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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-10 20:34:10 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-10 20:34:10 +0000 |
commit | e4ba6dbc3f1e76890b22773807ea37fe8fa2b1bc (patch) | |
tree | 68cb5ef9081156392f1dd62a00c6ccc1451b93df /epan/dissectors/packet-ieee8023.c | |
parent | Initial commit. (diff) | |
download | wireshark-e4ba6dbc3f1e76890b22773807ea37fe8fa2b1bc.tar.xz wireshark-e4ba6dbc3f1e76890b22773807ea37fe8fa2b1bc.zip |
Adding upstream version 4.2.2.upstream/4.2.2
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'epan/dissectors/packet-ieee8023.c')
-rw-r--r-- | epan/dissectors/packet-ieee8023.c | 138 |
1 files changed, 138 insertions, 0 deletions
diff --git a/epan/dissectors/packet-ieee8023.c b/epan/dissectors/packet-ieee8023.c new file mode 100644 index 0000000..626df26 --- /dev/null +++ b/epan/dissectors/packet-ieee8023.c @@ -0,0 +1,138 @@ +/* packet-ieee8023.c + * Routine for dissecting Ethernet packets with a length field (as opposed + * to a type field). + * + * The name "ieee8023" is historical, dating back to when IEEE Std 802.3 + * had only a length field and expected all packets to have an 802.2 + * header following the MAC header. Since IEEE 802.3y-1997, 802.3 + * supports either a type field or a length field, so it's no longer + * correct to refer to "802.3" vs. "D/I/X" or vs. "Ethernet II" frames. + * + * Wireshark - Network traffic analyzer + * By Gerald Combs <gerald@wireshark.org> + * Copyright 1998 Gerald Combs + * + * SPDX-License-Identifier: GPL-2.0-or-later + */ + +#include "config.h" + +#include <epan/packet.h> +#include <epan/exceptions.h> +#include <epan/expert.h> +#include <epan/show_exception.h> +#include "packet-ieee8023.h" +#include "packet-eth.h" + +void proto_reg_handoff_ieee802_3(void); + +static dissector_handle_t ipx_handle; +static dissector_handle_t llc_handle; +static dissector_handle_t ccsds_handle; + +void +dissect_802_3(volatile int length, gboolean is_802_2, tvbuff_t *tvb, + int offset_after_length, packet_info *pinfo, proto_tree *tree, + proto_tree *fh_tree, int length_id, int trailer_id, expert_field* ei_len, + int fcs_len) +{ + proto_item *length_it; + tvbuff_t *volatile next_tvb = NULL; + tvbuff_t *trailer_tvb = NULL; + const char *saved_proto; + gint captured_length, reported_length; + + length_it = proto_tree_add_uint(fh_tree, length_id, tvb, + offset_after_length - 2, 2, length); + + /* Get the length of the payload. + If the FCS length is positive, remove the FCS. + (If it's zero, there's no FCS; if it's negative, we don't know whether + there's an FCS, so we'll guess based on the length of the trailer.) */ + reported_length = tvb_reported_length_remaining(tvb, offset_after_length); + if (fcs_len > 0) { + if (reported_length >= fcs_len) + reported_length -= fcs_len; + } + + /* Make sure the length in the 802.3 header doesn't go past the end of + the payload. */ + if (length > reported_length) { + length = reported_length; + expert_add_info(pinfo, length_it, ei_len); + } + + /* Give the next dissector only 'length' number of bytes. */ + captured_length = tvb_captured_length_remaining(tvb, offset_after_length); + if (captured_length > length) + captured_length = length; + next_tvb = tvb_new_subset_length_caplen(tvb, offset_after_length, captured_length, length); + + /* Dissect the payload either as IPX or as an LLC frame. + Catch non-fatal exceptions, 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 { + if (is_802_2) + call_dissector(llc_handle, next_tvb, pinfo, tree); + else { + /* Check if first three bits of payload are 0x7. + If so, then payload is IPX. If not, then it's CCSDS. + Refer to packet-eth.c for setting of is_802_2 variable. */ + if (tvb_get_bits8(next_tvb, 0, 3) == 7) + call_dissector(ipx_handle, next_tvb, pinfo, tree); + else + call_dissector(ccsds_handle, next_tvb, pinfo, tree); + } + } + CATCH_NONFATAL_ERRORS { + /* Somebody threw an exception that means that there was a problem + dissecting the payload; that means that a dissector was found, + so we don't need to dissect the payload as data or update the + protocol or info columns. + + Just show the exception and then drive on to show the trailer, + after noting that a dissector was found and restoring the + protocol value that was in effect before we called the subdissector. */ + show_exception(next_tvb, pinfo, tree, EXCEPT_CODE, GET_MESSAGE); + } + ENDTRY; + + /* Restore the protocol value, so that any exception thrown by + tvb_new_subset_remaining() refers to the protocol for which + this is a trailer. */ + pinfo->current_proto = saved_proto; + + /* Construct a tvbuff for the trailer; if the trailer is past the + end of the captured data, this will throw a BoundsError, which + is what we want, as it'll report that the packet was cut short. */ + trailer_tvb = tvb_new_subset_remaining(tvb, offset_after_length + length); + + add_ethernet_trailer(pinfo, tree, fh_tree, trailer_id, tvb, trailer_tvb, fcs_len); +} + +void +proto_reg_handoff_ieee802_3(void) +{ + /* + * Get handles for the subdissectors. + */ + ipx_handle = find_dissector("ipx"); + llc_handle = find_dissector("llc"); + ccsds_handle = find_dissector("ccsds"); +} + +/* + * Editor modelines - https://www.wireshark.org/tools/modelines.html + * + * Local Variables: + * c-basic-offset: 2 + * tab-width: 8 + * indent-tabs-mode: nil + * End: + * + * ex: set shiftwidth=2 tabstop=8 expandtab: + * :indentSize=2:tabSize=8:noTabs=true: + */ |