Add "tvb_reported_length()" to get the "reported length" of a tvbuff

(i.e., the amount of data that was in the packet, even if not all of it
was captured), for use when dissecting packets containing data that
fills the packet (we want the dissector to try to dissect all of it; if
it runs past the end of the captured data, we want it to throw an
exception so that we'll put a "Short Frame" note in the protocol tree).

This means we always want a tvbuff to have a real reported length value,
so we make it an unsigned integer, and don't bother checking it for -1,
as it should never be -1.

If the reported length passed in to "tvb_set_subset()" is -1, set the
reported length to the reported length of the tvbuff of which the new
tvbuff will be a subset minus the offset in that tvbuff of the subset,
so that "-1" means "what's left of the packet after we chop off the
header".  This is necessary in order to ensure that all tvbuffs have a
real reported length value.

Have "dissect_packet()" set the reported length of the top-level tvbuff
to the reported length of the frame, so that we start out with a tvbuff
with a real reported length value.

Have "tvb_offset_exists()" return FALSE if the offset is past the end of
the tvbuff.

If the offset passed to it is postitive, have "compute_offset_length()"
check for that it's not more than one byte past the end of the tvbuff -
if it's just past the end, we don't want the check to fail, as we don't
want attempts to create a subset tvbuff containing zero bytes to fail;
that would be done if a captured packet was all header and no payload,
and we'd want the dissector of the payload, not the dissector of the
header, to throw an exception, as the problem isn't with the protocol
for the header, it's with the protocol for the payload.

Convert the ATM dissector, the SSCOP dissector, the Q.2931 dissector,
and the Q.931 dissector to use tvbuffs.

Make the LAPD dissector set up a tvbuff for the Q.931 dissector (it's
not converted yet).

svn path=/trunk/; revision=2023

1 files changed, 68 insertions, 65 deletions

diff --git a/packet-sscop.c b/packet-sscop.c
index 58514c72e6..100a1e8d0d 100644
--- a/packet-sscop.c
+++ b/packet-sscop.c
@@ -2,7 +2,7 @@
  * Routines for SSCOP (Q.2110, Q.SAAL) frame disassembly
  * Guy Harris <guy@alum.mit.edu>
  *
- * $Id: packet-sscop.c,v 1.7 2000/05/11 08:15:52 gram Exp $
+ * $Id: packet-sscop.c,v 1.8 2000/05/29 08:57:40 guy Exp $
  *
  * Ethereal - Network traffic analyzer
  * By Gerald Combs <gerald@zing.org>
@@ -108,54 +108,51 @@ static const value_string sscop_type_vals[] = {
 /*
  * PDU type.
  */
-#define	SSCOP_PDU_TYPE	(pi.len - 4)	/* single byte */
+#define	SSCOP_PDU_TYPE	(reported_length - 4)	/* single byte */
 
 /*
  * Begin PDU, Begin Acknowledge PDU (no N(SQ) in it), Resynchronization
  * PDU, Resynchronization Acknowledge PDU (no N(SQ) in it in Q.SAAL),
  * Error Recovery PDU, Error Recovery Acknoledge PDU (no N(SQ) in it).
  */
-#define	SSCOP_N_SQ	(pi.len - 5)	/* One byte */
-#define	SSCOP_N_MR	(pi.len - 4)	/* lower 3 bytes thereof */
+#define	SSCOP_N_SQ	(reported_length - 5)	/* One byte */
+#define	SSCOP_N_MR	(reported_length - 4)	/* lower 3 bytes thereof */
 
 /*
  * Sequenced Data PDU (no N(PS) in it), Sequenced Data with Poll PDU,
  * Poll PDU.
  */
-#define	SSCOP_N_PS	(pi.len - 8)	/* lower 3 bytes thereof */
-#define	SSCOP_N_S	(pi.len - 4)	/* lower 3 bytes thereof */
+#define	SSCOP_N_PS	(reported_length - 8)	/* lower 3 bytes thereof */
+#define	SSCOP_N_S	(reported_length - 4)	/* lower 3 bytes thereof */
 
 /*
  * Solicited Status PDU, Unsolicited Status PDU (no N(PS) in it).
  */
-#define	SSCOP_SS_N_PS	(pi.len - 12)	/* lower 3 bytes thereof */
-#define	SSCOP_SS_N_MR	(pi.len - 8)	/* lower 3 bytes thereof */
-#define	SSCOP_SS_N_R	(pi.len - 4)	/* lower 3 bytes thereof */
+#define	SSCOP_SS_N_PS	(reported_length - 12)	/* lower 3 bytes thereof */
+#define	SSCOP_SS_N_MR	(reported_length - 8)	/* lower 3 bytes thereof */
+#define	SSCOP_SS_N_R	(reported_length - 4)	/* lower 3 bytes thereof */
 
 void
-dissect_sscop(const u_char *pd, int offset, frame_data *fd, proto_tree *tree) 
+dissect_sscop(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
 {
+  guint reported_length;
   proto_item *ti;
   proto_tree *sscop_tree = NULL;
+  guint8 sscop_pdu_type;
   guint8 pdu_type;
   int pdu_len;
   int pad_len;
+  tvbuff_t *next_tvb;
 
-  /*
-   * The SSCOP "header" is a trailer, and the PDU type is in the
-   * last-minus-3 byte of the frame; if the captured length is less
-   * than the actual length by 3 or more bytes, give up, as we don't
-   * have the PDU type.
-   */
-  if ((pi.len - pi.captured_len) >= 3) {
-    dissect_data(pd, offset, fd, tree);
-    return;
-  }
-  pdu_type = pd[SSCOP_PDU_TYPE] & SSCOP_TYPE_MASK;
-  if (check_col(fd, COL_PROTOCOL))
-    col_add_str(fd, COL_PROTOCOL, "SSCOP");
-  if (check_col(fd, COL_INFO))
-    col_add_str(fd, COL_INFO, val_to_str(pdu_type, sscop_type_vals,
+  pinfo->current_proto = "SSCOP";
+
+  reported_length = tvb_reported_length(tvb);	/* frame length */
+  sscop_pdu_type = tvb_get_guint8(tvb, SSCOP_PDU_TYPE);
+  pdu_type = sscop_pdu_type & SSCOP_TYPE_MASK;
+  if (check_col(pinfo->fd, COL_PROTOCOL))
+    col_add_str(pinfo->fd, COL_PROTOCOL, "SSCOP");
+  if (check_col(pinfo->fd, COL_INFO))
+    col_add_str(pinfo->fd, COL_INFO, val_to_str(pdu_type, sscop_type_vals,
 					"Unknown PDU type (0x%02x)"));
 
   /*
@@ -165,7 +162,7 @@ dissect_sscop(const u_char *pd, int offset, frame_data *fd, proto_tree *tree)
   switch (pdu_type) {
 
   case SSCOP_SD:
-    pad_len = (pd[SSCOP_PDU_TYPE] >> 6) & 0x03;
+    pad_len = (sscop_pdu_type >> 6) & 0x03;
     pdu_len = 4;
     break;
 
@@ -177,26 +174,27 @@ dissect_sscop(const u_char *pd, int offset, frame_data *fd, proto_tree *tree)
 #if 0
   case SSCOP_SDP:
 #endif
-    pad_len = (pd[SSCOP_PDU_TYPE] >> 6) & 0x03;
+    pad_len = (sscop_pdu_type >> 6) & 0x03;
     pdu_len = 8;
     break;
 
   case SSCOP_UD:
-    pad_len = (pd[SSCOP_PDU_TYPE] >> 6) & 0x03;
+    pad_len = (sscop_pdu_type >> 6) & 0x03;
     pdu_len = 4;
     break;
 
   default:
     pad_len = 0;
-    pdu_len = pi.len;	/* No payload, just SSCOP */
+    pdu_len = reported_length;	/* No payload, just SSCOP */
     break;
   }
   if (tree) {
-    ti = proto_tree_add_protocol_format(tree, proto_sscop, NullTVB, pi.len - pdu_len,
+    ti = proto_tree_add_protocol_format(tree, proto_sscop, tvb,
+					reported_length - pdu_len,
     					pdu_len, "SSCOP");
     sscop_tree = proto_item_add_subtree(ti, ett_sscop);
 
