Export two versions of the Ethereal dissector, for use with encapsulated

Ethernet frames, one for encapsulated frames that include an FCS and one
for encapsulated frames that don't include an FCS.  Use the appropriate
versions.

In the ISL dissector, do the same sort of processing we do in the
Ethernet dissector to figure out whether the frame has a trailer or not
and whether it has an FCS or not.


git-svn-id: http://anonsvn.wireshark.org/wireshark/trunk@12593 f5534014-38df-0310-8fa8-9805f1628bb7

15 files changed, 187 insertions, 102 deletions

diff --git a/epan/dissectors/packet-ascend.c b/epan/dissectors/packet-ascend.c
index 1c3caa7f8d..a1274b2e4d 100644
--- a/epan/dissectors/packet-ascend.c
+++ b/epan/dissectors/packet-ascend.c
@@ -45,7 +45,7 @@ static const value_string encaps_vals[] = {
   {ASCEND_PFX_WDD,   "Ethernet"    },
   {0,                NULL          } };
 
-static dissector_handle_t eth_handle;
+static dissector_handle_t eth_withoutfcs_handle;
 static dissector_handle_t ppp_hdlc_handle;
 
 static void
@@ -108,7 +108,7 @@ dissect_ascend(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
       call_dissector(ppp_hdlc_handle, tvb, pinfo, tree);
       break;
     case ASCEND_PFX_WDD:
-      call_dissector(eth_handle, tvb, pinfo, tree);
+      call_dissector(eth_withoutfcs_handle, tvb, pinfo, tree);
       break;
     default:
       break;
@@ -161,7 +161,7 @@ proto_reg_handoff_ascend(void)
   /*
    * Get handles for the Ethernet and PPP-in-HDLC-like-framing dissectors.
    */
-  eth_handle = find_dissector("eth");
+  eth_withoutfcs_handle = find_dissector("eth_withoutfcs");
   ppp_hdlc_handle = find_dissector("ppp_hdlc");
 
   ascend_handle = create_dissector_handle(dissect_ascend, proto_ascend);
diff --git a/epan/dissectors/packet-atm.c b/epan/dissectors/packet-atm.c
index 5bf4de3dff..820643c62e 100644
--- a/epan/dissectors/packet-atm.c
+++ b/epan/dissectors/packet-atm.c
@@ -59,7 +59,7 @@ static gint ett_aal1 = -1;
 static gint ett_aal3_4 = -1;
 static gint ett_oamaal = -1;
 
-static dissector_handle_t eth_handle;
+static dissector_handle_t eth_withoutfcs_handle;
 static dissector_handle_t tr_handle;
 static dissector_handle_t llc_handle;
 static dissector_handle_t sscop_handle;
@@ -668,7 +668,7 @@ dissect_lane(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
 
     /* Dissect as Ethernet */
     next_tvb_le_client	= tvb_new_subset(tvb, 2, -1, -1);
-    call_dissector(eth_handle, next_tvb_le_client, pinfo, tree);
+    call_dissector(eth_withoutfcs_handle, next_tvb_le_client, pinfo, tree);
     break;
 
   case TRAF_ST_LANE_802_5:
@@ -1622,7 +1622,7 @@ proto_reg_handoff_atm(void)
 	 * Get handles for the Ethernet, Token Ring, LLC, SSCOP, LANE,
 	 * and ILMI dissectors.
 	 */
-	eth_handle = find_dissector("eth");
+	eth_withoutfcs_handle = find_dissector("eth_withoutfcs");
 	tr_handle = find_dissector("tr");
 	llc_handle = find_dissector("llc");
 	sscop_handle = find_dissector("sscop");
diff --git a/epan/dissectors/packet-cosine.c b/epan/dissectors/packet-cosine.c
index 2c8fa84666..8679904379 100644
--- a/epan/dissectors/packet-cosine.c
+++ b/epan/dissectors/packet-cosine.c
@@ -46,7 +46,7 @@ static int hf_err = -1;
 
 static gint ett_raw = -1;
 
-static dissector_handle_t eth_handle;
+static dissector_handle_t eth_withoutfcs_handle;
 static dissector_handle_t ppp_hdlc_handle;
 static dissector_handle_t llc_handle;
 static dissector_handle_t chdlc_handle;
@@ -112,7 +112,7 @@ dissect_cosine(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
 
