
   uint8_t node_id[DIGEST_LEN];
diff --git a/src/core/or/relay.c b/src/core/or/relay.c
index 75d2d479e7..6895591064 100644
--- a/src/core/or/relay.c
+++ b/src/core/or/relay.c
@@ -56,6 +56,7 @@
 #include "core/or/circuitlist.h"
 #include "core/or/circuituse.h"
 #include "core/or/circuitpadding.h"
+#include "core/or/extendinfo.h"
 #include "lib/compress/compress.h"
 #include "app/config/config.h"
 #include "core/mainloop/connection.h"
diff --git a/src/feature/client/bridges.c b/src/feature/client/bridges.c
index 66b04f3bc2..caa4776493 100644
--- a/src/feature/client/bridges.c
+++ b/src/feature/client/bridges.c
@@ -259,12 +259,26 @@ addr_is_a_configured_bridge(const tor_addr_t *addr,
 /** If we have a bridge configured whose digest matches
  * <b>ei->identity_digest</b>, or a bridge with no known digest whose address
  * matches <b>ei->addr</b>:<b>ei->port</b>, return 1.  Else return 0.
- * If <b>ei->onion_key</b> is NULL, check for address/port matches only. */
+ * If <b>ei->onion_key</b> is NULL, check for address/port matches only.
+ *
+ * Note that if the extend_info_t contains multiple addresses, we return true
+ * only if _every_ address is a bridge.
+ */
 int
 extend_info_is_a_configured_bridge(const extend_info_t *ei)
 {
   const char *digest = ei->onion_key ? ei->identity_digest : NULL;
-  return addr_is_a_configured_bridge(&ei->addr, ei->port, digest);
+  const tor_addr_port_t *ap1 = NULL, *ap2 = NULL;
+  if (! tor_addr_is_null(&ei->orports[0].addr))
+    ap1 = &ei->orports[0];
+  if (! tor_addr_is_null(&ei->orports[1].addr))
+    ap2 = &ei->orports[1];
+  IF_BUG_ONCE(ap1 == NULL) {
+    return 0;
+  }
+  return addr_is_a_configured_bridge(&ap1->addr, ap1->port, digest) &&
+    (ap2 == NULL ||
+     addr_is_a_configured_bridge(&ap2->addr, ap2->port, digest));
 }
 
 /** Wrapper around get_configured_bridge_by_addr_port_digest() to look
diff --git a/src/feature/control/control_cmd.c b/src/feature/control/control_cmd.c
index a37f285d9e..a8926c0b79 100644
--- a/src/feature/control/control_cmd.c
+++ b/src/feature/control/control_cmd.c
@@ -21,6 +21,7 @@
 #include "core/or/circuituse.h"
 #include "core/or/connection_edge.h"
 #include "core/or/circuitstats.h"
+#include "core/or/extendinfo.h"
 #include "feature/client/addressmap.h"
 #include "feature/client/dnsserv.h"
 #include "feature/client/entrynodes.h"
diff --git a/src/feature/hs/hs_circuit.c b/src/feature/hs/hs_circuit.c
index 447f664f81..5e7a3ac9c8 100644
--- a/src/feature/hs/hs_circuit.c
+++ b/src/feature/hs/hs_circuit.c
@@ -16,6 +16,7 @@
 #include "core/or/policies.h"
 #include "core/or/relay.h"
 #include "core/or/crypt_path.h"
+#include "core/or/extendinfo.h"
 #include "feature/client/circpathbias.h"
 #include "feature/hs/hs_cell.h"
 #include "feature/hs/hs_circuit.h"
diff --git a/src/feature/hs/hs_client.c b/src/feature/hs/hs_client.c
index c3697d0c1d..9670ed44b3 100644
--- a/src/feature/hs/hs_client.c
+++ b/src/feature/hs/hs_client.c
@@ -16,6 +16,7 @@
 #include "core/or/circuitlist.h"
 #include "core/or/circuituse.h"
 #include "core/or/connection_edge.h"
+#include "core/or/extendinfo.h"
 #include "core/or/reasons.h"
 #include "feature/client/circpathbias.h"
 #include "feature/dirclient/dirclient.h"
diff --git a/src/feature/hs/hs_common.c b/src/feature/hs/hs_common.c
index 4639cdb68a..706b42529f 100644
--- a/src/feature/hs/hs_common.c
+++ b/src/feature/hs/hs_common.c
@@ -16,6 +16,7 @@
 #include "app/config/config.h"
 #include "core/or/circuitbuild.h"
 #include "core/or/policies.h"
+#include "core/or/extendinfo.h"
 #include "feature/dirauth/shared_random_state.h"
 #include "feature/hs/hs_cache.h"
 #include "feature/hs/hs_circuitmap.h"
diff --git a/src/feature/hs/hs_service.c b/src/feature/hs/hs_service.c
index a42879a48f..249eb47b5d 100644
--- a/src/feature/hs/hs_service.c
+++ b/src/feature/hs/hs_service.c
@@ -16,6 +16,7 @@
 #include "core/or/circuitbuild.h"
 #include "core/or/circuitlist.h"
 #include "core/or/circuituse.h"
+#include "core/or/extendinfo.h"
 #include "core/or/relay.h"
 #include "feature/client/circpathbias.h"
 #include "feature/dirclient/dirclient.h"
diff --git a/src/feature/nodelist/describe.c b/src/feature/nodelist/describe.c
index 00896d5a44..f118436499 100644
--- a/src/feature/nodelist/describe.c
+++ b/src/feature/nodelist/describe.c
@@ -12,6 +12,7 @@
 #define DESCRIBE_PRIVATE
 
