A given protocol's packet format may depend, for example, on which
lower-level protocol is transporting the protocol in question. For
example, protocols that run atop both byte-stream protocols such as TCP
and TLS, and packet-oriented protocols such as UDP or DTLS, might begin
the packet with a length when running atop a byte-stream protocol, to
indicate where this packet ends and the next packet begins in the byte
stream, but not do so when running atop a packet-oriented protocol.
Dissectors can handle this in various ways:
For example, the dissector could attempt to determine the protocol over
which the packet was transported.
Unfortunately, many of those mechanisms do so by fetching data from the
packet_info structure, and many items in that structure act as global
variables, so that, for example, if there are two two PDUs for protocol
A inside a TCP segment, and the first protocol for PDU A contains a PDU
for protocol B, and protocol B's dissector, or a dissector it calls,
modifies the information in the packet_info structure so that it no
longer indicates that the parent protocol is TCP, the second PDU for
protocol A might not be correctly dissected.
Another such mechanism is to query the previous element in the layers
structure of the packet_info structure, which is a list of protocol IDs.
Unfortunately, that is not a list of earlier protocols in the protocol
stack, it's a list of earlier protocols in the dissection, which means
that, in the above example, when the second PDU for protocol A is
dissected, the list is {...,TCP,A,B,...,A}, which means that the
previous element in the list is not TCP, so, again, the second PDU for
protocol A will not be correctly dissected.
An alternative is to have multiple dissectors for the same protocol,
with the part of the protocol that's independent of the protocol
transporting the PDU being dissected by common code. Protocol B might
have an "over a byte-stream transport" dissector and an "over a packet
transport" dissector, with the first dissector being registered for use
over TCP and TLS and the other dissector being registered for use over
packet protocols. This mechanism, unlike the other mechanisms, is not
dependent on information in the packet_info structure that might be
affected by dissectors other than the one for the protocol that
transports protocol B.
Furthermore, in a LINKTYPE_WIRESHARK_UPPER_PDU pcap or pcapng packet for
protocol B, there might not be any information to indicate the protocol
that transports protocol B, so there would have to be separate
dissectors for protocol B, with separate names, so that a tag giving the
protocol name would differ for B-over-byte-stream and B-over-packets.
So:
We rename EXP_PDU_TAG_PROTO_NAME and EXP_PDU_TAG_HEUR_PROTO_NAME to
EXP_PDU_TAG_DISSECTOR_NAME and EXP_PDU_TAG_HEUR_DISSECTOR_NAME, to
emphasize that they are *not* protocol names, they are dissector names
(which has always been the case - if there's a protocol with that name,
but no dissector with that name, Wireshark will not be able to handle
the packet, as it will try to look up a dissector given that name and
fail).
We fix that exported PDU dissector to refer to those tags as dissector
names, not protocol names.
We update documentation to refer to them as DISSECTOR_NAME tags, not
PROTO_NAME tags. (If there is any documentation for this outside the
Wireshark source, it should be updated as well.)
We add comments for calls to dissector_handle_get_dissector_name() where
the dissector name is shown to the user, to indicate that it might be
that the protocol name should be used.
We update the TLS and DTLS dissectors to show the encapsulated protocol
as the string returned by dissector_handle_get_long_name(); as the
default is "Application Data", it appeaers that a descriptive name,
rather than a short API name, should be used. (We continue to use the
dissector name in debugging messages, to indicate which dissector was
called.)
Without that, you could add a comment to a record in a file format the
reading code for which doesn't allocate blocks, but the comment doesn't
get saved, as there's no block in which to save the comment option.
This simplifies some code paths, as we're either using the record's
modified block or we're using the block as read from the file, there's
no third possibility.
If we attempt to read a record, and we get an error, and a block was
allocated for the record, unreference it, so the individual file readers
don't have to worry about it.
Have wsutil/exported_pdu_tlvs.h define the LINKTYPE_WIRESHARK_UPPER_PDU
TLV type and length values, as well as the port type values written to
files in EXP_PDU_TAG_PORT_TYPE TLVs.