   switch (pseudo_header->cosine.encap) {
   case COSINE_ENCAP_ETH:
-    	  call_dissector(eth_handle, tvb_new_subset(tvb, 0, -1, -1),
+    	  call_dissector(eth_withoutfcs_handle, tvb_new_subset(tvb, 0, -1, -1),
 			 pinfo, tree);
 	  break;
   case COSINE_ENCAP_ATM:
@@ -181,7 +181,7 @@ proto_reg_handoff_cosine(void)
   /*
    * Get handles for dissectors.
    */
-  eth_handle = find_dissector("eth");
+  eth_withoutfcs_handle = find_dissector("eth_withoutfcs");
   ppp_hdlc_handle = find_dissector("ppp_hdlc");
   llc_handle = find_dissector("llc");
   chdlc_handle = find_dissector("chdlc");
diff --git a/epan/dissectors/packet-eth.c b/epan/dissectors/packet-eth.c
index e89df34539..be00065114 100644
--- a/epan/dissectors/packet-eth.c
+++ b/epan/dissectors/packet-eth.c
@@ -54,7 +54,6 @@ static int hf_eth_trailer = -1;
 static gint ett_ieee8023 = -1;
 static gint ett_ether2 = -1;
 
-static dissector_handle_t isl_handle;
 static dissector_handle_t fw1_handle;
 static heur_dissector_list_t heur_subdissector_list;
 
@@ -213,7 +212,7 @@ dissect_eth_common(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
 		tvb_get_guint8(tvb, 2) == 0x0C &&
 		tvb_get_guint8(tvb, 3) == 0x00 &&
 		tvb_get_guint8(tvb, 4) == 0x00 ) {
-      call_dissector(isl_handle, tvb, pinfo, tree);
+      dissect_isl(tvb, pinfo, tree, fcs_len);
       goto end_of_eth;
     }
   }
@@ -396,14 +395,21 @@ dissect_eth_maybefcs(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
   dissect_eth_common(tvb, pinfo, tree, pinfo->pseudo_header->eth.fcs_len);
 }
 
-/* Called by other dissectors - for now, we assume Ethernet encapsulated
-   inside other protocols doesn't include the FCS. */
+/* Called by other dissectors  This one's for encapsulated Ethernet
+   packets that don't include an FCS. */
 static void
-dissect_eth(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
+dissect_eth_withoutfcs(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
 {
   dissect_eth_common(tvb, pinfo, tree, 0);
 }
 
+/* ...and this one's for encapsulated packets that do. */
+static void
+dissect_eth_withfcs(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
+{
+  dissect_eth_common(tvb, pinfo, tree, 4);
+}
+
 void
 proto_register_eth(void)
 {
@@ -454,27 +460,27 @@ proto_register_eth(void)
             "Whether packets should be interpreted as coming from CheckPoint FireWall-1 monitor file if they look as if they do",
             &eth_interpret_as_fw1_monitor);
 
-	register_dissector("eth", dissect_eth, proto_eth);
+	register_dissector("eth_withoutfcs", dissect_eth_withoutfcs, proto_eth);
+	register_dissector("eth_withfcs", dissect_eth_withfcs, proto_eth);
 	eth_tap = register_tap("eth");
 }
 
 void
 proto_reg_handoff_eth(void)
 {
-	dissector_handle_t eth_handle, eth_maybefcs_handle;
+	dissector_handle_t eth_maybefcs_handle, eth_withoutfcs_handle;
 
 	/*
-	 * Get a handle for the ISL dissector.
+	 * Get a handle for the Firewall-1 dissector.
 	 */
-	isl_handle = find_dissector("isl");
 	fw1_handle = find_dissector("fw1");
 
 	eth_maybefcs_handle = create_dissector_handle(dissect_eth_maybefcs,
 	    proto_eth);
 	dissector_add("wtap_encap", WTAP_ENCAP_ETHERNET, eth_maybefcs_handle);
 
-	eth_handle = find_dissector("eth");
-	dissector_add("ethertype", ETHERTYPE_ETHBRIDGE, eth_handle);
-	dissector_add("chdlctype", ETHERTYPE_ETHBRIDGE, eth_handle);
-	dissector_add("gre.proto", ETHERTYPE_ETHBRIDGE, eth_handle);
+	eth_withoutfcs_handle = find_dissector("eth_withoutfcs");
+	dissector_add("ethertype", ETHERTYPE_ETHBRIDGE, eth_withoutfcs_handle);
+	dissector_add("chdlctype", ETHERTYPE_ETHBRIDGE, eth_withoutfcs_handle);
+	dissector_add("gre.proto", ETHERTYPE_ETHBRIDGE, eth_withoutfcs_handle);
 }
diff --git a/epan/dissectors/packet-etherip.c b/epan/dissectors/packet-etherip.c
index b24e2e89dd..9d75436be3 100644
--- a/epan/dissectors/packet-etherip.c
+++ b/epan/dissectors/packet-etherip.c
@@ -37,7 +37,7 @@ static int hf_etherip_ver = -1;
 
 static gint ett_etherip = -1;
 
