protodetect: improve midstream handling

Set "done flag" only if parsers for both directions are not found in a
case of midstream parsers from other direction are tried if nothing is found
for the initial one. "done flag" must be set if nothing is found in both
directions. Otherwise processing of incomplete data is terminated at the very
first try.

src/app-layer-detect-proto.c

@@ -515,6 +515,7 @@ static AppProto AppLayerProtoDetectPPGetProto(Flow *f, const uint8_t *buf, uint3
     uint8_t dir = idir;
     uint16_t dp = f->protodetect_dp ? f->protodetect_dp : FLOW_GET_DP(f);
     uint16_t sp = FLOW_GET_SP(f);
+    bool probe_is_found = false;
 
 again_midstream:
     if (idir != dir) {
@@ -577,9 +578,9 @@ again_midstream:
     if (pe1 == NULL && pe2 == NULL && pe0 == NULL) {
         SCLogDebug("%s - No probing parsers found for either port",
                 (dir == STREAM_TOSERVER) ? "toserver":"toclient");
-        if (dir == idir)
-            FLOW_SET_PP_DONE(f, dir);
         goto noparsers;
+    } else {
+        probe_is_found = true;
     }
 
     /* run the parser(s): always call with original direction */
@@ -615,8 +616,8 @@ again_midstream:
         }
     }
 
- noparsers:
-    if (stream_config.midstream == true && idir == dir) {
+noparsers:
+    if (stream_config.midstream && idir == dir) {
         if (idir == STREAM_TOSERVER) {
             dir = STREAM_TOCLIENT;
         } else {
@@ -625,6 +626,8 @@ again_midstream:
         SCLogDebug("no match + midstream, retry the other direction %s",
                 (dir == STREAM_TOSERVER) ? "toserver" : "toclient");
         goto again_midstream;
+    } else if (!probe_is_found) {
+        FLOW_SET_PP_DONE(f, idir);
     }
 
  end: