Add protocol extension for multi-client-compatible ping support

src/AudioStream.c

@@ -41,8 +41,7 @@ typedef struct _QUEUED_AUDIO_PACKET {
 } QUEUED_AUDIO_PACKET, *PQUEUED_AUDIO_PACKET;
 
 static void AudioPingThreadProc(void* context) {
-    // Ping in ASCII
-    char pingData[] = { 0x50, 0x49, 0x4E, 0x47 };
+    char legacyPingData[] = { 0x50, 0x49, 0x4E, 0x47 };
     LC_SOCKADDR saddr;
 
     LC_ASSERT(AudioPortNumber != 0);
@@ -50,19 +49,20 @@ static void AudioPingThreadProc(void* context) {
     memcpy(&saddr, &RemoteAddr, sizeof(saddr));
     SET_PORT(&saddr, AudioPortNumber);
 
-    // Send PING every 500 milliseconds
+    // We do not check for errors here. Socket errors will be handled
+    // on the read-side in ReceiveThreadProc(). This avoids potential
+    // issues related to receiving ICMP port unreachable messages due
+    // to sending a packet prior to the host PC binding to that port.
+    int pingCount = 0;
     while (!PltIsThreadInterrupted(&udpPingThread)) {
-        // We do not check for errors here. Socket errors will be handled
-        // on the read-side in ReceiveThreadProc(). This avoids potential
-        // issues related to receiving ICMP port unreachable messages due
-        // to sending a packet prior to the host PC binding to that port.
-        sendto(rtpSocket, pingData, sizeof(pingData), 0, (struct sockaddr*)&saddr, RemoteAddrLen);
+        if (AudioPingPayload.payload[0] != 0) {
+            pingCount++;
+            AudioPingPayload.sequenceNumber = BE32(pingCount);
 
-        if (firstReceiveTime == 0 && isSocketReadable(rtpSocket)) {
-            // Remember the time when we got our first incoming audio packet.
-            // We will need to adjust for the delay between this event and
-            // when the real receive thread is ready to avoid falling behind.
-            firstReceiveTime = PltGetMillis();
+            sendto(rtpSocket, (char*)&AudioPingPayload, sizeof(AudioPingPayload), 0, (struct sockaddr*)&saddr, RemoteAddrLen);
+        }
+        else {
+            sendto(rtpSocket, legacyPingData, sizeof(legacyPingData), 0, (struct sockaddr*)&saddr, RemoteAddrLen);
         }
 
         PltSleepMsInterruptible(&udpPingThread, 500);

src/Connection.c

@@ -29,6 +29,8 @@ uint16_t RtspPortNumber;
 uint16_t ControlPortNumber;
 uint16_t AudioPortNumber;
 uint16_t VideoPortNumber;
+SS_PING AudioPingPayload;
+SS_PING VideoPingPayload;
 
 // Connection stages
 static const char* stageNames[STAGE_MAX] = {

src/Limelight-internal.h

@@ -38,6 +38,9 @@ extern uint16_t ControlPortNumber;
 extern uint16_t AudioPortNumber;
 extern uint16_t VideoPortNumber;
 
+extern SS_PING AudioPingPayload;
+extern SS_PING VideoPingPayload;
+
 #ifndef UINT24_MAX
 #define UINT24_MAX 0xFFFFFF
 #endif

src/RtspConnection.c

@@ -893,6 +893,7 @@ int performRtspHandshake(PSERVER_INFORMATION serverInfo) {
     {
         RTSP_MESSAGE response;
         char* sessionId;
+        char* pingPayload;
         int error = -1;
 
         if (!setupStream(&response,
@@ -922,6 +923,13 @@ int performRtspHandshake(PSERVER_INFORMATION serverInfo) {
             Limelog("Audio port: %u\n", AudioPortNumber);
         }
 