 #include "core/or/or.h"
+#include "core/or/extendinfo.h"
 #include "feature/nodelist/describe.h"
 
 #include "core/or/extend_info_st.h"
@@ -208,11 +209,16 @@ extend_info_describe(const extend_info_t *ei)
   if (!ei)
     return "<null>";
 
+  const tor_addr_port_t *ap4 = extend_info_get_orport(ei, AF_INET);
+  const tor_addr_port_t *ap6 = extend_info_get_orport(ei, AF_INET6);
+  uint32_t addr4 = ap4 ? tor_addr_to_ipv4h(&ap4->addr) : 0;
+  const tor_addr_t *addr6 = ap6 ? &ap6->addr : NULL;
+
   return format_node_description(buf,
                                  ei->identity_digest,
                                  ei->nickname,
-                                 &ei->addr,
-                                 0);
+                                 addr6,
+                                 addr4);
 }
 
 /** Set <b>buf</b> (which must have MAX_VERBOSE_NICKNAME_LEN+1 bytes) to the
diff --git a/src/feature/nodelist/routerset.c b/src/feature/nodelist/routerset.c
index ebc08b7a51..cba7203d44 100644
--- a/src/feature/nodelist/routerset.c
+++ b/src/feature/nodelist/routerset.c
@@ -306,12 +306,19 @@ routerset_add_unknown_ccs(routerset_t **setp, int only_if_some_cc_set)
 int
 routerset_contains_extendinfo(const routerset_t *set, const extend_info_t *ei)
 {
-  return routerset_contains(set,
-                            &ei->addr,
-                            ei->port,
-                            ei->nickname,
-                            ei->identity_digest,
-                            -1 /*country*/);
+  const tor_addr_port_t *ap1 = NULL, *ap2 = NULL;
+  if (! tor_addr_is_null(&ei->orports[0].addr))
+    ap1 = &ei->orports[0];
+  if (! tor_addr_is_null(&ei->orports[1].addr))
+    ap2 = &ei->orports[1];
+  return routerset_contains2(set,
+                             ap1 ? &ap1->addr : NULL,
+                             ap1 ? ap1->port : 0,
+                             ap2 ? &ap2->addr : NULL,
+                             ap2 ? ap2->port : 0,
+                             ei->nickname,
+                             ei->identity_digest,
+                             -1 /*country*/);
 }
 
 /** Return true iff <b>ri</b> is in <b>set</b>.  If country is <b>-1</b>, we
diff --git a/src/feature/relay/circuitbuild_relay.c b/src/feature/relay/circuitbuild_relay.c
index 470e639aa7..881cbd51be 100644
--- a/src/feature/relay/circuitbuild_relay.c
+++ b/src/feature/relay/circuitbuild_relay.c
@@ -33,6 +33,7 @@
 #include "core/or/channel.h"
 #include "core/or/circuitbuild.h"
 #include "core/or/circuitlist.h"
+#include "core/or/extendinfo.h"
 #include "core/or/onion.h"
 #include "core/or/relay.h"
 
