Disable SIGPIPE for sockets created on iOS.

webrtc/base/physicalsocketserver.cc

Index: webrtc/base/physicalsocketserver.cc
diff --git a/webrtc/base/physicalsocketserver.cc b/webrtc/base/physicalsocketserver.cc
index a412703015e77f903b82c6126edd21a4c00a023d..4ab33fb673a1154e01a3eb58f45d136a4f9fd523 100644
--- a/webrtc/base/physicalsocketserver.cc
+++ b/webrtc/base/physicalsocketserver.cc
@@ -609,6 +609,15 @@ bool SocketDispatcher::Initialize() {
 #elif defined(WEBRTC_POSIX)
   fcntl(s_, F_SETFL, fcntl(s_, F_GETFL, 0) | O_NONBLOCK);
 #endif
+#if defined(WEBRTC_IOS)
+  // iOS may kill sockets when the app is moved to the background
+  // (specifically, if the app doesn't use the "voip" UIBackgroundMode). When
+  // we attempt to write to such a socket, SIGPIPE will be raised, which by
+  // default will terminate the process, which we don't want. By specifying
+  // this socket option, SIGPIPE will be disabled for the socket.
+  int value = 1;
+  ::setsockopt(s_, SOL_SOCKET, SO_NOSIGPIPE, &value, sizeof(value));
+#endif
   ss_->Add(this);
   return true;
 }