Read recv timestamps from socket (posix only).

webrtc/base/physicalsocketserver.cc

Index: webrtc/base/physicalsocketserver.cc
diff --git a/webrtc/base/physicalsocketserver.cc b/webrtc/base/physicalsocketserver.cc
index e2a0b6f14048b4007126ce9a13838f1858fbc1f8..7581280022cc83d8b00a00d4c8748579b778ecae 100644
--- a/webrtc/base/physicalsocketserver.cc
+++ b/webrtc/base/physicalsocketserver.cc
@@ -23,6 +23,7 @@
 #include <string.h>
 #include <errno.h>
 #include <fcntl.h>
+#include <sys/ioctl.h>
 #include <sys/time.h>
 #include <sys/select.h>
 #include <unistd.h>
@@ -55,8 +56,28 @@
 #include <netinet/tcp.h>  // for TCP_NODELAY
 #define IP_MTU 14 // Until this is integrated from linux/in.h to netinet/in.h
 typedef void* SockOptArg;
+
 #endif  // WEBRTC_POSIX
 
+#if defined(WEBRTC_POSIX) && !defined(WEBRTC_MAC)
+int64_t GetSocketRecvTimestamp(int socket) {
+  struct timeval tv_ioctl;
+  int ret = ioctl(socket, SIOCGSTAMP, &tv_ioctl);

[juberti2, 2016/05/11 05:03:34]

Do you need to set a socket option for this to work?

[stefan-webrtc, 2016/05/11 08:41:14]

No. There are two ways of getting the timestamp from the socket
1) this way which doesn't require a socket option
2) reading the timestamp with recvmsg(), which requires setting the
SO_TIMESTAMPING socket option. Doing that also disables the first way of reading
recv timestamps.

#1 is a lot simpler, so I suggest going with that for now at least.

+  if (ret != 0)
+    return -1;
+  int64_t timestamp =
+      rtc::kNumMicrosecsPerSec * static_cast<int64_t>(tv_ioctl.tv_sec) +
+      static_cast<int64_t>(tv_ioctl.tv_usec);
+  return timestamp;
+}
+
+#else
+
+int64_t GetSocketRecvTimestamp(int socket) {
+  return -1;
+}
+#endif
+
 #if defined(WEBRTC_WIN)
 typedef char* SockOptArg;
 #endif
@@ -324,7 +345,7 @@ int PhysicalSocket::SendTo(const void* buffer,
   return sent;
 }
 
-int PhysicalSocket::Recv(void* buffer, size_t length) {
+int PhysicalSocket::Recv(void* buffer, size_t length, int64_t* timestamp) {
   int received = ::recv(s_, static_cast<char*>(buffer),
                         static_cast<int>(length), 0);
   if ((received == 0) && (length != 0)) {
@@ -338,6 +359,7 @@ int PhysicalSocket::Recv(void* buffer, size_t length) {
     SetError(EWOULDBLOCK);
     return SOCKET_ERROR;
   }
+  *timestamp = GetSocketRecvTimestamp(s_);

[juberti2, 2016/05/11 05:03:34]

Allow NULL to be passed so that clients who don't care about timestamps don't
have to write more complex code.

[stefan-webrtc, 2016/05/11 08:41:14]

Done.

   UpdateLastError();
   int error = GetError();
   bool success = (received >= 0) || IsBlockingError(error);
@@ -352,12 +374,14 @@ int PhysicalSocket::Recv(void* buffer, size_t length) {
 
 int PhysicalSocket::RecvFrom(void* buffer,
                              size_t length,
-                             SocketAddress* out_addr) {
+                             SocketAddress* out_addr,
+                             int64_t* timestamp) {
   sockaddr_storage addr_storage;
   socklen_t addr_len = sizeof(addr_storage);
   sockaddr* addr = reinterpret_cast<sockaddr*>(&addr_storage);
   int received = ::recvfrom(s_, static_cast<char*>(buffer),
                             static_cast<int>(length), 0, addr, &addr_len);
+  *timestamp = GetSocketRecvTimestamp(s_);
   UpdateLastError();
   if ((received >= 0) && (out_addr != nullptr))
     SocketAddressFromSockAddrStorage(addr_storage, out_addr);