@@ -400,11 +401,7 @@ circuit_open_connection_for_extend(const struct extend_cell_t *ec,
 
   if (should_launch) {
     /* we should try to open a connection */
-    channel_t *n_chan = channel_connect_for_circuit(
-                                                &circ->n_hop->addr,
-                                                circ->n_hop->port,
-                                                circ->n_hop->identity_digest,
-                                                &circ->n_hop->ed_identity);
+    channel_t *n_chan = channel_connect_for_circuit(circ->n_hop);
     if (!n_chan) {
       log_info(LD_CIRC,"Launching n_chan failed. Closing circuit.");
       circuit_mark_for_close(circ, END_CIRC_REASON_CONNECTFAILED);
diff --git a/src/feature/relay/selftest.c b/src/feature/relay/selftest.c
index 101704e1c9..77c04abdd7 100644
--- a/src/feature/relay/selftest.c
+++ b/src/feature/relay/selftest.c
@@ -24,6 +24,7 @@
 #include "core/or/circuitlist.h"
 #include "core/or/circuituse.h"
 #include "core/or/crypt_path_st.h"
+#include "core/or/extendinfo.h"
 #include "core/or/extend_info_st.h"
 #include "core/or/origin_circuit_st.h"
 #include "core/or/relay.h"
@@ -255,14 +256,15 @@ router_do_orport_reachability_checks(const routerinfo_t *me,
    * be NULL. */
   if (ei) {
     const char *family_name = fmt_af_family(family);
+    const tor_addr_port_t *ap = extend_info_get_orport(ei, family);
     log_info(LD_CIRC, "Testing %s of my %s ORPort: %s.",
              !orport_reachable ? "reachability" : "bandwidth",
-             family_name, fmt_addrport(&ei->addr, ei->port));
+             family_name, fmt_addrport_ap(ap));
     if (!orport_reachable) {
       /* This is only a 'reachability test' if we don't already think that
        * the port is reachable.  If we _do_ think it's reachable, then
        * it counts as a 'bandwidth test'. */
-      inform_testing_reachability(&ei->addr, ei->port, false);
+      inform_testing_reachability(&ap->addr, ap->port, false);
     }
     circuit_launch_by_extend_info(CIRCUIT_PURPOSE_TESTING, ei,
                                   CIRCLAUNCH_NEED_CAPACITY|
diff --git a/src/feature/rend/rendclient.c b/src/feature/rend/rendclient.c
index 09db7045fa..e171562d17 100644
--- a/src/feature/rend/rendclient.c
+++ b/src/feature/rend/rendclient.c
@@ -15,6 +15,7 @@
 #include "core/or/circuitlist.h"
 #include "core/or/circuituse.h"
 #include "core/or/connection_edge.h"
+#include "core/or/extendinfo.h"
 #include "core/or/relay.h"
 #include "feature/client/circpathbias.h"
 #include "feature/control/control_events.h"
@@ -234,9 +235,15 @@ rend_client_send_introduction(origin_circuit_t *introcirc,
     /* version 2 format */
     extend_info_t *extend_info = rendcirc->build_state->chosen_exit;
     int klen;
+    const tor_addr_port_t *orport =
+      extend_info_get_orport(extend_info, AF_INET);
+    IF_BUG_ONCE(! orport) {
+      /* we should never put an IPv6 address here. */
+      goto perm_err;
+    }
     /* nul pads */
-    set_uint32(tmp+v3_shift+1, tor_addr_to_ipv4n(&extend_info->addr));
-    set_uint16(tmp+v3_shift+5, htons(extend_info->port));
+    set_uint32(tmp+v3_shift+1, tor_addr_to_ipv4n(&orport->addr));
+    set_uint16(tmp+v3_shift+5, htons(orport->port));
     memcpy(tmp+v3_shift+7, extend_info->identity_digest, DIGEST_LEN);
     klen = crypto_pk_asn1_encode(extend_info->onion_key,
                                  tmp+v3_shift+7+DIGEST_LEN+2,
diff --git a/src/feature/rend/rendcommon.c b/src/feature/rend/rendcommon.c
index 5d04755819..775d487805 100644
--- a/src/feature/rend/rendcommon.c
+++ b/src/feature/rend/rendcommon.c
@@ -14,6 +14,7 @@
 #include "core/or/circuitbuild.h"
 #include "core/or/circuitlist.h"
 #include "core/or/circuituse.h"
+#include "core/or/extendinfo.h"
 #include "app/config/config.h"
 #include "feature/control/control_events.h"
 #include "lib/crypt_ops/crypto_rand.h"
@@ -233,7 +234,12 @@ rend_encode_v2_intro_points(char **encoded, rend_service_descriptor_t *desc)
       goto done;
     }
     /* Assemble everything for this introduction point. */
-    address = tor_addr_to_str_dup(&info->addr);
+    const tor_addr_port_t *orport = extend_info_get_orport(info, AF_INET);
+    IF_BUG_ONCE(!orport) {
+      /* There must be an IPv4 address for v2 hs. */
+      goto done;
+    }
+    address = tor_addr_to_str_dup(&orport->addr);
     res = tor_snprintf(unenc + unenc_written, unenc_len - unenc_written,
                          "introduction-point %s\n"
                          "ip-address %s\n"
@@ -242,7 +248,7 @@ rend_encode_v2_intro_points(char **encoded, rend_service_descriptor_t *desc)
                          "service-key\n%s",
                        id_base32,
                        address,
-                       info->port,
+                       orport->port,
                        onion_key,
                        service_key);
     tor_free(address);
diff --git a/src/feature/rend/rendparse.c b/src/feature/rend/rendparse.c
index 0979d767a7..c28add5ca9 100644
--- a/src/feature/rend/rendparse.c
+++ b/src/feature/rend/rendparse.c
@@ -10,6 +10,7 @@
  **/
 