-static dissector_handle_t eth_handle;
+static dissector_handle_t eth_withoutfcs_handle;
 
 #ifndef offsetof
 #define	offsetof(type, member)	((size_t)(&((type *)0)->member))
@@ -92,7 +92,7 @@ dissect_etherip(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
   /* Set the tvbuff for the payload after the header */
   next_tvb = tvb_new_subset(tvb, sizeof(etheriph), -1, -1);
 
-  call_dissector(eth_handle, next_tvb, pinfo, tree);
+  call_dissector(eth_withoutfcs_handle, next_tvb, pinfo, tree);
 }
 
 void
@@ -120,7 +120,7 @@ proto_reg_handoff_etherip(void)
 {
   dissector_handle_t etherip_handle;
 
-  eth_handle = find_dissector("eth");
+  eth_withoutfcs_handle = find_dissector("eth_withoutfcs");
   etherip_handle = find_dissector("etherip");
   dissector_add("ip.proto", IP_PROTO_ETHERIP, etherip_handle);
 }
diff --git a/epan/dissectors/packet-fr.c b/epan/dissectors/packet-fr.c
index a8c8f0eec6..3868faa886 100644
--- a/epan/dissectors/packet-fr.c
+++ b/epan/dissectors/packet-fr.c
@@ -109,7 +109,7 @@ static gint hf_fr_pid   = -1;
 static gint hf_fr_snaptype = -1;
 static gint hf_fr_chdlctype = -1;
 
-static dissector_handle_t eth_handle;
+static dissector_handle_t eth_withfcs_handle;
 static dissector_handle_t gprs_ns_handle;
 static dissector_handle_t data_handle;
 
@@ -435,7 +435,7 @@ dissect_fr_common(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
   case RAW_ETHER:
     next_tvb = tvb_new_subset(tvb, offset, -1, -1);
     if (address != 0)
-      call_dissector(eth_handle, next_tvb, pinfo, tree);
+      call_dissector(eth_withfcs_handle, next_tvb, pinfo, tree);
     else
       dissect_lapf(next_tvb, pinfo, tree);
     break;
@@ -716,6 +716,14 @@ void proto_register_fr(void)
   register_dissector("fr", dissect_fr, proto_fr);
 
   frencap_module = prefs_register_protocol(proto_fr, NULL);
+  /*
+   * XXX - this should really be per-circuit - I've seen at least one
+   * capture where different DLCIs have different encapsulations - but
+   * we don't yet have any support for per-circuit encapsulations.
+   *
+   * Even with that, though, we might want a default encapsulation,
+   * so that people dealing with GPRS can make gprs-ns the default.
+   */
   prefs_register_enum_preference(frencap_module, "encap", "Encapsulation",
 				 "Encapsulation", &fr_encap,
 				 fr_encap_options, FALSE);
@@ -732,7 +740,7 @@ void proto_reg_handoff_fr(void)
   fr_phdr_handle = create_dissector_handle(dissect_fr_phdr, proto_fr);
   dissector_add("wtap_encap", WTAP_ENCAP_FRELAY_WITH_PHDR, fr_phdr_handle);
 
-  eth_handle = find_dissector("eth");
+  eth_withfcs_handle = find_dissector("eth_withfcs");
   gprs_ns_handle = find_dissector("gprs_ns");
   data_handle = find_dissector("data");
 
diff --git a/epan/dissectors/packet-ieee80211.c b/epan/dissectors/packet-ieee80211.c
index a42ca3e8dc..7dde6091ad 100644
--- a/epan/dissectors/packet-ieee80211.c
+++ b/epan/dissectors/packet-ieee80211.c
@@ -504,7 +504,7 @@ static const fragment_items frag_items = {
 
 static dissector_handle_t llc_handle;
 static dissector_handle_t ipx_handle;
-static dissector_handle_t eth_handle;
+static dissector_handle_t eth_withoutfcs_handle;
 static dissector_handle_t data_handle;
 
 /* ************************************************************************* */
@@ -2492,7 +2492,7 @@ dissect_ieee80211_common (tvbuff_t * tvb, packet_info * pinfo,
         break;
 
       case ENCAP_ETHERNET:
-        call_dissector(eth_handle, next_tvb, pinfo, tree);
+        call_dissector(eth_withoutfcs_handle, next_tvb, pinfo, tree);
         break;
 
       case ENCAP_IPX:
@@ -3226,7 +3226,7 @@ proto_reg_handoff_ieee80211(void)
    */
   llc_handle = find_dissector("llc");
   ipx_handle = find_dissector("ipx");
-  eth_handle = find_dissector("eth");
+  eth_withoutfcs_handle = find_dissector("eth_withoutfcs");
   data_handle = find_dissector("data");
 
   ieee80211_handle = find_dissector("wlan");
diff --git a/epan/dissectors/packet-isl.c b/epan/dissectors/packet-isl.c
index 2c455d72c0..c1544dc611 100644
--- a/epan/dissectors/packet-isl.c
+++ b/epan/dissectors/packet-isl.c
@@ -31,6 +31,7 @@
 #include "packet-isl.h"
 #include "packet-eth.h"
 #include "packet-tr.h"
+#include "packet-frame.h"
 #include "etypes.h"
 
