packet-lapd.c: Replace heuristic UDP dissector with "deterministic" one with prefs.

Remove the heuristic dissector that checks for arbitrary UDP ports in favor
of adding a preference for the range of UDP ports that can be used for LAPD.

Change-Id: Ib85fbee4a433727af24279fffb0cbf2c25f7d292
Reviewed-on: https://code.wireshark.org/review/21985
Petri-Dish: Michael Mann <mmann78@netscape.net>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Michael Mann <mmann78@netscape.net>

3 files changed, 2 insertions, 89 deletions

diff --git a/epan/dissectors/packet-lapd.c b/epan/dissectors/packet-lapd.c
index 5f91173504..b686daae68 100644
--- a/epan/dissectors/packet-lapd.c
+++ b/epan/dissectors/packet-lapd.c
@@ -569,28 +569,6 @@ dissect_lapd_full(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, gboolean
 		call_data_dissector(next_tvb, pinfo, tree);
 }
 
-static gboolean
-dissect_udp_lapd(tvbuff_t *tvb, packet_info *pinfo _U_ , proto_tree *tree, void *data _U_)
-{
-	if (pinfo->srcport < 3001 || pinfo->srcport > 3015
-		|| pinfo->destport < 3001 || pinfo->destport > 3015
-		|| pinfo->destport != pinfo->srcport)
-			return FALSE;
-
-	/*
-	 * XXX - check for a valid LAPD address field.
-	 */
-
-	/*
-	 * OK, check whether the control field looks valid.
-	 */
-	if (!check_xdlc_control(tvb, 2, NULL, NULL, FALSE, FALSE))
-		return FALSE;
-
-    dissect_lapd(tvb, pinfo, tree, data);
-	return TRUE;
-}
-
 void
 proto_register_lapd(void)
 {
@@ -748,10 +726,10 @@ proto_reg_handoff_lapd(void)
 		dissector_add_uint("wtap_encap", WTAP_ENCAP_LINUX_LAPD, lapd_handle);
 		dissector_add_uint("wtap_encap", WTAP_ENCAP_LAPD, lapd_handle);
 		dissector_add_uint("l2tp.pw_type", L2TPv3_PROTOCOL_LAPD, lapd_handle);
-		heur_dissector_add("udp", dissect_udp_lapd, "LAPD over UDP", "lapd_udp", proto_lapd, HEURISTIC_ENABLE);
 
 		dissector_add_for_decode_as("sctp.ppi", lapd_handle);
 		dissector_add_for_decode_as("sctp.port", lapd_handle);
+		dissector_add_uint_range_with_preference("udp.port", "", lapd_handle);
 
 		init = TRUE;
 	} else {
@@ -769,6 +747,7 @@ proto_reg_handoff_lapd(void)
 	lapd_sctp_ppi = pref_lapd_sctp_ppi;
 	if (lapd_sctp_ppi > 0)
 		dissector_add_uint("sctp.ppi", lapd_sctp_ppi, lapd_handle);
+
 }
 
 /*
diff --git a/epan/xdlc.c b/epan/xdlc.c
index d6c5453d14..06af5ec3f0 100644
--- a/epan/xdlc.c
+++ b/epan/xdlc.c
@@ -166,64 +166,6 @@ get_xdlc_control(const guchar *pd, int offset, gboolean is_extended)
     return control;
 }
 
-/*
- * Check whether the control field of the packet looks valid.
- */
-gboolean
-check_xdlc_control(tvbuff_t *tvb, int offset,
-  const value_string *u_modifier_short_vals_cmd,
-  const value_string *u_modifier_short_vals_resp, gboolean is_response,
-  gboolean is_extended _U_)
-{
-    guint16 control;
-
-    if (!tvb_bytes_exist(tvb, offset, 1))
-        return FALSE;   /* not enough data to check */
-    switch (tvb_get_guint8(tvb, offset) & 0x03) {
-
-    case XDLC_S:
-        /*
-         * Supervisory frame.
-         * No fields to check for validity here.
-         */
-        return TRUE;
-
-    case XDLC_U:
-        /*
-         * Unnumbered frame.
-         *
-         * XXX - is this two octets, with a P/F bit, in HDLC extended
-         * operation?  It's one octet in LLC, even though the control
-         * field of I and S frames is a 2-byte extended-operation field
-         * in LLC.  Given that there are no sequence numbers in the
-         * control field of a U frame, there doesn't appear to be any
-         * need for it to be 2 bytes in extended operation.
-         */
-        if (u_modifier_short_vals_cmd == NULL)
-                u_modifier_short_vals_cmd = modifier_short_vals_cmd;
-        if (u_modifier_short_vals_resp == NULL)
-                u_modifier_short_vals_resp = modifier_short_vals_resp;
-        control = tvb_get_guint8(tvb, offset);
-        if (is_response) {
-                if (try_val_to_str(control & XDLC_U_MODIFIER_MASK,
-                    u_modifier_short_vals_resp) == NULL)
-                        return FALSE;   /* unknown modifier */
-        } else {
-                if (try_val_to_str(control & XDLC_U_MODIFIER_MASK,
-                    u_modifier_short_vals_cmd) == NULL)
-                        return FALSE;   /* unknown modifier */
-        }
-        return TRUE;
-
-    default:
-        /*
-         * Information frame.
-         * No fields to check for validity here.
-         */
-        return TRUE;
-    }
-}
-
 int
 dissect_xdlc_control(tvbuff_t *tvb, int offset, packet_info *pinfo,
   proto_tree *xdlc_tree, int hf_xdlc_control, gint ett_xdlc_control,
diff --git a/epan/xdlc.h b/epan/xdlc.h
index 525f30b393..f7fc79fe00 100644
--- a/epan/xdlc.h
+++ b/epan/xdlc.h
@@ -134,14 +134,6 @@ extern const value_string modifier_vals_resp[];
 
 extern int get_xdlc_control(const guchar *pd, int offset, gboolean is_extended);
 
-/**
- * Check whether the control field of the packet looks valid.
- */
-WS_DLL_PUBLIC gboolean check_xdlc_control(tvbuff_t *tvb, int offset,
-  const value_string *u_modifier_short_vals_cmd,
-  const value_string *u_modifier_short_vals_resp, gboolean is_response,
-  gboolean is_extended _U_);
-
 WS_DLL_PUBLIC int dissect_xdlc_control(tvbuff_t *tvb, int offset, packet_info *pinfo,
   proto_tree *xdlc_tree, int hf_xdlc_control, gint ett_xdlc_control,
   const xdlc_cf_items *cf_items_nonext, const xdlc_cf_items *cf_items_ext,