 #include "core/or/or.h"
+#include "core/or/extendinfo.h"
 #include "feature/dirparse/parsecommon.h"
 #include "feature/dirparse/sigcommon.h"
 #include "feature/rend/rendcommon.h"
@@ -428,7 +429,8 @@ rend_parse_introduction_points(rend_service_descriptor_t *parsed,
     }
     /* Allocate new intro point and extend info. */
     intro = tor_malloc_zero(sizeof(rend_intro_point_t));
-    info = intro->extend_info = tor_malloc_zero(sizeof(extend_info_t));
+    info = intro->extend_info =
+      extend_info_new(NULL, NULL, NULL, NULL, NULL, NULL, 0);
     /* Parse identifier. */
     tok = find_by_keyword(tokens, R_IPO_IDENTIFIER);
     if (base32_decode(info->identity_digest, DIGEST_LEN,
@@ -446,12 +448,13 @@ rend_parse_introduction_points(rend_service_descriptor_t *parsed,
                   info->identity_digest, DIGEST_LEN);
     /* Parse IP address. */
     tok = find_by_keyword(tokens, R_IPO_IP_ADDRESS);
-    if (tor_addr_parse(&info->addr, tok->args[0])<0) {
+    tor_addr_t addr;
+    if (tor_addr_parse(&addr, tok->args[0])<0) {
       log_warn(LD_REND, "Could not parse introduction point address.");
       rend_intro_point_free(intro);
       goto err;
     }
-    if (tor_addr_family(&info->addr) != AF_INET) {
+    if (tor_addr_family(&addr) != AF_INET) {
       log_warn(LD_REND, "Introduction point address was not ipv4.");
       rend_intro_point_free(intro);
       goto err;
@@ -459,14 +462,18 @@ rend_parse_introduction_points(rend_service_descriptor_t *parsed,
 
     /* Parse onion port. */
     tok = find_by_keyword(tokens, R_IPO_ONION_PORT);
-    info->port = (uint16_t) tor_parse_long(tok->args[0],10,1,65535,
+    uint16_t port = (uint16_t) tor_parse_long(tok->args[0],10,1,65535,
                                            &num_ok,NULL);
-    if (!info->port || !num_ok) {
+    if (!port || !num_ok) {
       log_warn(LD_REND, "Introduction point onion port %s is invalid",
                escaped(tok->args[0]));
       rend_intro_point_free(intro);
       goto err;
     }
+
+    /* Add the address and port. */
+    extend_info_add_orport(info, &addr, port);
+
     /* Parse onion key. */
     tok = find_by_keyword(tokens, R_IPO_ONION_KEY);
     if (!crypto_pk_public_exponent_ok(tok->key)) {
diff --git a/src/feature/rend/rendservice.c b/src/feature/rend/rendservice.c
index a88c2080fd..1c456cb6ee 100644
--- a/src/feature/rend/rendservice.c
+++ b/src/feature/rend/rendservice.c
@@ -16,6 +16,7 @@
 #include "core/or/circuitbuild.h"
 #include "core/or/circuitlist.h"
 #include "core/or/circuituse.h"
+#include "core/or/extendinfo.h"
 #include "core/or/policies.h"
 #include "core/or/relay.h"
 #include "core/or/crypt_path.h"
@@ -1831,8 +1832,11 @@ rend_service_use_direct_connection(const or_options_t* options,
   /* We'll connect directly all reachable addresses, whether preferred or not.
    * The prefer_ipv6 argument to fascist_firewall_allows_address_addr is
    * ignored, because pref_only is 0. */
+  const tor_addr_port_t *ap = extend_info_get_orport(ei, AF_INET);
+  if (!ap)
+    return 0;
   return (rend_service_allow_non_anonymous_connection(options) &&
-          fascist_firewall_allows_address_addr(&ei->addr, ei->port,
+          fascist_firewall_allows_address_addr(&ap->addr, ap->port,
                                                FIREWALL_OR_CONNECTION, 0, 0));
 }
 
