Instead of tweaking a "Protocol configuration options" extension header

item to look more-or-less like a PPP packet, just dissect it in place
and hand off to the appropriate subdissector using the PPP dissector's
handoff table (which we export, along with its value_string table for
protocol IDs, which we use to report the protocol ID symbolically).

This means there's no point in having a configurable option to control
whether to do that tweaking; make it an obsolete option.

Bring "col_get_writable()" back from the dead, and have the GTP
dissector save the current "writable" flag for columns, mark the columns
non-writable before calling the subdissector for the PPP configuration
protocol, and restore the state of the writable flag, rather than
putting the columns back after the PPP configuration protocol's
dissector is done.

Fix some more typos in comments.

Don't register the IP dissector in the "ppp.protocol" table in the GTP
dissector's handoff registration routine - it's already being done in
the IP dissector's handoff routine.

Fix the name for CHAP to match what RFC 1994 calls it (if the name
changed, it should be changed in all places, but, at least according to
this message, a while ago, from Bob Sutterfield, "since the RFC defines
the protocol, the RFC defines the name":

	http://mail-index.netbsd.org/netbsd-help/1996/05/16/0011.html

and the RFC defines the name as "PPP Challenge Handshake Authentication
Protocol (CHAP)").

svn path=/trunk/; revision=6617

1 files changed, 39 insertions, 35 deletions

diff --git a/packet-gtp.c b/packet-gtp.c
index a84a759ab0..76e5cfba07 100644
--- a/packet-gtp.c
+++ b/packet-gtp.c
@@ -4,7 +4,7 @@
  * Copyright 2001, Michal Melerowicz <michal.melerowicz@nokia.com>
  *                 Nicolas Balkota <balkota@mac.com>
  *
- * $Id: packet-gtp.c,v 1.45 2002/11/11 17:41:37 guy Exp $
+ * $Id: packet-gtp.c,v 1.46 2002/11/11 19:23:11 guy Exp $
  *
  * Ethereal - Network traffic analyzer
  * By Gerald Combs <gerald@ethereal.com>
@@ -38,7 +38,7 @@
 #include <epan/packet.h>
 #include "packet-gtp.h"
 #include "packet-ipv6.h"
-#include "ppptypes.h"
+#include "packet-ppp.h"
 #include "prefs.h"
 
 /*
@@ -347,7 +347,6 @@ static gboolean	gtpv1_etsi_order	= FALSE;
 static int	gtpv0_port		= 0;
 static int	gtpv1c_port		= 0;
 static int	gtpv1u_port		= 0;
-static gboolean ppp_reorder		= TRUE;
 
 /* Definition of flags masks */
 #define GTP_VER_MASK 0xE0
@@ -1332,6 +1331,7 @@ static const value_string cdr_close_type[] = {
 static dissector_handle_t ip_handle;
 static dissector_handle_t ipv6_handle;
 static dissector_handle_t ppp_handle;
+static dissector_handle_t data_handle;
 
 static int decode_gtp_cause		(tvbuff_t *tvb, int offset, packet_info *pinfo, proto_tree *tree);
 static int decode_gtp_imsi		(tvbuff_t *tvb, int offset, packet_info *pinfo, proto_tree *tree);
@@ -3751,10 +3751,12 @@ int
 decode_gtp_proto_conf(tvbuff_t *tvb, int offset, packet_info *pinfo, proto_tree *tree) {
 
 	guint16         length, proto_offset;
-	guint8          *ptr, conf, proto_len, tmp, msg, cnt = 1;
+	guint16		proto_id;
+	guint8          conf, proto_len, cnt = 1;
 	tvbuff_t        *next_tvb;
 	proto_tree      *ext_tree_proto;
 	proto_item      *te;
+	gboolean	save_writable;
 
 	length = tvb_get_ntohs(tvb, offset + 1);
 
@@ -3773,36 +3775,39 @@ decode_gtp_proto_conf(tvbuff_t *tvb, int offset, packet_info *pinfo, proto_tree
 
 	for (;;) {
 		if (proto_offset >= length) break;
+		proto_id = tvb_get_ntohs (tvb, offset);
 		proto_len = tvb_get_guint8 (tvb, offset + 2);
 		proto_offset += proto_len + 3;		/* 3 = proto id + length byte */
 