-    proto_tree_add_text(sscop_tree, NullTVB, SSCOP_PDU_TYPE, 1,
+    proto_tree_add_text(sscop_tree, tvb, SSCOP_PDU_TYPE, 1,
 			"PDU Type: %s",
 			val_to_str(pdu_type, sscop_type_vals,
 				"Unknown (0x%02x)"));
@@ -206,63 +204,63 @@ dissect_sscop(const u_char *pd, int offset, frame_data *fd, proto_tree *tree)
     case SSCOP_BGN:
     case SSCOP_RS:
     case SSCOP_ER:
-      proto_tree_add_text(sscop_tree, NullTVB, SSCOP_N_SQ, 1,
-          "N(SQ): %u", pd[SSCOP_N_SQ]);
-      proto_tree_add_text(sscop_tree, NullTVB, SSCOP_N_MR + 1, 3,
-          "N(MR): %u", pntohl(&pd[SSCOP_N_MR]) & 0xFFFFFF);
+      proto_tree_add_text(sscop_tree, tvb, SSCOP_N_SQ, 1,
+          "N(SQ): %u", tvb_get_guint8(tvb, SSCOP_N_SQ));
+      proto_tree_add_text(sscop_tree, tvb, SSCOP_N_MR + 1, 3,
+          "N(MR): %u", tvb_get_ntohl(tvb, SSCOP_N_MR) & 0xFFFFFF);
       break;
 
     case SSCOP_END:
-      proto_tree_add_text(sscop_tree, NullTVB, SSCOP_PDU_TYPE, 1,
-          "Source: %s", (pd[SSCOP_PDU_TYPE] & SSCOP_S) ? "SSCOP" : "User");
+      proto_tree_add_text(sscop_tree, tvb, SSCOP_PDU_TYPE, 1,
+          "Source: %s", (sscop_pdu_type & SSCOP_S) ? "SSCOP" : "User");
       break;
 
     case SSCOP_BGAK:
     case SSCOP_RSAK:
-      proto_tree_add_text(sscop_tree, NullTVB, SSCOP_N_MR + 1, 3,
-          "N(MR): %u", pntohl(&pd[SSCOP_N_MR]) & 0xFFFFFF);
+      proto_tree_add_text(sscop_tree, tvb, SSCOP_N_MR + 1, 3,
+          "N(MR): %u", tvb_get_ntohl(tvb, SSCOP_N_MR) & 0xFFFFFF);
       break;
 
     case SSCOP_ERAK:
-      proto_tree_add_text(sscop_tree, NullTVB, SSCOP_N_MR + 3, 3,
-          "N(MR): %u", pntohl(&pd[SSCOP_N_MR]) & 0xFFFFFF);
+      proto_tree_add_text(sscop_tree, tvb, SSCOP_N_MR + 3, 3,
+          "N(MR): %u", tvb_get_ntohl(tvb, SSCOP_N_MR) & 0xFFFFFF);
       break;
 
     case SSCOP_SD:
-      proto_tree_add_text(sscop_tree, NullTVB, SSCOP_N_S + 1, 3,
-          "N(S): %u", pntohl(&pd[SSCOP_N_S]) & 0xFFFFFF);
+      proto_tree_add_text(sscop_tree, tvb, SSCOP_N_S + 1, 3,
+          "N(S): %u", tvb_get_ntohl(tvb, SSCOP_N_S) & 0xFFFFFF);
       break;
 
 #if 0
     case SSCOP_SDP:
 #endif
     case SSCOP_POLL:
-      proto_tree_add_text(sscop_tree, NullTVB, SSCOP_N_PS + 1, 3,
-          "N(PS): %u", pntohl(&pd[SSCOP_N_PS]) & 0xFFFFFF);
-      proto_tree_add_text(sscop_tree, NullTVB, SSCOP_N_S + 1, 3,
-          "N(S): %u", pntohl(&pd[SSCOP_N_S]) & 0xFFFFFF);
+      proto_tree_add_text(sscop_tree, tvb, SSCOP_N_PS + 1, 3,
+          "N(PS): %u", tvb_get_ntohl(tvb, SSCOP_N_PS) & 0xFFFFFF);
+      proto_tree_add_text(sscop_tree, tvb, SSCOP_N_S + 1, 3,
+          "N(S): %u", tvb_get_ntohl(tvb, SSCOP_N_S) & 0xFFFFFF);
       break;
 