@@ -2261,7 +2265,8 @@ find_rp_for_intro(const rend_intro_cell_t *intro,
   /* Make sure the RP we are being asked to connect to is _not_ a private
    * address unless it's allowed. Let's avoid to build a circuit to our
    * second middle node and fail right after when extending to the RP. */
-  if (!extend_info_addr_is_allowed(&rp->addr)) {
+  const tor_addr_port_t *orport = extend_info_get_orport(rp, AF_INET);
+  if (! orport || !extend_info_addr_is_allowed(&orport->addr)) {
     if (err_msg_out) {
       tor_asprintf(&err_msg,
                    "Relay IP in INTRODUCE2 cell is private address.");
@@ -2530,9 +2535,11 @@ rend_service_parse_intro_for_v2(
     goto err;
   }
 
-  extend_info = tor_malloc_zero(sizeof(extend_info_t));
-  tor_addr_from_ipv4n(&extend_info->addr, get_uint32(buf + 1));
-  extend_info->port = ntohs(get_uint16(buf + 5));
+  extend_info = extend_info_new(NULL, NULL, NULL, NULL, NULL, NULL, 0);
+  tor_addr_t addr;
+  tor_addr_from_ipv4n(&addr, get_uint32(buf + 1));
+  uint16_t port = ntohs(get_uint16(buf + 5));
+  extend_info_add_orport(extend_info, &addr, port);
   memcpy(extend_info->identity_digest, buf + 7, DIGEST_LEN);
   extend_info->nickname[0] = '$';
   base16_encode(extend_info->nickname + 1, sizeof(extend_info->nickname) - 1,
diff --git a/src/lib/net/address.h b/src/lib/net/address.h
index 5ab654ef1d..6b18919f6d 100644
--- a/src/lib/net/address.h
+++ b/src/lib/net/address.h
@@ -95,6 +95,7 @@ static inline uint32_t tor_addr_to_ipv4n(const tor_addr_t *a);
 static inline uint32_t tor_addr_to_ipv4h(const tor_addr_t *a);
 static inline uint32_t tor_addr_to_mapped_ipv4h(const tor_addr_t *a);
 static inline sa_family_t tor_addr_family(const tor_addr_t *a);
+static inline bool tor_addr_is_unspec(const tor_addr_t *a);
 static inline const struct in_addr *tor_addr_to_in(const tor_addr_t *a);
 static inline int tor_addr_eq_ipv4h(const tor_addr_t *a, uint32_t u);
 
@@ -188,6 +189,15 @@ tor_addr_family(const tor_addr_t *a)
   return a->family;
 }
 
+/**
+ * Return true if the address @a is in the UNSPEC family.
+ **/
+static inline bool
+tor_addr_is_unspec(const tor_addr_t *a)
+{
+  return a->family == AF_UNSPEC;
+}
+
 /** Return an in_addr* equivalent to <b>a</b>, or NULL if <b>a</b> is not
  * an IPv4 address. */
 static inline const struct in_addr *
diff --git a/src/test/rend_test_helpers.c b/src/test/rend_test_helpers.c
index 61bacb4d2e..8e40167aeb 100644
--- a/src/test/rend_test_helpers.c
+++ b/src/test/rend_test_helpers.c
@@ -2,6 +2,7 @@
 /* See LICENSE for licensing information */
 