 /*
@@ -67,6 +68,7 @@ static int hf_isl_dst_route_descriptor = -1;
 static int hf_isl_src_route_descriptor = -1;
 static int hf_isl_fcs_not_incl = -1;
 static int hf_isl_esize = -1;
+static int hf_isl_trailer = -1;
 
 static gint ett_isl = -1;
 
@@ -77,7 +79,7 @@ static gint ett_isl = -1;
 #define	TYPE_FDDI	0x2
 #define	TYPE_ATM	0x3
 
-static dissector_handle_t eth_handle;
+static dissector_handle_t eth_withfcs_handle;
 static dissector_handle_t tr_handle;
 static dissector_handle_t data_handle;
 
@@ -137,16 +139,18 @@ static const true_false_string explorer_tfs = {
 	"Data frame"
 };
 
-static void
-dissect_isl(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
+void
+dissect_isl(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, int fcs_len)
 {
-  proto_tree *fh_tree = NULL;
+  proto_tree *volatile fh_tree = NULL;
   proto_item *ti;
   guint8 type;
-  guint16 length;
-  gint crc_offset;
+  volatile guint16 length;
   gint captured_length;
-  tvbuff_t *next_tvb;
+  tvbuff_t *volatile payload_tvb;
+  tvbuff_t *volatile next_tvb;
+  tvbuff_t *volatile trailer_tvb;
+  const char *saved_proto;
 
   if (check_col(pinfo->cinfo, COL_PROTOCOL))
     col_set_str(pinfo->cinfo, COL_PROTOCOL, "ISL");
@@ -178,38 +182,65 @@ dissect_isl(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
     proto_tree_add_item_hidden(fh_tree, hf_isl_addr, tvb, 6, 6, FALSE);
   }
   length = tvb_get_ntohs(tvb, 12);
-  if (tree) {
+  if (tree)
     proto_tree_add_uint(fh_tree, hf_isl_len, tvb, 12, 2, length);
 
+  if (length != 0) {
+    /* The length field was set; it's like an 802.3 length field, so
+       treat it similarly, by constructing a tvbuff containing only
+       the data specified by the length field. */
+
+    TRY {
+      payload_tvb = tvb_new_subset(tvb, 14, length, length);
+      trailer_tvb = tvb_new_subset(tvb, 14 + length, -1, -1);
+    }
+    CATCH2(BoundsError, ReportedBoundsError) {
+      /* Either:
+
+	  the packet doesn't have "length" bytes worth of
+	  captured data left in it - or it may not even have
+	  "length" bytes worth of data in it, period -
+	  so the "tvb_new_subset()" creating "payload_tvb"
+	  threw an exception
+
+         or
+
+	  the packet has exactly "length" bytes worth of
+	  captured data left in it, so the "tvb_new_subset()"
+	  creating "trailer_tvb" threw an exception.
+
+         In either case, this means that all the data in the frame
+         is within the length value, so we give all the data to the
+         next protocol and have no trailer. */
+      payload_tvb = tvb_new_subset(tvb, 14, -1, length);
+      trailer_tvb = NULL;
+    }
+    ENDTRY;
+  } else {
+    /* The length field is 0; make it the length remaining in the packet
+       after the first 14 bytes. */
+    length = tvb_reported_length_remaining(tvb, 14);
+    payload_tvb = tvb_new_subset(tvb, 14, -1, -1);
+    trailer_tvb = NULL;
+  }
+
+  if (tree) {
     /* This part looks sort of like a SNAP-encapsulated LLC header... */
-    proto_tree_add_text(fh_tree, tvb, 14, 1, "DSAP: 0x%X", tvb_get_guint8(tvb, 14));
-    proto_tree_add_text(fh_tree, tvb, 15, 1, "SSAP: 0x%X", tvb_get_guint8(tvb, 15));
-    proto_tree_add_text(fh_tree, tvb, 16, 1, "Control: 0x%X", tvb_get_guint8(tvb, 16));
+    proto_tree_add_text(fh_tree, payload_tvb, 0, 1, "DSAP: 0x%X", tvb_get_guint8(tvb, 14));
+    proto_tree_add_text(fh_tree, payload_tvb, 1, 1, "SSAP: 0x%X", tvb_get_guint8(tvb, 15));
+    proto_tree_add_text(fh_tree, payload_tvb, 2, 1, "Control: 0x%X", tvb_get_guint8(tvb, 16));
 
