The only LLC frame types that should be dissected based on their SAP or,

if the SAPs are SNAP, based on their ethertype are I frames and UI
frames; others don't have payload to be dissected as belonging to other
protocols.

svn path=/trunk/; revision=555

3 files changed, 154 insertions, 65 deletions

diff --git a/packet-llc.c b/packet-llc.c
index baeffc5779..819cd1b65a 100644
--- a/packet-llc.c
+++ b/packet-llc.c
@@ -2,7 +2,7 @@
  * Routines for IEEE 802.2 LLC layer
  * Gilbert Ramirez <gramirez@tivoli.com>
  *
- * $Id: packet-llc.c,v 1.19 1999/08/10 20:05:40 guy Exp $
+ * $Id: packet-llc.c,v 1.20 1999/08/23 22:47:13 guy Exp $
  *
  * Ethereal - Network traffic analyzer
  * By Gerald Combs <gerald@unicom.net>
@@ -162,29 +162,59 @@ sap_dissect_func(u_char sap) {
 void
 capture_llc(const u_char *pd, int offset, guint32 cap_len, packet_counts *ld) {
 
-	guint16		etype;
 	int		is_snap;
+	int		control;
+	guint16		etype;
 	capture_func_t	*capture;
 
 	is_snap = (pd[offset] == 0xAA) && (pd[offset+1] == 0xAA);
-	if (is_snap) {
-		etype  = (pd[offset+6] << 8) | pd[offset+7];
-		offset += 8;
-		capture_ethertype(etype, offset, pd, cap_len, ld);
-	}		
-	else {
-		capture = sap_capture_func(pd[offset]);
 
-		/* non-SNAP */
-		offset += 3;
+	/*
+	 * The low-order bit of the SSAP apparently determines whether this
+	 * is a request or a response.  (RFC 1390, "Transmission of IP and
+	 * ARP over FDDI Networks", says
+	 *
+	 *	Command frames are identified by having the low order
+	 *	bit of the SSAP address reset to zero.  Response frames
+	 *	have the low order bit of the SSAP address set to one.
+	 *
+	 * and a page I've seen seems to imply that's part of 802.2.)
+	 *
+	 * XXX - that page also implies that LLC Type 2 always uses
+	 * extended operation, so we don't need to determine whether
+	 * it's basic or extended operation; is that the case?
+	 */
+	control = get_xdlc_control(pd, offset+2, pd[offset+1] & 0x01, TRUE);
 
-		if (capture) {
-			capture(pd, offset, cap_len, ld);
+	if (is_snap) {
+		if (control == XDLC_I || control == (XDLC_U|XDLC_UI)) {
+			/*
+			 * Unnumbered Information - analyze it based on
+			 * the Ethernet packet type.
+			 */
+			etype  = (pd[offset+6] << 8) | pd[offset+7];
+			offset += 8;
+			capture_ethertype(etype, offset, pd, cap_len, ld);
 		}
-		else {
-			ld->other++;
+	}		
+	else {
+		if (control == XDLC_I || control == (XDLC_U|XDLC_UI)) {
+			/*
+			 * Unnumbered Information - analyze it based on
+			 * the DSAP.
+			 */
+			capture = sap_capture_func(pd[offset]);
+
+			/* non-SNAP */
+			offset += 3;
+
+			if (capture) {
+				capture(pd, offset, cap_len, ld);
+			}
+			else {
+				ld->other++;
+			}
 		}
-
 	}
 }
 
@@ -193,8 +223,9 @@ dissect_llc(const u_char *pd, int offset, frame_data *fd, proto_tree *tree) {
 
 	proto_tree	*llc_tree = NULL;
 	proto_item	*ti;
-	guint16		etype;
 	int		is_snap;
+	int		control;
+	guint16		etype;
 	dissect_func_t	*dissect;
 
 	is_snap = (pd[offset] == 0xAA) && (pd[offset+1] == 0xAA);
@@ -226,17 +257,13 @@ dissect_llc(const u_char *pd, int offset, frame_data *fd, proto_tree *tree) {
 	 * extended operation, so we don't need to determine whether
 	 * it's basic or extended operation; is that the case?
 	 */
-	dissect_xdlc_control(pd, offset+2, fd, llc_tree, hf_llc_ctrl,
+	control = dissect_xdlc_control(pd, offset+2, fd, llc_tree, hf_llc_ctrl,
 	    pd[offset+1] & 0x01, TRUE);
 
 	/*
 	 * XXX - do we want to append the SAP information to the stuff
 	 * "dissect_xdlc_control()" put in the COL_INFO column, rather
 	 * than overwriting it?
-	 *
-	 * XXX - we shouldn't, as far as I know, pass S frames to
-	 * "ethertype" or "dissect", and we may have to treat I frames
-	 * differently from U frames.
 	 */
 	if (is_snap) {
 		if (check_col(fd, COL_INFO)) {
@@ -246,10 +273,17 @@ dissect_llc(const u_char *pd, int offset, frame_data *fd, proto_tree *tree) {
 			proto_tree_add_item(llc_tree, hf_llc_oui, offset+3, 3,
 				pd[offset+3] << 16 | pd[offset+4] << 8 | pd[offset+5]);
 		}
-		etype = pntohs(&pd[offset+6]);
-		offset += 8;
-		/* w/o even checking, assume OUI is ethertype */
-		ethertype(etype, offset, pd, fd, tree, llc_tree, hf_llc_type);
+		if (control == (XDLC_U|XDLC_UI)) {
+			/*
+			 * Unnumbered Information - dissect it based on
+			 * the Ethernet packet type.
+			 */
+			etype = pntohs(&pd[offset+6]);
+			offset += 8;
+			/* w/o even checking, assume OUI is ethertype */
+			ethertype(etype, offset, pd, fd, tree, llc_tree,
+			    hf_llc_type);
+		}
 	}		
 	else {
 		if (check_col(fd, COL_INFO)) {
@@ -257,18 +291,23 @@ dissect_llc(const u_char *pd, int offset, frame_data *fd, proto_tree *tree) {
 				val_to_str(pd[offset], sap_vals, "%02x"));
 		}
 
-		dissect = sap_dissect_func(pd[offset]);
-
-		/* non-SNAP */
-		offset += 3;
-
-		if (dissect) {
-			dissect(pd, offset, fd, tree);
+		if (control == (XDLC_U|XDLC_UI)) {
+			/*
+			 * Unnumbered Information - dissect it based on
+			 * the DSAP.
+			 */
+			dissect = sap_dissect_func(pd[offset]);
+
+			/* non-SNAP */
+			offset += 3;
+
+			if (dissect) {
+				dissect(pd, offset, fd, tree);
+			}
+			else {
+				dissect_data(pd, offset, fd, tree);
+			}
 		}
-		else {
-			dissect_data(pd, offset, fd, tree);
-		}
-
 	}
 }
 
diff --git a/xdlc.c b/xdlc.c
index 966d80cb67..896b52ab33 100644
--- a/xdlc.c
+++ b/xdlc.c
@@ -2,7 +2,7 @@
  * Routines for use by various SDLC-derived protocols, such as HDLC
  * and its derivatives LAPB, IEEE 802.2 LLC, etc..
  *
- * $Id: xdlc.c,v 1.3 1999/08/16 05:54:32 guy Exp $
+ * $Id: xdlc.c,v 1.4 1999/08/23 22:47:13 guy Exp $
  *
  * Ethereal - Network traffic analyzer
  * By Gerald Combs <gerald@unicom.net>
@@ -74,31 +74,6 @@ static const value_string stype_vals[] = {
     { 0,         NULL }
 };
 
-/*
- * U-format modifiers.
- */
-#define XDLC_U_MODIFIER_MASK	0xEC
-#define XDLC_UI		0x00	/* Unnumbered Information */
-#define XDLC_UP		0x20	/* Unnumbered Poll */
-#define XDLC_DISC	0x40	/* Disconnect (command) */
-#define XDLC_RD		0x40	/* Request Disconnect (response) */
-#define XDLC_UA		0x60	/* Unnumbered Acknowledge */
-#define XDLC_SNRM	0x80	/* Set Normal Response Mode */
-#define XDLC_TEST	0xC0	/* Test */
-#define XDLC_SIM	0x04	/* Set Initialization Mode (command) */
-#define XDLC_RIM	0x04	/* Request Initialization Mode (response) */
-#define XDLC_FRMR	0x84	/* Frame reject */
-#define XDLC_CFGR	0xC4	/* Configure */
-#define XDLC_SARM	0x0C	/* Set Asynchronous Response Mode (command) */
-#define XDLC_DM		0x0C	/* Disconnected mode (response) */
-#define XDLC_SABM	0x2C	/* Set Asynchronous Balanced Mode */
-#define XDLC_SARME	0x4C	/* Set Asynchronous Response Mode Extended */
-#define XDLC_SABME	0x6C	/* Set Asynchronous Balanced Mode Extended */
-#define XDLC_RESET	0x8C	/* Reset */
-#define XDLC_XID	0xAC	/* Exchange identification */
-#define XDLC_SNRME	0xCC	/* Set Normal Response Mode Extended */
-#define XDLC_BCN	0xEC	/* Beacon */
-
 static const value_string modifier_short_vals_cmd[] = {
     { XDLC_UI,    "UI" },
     { XDLC_UP,    "UP" },
@@ -184,6 +159,47 @@ static const value_string modifier_vals_resp[] = {
 };
 
