Call the dissector for PPP-in-HDLC-like-framing (RFC 1662) the

"ppp_hdlc" dissector, and call the dissector for "raw" PPP (just RFC
1661, no HDLC encapsulation) the "ppp" dissector.

Have the common routine used by both those dissectors take the offset in
the tvbuff of the PPP protocol field as an argument, rather than
assuming that the protocol field begins at the beginning of the tvbuff,
so we don't have to construct a new tvbuff in the
PPP-in-HDLC-like-framing dissector.

Use the PPP dissector, not the PPP-in-HDLC-like-framing dissector, for
PPP over Frame Relay - there's no HDLC header in PPP over Frame Relay,
at least according to

	http://www.cisco.com/univercd/cc/td/doc/product/software/ios120/120newft/120t/120t1/pppframe.htm

svn path=/trunk/; revision=3208

1 files changed, 19 insertions, 26 deletions

diff --git a/packet-ppp.c b/packet-ppp.c
index da71cf4b86..3f52f9c6cc 100644
--- a/packet-ppp.c
+++ b/packet-ppp.c
@@ -1,7 +1,7 @@
 /* packet-ppp.c
  * Routines for ppp packet disassembly
  *
- * $Id: packet-ppp.c,v 1.58 2001/03/29 09:18:34 guy Exp $
+ * $Id: packet-ppp.c,v 1.59 2001/03/30 06:10:54 guy Exp $
  *
  * Ethereal - Network traffic analyzer
  * By Gerald Combs <gerald@zing.org>
@@ -522,7 +522,7 @@ static const ip_tcp_opt ipcp_opts[] = {
 
 #define N_IPCP_OPTS	(sizeof ipcp_opts / sizeof ipcp_opts[0])
 
-static void dissect_payload_ppp(tvbuff_t *tvb, packet_info *pinfo,
+static void dissect_ppp(tvbuff_t *tvb, packet_info *pinfo,
     proto_tree *tree);
 
 const unsigned int fcstab_32[256] =
@@ -1157,20 +1157,20 @@ dissect_cp( tvbuff_t *tvb, int proto_id, int proto_subtree_index,
 #define PFC_BIT 0x01
 
 static void
-dissect_ppp_stuff( tvbuff_t *tvb, packet_info *pinfo,
+dissect_ppp_common( tvbuff_t *tvb, int offset, packet_info *pinfo,
 		proto_tree *tree, proto_tree *fh_tree,
 		proto_item *ti ) {
   guint16 ppp_prot;
   int     proto_len;
   tvbuff_t	*next_tvb;
 
-  ppp_prot = tvb_get_guint8(tvb, 0);
+  ppp_prot = tvb_get_guint8(tvb, offset);
   if (ppp_prot & PFC_BIT) {
     /* Compressed protocol field - just the byte we fetched. */
     proto_len = 1;
   } else {
     /* Uncompressed protocol field - fetch all of it. */
-    ppp_prot = tvb_get_ntohs(tvb, 0);
+    ppp_prot = tvb_get_ntohs(tvb, offset);
     proto_len = 2;
   }
 
@@ -1182,11 +1182,11 @@ dissect_ppp_stuff( tvbuff_t *tvb, packet_info *pinfo,
     proto_item_set_len(ti, proto_item_get_len(ti) + proto_len);
 
   if (tree) {
-    proto_tree_add_text(fh_tree, tvb, 0, proto_len, "Protocol: %s (0x%04x)",
+    proto_tree_add_text(fh_tree, tvb, offset, proto_len, "Protocol: %s (0x%04x)",
       val_to_str(ppp_prot, ppp_vals, "Unknown"), ppp_prot);
   }
 
-  next_tvb = tvb_new_subset(tvb, proto_len, -1, -1);
+  next_tvb = tvb_new_subset(tvb, offset + proto_len, -1, -1);
 