 #include "core/or/or.h"
+#include "core/or/extendinfo.h"
 #include "lib/crypt_ops/crypto_rand.h"
 #include "test/test.h"
 #include "feature/rend/rendcommon.h"
@@ -58,7 +59,8 @@ create_descriptor(rend_service_descriptor_t **generated, char **service_id,
   for (i = 0; i < intro_points; i++) {
     rend_intro_point_t *intro = tor_malloc_zero(sizeof(rend_intro_point_t));
     crypto_pk_t *okey = pk_generate(2 + i);
-    intro->extend_info = tor_malloc_zero(sizeof(extend_info_t));
+    intro->extend_info =
+      extend_info_new(NULL, NULL, NULL, NULL, NULL, NULL, 0);
     intro->extend_info->onion_key = okey;
     crypto_pk_get_digest(intro->extend_info->onion_key,
                          intro->extend_info->identity_digest);
@@ -66,8 +68,12 @@ create_descriptor(rend_service_descriptor_t **generated, char **service_id,
     base16_encode(intro->extend_info->nickname + 1,
                   sizeof(intro->extend_info->nickname) - 1,
                   intro->extend_info->identity_digest, DIGEST_LEN);
-    tor_addr_from_ipv4h(&intro->extend_info->addr, crypto_rand_int(65536));
-    intro->extend_info->port = 1 + crypto_rand_int(65535);
+    tor_addr_t addr;
+    uint16_t port;
+    /* Does not cover all IP addresses. */
+    tor_addr_from_ipv4h(&addr, crypto_rand_int(65536) + 1);
+    port = 1 + crypto_rand_int(65535);
+    extend_info_add_orport(intro->extend_info, &addr, port);
     intro->intro_key = crypto_pk_dup_key(pk2);
     smartlist_add((*generated)->intro_nodes, intro);
   }
@@ -91,4 +97,3 @@ mock_rend_data(const char *onion_address)
                                                  DIGEST_LEN));
   return rend_query;
 }
-
diff --git a/src/test/test.c b/src/test/test.c
index 4b6082ce4f..2961669c46 100644
--- a/src/test/test.c
+++ b/src/test/test.c
@@ -1,5 +1,5 @@
 /* Copyright (c) 2001-2004, Roger Dingledine.
- * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
+->a * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
  * Copyright (c) 2007-2020, The Tor Project, Inc. */
 /* See LICENSE for licensing information */
 
@@ -44,6 +44,7 @@
 #include "lib/compress/compress.h"
 #include "app/config/config.h"
 #include "core/or/connection_edge.h"
+#include "core/or/extendinfo.h"
 #include "feature/rend/rendcommon.h"
 #include "feature/rend/rendcache.h"
 #include "feature/rend/rendparse.h"
@@ -564,7 +565,8 @@ test_rend_fns(void *arg)
   for (i = 0; i < 3; i++) {
     rend_intro_point_t *intro = tor_malloc_zero(sizeof(rend_intro_point_t));
     crypto_pk_t *okey = pk_generate(2 + i);
-    intro->extend_info = tor_malloc_zero(sizeof(extend_info_t));
+    intro->extend_info =
+      extend_info_new(NULL, NULL, NULL, NULL, NULL, NULL, 0);
     intro->extend_info->onion_key = okey;
     crypto_pk_get_digest(intro->extend_info->onion_key,
                          intro->extend_info->identity_digest);
@@ -573,9 +575,12 @@ test_rend_fns(void *arg)
     base16_encode(intro->extend_info->nickname + 1,
                   sizeof(intro->extend_info->nickname) - 1,
                   intro->extend_info->identity_digest, DIGEST_LEN);
+    tor_addr_t addr;
+    uint16_t port;
     /* Does not cover all IP addresses. */
-    tor_addr_from_ipv4h(&intro->extend_info->addr, crypto_rand_int(65536));
-    intro->extend_info->port = 1 + crypto_rand_int(65535);
+    tor_addr_from_ipv4h(&addr, crypto_rand_int(65536) + 1);
+    port = 1 + crypto_rand_int(65535);
+    extend_info_add_orport(intro->extend_info, &addr, port);
     intro->intro_key = crypto_pk_dup_key(pk2);
     smartlist_add(generated->intro_nodes, intro);
   }
@@ -613,8 +618,12 @@ test_rend_fns(void *arg)
     tt_mem_op(gen_info->identity_digest,OP_EQ, par_info->identity_digest,
                DIGEST_LEN);
     tt_str_op(gen_info->nickname,OP_EQ, par_info->nickname);
-    tt_assert(tor_addr_eq(&gen_info->addr, &par_info->addr));
-    tt_int_op(gen_info->port,OP_EQ, par_info->port);
+    const tor_addr_port_t *a1, *a2;
+    a1 = extend_info_get_orport(gen_info, AF_INET);
+    a2 = extend_info_get_orport(par_info, AF_INET);
+    tt_assert(a1 && a2);
+    tt_assert(tor_addr_eq(&a1->addr, &a2->addr));
+    tt_int_op(a2->port,OP_EQ, a2->port);
   }
 
   rend_service_descriptor_free(parsed);
diff --git a/src/test/test_circuitbuild.c b/src/test/test_circuitbuild.c
index e1fbd333d7..8f0e8b54e8 100644
--- a/src/test/test_circuitbuild.c
+++ b/src/test/test_circuitbuild.c
@@ -1001,15 +1001,9 @@ mock_circuit_mark_for_close_(circuit_t *circ, int reason,
 static int mock_channel_connect_calls = 0;
 static channel_t *mock_channel_connect_nchan = NULL;
 static channel_t *
-mock_channel_connect_for_circuit(const tor_addr_t *addr,
-                                 uint16_t port,
-                                 const char *id_digest,
-                                 const struct ed25519_public_key_t *ed_id)
+mock_channel_connect_for_circuit(const extend_info_t *ei)
 {
-  (void)addr;
-  (void)port;
-  (void)id_digest;
-  (void)ed_id;
+  (void)ei;
   mock_channel_connect_calls++;
   return mock_channel_connect_nchan;
 }
@@ -1683,14 +1677,14 @@ test_circuit_send_next_onion_skin(void *arg)
 
   extend_info_t ipv6_hop;
   memset(&ipv6_hop, 0, sizeof(ipv6_hop));
-  tor_addr_make_null(&ipv6_hop.addr, AF_INET6);
+  tor_addr_parse(&ipv6_hop.orports[0].addr, "1::2");
   extend_info_t *multi_ipv6_hop[DEFAULT_ROUTE_LEN] = {&ipv6_hop,
                                                       &ipv6_hop,
                                                       &ipv6_hop};
 
   extend_info_t ipv4_hop;
   memset(&ipv4_hop, 0, sizeof(ipv4_hop));
-  tor_addr_make_null(&ipv4_hop.addr, AF_INET);
+  tor_addr_from_ipv4h(&ipv4_hop.orports[0].addr, 0x20304050);
   extend_info_t *multi_ipv4_hop[DEFAULT_ROUTE_LEN] = {&ipv4_hop,
                                                       &ipv4_hop,
                                                       &ipv4_hop};
@@ -1743,7 +1737,7 @@ test_circuit_send_next_onion_skin(void *arg)
   /* Fail because the address family is invalid */
   tt_int_op(circuit_send_next_onion_skin(origin_circ), OP_EQ,
             -END_CIRC_REASON_INTERNAL);
-  expect_log_msg("Client trying to extend to a non-IPv4 address.\n");
+  expect_log_msg("No supported address family found in extend_info.\n");
   mock_clean_saved_logs();
 
   /* Try an extend, but fail the server valid address check */
@@ -1757,7 +1751,7 @@ test_circuit_send_next_onion_skin(void *arg)
   mock_circuit_deliver_create_cell_expect_direct = false;
   tt_int_op(circuit_send_next_onion_skin(origin_circ), OP_EQ,
             -END_CIRC_REASON_INTERNAL);
-  expect_log_msg("Server trying to extend to an invalid address family.\n");
+  expect_log_msg("No supported address family found in extend_info.\n");
   mock_clean_saved_logs();
 
   /* Try an extend, but fail in the client code, with an IPv6 address */
@@ -1771,7 +1765,7 @@ test_circuit_send_next_onion_skin(void *arg)
   mock_circuit_deliver_create_cell_expect_direct = false;
   tt_int_op(circuit_send_next_onion_skin(origin_circ), OP_EQ,
             -END_CIRC_REASON_INTERNAL);
-  expect_log_msg("Client trying to extend to a non-IPv4 address.\n");
+  expect_log_msg("No supported address family found in extend_info.\n");
   mock_clean_saved_logs();
 
