slow TLS handshake (2 seconds) when gnutls is used

[dinutine]

gnutls_handshake returns GNUTLS_E_AGAIN, when it is waiting for data to be received by the server. gnutls_handshake should be called again when new data is received (as soon as possible)

Suggestion: replace the sleep of 1 second with a poll on the tcp socket with a 1000ms timeout

diff --git a/libvncclient/tls_gnutls.c b/libvncclient/tls_gnutls.c
index a87baf2..964a675 100644
--- a/libvncclient/tls_gnutls.c
+++ b/libvncclient/tls_gnutls.c
@@ -22,6 +22,7 @@
 #include <gnutls/x509.h>
 #include <rfb/rfbclient.h>
 #include <errno.h>
+#include <poll.h>
 #ifdef WIN32
 #include <windows.h>           /* for Sleep() */
 #define sleep(X) Sleep(1000*X) /* MinGW32 has no sleep() */
@@ -286,8 +287,14 @@ HandshakeTLS(rfbClient* client)
   {
     if (!gnutls_error_is_fatal(ret))
     {
-      rfbClientLog("TLS handshake blocking.\n");
-      sleep(1);
+      rfbClientLog("TLS handshake blocking, ret=%d.\n", ret);
+
+      // wait until new data is received on the socket
+      struct pollfd poll_fd;
+      poll_fd.fd = client->sock;
+      poll_fd.events = POLLIN;
+      poll_fd.revents = 0;
+      poll(&poll_fd, 1, 1000);
       timeout--;
       continue;
     }
-- 

[bk138]

I reckon this won't work on Win32. Why not simply shorten the sleep?

[mdevaev]

I tried to fix it the right way (lol) with native GNUTLS timeouts #531