Merged revisions 210992 via svnmerge from

https://origsvn.digium.com/svn/asterisk/trunk

........
  r210992 | kpfleming | 2009-08-07 08:08:00 -0500 (Fri, 07 Aug 2009) | 13 lines

  Workaround broken T.38 endpoints that offer tiny MaxDatagram sizes.

  Some T.38 endpoints treat T38FaxMaxDatagram as the maximum IFP size that should
  be sent to them, rather than the maximum packet payload size. If such an
  endpoint also requests UDPRedundancy as the error correction mode, we'll end
  up calculating a tiny maximum IFP size, so small as to be unusable. This patch
  sets a lower bound on what we'll consider the remote's maximum IFP size to be,
  assuming that endpoints that do this really can accept larger packets than
  they've offered to accept.

  (closes issue #15649)
  Reported by: dazza76
........

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/1.6.1@210994 65c4cc65-6c06-0410-ace0-fbb531ad65f3

diff --git a/main/udptl.c b/main/udptl.c
index 42cbd0e8938ba7f352995251bc2b2462f3b8cc05..ecbacf449c6c8e91fbb95045ee513f6802c25ff4 100644 (file)
--- a/main/udptl.c
+++ b/main/udptl.c
@@ -742,28 +742,32 @@ static void calculate_local_max_datagram(struct ast_udptl *udptl)
 
 static void calculate_far_max_ifp(struct ast_udptl *udptl)
 {
-       unsigned new_max = 40;
+       unsigned new_max = 60;
 
        /* calculate the maximum IFP the local endpoint should
         * generate based on the far end's maximum datagram size
-        * and the current error correction mode
+        * and the current error correction mode. some endpoints
+        * bogus 'max datagram' values that would result in unusable
+        * (too small) maximum IFP values, so we have a a reasonable
+        * minimum value to ensure that we can actually construct
+        * UDPTL packets.
         */
        switch (udptl->error_correction_scheme) {
        case UDPTL_ERROR_CORRECTION_NONE:
                /* only need room for sequence number and length indicators */
-               new_max = udptl->far_max_datagram - 6;
+               new_max = MAX(new_max, udptl->far_max_datagram - 6);
                break;
        case UDPTL_ERROR_CORRECTION_REDUNDANCY:
                /* need room for sequence number, length indicators and the
                 * configured number of redundant packets
                 */
-               new_max = (udptl->far_max_datagram - 8) / (udptl->error_correction_entries + 1);
+               new_max = MAX(new_max, (udptl->far_max_datagram - 8) / (udptl->error_correction_entries + 1));
                break;
        case UDPTL_ERROR_CORRECTION_FEC:
                /* need room for sequence number, length indicators and a
                 * a single IFP of the maximum size expected
                 */
-               new_max = (udptl->far_max_datagram - 10) / 2;
+               new_max = MAX(new_max, (udptl->far_max_datagram - 10) / 2);
                break;
        }
        /* subtract 25% of space for insurance */