Revert "MPLS: relax pw_eth_heuristic and improve 1st nibble logic"

This reverts commit 01ddd93a7296b54a2048de74691984a7e78e4cb9.

Change-Id: I90f19fec52d3f1edc63fd00e614173a0154503d4
Reviewed-on: https://code.wireshark.org/review/19820
Reviewed-by: Anders Broman <a.broman58@gmail.com>

2 files changed, 24 insertions, 51 deletions

diff --git a/epan/dissectors/packet-mpls.c b/epan/dissectors/packet-mpls.c
index 03f8ea3b01..4ea63e589e 100644
--- a/epan/dissectors/packet-mpls.c
+++ b/epan/dissectors/packet-mpls.c
@@ -479,51 +479,29 @@ dissect_mpls(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_
     }
 
     /*
-     * No, there isn't, so use a mix of the 1st nibble logic (see BCP 4928,
-     * RFC 4385 and 5586) + heuristic.
+     * No, there isn't, so use the 1st nibble logic (see BCP 4928,
+     * RFC 4385 and 5586).
      */
     switch(first_nibble) {
     case 4:
-        {
-            /*
-             * This could be from an Ethernet pseudo-wire without a
-             * control word, with the MAC address's first nibble being 4
-             * or an IPv4 packet (or something else).
-             */
-            guint iplen = tvb_get_ntohs(next_tvb, 2);
-            guint reported_len = tvb_reported_length(next_tvb);
-            if (iplen >= (reported_len - 4) && iplen <= reported_len) {
-                /* the supposed IP total len is equal to the reported len plus
-                   the possible padding, we have a good indication this is IP */
-                call_dissector(dissector_ip, next_tvb, pinfo, tree);
-                /* IP dissector may reduce the length of the tvb.
-                   We need to do the same, so that ethernet trailer is detected. */
-                set_actual_length(tvb, offset + tvb_reported_length(next_tvb));
-                break;
-            }
-            /* last resort */
-            call_dissector(dissector_pw_eth_heuristic, next_tvb, pinfo, tree);
-        }
+        /*
+         * XXX - this could be from an Ethernet pseudo-wire without a
+         * control word, with the MAC address's first nibble being 4.
+         */
+        call_dissector(dissector_ip, next_tvb, pinfo, tree);
+        /* IP dissector may reduce the length of the tvb.
+           We need to do the same, so that ethernet trailer is detected. */
+        set_actual_length(tvb, offset+tvb_reported_length(next_tvb));
         break;
     case 6:
-        {
-            /*
-             * This could be from an Ethernet pseudo-wire without a
-             * control word, with the MAC address's first nibble being 6
-             * or an IPv6 packet (or something else).
-             */
-            guint ip6len = tvb_get_guint16(next_tvb, offset + 4, ENC_BIG_ENDIAN);
-            guint reported_len = tvb_reported_length(next_tvb);
-            if (ip6len >= (reported_len - 4) && ip6len <= reported_len) {
-                call_dissector(dissector_ipv6, next_tvb, pinfo, tree);
-                /* IPv6 dissector may reduce the length of the tvb.
-                   We need to do the same, so that ethernet trailer is detected. */
-                set_actual_length(tvb, offset + tvb_reported_length(next_tvb));
-                break;
-            }
-            /* last resort */
-            call_dissector(dissector_pw_eth_heuristic, next_tvb, pinfo, tree);
-        }
+        /*
+         * XXX - this could be from an Ethernet pseudo-wire without a
+         * control word, with the MAC address's first nibble being 6.
+         */
+        call_dissector(dissector_ipv6, next_tvb, pinfo, tree);
+        /* IPv6 dissector may reduce the length of the tvb.
+           We need to do the same, so that ethernet trailer is detected. */
+        set_actual_length(tvb, offset+tvb_reported_length(next_tvb));
         break;
     case 1:
         /*
diff --git a/epan/dissectors/packet-pw-eth.c b/epan/dissectors/packet-pw-eth.c
index 58f8f3cb65..2c245331f7 100644
--- a/epan/dissectors/packet-pw-eth.c
+++ b/epan/dissectors/packet-pw-eth.c
@@ -108,32 +108,27 @@ dissect_pw_eth_nocw(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* d
 }
 
 /*
- * FF: this function returns 2 if the first 12 bytes in tvb looks like
- *     two valid ethernet addresses, 1 if either one of them contains a
- *     registered OUI and 0 otherwise.
+ * FF: this function returns TRUE if the first 12 bytes in tvb looks like
+ *     two valid ethernet addresses.  FALSE otherwise.
  */
-static int
+static gboolean
 looks_like_plain_eth(tvbuff_t *tvb _U_)
 {
     const gchar *manuf_name_da;
     const gchar *manuf_name_sa;
 
     if (tvb_reported_length_remaining(tvb, 0) < 14) {
-        return 0;
+        return FALSE;
     }
 
     manuf_name_da = tvb_get_manuf_name_if_known(tvb, 0);
     manuf_name_sa = tvb_get_manuf_name_if_known(tvb, 6);
 
     if (manuf_name_da && manuf_name_sa) {
-        return 2;
-    }
-
-    if (manuf_name_da || manuf_name_sa) {
-        return 1;
+        return TRUE;
     }
 
-    return 0;
+    return FALSE;
 }
 
 static int