   /* Stop capturing bugs, but keep capturing logs */
diff --git a/src/test/test_circuitpadding.c b/src/test/test_circuitpadding.c
index 3e3a59dc96..cc8c63d608 100644
--- a/src/test/test_circuitpadding.c
+++ b/src/test/test_circuitpadding.c
@@ -23,6 +23,7 @@
 #include "core/or/circuitbuild.h"
 #include "core/or/circuitpadding.h"
 #include "core/or/circuitpadding_machines.h"
+#include "core/or/extendinfo.h"
 #include "core/mainloop/netstatus.h"
 #include "core/crypto/relay_crypto.h"
 #include "core/or/protover.h"
diff --git a/src/test/test_hs_client.c b/src/test/test_hs_client.c
index ae5cc5ed84..f965344ce0 100644
--- a/src/test/test_hs_client.c
+++ b/src/test/test_hs_client.c
@@ -41,6 +41,7 @@
 #include "feature/rend/rendcache.h"
 #include "core/or/circuitlist.h"
 #include "core/or/circuitbuild.h"
+#include "core/or/extendinfo.h"
 #include "core/mainloop/connection.h"
 #include "core/or/connection_edge.h"
 #include "feature/nodelist/networkstatus.h"
@@ -529,7 +530,7 @@ test_client_pick_intro(void *arg)
         get_options_mutable()->ClientUseIPv6 = 1;
         intro_ei = hs_get_extend_info_from_lspecs(ip->link_specifiers,
                                                   &ip->onion_key, 1);
-        tt_assert(tor_addr_family(&intro_ei->addr) == AF_INET6);
+        tt_assert(tor_addr_family(&intro_ei->orports[0].addr) == AF_INET6);
       }
       tt_assert(intro_ei);
       if (intro_ei) {
@@ -537,7 +538,8 @@ test_client_pick_intro(void *arg)
         char ip_addr[TOR_ADDR_BUF_LEN];
         /* We need to decorate in case it is an IPv6 else routerset_parse()
          * doesn't like it. */
-        ptr = tor_addr_to_str(ip_addr, &intro_ei->addr, sizeof(ip_addr), 1);
+        ptr = tor_addr_to_str(ip_addr, &intro_ei->orports[0].addr,
+                              sizeof(ip_addr), 1);
         tt_assert(ptr == ip_addr);
         ret = routerset_parse(get_options_mutable()->ExcludeNodes,
                               ip_addr, "");
diff --git a/src/test/test_nodelist.c b/src/test/test_nodelist.c
index fbbbf0a99f..93d1ce453b 100644
--- a/src/test/test_nodelist.c
+++ b/src/test/test_nodelist.c
@@ -1182,11 +1182,11 @@ test_nodelist_extend_info_describe(void *arg)
          sizeof(mock_ei_ipv4.identity_digest));
   strlcpy(mock_ei_ipv4.nickname, "TestOR7890123456789",
           sizeof(mock_ei_ipv4.nickname));
-  tor_addr_parse(&mock_ei_ipv4.addr, "111.222.233.244");
+  tor_addr_parse(&mock_ei_ipv4.orports[0].addr, "111.222.233.244");
 
   /* Create and modify the other extend info. */
   memcpy(&mock_ei_ipv6, &mock_ei_ipv4, sizeof(mock_ei_ipv6));
-  tor_addr_parse(&mock_ei_ipv6.addr,
+  tor_addr_parse(&mock_ei_ipv6.orports[0].addr,
                  "[1111:2222:3333:4444:5555:6666:7777:8888]");
 
   /* We don't test the no-nickname and no-IP cases, because they're covered by
diff --git a/src/test/test_policy.c b/src/test/test_policy.c
index 7949e90e9e..388b5c74c9 100644
--- a/src/test/test_policy.c
+++ b/src/test/test_policy.c
@@ -8,6 +8,7 @@
 #include "app/config/config.h"
 #include "core/or/circuitbuild.h"
 #include "core/or/policies.h"
+#include "core/or/extendinfo.h"
 #include "feature/dirparse/policy_parse.h"
 #include "feature/hs/hs_common.h"
 #include "feature/hs/hs_descriptor.h"
@@ -2084,8 +2085,8 @@ test_policies_fascist_firewall_allows_address(void *arg)
       expect_single_log_msg("Specified link specifiers is null"); \
     } else { \
       expect_no_log_entry(); \
-      tt_assert(tor_addr_eq(&(expect_ap).addr, &ei->addr)); \
-      tt_int_op((expect_ap).port, OP_EQ, ei->port); \
+      tt_assert(tor_addr_eq(&(expect_ap).addr, &ei->orports[0].addr)); \
+      tt_int_op((expect_ap).port, OP_EQ, ei->orports[0].port); \
       extend_info_free(ei); \
     } \
     teardown_capture_of_logs(); \