diff options
Diffstat (limited to 'epan/dissectors/packet-isl.c')
| -rw-r--r-- | epan/dissectors/packet-isl.c | 166 |
1 files changed, 113 insertions, 53 deletions
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"); } |