Merge pull request #85 from bernardotorres/master

Add -f <pcap filter> option to rtp_decoder.  Thanks for the contribution.
diff --git a/test/rtp_decoder.c b/test/rtp_decoder.c
index 60b8d18..57e2d33 100644
--- a/test/rtp_decoder.c
+++ b/test/rtp_decoder.c
@@ -92,7 +92,7 @@
 
   /* check args */
   while (1) {
-    c = getopt_s(argc, argv, "b:k:gt:ae:ld:");
+    c = getopt_s(argc, argv, "b:k:gt:ae:ld:f:");
     if (c == -1) {
       break;
     }
@@ -133,6 +133,14 @@
         exit(1);
       }
       break;
+    case 'f':
+      if(strlen(optarg_s) > MAX_FILTER){
+        fprintf(stderr, "error: filter bigger than %d characters\n", MAX_FILTER);
+        exit(1);
+      }
+      fprintf(stderr, "Setting filter as %s\n", optarg_s);
+      strcpy(filter_exp, optarg_s);
+      break;
     case 'l':
       do_list_mods = 1;
       break;
@@ -390,6 +398,7 @@
 	 "       -k <key>  sets the srtp master key given in hexadecimal\n"
 	 "       -b <key>  sets the srtp master key given in base64\n"
 	 "       -l list debug modules\n"
+	 "       -f \"<pcap filter>\" to filter only the desired SRTP packets\n"
 	 "       -d <debug> turn on debugging for module <debug>\n",
 	 string, string);
   exit(1);