[glib-networking/wip/pwithnall/dtls: 18/24] gnutls: Convert MTU-exceeded errors

[Philip Withnall <pwithnall src gnome org>]

commit 89ea059ce182eb2f4e8a11d6e5388580978f0481
Author: Olivier Crête <olivier crete collabora com>
Date:   Fri Mar 29 18:43:22 2013 -0400

    gnutls: Convert MTU-exceeded errors
    
    This is necessary for handling DTLS datagrams, as GnuTLS enforces an MTU
    on them.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=697908

 tls/gnutls/gtlsconnection-gnutls.c |   19 +++++++++++++++++++
 1 files changed, 19 insertions(+), 0 deletions(-)
---
diff --git a/tls/gnutls/gtlsconnection-gnutls.c b/tls/gnutls/gtlsconnection-gnutls.c
index 161bedd..e88d733 100644
--- a/tls/gnutls/gtlsconnection-gnutls.c
+++ b/tls/gnutls/gtlsconnection-gnutls.c
@@ -26,6 +26,7 @@
 #include <errno.h>
 #include <stdarg.h>
 #include <gnutls/gnutls.h>
+#include <gnutls/dtls.h>
 #include <gnutls/x509.h>
 
 #include "gtlsconnection-gnutls.h"
@@ -327,6 +328,10 @@ g_tls_connection_gnutls_initable_init (GInitable     *initable,
                                               g_tls_connection_gnutls_pull_timeout_func);
   gnutls_transport_set_ptr (gnutls->priv->session, gnutls);
 
+  /* Don't enforce MTU */
+  if (flags & GNUTLS_DATAGRAM)
+    gnutls_dtls_set_mtu (gnutls->priv->session, 65535);
+
   gnutls->priv->tls_istream = g_tls_input_stream_gnutls_new (gnutls);
   gnutls->priv->tls_ostream = g_tls_output_stream_gnutls_new (gnutls);
 
@@ -1089,6 +1094,8 @@ set_gnutls_error (GTlsConnectionGnutls *gnutls,
     gnutls_transport_set_errno (gnutls->priv->session, EINTR);
   else if (g_error_matches (error, G_IO_ERROR, G_IO_ERROR_TIMED_OUT))
     gnutls_transport_set_errno (gnutls->priv->session, EINTR);
+  else if (g_error_matches (error, G_IO_ERROR, G_IO_ERROR_MESSAGE_TOO_LARGE))
+    gnutls_transport_set_errno (gnutls->priv->session, EMSGSIZE);
   else
     gnutls_transport_set_errno (gnutls->priv->session, EIO);
 }
@@ -1636,10 +1643,22 @@ g_tls_connection_gnutls_write (GTlsConnectionGnutls  *gnutls,
                 blocking, cancellable, error))
     return -1;
 
+  if (gnutls_dtls_get_data_mtu (gnutls->priv->session) < count)
+    {
+      ret = GNUTLS_E_LARGE_PACKET;
+      g_set_error (error, G_IO_ERROR, G_IO_ERROR_MESSAGE_TOO_LARGE,
+                   _("Message of size %lu bytes is too large for "
+                     "DTLS connection, maximum is %u bytes"),
+                   count,
+                   (guint) gnutls_dtls_get_data_mtu (gnutls->priv->session));
+      goto done;
+    }
+
   BEGIN_GNUTLS_IO (gnutls, G_IO_OUT, blocking, cancellable);
   ret = gnutls_record_send (gnutls->priv->session, buffer, count);
   END_GNUTLS_IO (gnutls, G_IO_OUT, ret, _("Error writing data to TLS socket: %s"), error);
 
+ done:
   yield_op (gnutls, G_TLS_CONNECTION_GNUTLS_OP_WRITE);
 
   if (ret >= 0)