Update the comment that describes the LINKTYPE_WIRESHARK_UPPER_PDU TLVs
to more completely and correctly reflect reality (it was moved from
epan/exported_pdu.h to wsutil/exported_pdu_tlvs.h).
Rename those port type values from OLD_PT_ to EXP_PDU_PT_; there is
nothing "old" about them - yes, they originally had the same numerical
values as the PT_ enum values in libwireshark, but that's no longer the
case, and the two are now defined independently. Rename routines that
map between libwireshark PT_ values and EXP_PDU_PT_ values to remove
"old" from the name while we're at it.
Don't include epan/exported_pdu.h if we only need the
LINKTYPE_WIRESHARK_UPPER_PDU definitions - just include
wsutil/exported_pdu_tlvs.h.
In extcap/udpdump.c, include wsutil/exported_pdu_tlvs.h rather than
defining the TLV types ourselves.
It only registers one file type/subtype, so rename it to
wtap_register_file_type_subtype().
That will also force plugins to be recompiled; that will produce compile
errors for some plugins that didn't change to match the new contents of
the file_type_subtype_info structure.
Also check to make sure that the registered file type/subtype supports
at least one type of block; a file type/subtype that doesn't return
*any* blocks and doesn't permit *any* block types to be written is not
very useful. That should also catch most if not all other plugins that
didn't change to match the new contents of the file_type_subtype_info
structure.
Don't make errors registering a file type/subtype fatal; just complain,
don't register the bogus file type/subtype, and drive on.
Instead of a "supports name resolution" Boolean and bitflags for types of
comments supported, provide a list of block types that the file
type/subtype supports, with each block type having a list of options
supported. Indicate whether "supported" means "one instance" or
"multiple instances".
"Supports" doesn't just mean "can be written", it also means "could be
read".
Rename WTAP_BLOCK_IF_DESCRIPTION to WTAP_BLOCK_IF_ID_AND_INFO, to
indicate that it provides, in addition to information about the
interface, an ID (implicitly, in pcapng files, by its ordinal number)
that is associated with every packet in the file. Emphasize that in
comments - just because your capture file format can list the interfaces
on which a capture was done, that doesn't mean it supports this; it
doesn't do so if the file doesn't indicate, for every packet, on which
of those interfaces it was captured (I'm looking at *you*, Microsoft
Network Monitor...).
Use APIs to query that information to do what the "does this file
type/subtype support name resolution information", "does this file
type/subtype support all of these comment types", and "does this file
type/subtype support - and require - interface IDs" APIs did.
Provide backwards compatibility for Lua.
This allows us to eliminate the WTAP_FILE_TYPE_SUBTYPE_ values for IBM's
iptrace; do so.
You either have to set it to 1 or 0 if you know whether it's shifted
time or set it to -1 if you don't.
Should address Coverity CID 1452227.
Change-Id: I7d435bb6b7dd8897b44bf5103578e3db1a30379e
Reviewed-on: https://code.wireshark.org/review/34175
Reviewed-by: Guy Harris <guy@alum.mit.edu>
Only CAN protocol is supported. Extra information available in J1939
entries is ignored since the J1939 wireshark dissector works with
raw CAN frames and makes no use of this extra information.
The log format may also encapsulate LIN messages which are not
supported by wireshark and thus are ignored.
The only limitation is that relative timestamp format is not
supported. If a file defines relative format of timestamps, packets
are extracted, but timestamps are omitted, since random access deems
impossible without reparsing the whole file up to the packet of
interest. In order to support relative timestamps we need to parse
the whole file at once on open and either dump into a temporary
PCAP file or keep messages in a private list and provide access
to them on read()/seek_read().
The change also creates a separate header for CAN frame structure
definitions which are used by several file readers (candump and
busmaster for now).
Bug: 15939
Change-Id: I87c5555e4e5e1b142b9984b24544b2591d494fbc
Reviewed-on: https://code.wireshark.org/review/34083
Petri-Dish: Anders Broman <a.broman58@gmail.com>
Tested-by: Petri Dish Buildbot
Reviewed-by: Anders Broman <a.broman58@gmail.com>
Guy Harris