     case SSCOP_STAT:
       /*
        * XXX - dissect the list elements....
        */
-      proto_tree_add_text(sscop_tree, NullTVB, SSCOP_SS_N_PS + 1, 3,
-          "N(PS): %u", pntohl(&pd[SSCOP_SS_N_PS]) & 0xFFFFFF);
-      proto_tree_add_text(sscop_tree, NullTVB, SSCOP_SS_N_MR + 1, 3,
-          "N(MR): %u", pntohl(&pd[SSCOP_SS_N_MR]) & 0xFFFFFF);
-      proto_tree_add_text(sscop_tree, NullTVB, SSCOP_SS_N_R + 1, 3,
-          "N(R): %u", pntohl(&pd[SSCOP_SS_N_R]) & 0xFFFFFF);
+      proto_tree_add_text(sscop_tree, tvb, SSCOP_SS_N_PS + 1, 3,
+          "N(PS): %u", tvb_get_ntohl(tvb, SSCOP_SS_N_PS) & 0xFFFFFF);
+      proto_tree_add_text(sscop_tree, tvb, SSCOP_SS_N_MR + 1, 3,
+          "N(MR): %u", tvb_get_ntohl(tvb, SSCOP_SS_N_MR) & 0xFFFFFF);
+      proto_tree_add_text(sscop_tree, tvb, SSCOP_SS_N_R + 1, 3,
+          "N(R): %u", tvb_get_ntohl(tvb, SSCOP_SS_N_R) & 0xFFFFFF);
       break;
 
     case SSCOP_USTAT:
       /*
        * XXX - dissect the list elements....
        */
-      proto_tree_add_text(sscop_tree, NullTVB, SSCOP_SS_N_MR + 1, 3,
-          "N(MR): %u", pntohl(&pd[SSCOP_SS_N_MR]) & 0xFFFFFF);
-      proto_tree_add_text(sscop_tree, NullTVB, SSCOP_SS_N_R + 1, 3,
-          "N(R): %u", pntohl(&pd[SSCOP_SS_N_R]) & 0xFFFFFF);
+      proto_tree_add_text(sscop_tree, tvb, SSCOP_SS_N_MR + 1, 3,
+          "N(MR): %u", tvb_get_ntohl(tvb, SSCOP_SS_N_MR) & 0xFFFFFF);
+      proto_tree_add_text(sscop_tree, tvb, SSCOP_SS_N_R + 1, 3,
+          "N(R): %u", tvb_get_ntohl(tvb, SSCOP_SS_N_R) & 0xFFFFFF);
       break;
     }
   }
@@ -285,27 +283,32 @@ dissect_sscop(const u_char *pd, int offset, frame_data *fd, proto_tree *tree)
   case SSCOP_SDP:
 #endif
     if (tree) {
-      proto_tree_add_text(sscop_tree, NullTVB, SSCOP_PDU_TYPE, 1,
+      proto_tree_add_text(sscop_tree, tvb, SSCOP_PDU_TYPE, 1,
 			"Pad length: %u", pad_len);
     }
 
     /*
      * Compute length of data in PDU - subtract the trailer length
-     * and the pad length.
+     * and the pad length from the reported length.
      */
-    pi.len -= (pdu_len + pad_len);
-    if (pi.len < pi.captured_len)
-      pi.captured_len = pi.len;
+    reported_length -= (pdu_len + pad_len);
 
     /*
      * XXX - if more than just Q.2931 uses SSCOP, we need to tell
      * SSCOP what dissector to use here.
      */
-    if (pi.len != 0) {
+    if (reported_length != 0) {
+      /*
+       * We know that we have all of the payload, because we know we have
+       * at least 4 bytes of data after the payload, i.e. the SSCOP trailer.
+       * Therefore, we know that the captured length of the payload is
+       * equal to the length of the payload.
+       */
+      next_tvb = tvb_new_subset(tvb, 0, reported_length, reported_length);
       if (pdu_type == SSCOP_SD)
-        dissect_q2931(pd, offset, fd, tree);
+        dissect_q2931(next_tvb, pinfo, tree);
       else
-        dissect_data(pd, offset, fd, tree);
+        dissect_data_tvb(next_tvb, pinfo, tree);
     }
     break;
   }