Wireshark · Wireshark-bugs: [Wireshark-bugs] [Bug 1633] New: Fibre Channel BLS ABTS frames cause message "malformed packet"

[bugzilla-daemon@xxxxxxxxxxxxx]

http://bugs.wireshark.org/bugzilla/show_bug.cgi?id=1633

           Summary: Fibre Channel BLS ABTS frames cause message "malformed
                    packet"
           Product: Wireshark
           Version: 0.99.6
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: Minor
          Priority: Low
         Component: Wireshark
        AssignedTo: wireshark-bugs@xxxxxxxxxxxxx
        ReportedBy: joe@xxxxxxxxxxxxxxxx


Build Information:
wireshark 0.99.6 (SVN Rev 21910)

Copyright 1998-2007 Gerald Combs <gerald@xxxxxxxxxxxxx> and contributors.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Compiled with GTK+ 2.8.3, with GLib 2.8.1, with libpcap 0.9.2, with libz 1.2.3,
with libpcre 6.2, without Net-SNMP, without ADNS, without Lua, with GnuTLS
1.2.5, with Gcrypt 1.2.1, without Kerberos, without PortAudio, without AirPcap.

Running on Linux 2.6.13-15.13-default, with libpcap version 0.9.2.

Built using gcc 4.0.2 20050901 (prerelease) (SUSE Linux).
--
The Fibre Channel dissector reports a bounds error on legitimate BLS ABTS
frames.  This can be seen at frame 101 in the fcoe1.cap file in the sample
traces.
http://wiki.wireshark.org/SampleCaptures?action=AttachFile&do=get&target=fcoe1.cap

Here's the tshark output for that frame:

101  16.837356 FCoE_ed:01:00 -> FCoE_ed:00:00     ed.01.00 -> ed.00.00     0x1b
0xffff FC Basic Link Svc[Malformed Packet]

The error is thrown when the length is less than or equal to the header size,
and since ABTS has no payload, a length equal to the header size is normal.

Also, the BLS (basic link services) code isn't nicely printed, and neither is
the ABTS opcode.  I'm also fixing a problem marked by a comment where the
F_CTL bit isn't being found correctly, although it was previously fetched
into a local variable.

With these fixes, frame 101 shows up correctly:

101  16.837356 fc:fc:fc:ed:01:00 -> fc:fc:fc:ed:00:00     ed.01.00 -> ed.00.00 
   0x1b 0xffff BLS ABTS

I've put the three fixes in the patch below.

Index: epan/dissectors/packet-fc.c
===================================================================
--- epan/dissectors/packet-fc.c (revision 21989)
+++ epan/dissectors/packet-fc.c (working copy)
@@ -192,6 +192,7 @@


 const value_string fc_fc4_val[] = {
+    {FC_TYPE_BLS,        "Basic Link Svc"},
     {FC_TYPE_ELS,        "Ext Link Svc"},
     {FC_TYPE_LLCSNAP,    "LLC_SNAP"},
     {FC_TYPE_IP,         "IP/FC"},
@@ -969,11 +970,10 @@
          */
         is_lastframe_inseq = TRUE;
     } else {
-       /* XXX is this right?   offset 20, shouldnt it be offset 9? */
-        is_exchg_resp = ((tvb_get_guint8 (tvb, offset+20) & 0x80) == 0x80);
+        is_exchg_resp = (f_ctl & FC_FCTL_EXCHANGE_RESPONDER) != 0;
     }

-    if (tvb_reported_length (tvb) <= FC_HEADER_SIZE)
+    if (tvb_reported_length (tvb) < FC_HEADER_SIZE)
         THROW(ReportedBoundsError);

     frag_size = tvb_reported_length (tvb)-FC_HEADER_SIZE;
@@ -1124,9 +1124,15 @@
             dissect_fc_ba_acc (next_tvb, pinfo, tree);
         } else if ((fchdr.r_ctl & 0x0F) == FC_BLS_BARJT) {
             dissect_fc_ba_rjt (next_tvb, pinfo, tree);
+        } else if ((fchdr.r_ctl & 0x0F) == FC_BLS_ABTS) {
+            if (check_col(pinfo->cinfo, COL_PROTOCOL)) {
+                col_set_str(pinfo->cinfo, COL_PROTOCOL, "BLS");
+            }
+            if (check_col(pinfo->cinfo, COL_INFO)) {
+                col_set_str(pinfo->cinfo, COL_INFO, "ABTS");
+            }
         }
     }
-
     tap_queue_packet(fc_tap, pinfo, &fchdr);
 }

Index: epan/dissectors/packet-fc.h
===================================================================
--- epan/dissectors/packet-fc.h (revision 21989)
+++ epan/dissectors/packet-fc.h (working copy)
@@ -39,6 +39,7 @@
 #define FC_TYPE_CMNSVC         0x0  /* Used in PRLI Svc Param Page */

 /* TYPE definitions for Basic or Extended Link_Data */
+#define FC_TYPE_BLS            0x0
 #define FC_TYPE_ELS            0x1

 /* TYPE definitions for FC-4 */


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