   /* do lookup with the subdissector table */
   if (!dissector_try_port(subdissector_table, ppp_prot, next_tvb, pinfo, tree)) {
@@ -1276,15 +1276,15 @@ dissect_mp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
 
   if (tvb_reported_length_remaining(tvb, 4) > 0) {
     next_tvb = tvb_new_subset(tvb, 4, -1, -1);
-    dissect_payload_ppp(next_tvb, pinfo, tree);
+    dissect_ppp(next_tvb, pinfo, tree);
   }
 }
 
 /*
- * Handles PPP without HDLC headers, just a protocol field.
+ * Handles PPP without HDLC framing, just a protocol field (RFC 1661).
  */
 static void
-dissect_payload_ppp( tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree ) {
+dissect_ppp( tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree ) {
   proto_item *ti = NULL;
   proto_tree *fh_tree = NULL;
 
@@ -1293,25 +1293,19 @@ dissect_payload_ppp( tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree ) {
     fh_tree = proto_item_add_subtree(ti, ett_ppp);
   }
 
-  dissect_ppp_stuff(tvb, pinfo, tree, fh_tree, ti);
+  dissect_ppp_common(tvb, 0, pinfo, tree, fh_tree, ti);
 }
 
 /*
- * Handles link-layer encapsulations where the frame might be:
- *
- *	a PPP frame with no HDLC header;
- *
- *	a PPP frame with an HDLC header (FF 03);
- *
- *	a Cisco HDLC frame.
+ * Handles link-layer encapsulations where the frame might be
+ * a PPP in HDLC-like Framing frame (RFC 1662) or a Cisco HDLC frame.
  */
 static void
-dissect_ppp( tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree ) {
+dissect_ppp_hdlc( tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree ) {
   proto_item *ti = NULL;
   proto_tree *fh_tree = NULL;
   guint8     byte0;
   int        proto_offset;
-  tvbuff_t   *next_tvb;
   int        rx_fcs_offset;
   guint32    rx_fcs_exp;
   guint32    rx_fcs_got;
@@ -1356,8 +1350,7 @@ dissect_ppp( tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree ) {
     }
   }
 
-  next_tvb = tvb_new_subset(tvb, proto_offset, -1, -1);
-  dissect_ppp_stuff(next_tvb, pinfo, tree, fh_tree, ti);
+  dissect_ppp_common(tvb, proto_offset, pinfo, tree, fh_tree, ti);
 
   /* Calculate the FCS check */
   /* XXX - deal with packets cut off by the snapshot length */
@@ -1410,8 +1403,8 @@ proto_register_ppp(void)
 /* subdissector code */
 	subdissector_table = register_dissector_table("ppp.protocol");
 
+	register_dissector("ppp_hdlc", dissect_ppp_hdlc, proto_ppp);
 	register_dissector("ppp", dissect_ppp, proto_ppp);
-	register_dissector("payload_ppp", dissect_payload_ppp, proto_ppp);
 
 	/* Register the preferences for the ppp protocol */
 	ppp_module = prefs_register_protocol(proto_ppp, NULL);
@@ -1432,10 +1425,10 @@ proto_reg_handoff_ppp(void)
    */
   chdlc_handle = find_dissector("chdlc");
 
-  dissector_add("wtap_encap", WTAP_ENCAP_PPP, dissect_ppp, proto_ppp);
-  dissector_add("wtap_encap", WTAP_ENCAP_PPP_WITH_PHDR, dissect_ppp, proto_ppp);
+  dissector_add("wtap_encap", WTAP_ENCAP_PPP, dissect_ppp_hdlc, proto_ppp);
+  dissector_add("wtap_encap", WTAP_ENCAP_PPP_WITH_PHDR, dissect_ppp_hdlc, proto_ppp);
   dissector_add("fr.ietf", NLPID_PPP, dissect_ppp, proto_ppp);
-  dissector_add("gre.proto", ETHERTYPE_PPP, dissect_ppp, proto_ppp);
+  dissector_add("gre.proto", ETHERTYPE_PPP, dissect_ppp_hdlc, proto_ppp);
 }
 
 void