From 8b8199180766e3eab6014feaa64ccaedcdc12816 Mon Sep 17 00:00:00 2001
From: Ben Ford <bford@digium.com>
Date: Mon, 23 Dec 2019 11:11:13 -0600
Subject: [PATCH] ICE: Add callback for finding valid pair.

It's possible to start sending as soon as one valid pair is found during
ICE negotiation. The reason we would want to do this is because it is
possible for a delay to occur at the start of a call for up to 3 seconds
until ICE negotiation has actually completed. More information can be
found here:
https://bugs.chromium.org/p/chromium/issues/detail?id=1024096

This patch adds a callback once a valid pair is found that applications
can use to start sending to avoid this scenario. Since only one valid
pair is needed to start media, we only trigger the callback once.
---
 pjnath/include/pjnath/ice_session.h |  9 +++++++++
 pjnath/src/pjnath/ice_session.c     | 16 ++++++++++++++++
 2 files changed, 25 insertions(+)

diff --git a/pjnath/include/pjnath/ice_session.h b/pjnath/include/pjnath/ice_session.h
index 15f0d04..8971220 100644
--- a/pjnath/include/pjnath/ice_session.h
+++ b/pjnath/include/pjnath/ice_session.h
@@ -468,6 +468,14 @@ typedef struct pj_ice_sess_cb
 {
     /**
      * An optional callback that will be called by the ICE session when
+     * a valid pair has been found during ICE negotiation.
+     *
+     * @param ice           The ICE session.
+     */
+    void	(*on_valid_pair)(pj_ice_sess *ice);
+
+    /**
+     * An optional callback that will be called by the ICE session when
      * ICE negotiation has completed, successfully or with failure.
      *
      * @param ice	    The ICE session.
@@ -625,6 +633,7 @@ struct pj_ice_sess
     pj_bool_t		 is_nominating;		    /**< Nominating stage   */
     pj_bool_t		 is_complete;		    /**< Complete?	    */
     pj_bool_t		 is_destroying;		    /**< Destroy is called  */
+    pj_bool_t            valid_pair_found;          /**< First pair found   */
     pj_status_t		 ice_status;		    /**< Error status.	    */
     pj_timer_entry	 timer;			    /**< ICE timer.	    */
     pj_ice_sess_cb	 cb;			    /**< Callback.	    */
diff --git a/pjnath/src/pjnath/ice_session.c b/pjnath/src/pjnath/ice_session.c
index c51dba7..ed4138a 100644
--- a/pjnath/src/pjnath/ice_session.c
+++ b/pjnath/src/pjnath/ice_session.c
@@ -418,6 +418,8 @@ PJ_DEF(pj_status_t) pj_ice_sess_create(pj_stun_config *stun_cfg,
 
     pj_list_init(&ice->early_check);
 
+    ice->valid_pair_found = PJ_FALSE;
+
     /* Done */
     *p_ice = ice;
 
@@ -1348,6 +1350,20 @@ static pj_bool_t on_check_complete(pj_ice_sess *ice,
 	     GET_CHECK_ID(&ice->clist, check),
 	     (check->nominated ? "  and nominated" : "")));
 
+	{
+	    /* On the first valid pair, we call the callback, if present */
+	    if (ice->valid_pair_found == PJ_FALSE) {
+	        void (*on_valid_pair)(pj_ice_sess *ice);
+
+		ice->valid_pair_found = PJ_TRUE;
+	        on_valid_pair = ice->cb.on_valid_pair;
+
+	        if (on_valid_pair) {
+		    (*on_valid_pair)(ice);
+	        }
+	    }
+	}
+
     }
 
     /* 8.2.  Updating States
-- 
2.7.4