     /* ...but this is the manufacturer's ID portion of the source address
        field (which is, admittedly, an OUI). */
-    proto_tree_add_item(fh_tree, hf_isl_hsa, tvb, 17, 3, FALSE);
+    proto_tree_add_item(fh_tree, hf_isl_hsa, payload_tvb, 3, 3, FALSE);
   }
   if (check_col(pinfo->cinfo, COL_INFO))
     col_add_fstr(pinfo->cinfo, COL_INFO, "VLAN ID: 0x%04X",
 		 tvb_get_ntohs(tvb, 20) >> 1);
   if (tree) {
-    proto_tree_add_item(fh_tree, hf_isl_vlan_id, tvb, 20, 2, FALSE);
-    proto_tree_add_item(fh_tree, hf_isl_bpdu, tvb, 20, 2, FALSE);
-    proto_tree_add_item(fh_tree, hf_isl_index, tvb, 22, 2, FALSE);
-
-    /* Now for the encapsulated frame's CRC, which is at the *end* of the
-       packet; "length" is the length of the frame, not including the
-       first 14 bytes of the frame, but including the encapsulated
-       frame's CRC, which is 4 bytes long, so the offset of the
-       encapsulated CRC is "length + 14 - 4".
-
-       We check for the CRC and display it only if we have that data,
-       rather than throwing an exception before we've dissected any
-       of the rest of the frame. */
-    crc_offset = length + 14 - 4;
-    if (tvb_bytes_exist(tvb, crc_offset, 4))
-      proto_tree_add_item(fh_tree, hf_isl_crc, tvb, crc_offset, 4, FALSE);
+    proto_tree_add_item(fh_tree, hf_isl_vlan_id, payload_tvb, 6, 2, FALSE);
+    proto_tree_add_item(fh_tree, hf_isl_bpdu, payload_tvb, 6, 2, FALSE);
+    proto_tree_add_item(fh_tree, hf_isl_index, payload_tvb, 8, 2, FALSE);
   }
 
   switch (type) {
@@ -217,46 +248,73 @@ dissect_isl(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
   case TYPE_ETHER:
     /* The length of the encapsulated frame is the length from the
        header, minus 12 bytes for the part of the ISL header that
-       follows the length and 4 bytes for the encapsulated frame
-       CRC. */
-    if (length >= 12+4) {
+       follows the length. */
+    if (length >= 12) {
       /* Well, we at least had that much data in the frame.  Try
          dissecting what's left as an Ethernet frame. */
-      length -= 12+4;
+      length -= 12;
 
       /* Trim the captured length. */
-      captured_length = tvb_length_remaining(tvb, ISL_HEADER_SIZE);
-      if (captured_length > 4) {
-        /* Subtract the encapsulated frame CRC. */
-        captured_length -= 4;
+      captured_length = tvb_length_remaining(payload_tvb, 12);
+
+      /* Make sure it's not bigger than the actual length. */
+      if (captured_length > length)
+        captured_length = length;
 
-        /* Make sure it's not bigger than the actual length. */
-        if (captured_length > length)
-          captured_length = length;
+      next_tvb = tvb_new_subset(payload_tvb, 12, captured_length, length);
 
-        next_tvb = tvb_new_subset(tvb, ISL_HEADER_SIZE, captured_length, length);
+      /* Dissect the payload as an Etherner frame.
 
-        call_dissector(eth_handle, next_tvb, pinfo, tree);
+        Catch BoundsError and ReportedBoundsError, so that if the
+        reported length of "next_tvb" was reduced by some dissector
+        before an exception was thrown, we can still put in an item
+        for the trailer. */
+      saved_proto = pinfo->current_proto;
+      TRY {
+        /* Frames encapsulated in ISL include an FCS. */
+        call_dissector(eth_withfcs_handle, next_tvb, pinfo, tree);
+      }
+      CATCH(BoundsError) {
+       /* Somebody threw BoundsError, which means that dissecting the payload
+          found that the packet was cut off by a snapshot length before the
+          end of the payload.  The trailer comes after the payload, so *all*
+          of the trailer is cut off - don't bother adding the trailer, just
+          rethrow the exception so it gets reported. */
+       RETHROW;
+      }
+      CATCH_ALL {
+        /* Well, somebody threw an exception other than BoundsError.
+           Show the exception, and then drive on to show the trailer,
+           restoring the protocol value that was in effect before we
+           called the subdissector. */
+        show_exception(next_tvb, pinfo, tree, EXCEPT_CODE);
+        pinfo->current_proto = saved_proto;
       }
+      ENDTRY;
+
+      /* Now add the Ethernet trailer and FCS.
+         XXX - do this only if we're encapsulated in Ethernet? */
+      add_ethernet_trailer(fh_tree, hf_isl_trailer, tvb, trailer_tvb, fcs_len);
     }
     break;
 
