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修改Janus,支援datachannel通過rtp通道傳輸

Janus的datachannel支援的協議主要是:“DTLS/SCTP”、"UDP/DTLS/SCTP",而RTP通道使用的是"UDP/TLS/RTP/SAVPF",修改的思路包括SDP返回的修改,RTP資料包中提取datachannel包對應SSRC的包。

1、給janus_ice_stream結構體新增data的ssrc欄位和初始化:

    guint32 data_ssrc_peer;//[email protected]
    guint32 data_ssrc, sequence_data;

    int janus_sdp_process(void *ice_handle, janus_sdp *remote_sdp, gboolean update) 方法中增加如下邏輯:
                    if(!strcasecmp(m->proto, "UDP/DTLS/SCTP")  || !strcasecmp(m->proto, "UDP/TLS/RTP/SAVPF")) {
                        stream->data_ssrc = janus_random_uint32();    /* FIXME Should we look for conflicts? */
                        stream->sequence_data = janus_random_uint32();    
                        janus_flags_set(&handle->webrtc_flags, JANUS_ICE_HANDLE_WEBRTC_NEW_DATACHAN_SDP);
                        janus_flags_clear(&handle->webrtc_flags, JANUS_ICE_HANDLE_WEBRTC_DATA_CHANNELS);//
[email protected]
add                     } else {                         janus_flags_clear(&handle->webrtc_flags, JANUS_ICE_HANDLE_WEBRTC_NEW_DATACHAN_SDP);                     }

2、SDP返回資料:

m->fmts = g_list_append(m->fmts, g_strdup("109"));
            janus_sdp_attribute *aa = janus_sdp_attribute_create("rtpmap", "109 google-data/90000");
            m->attributes = g_list_append(m->attributes, aa);        
            m->ptypes = g_list_append(m->ptypes, GINT_TO_POINTER(109));  

          

3、接收RTP資料函式janus_ice_cb_nice_recv中,增加對datachannel的資料處理的邏輯:

if (header->type == 109 || stream->data_ssrc_peer == packet_ssrc){ 
                        /* Pass the data to the responsible plugin */ 
                        janus_plugin *plugin = (janus_plugin *)handle->app;
                        
                        if(plugin && plugin->incoming_data &&
                                !g_atomic_int_get(&handle->app_handle->stopped) &&
                                !g_atomic_int_get(&handle->destroyed)){
                                
                            plugin->incoming_data(handle->app_handle, (char *)buf + RTP_HEADER_SIZE, buflen - RTP_HEADER_SIZE);
                        }
                        return;
                    }

4、傳送RTP資料時,使用RTP通道傳送datachannel的資料:

void janus_plugin_relay_data(janus_plugin_session *plugin_session, char *buf, int len) {
    if((plugin_session < (janus_plugin_session *)0x1000) || g_atomic_int_get(&plugin_session->stopped) || buf == NULL || len < 1)
        return;
    janus_ice_handle *handle = (janus_ice_handle *)plugin_session->gateway_handle;
    if(!handle || janus_flags_is_set(&handle->webrtc_flags, JANUS_ICE_HANDLE_WEBRTC_STOP)
            || janus_flags_is_set(&handle->webrtc_flags, JANUS_ICE_HANDLE_WEBRTC_ALERT)){
        return;
    }
#ifdef HAVE_SCTP
    if (janus_flags_is_set(&handle->webrtc_flags, JANUS_ICE_HANDLE_WEBRTC_NEW_DATACHAN_SDP)){
        janus_ice_relay_data_withrtp(handle, buf, len);//relay daa with rtp only.
    }else{
        janus_ice_relay_data(handle, buf, len);
    }
#else
    JANUS_LOG(LOG_WARN, "Asked to relay data, but Data Channels support has not been compiled...\n");
#endif
}


void janus_ice_relay_data_withrtp(janus_ice_handle *handle, char *buf, int len) {
    struct timeval now;
    if(!handle || handle->queued_packets == NULL || buf == NULL || len < 1){
        return;
    }
    /* Queue this packet */
    janus_ice_queued_packet *pkt = g_malloc(sizeof(janus_ice_queued_packet));
    pkt->data = g_malloc(RTP_HEADER_SIZE+len+SRTP_MAX_TAG_LEN+4);
    janus_rtp_header *header = (janus_rtp_header *)pkt->data;
    header->ssrc = (handle->stream->data_ssrc);
    header->type = 109;
    header->version = 2;
    header->markerbit = 1;
    header->extension = 0; 
    handle->stream->sequence_data++;
    header->seq_number = (handle->stream->sequence_data + 100);
    gettimeofday(&now,0);
    header->timestamp = htonl(now.tv_sec);
    
    memcpy((char *)pkt->data + RTP_HEADER_SIZE, buf, len);
    pkt->length = RTP_HEADER_SIZE + len;
    pkt->type = JANUS_ICE_PACKET_DATA_WITH_RTP;
    pkt->control = FALSE;
    pkt->encrypted = FALSE;
    pkt->retransmission = FALSE;
    pkt->added = janus_get_monotonic_time();
    janus_ice_queue_packet(handle, pkt);
}
傳送函式static gboolean janus_ice_outgoing_traffic_handle的邏輯中,對ssrc的處理需要修改為:
     header->ssrc = htonl(video ? stream->video_ssrc : ((pkt->type == JANUS_ICE_PACKET_DATA_WITH_RTP)?stream->data_ssrc : stream->audio_ssrc));