conncheck: NOMINATION STUN attribute support

Attribute is proposed here: https://tools.ietf.org/html/draft-thatcher-ice-renomination-00
WebRTC supports this attribute: controlling side provides attribute value increased by one each time selected pair is changed:
https://chromium.googlesource.com/external/webrtc/+/3c7d599750405bc734e1d5adbf1b54265b725a9d/p2p/base/p2ptransportchannel.cc#1821

5 files changed, 98 insertions, 2 deletions

diff --git a/agent/agent-priv.h b/agent/agent-priv.h
index a38aa23..91f73a3 100644
--- a/agent/agent-priv.h
+++ b/agent/agent-priv.h
@@ -156,6 +156,7 @@ struct _NiceAgent
   guint stun_initial_timeout;     /* property: stun initial timeout, RTO */
   guint stun_reliable_timeout;    /* property: stun reliable timeout */
   NiceNominationMode nomination_mode; /* property: Nomination mode */
+  gboolean support_renomination;  /* property: support RENOMINATION STUN attribute */
 
   GSList *local_addresses;        /* list of NiceAddresses for local
 				     interfaces */
diff --git a/agent/agent.c b/agent/agent.c
index 59028ce..86bf37a 100644
--- a/agent/agent.c
+++ b/agent/agent.c
@@ -119,6 +119,7 @@ enum
   PROP_STUN_RELIABLE_TIMEOUT,
   PROP_NOMINATION_MODE,
   PROP_ICE_TRICKLE,
+  PROP_SUPPORT_RENOMINATION,
 };
 
 
@@ -466,6 +467,24 @@ nice_agent_class_init (NiceAgentClass *klass)
          G_PARAM_READWRITE | G_PARAM_CONSTRUCT_ONLY));
 
   /**
+   * NiceAgent:support-renomination:
+   *
+   * Support RENOMINATION STUN attribute proposed here:
+   * https://tools.ietf.org/html/draft-thatcher-ice-renomination-00 As
+   * soon as RENOMINATION attribute is received from remote
+   * candidate's address, corresponding candidates pair gets
+   * selected. This is specific to Google Chrome/libWebRTC.
+   */
+  g_object_class_install_property (gobject_class, PROP_SUPPORT_RENOMINATION,
+      g_param_spec_boolean (
+         "support-renomination",
+         "Support RENOMINATION STUN attribute",
+         "As soon as RENOMINATION attribute is received from remote candidate's address, "
+         "corresponding candidates pair gets selected.",
+         FALSE,
+         G_PARAM_READWRITE));
+
+  /**
    * NiceAgent:proxy-ip:
    *
    * The proxy server IP used to bypass a proxy firewall
@@ -1183,6 +1202,7 @@ nice_agent_init (NiceAgent *agent)
   agent->saved_controlling_mode = TRUE;
   agent->max_conn_checks = NICE_AGENT_MAX_CONNECTIVITY_CHECKS_DEFAULT;
   agent->nomination_mode = NICE_NOMINATION_MODE_AGGRESSIVE;
+  agent->support_renomination = FALSE;
 
   agent->discovery_list = NULL;
   agent->discovery_unsched_items = 0;
@@ -1246,6 +1266,7 @@ nice_agent_new_full (GMainContext *ctx,
       NICE_NOMINATION_MODE_REGULAR : NICE_NOMINATION_MODE_AGGRESSIVE,
       "full-mode", (flags & NICE_AGENT_OPTION_LITE_MODE) ? FALSE : TRUE,
       "ice-trickle", (flags & NICE_AGENT_OPTION_ICE_TRICKLE) ? TRUE : FALSE,
+      "support-renomination", (flags & NICE_AGENT_OPTION_SUPPORT_RENOMINATION) ? TRUE : FALSE,
       NULL);
 
   return agent;
@@ -1302,6 +1323,10 @@ nice_agent_get_property (
       g_value_set_enum (value, agent->nomination_mode);
       break;
 
+    case PROP_SUPPORT_RENOMINATION:
+      g_value_set_boolean (value, agent->support_renomination);
+      break;
+
     case PROP_PROXY_IP:
       g_value_set_string (value, agent->proxy_ip);
       break;
@@ -1514,6 +1539,10 @@ nice_agent_set_property (
       agent->nomination_mode = g_value_get_enum (value);
       break;
 
+    case PROP_SUPPORT_RENOMINATION:
+      agent->support_renomination = g_value_get_boolean (value);
+      break;
+
     case PROP_PROXY_IP:
       g_free (agent->proxy_ip);
       agent->proxy_ip = g_value_dup_string (value);
diff --git a/agent/agent.h b/agent/agent.h
index 2ad700c..688d784 100644
--- a/agent/agent.h
+++ b/agent/agent.h
@@ -405,6 +405,8 @@ typedef enum
  * @NICE_AGENT_OPTION_RELIABLE: Enables reliable mode, possibly using PseudoTCP, *  see nice_agent_new_reliable().
  * @NICE_AGENT_OPTION_LITE_MODE: Enable lite mode
  * @NICE_AGENT_OPTION_ICE_TRICKLE: Enable ICE trickle mode
+ * @NICE_AGENT_OPTION_SUPPORT_RENOMINATION: Enable renomination triggered by NOMINATION STUN attribute
+ * proposed here: https://tools.ietf.org/html/draft-thatcher-ice-renomination-00
  *
  * These are options that can be passed to nice_agent_new_full(). They set
  * various properties on the agent. Not including them sets the property to
@@ -417,6 +419,7 @@ typedef enum {
   NICE_AGENT_OPTION_RELIABLE = 1 << 1,
   NICE_AGENT_OPTION_LITE_MODE = 1 << 2,
   NICE_AGENT_OPTION_ICE_TRICKLE = 1 << 3,
+  NICE_AGENT_OPTION_SUPPORT_RENOMINATION = 1 << 4,
 } NiceAgentOption;
 