   case TYPE_TR:
     if (tree) {
-      proto_tree_add_item(fh_tree, hf_isl_src_vlan_id, tvb, 24, 2, FALSE);
-      proto_tree_add_item(fh_tree, hf_isl_explorer, tvb, 24, 2, FALSE);
-      proto_tree_add_item(fh_tree, hf_isl_dst_route_descriptor, tvb, 26, 2, FALSE);
-      proto_tree_add_item(fh_tree, hf_isl_src_route_descriptor, tvb, 28, 2, FALSE);
-      proto_tree_add_item(fh_tree, hf_isl_fcs_not_incl, tvb, 30, 1, FALSE);
-      proto_tree_add_item(fh_tree, hf_isl_esize, tvb, 30, 1, FALSE);
+      proto_tree_add_item(fh_tree, hf_isl_src_vlan_id, payload_tvb, 10, 2, FALSE);
+      proto_tree_add_item(fh_tree, hf_isl_explorer, payload_tvb, 10, 2, FALSE);
+      proto_tree_add_item(fh_tree, hf_isl_dst_route_descriptor, payload_tvb, 12, 2, FALSE);
+      proto_tree_add_item(fh_tree, hf_isl_src_route_descriptor, payload_tvb, 14, 2, FALSE);
+      /* This doesn't appear to be present in at least one capture I've seen. */
+      proto_tree_add_item(fh_tree, hf_isl_fcs_not_incl, payload_tvb, 16, 1, FALSE);
+      proto_tree_add_item(fh_tree, hf_isl_esize, payload_tvb, 16, 1, FALSE);
     }
-    next_tvb = tvb_new_subset(tvb, 31, -1, -1);
+    next_tvb = tvb_new_subset(payload_tvb, 17, -1, -1);
     call_dissector(tr_handle, next_tvb, pinfo, tree);
     break;
 
   default:
-    next_tvb = tvb_new_subset(tvb, ISL_HEADER_SIZE, -1, -1);
-    call_dissector(data_handle,next_tvb, pinfo, tree);
+    next_tvb = tvb_new_subset(payload_tvb, 12, -1, -1);
+    call_dissector(data_handle, next_tvb, pinfo, tree);
     break;
   }
 }
@@ -321,6 +379,10 @@ proto_register_isl(void)
 	{ &hf_isl_esize,
 	{ "Esize",	"isl.esize", FT_UINT8, BASE_DEC, NULL,
 		0x3F, "Frame size for frames less than 64 bytes", HFILL }},
+	{ &hf_isl_trailer,
+	{ "Trailer",	"isl.trailer", FT_BYTES, BASE_NONE, NULL, 0x0,
+		"Ethernet Trailer or Checksum", HFILL }},
+
   };
   static gint *ett[] = {
 	&ett_isl,
@@ -329,8 +391,6 @@ proto_register_isl(void)
   proto_isl = proto_register_protocol("Cisco ISL", "ISL", "isl");
   proto_register_field_array(proto_isl, hf, array_length(hf));
   proto_register_subtree_array(ett, array_length(ett));
-
-  register_dissector("isl", dissect_isl, proto_isl);
 }
 
 void
@@ -339,7 +399,7 @@ proto_reg_handoff_isl(void)
   /*
    * Get handles for the Ethernet and Token Ring dissectors.
    */
-  eth_handle = find_dissector("eth");
+  eth_withfcs_handle = find_dissector("eth_withfcs");
   tr_handle = find_dissector("tr");
   data_handle = find_dissector("data");
 }
diff --git a/epan/dissectors/packet-isl.h b/epan/dissectors/packet-isl.h
index d26417c9f0..c926480ea5 100644
--- a/epan/dissectors/packet-isl.h
+++ b/epan/dissectors/packet-isl.h
@@ -26,4 +26,7 @@
 
 void capture_isl(const guchar *, int, int, packet_counts *);
 
