[FFmpeg-devel] [PATCH v4 07/11] avformat/whip: add support for active dtls role

[Jack Lau <jacklau1222gm@gmail.com>]

add dtls_active flag to specify the dtls role

properly set the send key and recv key depends on DTLS role

As DTLS server, the recv key is client master key plus salt,
the send key is server master key plus salt.
As DTLS client, the recv key is server master key plus salt,
the send key is client master key plus salt.

Signed-off-by: Jack Lau <jacklau1222@qq.com>
---
 libavformat/whip.c | 32 ++++++++++++++++++++------------
 1 file changed, 20 insertions(+), 12 deletions(-)

diff --git a/libavformat/whip.c b/libavformat/whip.c
index 094d3a0a4c..e02ed7a8a4 100644
--- a/libavformat/whip.c
+++ b/libavformat/whip.c
@@ -201,7 +201,8 @@ enum WHIPState {
 
 typedef enum WHIPFlags {
     WHIP_FLAG_IGNORE_IPV6  = (1 << 0), // Ignore ipv6 candidate
-    WHIP_FLAG_DISABLE_RTX     = (1 << 1)  // Enable NACK and RTX
+    WHIP_FLAG_DISABLE_RTX     = (1 << 1),  // Enable NACK and RTX
+    WHIP_FLAG_DTLS_ACTIVE  = (1 << 2), // DTLS active role
 } WHIPFlags;
 
 typedef struct RtpHistoryItem {
@@ -611,6 +612,7 @@ static int generate_sdp_offer(AVFormatContext *s)
     const char *acodec_name = NULL, *vcodec_name = NULL;
     AVBPrint bp;
     WHIPContext *whip = s->priv_data;
+    int is_dtls_active = whip->flags & WHIP_FLAG_DTLS_ACTIVE;
 
     /* To prevent a crash during cleanup, always initialize it. */
     av_bprint_init(&bp, 1, MAX_SDP_SIZE);
@@ -664,7 +666,7 @@ static int generate_sdp_offer(AVFormatContext *s)
             "a=ice-ufrag:%s\r\n"
             "a=ice-pwd:%s\r\n"
             "a=fingerprint:sha-256 %s\r\n"
-            "a=setup:passive\r\n"
+            "a=setup:%s\r\n"
             "a=mid:0\r\n"
             "a=sendonly\r\n"
             "a=msid:FFmpeg audio\r\n"
@@ -676,6 +678,7 @@ static int generate_sdp_offer(AVFormatContext *s)
             whip->ice_ufrag_local,
             whip->ice_pwd_local,
             whip->dtls_fingerprint,
+            is_dtls_active ? "active" : "passive",
             whip->audio_payload_type,
             acodec_name,
             whip->audio_par->sample_rate,
@@ -698,7 +701,7 @@ static int generate_sdp_offer(AVFormatContext *s)
             "a=ice-ufrag:%s\r\n"
             "a=ice-pwd:%s\r\n"
             "a=fingerprint:sha-256 %s\r\n"
-            "a=setup:passive\r\n"
+            "a=setup:%s\r\n"
             "a=mid:1\r\n"
             "a=sendonly\r\n"
             "a=msid:FFmpeg video\r\n"
@@ -719,6 +722,7 @@ static int generate_sdp_offer(AVFormatContext *s)
             whip->ice_ufrag_local,
             whip->ice_pwd_local,
             whip->dtls_fingerprint,
+            is_dtls_active ? "active" : "passive",
             whip->video_payload_type,
             vcodec_name,
             whip->video_payload_type,
@@ -1270,6 +1274,7 @@ static int ice_dtls_handshake(AVFormatContext *s)
     int ret = 0, size, i;
     int64_t starttime = av_gettime(), now;
     WHIPContext *whip = s->priv_data;
+    int is_dtls_active = whip->flags & WHIP_FLAG_DTLS_ACTIVE;
     AVDictionary *opts = NULL;
     char buf[256], *cert_buf = NULL, *key_buf = NULL;
 
@@ -1319,12 +1324,14 @@ next_packet:
                 av_usleep(5 * 1000);
                 continue;
             }
+            if (is_dtls_active)
+                break;
             av_log(whip, AV_LOG_ERROR, "Failed to read message\n");
             goto end;
         }
 
         /* Got nothing, continue to process handshake. */
-        if (ret <= 0 && whip->state < WHIP_STATE_DTLS_CONNECTING)
+        if (ret <= 0 && (is_dtls_active ? whip->state < WHIP_STATE_ICE_CONNECTED : whip->state < WHIP_STATE_DTLS_CONNECTING))
             continue;
 
