[FFmpeg-devel] [PATCH] avformat/whip: add PRIORITY and ICE_CONTROLLING for STUN binding request (PR #20405)

[FFmpeg-devel] [PATCH] avformat/whip: add PRIORITY and ICE_CONTROLLING for STUN binding request (PR #20405)

[Jack Lau via ffmpeg-devel]

PR #20405 opened by Jack Lau (JackLau)
URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/20405
Patch URL: https://code.ffmpeg.org/FFmpeg/FFmpeg/pulls/20405.patch

fix issue 20402

See RFC 8445 7.1,
The PRIORITY and ICE-CONTROLLED or ICE-CONTROLLING must be included
in a Binding request.

FFmpeg is always ICE Controlling role so we use ICE-CONTROLLING attr.

Co-author-by: Jack Lau <jacklau1222@qq.com>
Signed-off-by: Sergio Garcia Murillo <sergio.garcia.murillo@gmail.com>


>From d2fb437542816460905afd92fc4fad577b9ce9c3 Mon Sep 17 00:00:00 2001
From: Sergio Garcia Murillo <sergio.garcia.murillo@gmail.com>
Date: Wed, 3 Sep 2025 10:43:36 +0800
Subject: [PATCH] avformat/whip: add PRIORITY and ICE_CONTROLLING for STUN
 binding request

fix issue 20402

See RFC 8445 7.1,
The PRIORITY and ICE-CONTROLLED or ICE-CONTROLLING must be included
in a Binding request.

FFmpeg is always ICE Controlling role so we use ICE-CONTROLLING attr.

Co-author-by: Jack Lau <jacklau1222@qq.com>
Signed-off-by: Sergio Garcia Murillo <sergio.garcia.murillo@gmail.com>
---
 libavformat/whip.c | 25 +++++++++++++++++++++++--
 1 file changed, 23 insertions(+), 2 deletions(-)

diff --git a/libavformat/whip.c b/libavformat/whip.c
index 1fcf19aaa3..4ea9cefa89 100644
--- a/libavformat/whip.c
+++ b/libavformat/whip.c
@@ -80,6 +80,13 @@
 /* The magic cookie for Session Traversal Utilities for NAT (STUN) messages. */
 #define STUN_MAGIC_COOKIE 0x2112A442
 
+/**
+ * See RFC 8445 5.1.2
+ * priority = (2^24)*(type preference) + (2^8)*(local preference) + (2^0)*(256 - component ID)
+ * host candidate priority is 126 << 24 | 65535 << 8 | 255
+ */
+#define STUN_HOST_CANDIDATE_PRIORITY 126 << 24 | 65535 << 8 | 255
+
 /**
  * The DTLS content type.
  * See https://tools.ietf.org/html/rfc2246#section-6.2.1
@@ -156,9 +163,11 @@
 /* STUN Attribute, comprehension-required range (0x0000-0x7FFF) */
 enum STUNAttr {
     STUN_ATTR_USERNAME                  = 0x0006, /// shared secret response/bind request
+    STUN_ATTR_PRIORITY                  = 0x0024, /// must be included in a Binding request
     STUN_ATTR_USE_CANDIDATE             = 0x0025, /// bind request
     STUN_ATTR_MESSAGE_INTEGRITY         = 0x0008, /// bind request/response
     STUN_ATTR_FINGERPRINT               = 0x8028, /// rfc5389
+    STUN_ATTR_ICE_CONTROLLING           = 0x802A, /// ICE controlling role
 };
 
 enum WHIPState {
@@ -231,6 +240,7 @@ typedef struct WHIPContext {
      */
     char *sdp_offer;
 
+    uint64_t ice_tie_breaker; // random 64 bit, for ICE-CONTROLLING
     /* The ICE username and pwd from remote server. */
     char *ice_ufrag_remote;
     char *ice_pwd_remote;
@@ -382,6 +392,9 @@ static av_cold int initialize(AVFormatContext *s)
     seed = av_get_random_seed();
     av_lfg_init(&whip->rnd, seed);
 
+    /* 64 bit tie breaker for ICE-CONTROLLING (RFC 8445 16.1) */
+    whip->ice_tie_breaker = ((uint64_t)av_lfg_get(&whip->rnd) << 32) | (uint64_t)av_lfg_get(&whip->rnd);
+
     whip->audio_first_seq = av_lfg_get(&whip->rnd) & 0x0fff;
     whip->video_first_seq = whip->audio_first_seq + 1;
 
@@ -912,8 +925,8 @@ end:
  * Creates and marshals an ICE binding request packet.
  *
  * This function creates and marshals an ICE binding request packet. The function only
- * generates the username attribute and does not include goog-network-info, ice-controlling,
- * use-candidate, and priority. However, some of these attributes may be added in the future.
+ * generates the username attribute and does not include goog-network-info,
+ * use-candidate. However, some of these attributes may be added in the future.
  *
  * @param s Pointer to the AVFormatContext
  * @param buf Pointer to memory buffer to store the request packet
@@ -966,6 +979,14 @@ static int ice_create_request(AVFormatContext *s, uint8_t *buf, int buf_size, in
     avio_wb16(pb, STUN_ATTR_USE_CANDIDATE); /* attribute type use-candidate */
     avio_wb16(pb, 0); /* size of use-candidate */
 
+    avio_wb16(pb, STUN_ATTR_PRIORITY);
+    avio_wb16(pb, 4);
+    avio_wb32(pb, STUN_HOST_CANDIDATE_PRIORITY);
+
+    avio_wb16(pb, STUN_ATTR_ICE_CONTROLLING);
+    avio_wb16(pb, 8);
+    avio_wb64(pb, whip->ice_tie_breaker);
+
     /* Build and update message integrity */
     avio_wb16(pb, STUN_ATTR_MESSAGE_INTEGRITY); /* attribute type message integrity */
     avio_wb16(pb, 20); /* size of message integrity */
-- 
2.49.1

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