+void dissect_isl(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
+    int fcs_len);
+
 #endif
diff --git a/epan/dissectors/packet-llc.c b/epan/dissectors/packet-llc.c
index 0d60f70b3c..8150a101c3 100644
--- a/epan/dissectors/packet-llc.c
+++ b/epan/dissectors/packet-llc.c
@@ -80,7 +80,8 @@ static dissector_table_t subdissector_table;
 static dissector_table_t xid_subdissector_table;
 
 static dissector_handle_t bpdu_handle;
-static dissector_handle_t eth_handle;
+static dissector_handle_t eth_withoutfcs_handle;
+static dissector_handle_t eth_withfcs_handle;
 static dissector_handle_t fddi_handle;
 static dissector_handle_t tr_handle;
 static dissector_handle_t data_handle;
@@ -512,10 +513,16 @@ dissect_snap(tvbuff_t *tvb, int offset, packet_info *pinfo, proto_tree *tree,
 		switch (etype) {
 
 		case BPID_ETH_WITH_FCS:
+			next_tvb = tvb_new_subset(tvb, offset+5+bridge_pad,
+			    -1, -1);
+			call_dissector(eth_withfcs_handle, next_tvb, pinfo,
+			    tree);
+			break;
+
 		case BPID_ETH_WITHOUT_FCS:
 			next_tvb = tvb_new_subset(tvb, offset+5+bridge_pad,
 			    -1, -1);
-			call_dissector(eth_handle, next_tvb, pinfo, tree);
+			call_dissector(eth_withoutfcs_handle, next_tvb, pinfo, tree);
 			break;
 
 		case BPID_802_5_WITH_FCS:
@@ -720,7 +727,8 @@ proto_reg_handoff_llc(void)
 	 * dissectors.
 	 */
 	bpdu_handle = find_dissector("bpdu");
-	eth_handle = find_dissector("eth");
+	eth_withoutfcs_handle = find_dissector("eth_withoutfcs");
+	eth_withfcs_handle = find_dissector("eth_withfcs");
 	fddi_handle = find_dissector("fddi");
 	tr_handle = find_dissector("tr");
 	data_handle = find_dissector("data");
diff --git a/epan/dissectors/packet-lwapp.c b/epan/dissectors/packet-lwapp.c
index f2d87cd933..cdba063454 100644
--- a/epan/dissectors/packet-lwapp.c
+++ b/epan/dissectors/packet-lwapp.c
@@ -74,7 +74,7 @@ static gint hf_lwapp_control_type = -1;
 static gint hf_lwapp_control_seq_no = -1;
 static gint hf_lwapp_control_length = -1;
 
-static dissector_handle_t eth_handle;
+static dissector_handle_t eth_withoutfcs_handle;
 static dissector_handle_t wlan_handle;
 static dissector_handle_t wlan_bsfc_handle;
 static dissector_handle_t data_handle;
@@ -331,7 +331,7 @@ static void dissect_lwapp_l3(tvbuff_t *tvb, packet_info *pinfo,
 
     /* Dissect as Ethernet */
     next_client	= tvb_new_subset(tvb, 0, -1, -1);
-    call_dissector(eth_handle, next_client, pinfo, tree);
+    call_dissector(eth_withoutfcs_handle, next_client, pinfo, tree);
     return;
 
 } /* dissect_lwapp_l3*/
@@ -543,7 +543,7 @@ proto_reg_handoff_lwapp(void)
     /*
      * Get handles for the Ethernet and wireless dissectors.
      */
-    eth_handle = find_dissector("eth");
+    eth_withoutfcs_handle = find_dissector("eth_withoutfcs");
     wlan_handle = find_dissector("wlan");
     wlan_bsfc_handle = find_dissector("wlan_bsfc");
     data_handle = find_dissector("data");
diff --git a/epan/dissectors/packet-mpls.c b/epan/dissectors/packet-mpls.c
index e88aef39ae..bacb9634db 100644
--- a/epan/dissectors/packet-mpls.c
+++ b/epan/dissectors/packet-mpls.c
@@ -120,7 +120,7 @@ static hf_register_info mplsf_info[] = {
 
 static dissector_handle_t ipv4_handle;
 static dissector_handle_t ipv6_handle;
-static dissector_handle_t eth_handle;
+static dissector_handle_t eth_withoutfcs_handle;
 static dissector_handle_t data_handle;
 static dissector_table_t ppp_subdissector_table;
 
@@ -252,7 +252,7 @@ dissect_mpls(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
     } else if (ipvers == 1) {
       dissect_mpls_control(next_tvb, pinfo, tree);
     } else {
-      call_dissector(eth_handle, next_tvb, pinfo, tree);
+      call_dissector(eth_withoutfcs_handle, next_tvb, pinfo, tree);
     }
 }
 