 int
+get_xdlc_control(const u_char *pd, int offset, int is_response, int is_extended)
+{
+    guint16 control;
+
+    switch (pd[offset] & 0x03) {
+
+    case XDLC_S:
+        /*
+	 * Supervisory frame.
+	 */
+	return XDLC_S;
+
+    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.
+	 */
+	control = pd[offset];
+
+	/*
+	 * Return the modifier as well as the XDLC_U bits, so that
+	 * our caller knows whether the packet is UI or something
+	 * else.
+	 */
+	return control & (XDLC_U_MODIFIER_MASK|0x03);
+
+    default:
+	/*
+	 * Information frame.
+	 */
+	return XDLC_I;
+    }
+}
+
+int
 dissect_xdlc_control(const u_char *pd, int offset, frame_data *fd,
   proto_tree *xdlc_tree, int hf_xdlc_control, 
   int is_response, int is_extended)
@@ -331,7 +347,13 @@ dissect_xdlc_control(const u_char *pd, int offset, frame_data *fd,
 		decode_boolean_bitfield(control, 0x03, 1*8,
 		    "Unnumbered frame", NULL));
 	}
-	return XDLC_U;
+
+	/*
+	 * Return the modifier as well as the XDLC_U bits, so that
+	 * our caller knows whether the packet is UI or something
+	 * else.
+	 */
+	return control & (XDLC_U_MODIFIER_MASK|0x03);
 
     default:
 	/*
diff --git a/xdlc.h b/xdlc.h
index cbc699a37b..3f2bc0e8bf 100644
--- a/xdlc.h
+++ b/xdlc.h
@@ -2,7 +2,7 @@
  * Define *DLC frame types, and routine to dissect the control field of
  * a *DLC frame.
  *
- * $Id: xdlc.h,v 1.1 1999/08/04 04:37:46 guy Exp $
+ * $Id: xdlc.h,v 1.2 1999/08/23 22:47:13 guy Exp $
  *
  * Ethereal - Network traffic analyzer
  * By Gerald Combs <gerald@unicom.net>
@@ -32,5 +32,33 @@
 #define XDLC_S		0x01	/* Supervisory frames */
 #define XDLC_U		0x03	/* Unnumbered frames */
 
+/*
+ * U-format modifiers.
+ */
+#define XDLC_U_MODIFIER_MASK	0xEC
+#define XDLC_UI		0x00	/* Unnumbered Information */
+#define XDLC_UP		0x20	/* Unnumbered Poll */
+#define XDLC_DISC	0x40	/* Disconnect (command) */
+#define XDLC_RD		0x40	/* Request Disconnect (response) */
+#define XDLC_UA		0x60	/* Unnumbered Acknowledge */
+#define XDLC_SNRM	0x80	/* Set Normal Response Mode */
+#define XDLC_TEST	0xC0	/* Test */
+#define XDLC_SIM	0x04	/* Set Initialization Mode (command) */
+#define XDLC_RIM	0x04	/* Request Initialization Mode (response) */
+#define XDLC_FRMR	0x84	/* Frame reject */
+#define XDLC_CFGR	0xC4	/* Configure */
+#define XDLC_SARM	0x0C	/* Set Asynchronous Response Mode (command) */
+#define XDLC_DM		0x0C	/* Disconnected mode (response) */
+#define XDLC_SABM	0x2C	/* Set Asynchronous Balanced Mode */
+#define XDLC_SARME	0x4C	/* Set Asynchronous Response Mode Extended */
+#define XDLC_SABME	0x6C	/* Set Asynchronous Balanced Mode Extended */
+#define XDLC_RESET	0x8C	/* Reset */
+#define XDLC_XID	0xAC	/* Exchange identification */
+#define XDLC_SNRME	0xCC	/* Set Normal Response Mode Extended */
+#define XDLC_BCN	0xEC	/* Beacon */
+
+int get_xdlc_control(const u_char *pd, int offset, int is_response,
+  int extended);
+
 int dissect_xdlc_control(const u_char *pd, int offset, frame_data *fd,
   proto_tree *xdlc_tree, int hf_xdlc_control, int is_response, int extended);