+        // Parse the Sunshine ping payload protocol extension if present
+        memset(&AudioPingPayload, 0, sizeof(AudioPingPayload));
+        pingPayload = getOptionContent(response.options, "X-SS-Ping-Payload");
+        if (pingPayload != NULL && strlen(pingPayload) == sizeof(AudioPingPayload.payload)) {
+            memcpy(AudioPingPayload.payload, pingPayload, sizeof(AudioPingPayload.payload));
+        }
+
         // Let the audio stream know the port number is now finalized.
         // NB: This is needed because audio stream init happens before RTSP,
         // which is not the case for the video stream.
@@ -955,6 +963,7 @@ int performRtspHandshake(PSERVER_INFORMATION serverInfo) {
     {
         RTSP_MESSAGE response;
         int error = -1;
+        char* pingPayload;
 
         if (!setupStream(&response,
                          AppVersionQuad[0] >= 5 ? "streamid=video/0/0" : "streamid=video",
@@ -971,6 +980,13 @@ int performRtspHandshake(PSERVER_INFORMATION serverInfo) {
             goto Exit;
         }
 
+        // Parse the Sunshine ping payload protocol extension if present
+        memset(&VideoPingPayload, 0, sizeof(VideoPingPayload));
+        pingPayload = getOptionContent(response.options, "X-SS-Ping-Payload");
+        if (pingPayload != NULL && strlen(pingPayload) == sizeof(VideoPingPayload.payload)) {
+            memcpy(VideoPingPayload.payload, pingPayload, sizeof(VideoPingPayload.payload));
+        }
+
         // Parse the video port out of the RTSP SETUP response
         LC_ASSERT(VideoPortNumber == 0);
         if (!parseServerPortFromTransport(&response, &VideoPortNumber)) {

src/Video.h

@@ -36,4 +36,9 @@ typedef struct _RTP_PACKET {
     uint32_t ssrc;
 } RTP_PACKET, *PRTP_PACKET;
 
+typedef struct _SS_PING {
+    char payload[16];
+    uint32_t sequenceNumber;
+} SS_PING, *PSS_PING;
+
 #pragma pack(pop)

src/VideoStream.c

@@ -43,7 +43,7 @@ void destroyVideoStream(void) {
 
 // UDP Ping proc
 static void VideoPingThreadProc(void* context) {
-    char pingData[] = { 0x50, 0x49, 0x4E, 0x47 };
+    char legacyPingData[] = { 0x50, 0x49, 0x4E, 0x47 };
     LC_SOCKADDR saddr;
 
     LC_ASSERT(VideoPortNumber != 0);
@@ -51,12 +51,21 @@ static void VideoPingThreadProc(void* context) {
     memcpy(&saddr, &RemoteAddr, sizeof(saddr));
     SET_PORT(&saddr, VideoPortNumber);
 
+    // We do not check for errors here. Socket errors will be handled
+    // on the read-side in ReceiveThreadProc(). This avoids potential
+    // issues related to receiving ICMP port unreachable messages due
+    // to sending a packet prior to the host PC binding to that port.
+    int pingCount = 0;
     while (!PltIsThreadInterrupted(&udpPingThread)) {
-        // We do not check for errors here. Socket errors will be handled
-        // on the read-side in ReceiveThreadProc(). This avoids potential
-        // issues related to receiving ICMP port unreachable messages due
-        // to sending a packet prior to the host PC binding to that port.
-        sendto(rtpSocket, pingData, sizeof(pingData), 0, (struct sockaddr*)&saddr, RemoteAddrLen);
+        if (VideoPingPayload.payload[0] != 0) {
+            pingCount++;
+            VideoPingPayload.sequenceNumber = BE32(pingCount);
+
+            sendto(rtpSocket, (char*)&VideoPingPayload, sizeof(VideoPingPayload), 0, (struct sockaddr*)&saddr, RemoteAddrLen);
+        }
+        else {
+            sendto(rtpSocket, legacyPingData, sizeof(legacyPingData), 0, (struct sockaddr*)&saddr, RemoteAddrLen);
+        }
 
         PltSleepMsInterruptible(&udpPingThread, 500);
     }