@@ -280,7 +280,7 @@ proto_reg_handoff_mpls(void)
 	 */
 	ipv4_handle = find_dissector("ip");
 	ipv6_handle = find_dissector("ipv6");
-	eth_handle = find_dissector("eth");
+	eth_withoutfcs_handle = find_dissector("eth_withoutfcs");
         data_handle = find_dissector("data");
         ppp_subdissector_table = find_dissector_table("ppp.protocol");
 
diff --git a/epan/dissectors/packet-sflow.c b/epan/dissectors/packet-sflow.c
index 9177a7be74..a144219b42 100644
--- a/epan/dissectors/packet-sflow.c
+++ b/epan/dissectors/packet-sflow.c
@@ -307,7 +307,7 @@ static gint ett_sflow_extended_data = -1;
 static gint ett_sflow_sampled_header = -1;
 
 /* dissectors for other protocols */
-static dissector_handle_t eth_handle;
+static dissector_handle_t eth_withoutfcs_handle;
 static dissector_handle_t tr_handle;
 static dissector_handle_t fddi_handle;
 static dissector_handle_t fr_handle;
@@ -375,7 +375,7 @@ dissect_sflow_sampled_header(tvbuff_t *tvb, packet_info *pinfo,
 	TRY {
 		switch (header_proto) {
 		case SFLOW_HEADER_ETHERNET:
-			call_dissector(eth_handle, next_tvb, pinfo, sflow_header_tree);
+			call_dissector(eth_withoutfcs_handle, next_tvb, pinfo, sflow_header_tree);
 			break;
 		case SFLOW_HEADER_TOKENRING:
 			call_dissector(tr_handle, next_tvb, pinfo, sflow_header_tree);
@@ -1050,7 +1050,7 @@ proto_reg_handoff_sflow(void)
 {
 	dissector_handle_t sflow_handle;
 
-	eth_handle = find_dissector("eth");
+	eth_withoutfcs_handle = find_dissector("eth_withoutfcs");
 	tr_handle = find_dissector("tr");
 	fddi_handle = find_dissector("fddi");
 	fr_handle = find_dissector("fr");
diff --git a/epan/dissectors/packet-wfleet-hdlc.c b/epan/dissectors/packet-wfleet-hdlc.c
index ecc8665c67..51f6712375 100644
--- a/epan/dissectors/packet-wfleet-hdlc.c
+++ b/epan/dissectors/packet-wfleet-hdlc.c
@@ -40,7 +40,7 @@ static int hf_wfleet_hdlc_cmd = -1;
 
 static gint ett_wfleet_hdlc = -1;
 
-dissector_handle_t eth_handle;
+dissector_handle_t eth_withoutfcs_handle;
 
 static const value_string wfleet_hdlc_cmd_vals[] = {
   { 0x03, "Un-numbered I frame"},
@@ -84,7 +84,7 @@ dissect_wfleet_hdlc(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
 
   next_tvb = tvb_new_subset(tvb, 2, -1, -1);
 
-  call_dissector(eth_handle, next_tvb, pinfo, tree);
+  call_dissector(eth_withoutfcs_handle, next_tvb, pinfo, tree);
 
 }
 
@@ -123,5 +123,5 @@ proto_reg_handoff_wfleet_hdlc(void)
    * Find the eth dissector and save a ref to it
    */
 
-  eth_handle = find_dissector("eth");
+  eth_withoutfcs_handle = find_dissector("eth_withoutfcs");
 }
diff --git a/plugins/docsis/packet-docsis.c b/plugins/docsis/packet-docsis.c
index 75ecacb1c5..cd7ed7943f 100644
--- a/plugins/docsis/packet-docsis.c
+++ b/plugins/docsis/packet-docsis.c
@@ -122,7 +122,7 @@ static int hf_docsis_ehdr_grants = -1;
 static int hf_docsis_reserved = -1;
 
 static dissector_handle_t docsis_handle;
-static dissector_handle_t eth_handle;
+static dissector_handle_t eth_withoutfcs_handle;
 static dissector_handle_t data_handle;
 static dissector_handle_t docsis_mgmt_handle;
 static dissector_table_t docsis_dissector_table;
@@ -513,7 +513,7 @@ dissect_docsis (tvbuff_t * tvb, packet_info * pinfo, proto_tree * tree)
 	  if (pdulen > 0)
 	    {
 	      next_tvb = tvb_new_subset (tvb, hdrlen, captured_length, pdulen);
-	      call_dissector (eth_handle, next_tvb, pinfo, tree);
+	      call_dissector (eth_withoutfcs_handle, next_tvb, pinfo, tree);
 	    }
 	  if (concatlen > 0)
 	    {
@@ -765,7 +765,7 @@ proto_reg_handoff_docsis (void)
   dissector_add ("wtap_encap", WTAP_ENCAP_DOCSIS, docsis_handle);
 
   docsis_mgmt_handle = find_dissector ("docsis_mgmt");
-  eth_handle = find_dissector ("eth");
+  eth_withoutfcs_handle = find_dissector ("eth_withoutfcs");
 }
 
 /* Start the functions we need for the plugin stuff */