 /**
diff --git a/agent/conncheck.c b/agent/conncheck.c
index 06ba940..f8acfd6 100644
--- a/agent/conncheck.c
+++ b/agent/conncheck.c
@@ -3913,6 +3913,62 @@ static bool conncheck_stun_validater (StunAgent *agent,
   return FALSE;
 }
 
+/*
+ * handle RENOMINATION stun attribute
+ * @return TRUE if nomination changed. FALSE otherwise
+ */
+static gboolean conn_check_handle_renomination (NiceAgent *agent, NiceStream *stream,
+    NiceComponent *component, StunMessage *req,
+    NiceCandidate *remote_candidate, NiceCandidate *local_candidate)
+{
+  GSList *lst;
+  if (!agent->controlling_mode && NICE_AGENT_IS_COMPATIBLE_WITH_RFC5245_OR_OC2007R2 (agent) &&
+      agent->support_renomination && remote_candidate && local_candidate)
+  {
+    uint32_t nom_value = 0;
+    uint16_t nom_len = 0;
+    const void *value = stun_message_find (req, STUN_ATTRIBUTE_NOMINATION, &nom_len);
+    if (nom_len == 0) {
+      return FALSE;
+    }
+    if (nom_len == 4) {
+      memcpy (&nom_value, value, 4);
+      nom_value = ntohl (nom_value);
+    } else {
+      nice_debug ("Agent %p : received NOMINATION attr with incorrect octet length %u, expected 4 bytes",
+          agent, nom_len);
+      return FALSE;
+    }
+
+    if (nice_debug_is_enabled ()) {
+      gchar remote_str[INET6_ADDRSTRLEN];
+      nice_address_to_string(&remote_candidate->addr, remote_str);
+      nice_debug ("Agent %p : received NOMINATION attr for remote candidate [%s]:%u, value is %u",
+          agent, remote_str, nice_address_get_port (&remote_candidate->addr), nom_value);
+    }
+
+    /*
+     * If another pair is SELECTED, change this pair's priority to be greater than
+     * selected pair's priority so this pair gets SELECTED!
+     */
+    if (component->selected_pair.priority &&
+        component->selected_pair.remote && component->selected_pair.remote != remote_candidate &&
+        component->selected_pair.local && component->selected_pair.local != local_candidate) {
+      for (lst = stream->conncheck_list; lst; lst = lst->next) {
+        CandidateCheckPair *pair = lst->data;
+        if (pair->local == local_candidate && pair->remote == remote_candidate) {
+          if (pair->valid) {
+            pair->priority = component->selected_pair.priority + 1;
+          }
+          break;
+        }
+      }
+    }
+    priv_mark_pair_nominated (agent, stream, component, local_candidate, remote_candidate);
+    return TRUE;
+  }
+  return FALSE;
+}
 
 /*
  * Processing an incoming STUN message.
@@ -4278,6 +4334,9 @@ gboolean conn_check_handle_inbound_stun (NiceAgent *agent, NiceStream *stream,
             "probably a keepalive.", agent);
   }
 
+  /* RENOMINATION attribute support */
+  conn_check_handle_renomination(agent, stream, component, &req, local_candidate, remote_candidate);
+
   return TRUE;
 }
 
diff --git a/stun/stunmessage.h b/stun/stunmessage.h
index 26ee12d..0ac9977 100644
--- a/stun/stunmessage.h
+++ b/stun/stunmessage.h
@@ -230,6 +230,8 @@ typedef enum
  * attribute as defined by [MS-ICE2]
  * @STUN_ATTRIBUTE_MS_IMPLEMENTATION_VERSION: The IMPLEMENTATION-VERSION
  * optional attribute as defined by [MS-ICE2]
+ * @STUN_ATTRIBUTE_NOMINATION: The NOMINATION attribute as defined by
+ * draft-thatcher-ice-renomination-00 and deployed in Google Chrome
  *
  * Known STUN attribute types as defined by various RFCs and drafts
  */
@@ -309,8 +311,10 @@ typedef enum
   /* 0x8051-0x8053 */      /* reserved */
   STUN_ATTRIBUTE_CANDIDATE_IDENTIFIER=0x8054,     /* MS-ICE2 */
   /* 0x8055-0x806F */      /* reserved */
-  STUN_ATTRIBUTE_MS_IMPLEMENTATION_VERSION=0x8070 /* MS-ICE2 */
-  /* 0x8071-0xFFFF */      /* reserved */
+  STUN_ATTRIBUTE_MS_IMPLEMENTATION_VERSION=0x8070, /* MS-ICE2 */
+  /* 0x8071-0xC000 */      /* reserved */
+  STUN_ATTRIBUTE_NOMINATION=0xC001 /* https://tools.ietf.org/html/draft-thatcher-ice-renomination-00 */
+  /* 0xC002-0xFFFF */      /* reserved */
 } StunAttribute;