-		if ((proto_len > 0) && ppp_reorder) {
-
-			/* this part changes layout of GTP payload:
-			 * it swaps "length field" with "protocol header"  */
-
-			ptr = (guint8 *)tvb_get_ptr(tvb, offset, 3);
-
-			tmp = ptr[2];
-			ptr[2] = ptr[1];
-			ptr[1] = ptr[0];
-			ptr[0] = tmp;
-
-			proto_tree_add_text (ext_tree_proto, tvb, offset, 3, "[WARNING] Next 3 bytes were swapped to allow processing PPP section");
-			proto_tree_add_text (ext_tree_proto, tvb, offset, 1, "Protocol %u length: %u", cnt, proto_len);
-
-			next_tvb = tvb_new_subset (tvb, offset + 1, proto_len + 2, proto_len + 2);
-			call_dissector(ppp_handle, next_tvb, pinfo, ext_tree_proto);
-
-			if (check_col(pinfo->cinfo, COL_PROTOCOL))
-				col_set_str(pinfo->cinfo, COL_PROTOCOL, "GTP");
-
-			if (check_col(pinfo->cinfo, COL_INFO)) {
-
-				msg = tvb_get_guint8(tvb, 1);
-
-				col_set_str(pinfo->cinfo, COL_INFO, val_to_str(msg, message_type, "Unknown"));
+		if (proto_len > 0) {
+
+			proto_tree_add_text (ext_tree_proto, tvb, offset, 2, "Protocol %u ID: %s (0x%04x)",
+			    cnt, val_to_str(proto_id, ppp_vals, "Unknown"),
+			    proto_id);
+			proto_tree_add_text (ext_tree_proto, tvb, offset+2, 1, "Protocol %u length: %u", cnt, proto_len);
+
+			/*
+			 * Don't allow the dissector for the configuration
+			 * protocol in question to update the columns - this
+			 * is GTP, not PPP.
+			 */
+			save_writable = col_get_writable(pinfo->cinfo);
+			col_set_writable(pinfo->cinfo, FALSE);
+
+			/*
+			 * XXX - should we have our own dissector table,
+			 * solely for configuration protocols, so that bogus
+			 * values don't cause us to dissect the protocol
+			 * data as, for example, IP?
+			 */
+			next_tvb = tvb_new_subset (tvb, offset + 3, proto_len, proto_len);
+			if (!dissector_try_port(ppp_subdissector_table,
+			    proto_id, next_tvb, pinfo, ext_tree_proto)) {
+				call_dissector(data_handle, next_tvb, pinfo,
+				    ext_tree_proto);
 			}
+
+			col_set_writable(pinfo->cinfo, save_writable);
 		}
 
 		offset += proto_len + 3;
@@ -4923,7 +4928,7 @@ dissect_gtpv0(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
                         /* this might be an address field, even it shouldn't be here */
                         guint8 control_field = tvb_get_guint8(tvb,GTPv0_HDR_LENGTH + 1);
                         if (control_field == 0x03) {
-                            /* now we are pretty sure that adress and control field are mistakenly inserted -> ignore it for PPP dissection */
+                            /* now we are pretty sure that address and control field are mistakenly inserted -> ignore it for PPP dissection */
                             acfield_len = 2;
                         }
                     }
@@ -5075,7 +5080,7 @@ dissect_gtpv1(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree) {
                         control_field = tvb_get_guint8(tvb,GTPv1_HDR_LENGTH - hdr_offset + 1);
                         if (control_field == 0x03)
                         {
-                            /* now we are pretty sure that adress and control field are mistakenly inserted -> ignore it for PPP dissection */
+                            /* now we are pretty sure that address and control field are mistakenly inserted -> ignore it for PPP dissection */
                             acfield_len = 2;
                         }
                     }
@@ -5325,11 +5330,10 @@ proto_register_gtp(void)
 	prefs_register_enum_preference(gtp_module, "gtpv0_dissect_cdr_as", "Dissect GTP'v0 CDRs as ", "Dissect GTP'v0 CDRs as", &gtpv0_cdr_as, gtpv0_cdr_options, FALSE);
 	prefs_register_bool_preference(gtp_module, "gtpv0_check_etsi", "Compare GTPv0 order with ETSI ", "GTPv0 ETSI order", &gtpv0_etsi_order);
 	prefs_register_bool_preference(gtp_module, "gtpv1_check_etsi", "Compare GTPv1 order with ETSI ", "GTPv1 ETSI order", &gtpv1_etsi_order);
-	prefs_register_bool_preference(gtp_module, "ppp_reorder", "Reorder & dissect PPP in Protocol conf. options", "Reorder & dissect PPP inside of Protocol Configuration Options, 3 bytes will be swapped to allow processing PPP section: 1 byte of length with 2 bytes of protocol id (refer to ETSI 29.060, 7.7.21 & 24.008 10.5.6.3)", &ppp_reorder);
+	prefs_register_obsolete_preference(gtp_module, "ppp_reorder");
 
 	register_dissector("gtpv0", dissect_gtpv0, proto_gtpv0);
 	register_dissector("gtpv1", dissect_gtpv1, proto_gtpv1);
-
 }
 
 void
@@ -5373,9 +5377,9 @@ proto_reg_handoff_gtp(void)
 	dissector_add("tcp.port", g_gtpv1c_port, gtpv1_handle);
 	dissector_add("udp.port", g_gtpv1u_port, gtpv1_handle);
 	dissector_add("tcp.port", g_gtpv1u_port, gtpv1_handle);
-	dissector_add("ppp.protocol", PPP_IP, ip_handle);
 
 	ip_handle = find_dissector("ip");
         ipv6_handle = find_dissector("ipv6");
 	ppp_handle = find_dissector("ppp");
+	data_handle = find_dissector("data");
 }