Correctly handle EINTR during sendmsg in QuicSocketUtils::WritePacket.

net/tools/quic/quic_socket_utils.cc

Index: net/tools/quic/quic_socket_utils.cc
diff --git a/net/tools/quic/quic_socket_utils.cc b/net/tools/quic/quic_socket_utils.cc
index 42141dfa17b436892d7efe1d444bb59a181e3417..9c8cac7eef4e56a280329b3dcf1703b51cfa1fc4 100644
--- a/net/tools/quic/quic_socket_utils.cc
+++ b/net/tools/quic/quic_socket_utils.cc
@@ -213,7 +213,10 @@ WriteResult QuicSocketUtils::WritePacket(int fd,
     hdr.msg_controllen = cmsg->cmsg_len;
   }
 
-  int rc = sendmsg(fd, &hdr, 0);
+  int rc;
+  do {
+    rc = sendmsg(fd, &hdr, 0);
+  } while (rc < 0 && errno == EINTR);
   if (rc >= 0) {
     return WriteResult(WRITE_STATUS_OK, rc);
   }