         /* Handle the ICE binding response. */
@@ -1348,7 +1355,7 @@ next_packet:
                 } else
                     av_dict_set(&opts, "key_pem", whip->key_buf, 0);
                 av_dict_set_int(&opts, "external_sock", 1, 0);
-                av_dict_set_int(&opts, "listen", 1, 0);
+                av_dict_set_int(&opts, "listen", is_dtls_active ? 0 : 1, 0);
                 /* If got the first binding response, start DTLS handshake. */
                 ret = ffurl_open_whitelist(&whip->dtls_uc, buf, AVIO_FLAG_READ_WRITE, &s->interrupt_callback,
                     &opts, s->protocol_whitelist, s->protocol_blacklist, NULL);
@@ -1368,7 +1375,7 @@ next_packet:
         }
 
         /* If got any DTLS messages, handle it. */
-        if (is_dtls_packet(whip->buf, ret) && whip->state >= WHIP_STATE_ICE_CONNECTED || whip->state == WHIP_STATE_DTLS_CONNECTING) {
+        if ((is_dtls_packet(whip->buf, ret) || is_dtls_active) && whip->state >= WHIP_STATE_ICE_CONNECTED || whip->state == WHIP_STATE_DTLS_CONNECTING) {
             whip->state = WHIP_STATE_DTLS_CONNECTING;
             if ((ret = ffurl_handshake(whip->dtls_uc)) < 0)
                 goto end;
@@ -1406,6 +1413,8 @@ static int setup_srtp(AVFormatContext *s)
      */
     const char* suite = "SRTP_AES128_CM_HMAC_SHA1_80";
     WHIPContext *whip = s->priv_data;
+    int is_dtls_active = whip->flags & WHIP_FLAG_DTLS_ACTIVE;
+
     ret = ff_dtls_export_materials(whip->dtls_uc, whip->dtls_srtp_materials, sizeof(whip->dtls_srtp_materials));
     if (ret < 0)
         goto end;
@@ -1420,13 +1429,11 @@ static int setup_srtp(AVFormatContext *s)
     char *client_salt = server_key + DTLS_SRTP_KEY_LEN;
     char *server_salt = client_salt + DTLS_SRTP_SALT_LEN;
 
-    /* As DTLS server, the recv key is client master key plus salt. */
-    memcpy(recv_key, client_key, DTLS_SRTP_KEY_LEN);
-    memcpy(recv_key + DTLS_SRTP_KEY_LEN, client_salt, DTLS_SRTP_SALT_LEN);
+    memcpy(is_dtls_active ? send_key : recv_key, client_key, DTLS_SRTP_KEY_LEN);
+    memcpy(is_dtls_active ? send_key + DTLS_SRTP_KEY_LEN : recv_key + DTLS_SRTP_KEY_LEN, client_salt, DTLS_SRTP_SALT_LEN);
 
-    /* As DTLS server, the send key is server master key plus salt. */
-    memcpy(send_key, server_key, DTLS_SRTP_KEY_LEN);
-    memcpy(send_key + DTLS_SRTP_KEY_LEN, server_salt, DTLS_SRTP_SALT_LEN);
+    memcpy(is_dtls_active ? recv_key : send_key, server_key, DTLS_SRTP_KEY_LEN);
+    memcpy(is_dtls_active ? recv_key + DTLS_SRTP_KEY_LEN : send_key + DTLS_SRTP_KEY_LEN, server_salt, DTLS_SRTP_SALT_LEN);
 
     /* Setup SRTP context for outgoing packets */
     if (!av_base64_encode(buf, sizeof(buf), send_key, sizeof(send_key))) {
@@ -2098,6 +2105,7 @@ static const AVOption options[] = {
     { "whip_flags", "Set flags affecting WHIP connection behavior", OFFSET(flags), AV_OPT_TYPE_FLAGS,  { .i64 = 0 }, 0, 0, ENC, .unit = "flags" },
     { "ignore_ipv6", "Ignore any IPv6 ICE candidate", 0, AV_OPT_TYPE_CONST,  { .i64 = WHIP_FLAG_IGNORE_IPV6 }, 0, UINT_MAX, ENC, .unit = "flags" },
     { "disable_rtx", "Disable RFC 4588 RTX", 0, AV_OPT_TYPE_CONST,  { .i64 = WHIP_FLAG_DISABLE_RTX }, 0, UINT_MAX, ENC, .unit = "flags" },
+    { "dtls_active", "Set dtls role as active", 0, AV_OPT_TYPE_CONST, { .i64 = WHIP_FLAG_DTLS_ACTIVE }, 0, UINT_MAX, ENC, .unit = "flags" },
     { "rtx_history_size", "Packet history size", OFFSET(history_size), AV_OPT_TYPE_INT, { .i64 = HISTORY_SIZE_DEFAULT }, 64, 2048, ENC },
     { NULL },
 };
-- 
2.49.0

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