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.)
Done by scanning the asan1 template files. If there are spelling
mistakes in the specifications, we should ignore. Note that for z3950, I had
already found and accidentally fixed the same errors in the generated
file (before I taught my script to ignore gnerated dissector files).
Similar to the "tcp.port" changes in I99604f95d426ad345f4b494598d94178b886eb67,
convert dissectors that use "udp.port".
More cleanup done on dissectors that use both TCP and UDP dissector
tables, so that less preference callbacks exist.
Change-Id: If07be9b9e850c244336a7069599cd554ce312dd3
Reviewed-on: https://code.wireshark.org/review/18120
Petri-Dish: Michael Mann <mmann78@netscape.net>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Michael Mann <mmann78@netscape.net>
This patch introduces new APIs to allow dissectors to have a preference for
a (TCP) port, but the underlying data is actually part of Decode As functionality.
For now the APIs are intentionally separate from the regular APIs that register a
dissector within a dissector table. It may be possible to eventually combine the
two so that all dissectors that register with a dissector table have an opportunity
to "automatically" have a preference to adjust the "table value" through the
preferences dialog.
The tcp.port dissector table was used as the guinea pig. This will eventually be
expanded to other dissector tables as well (most notably UDP ports). Some
dissectors that "shared" a TCP/UDP port preference were also converted. It also
removed the need for some preference callback functions (mostly when the callback
function was the proto_reg_handoff function) so there is cleanup around that.
Dissectors that has a port preference whose default was 0 were switched to using
the dissector_add_for_decode_as_with_preference API rather than dissector_add_uint_with_preference
Also added comments for TCP ports used that aren't IANA registered.
Change-Id: I99604f95d426ad345f4b494598d94178b886eb67
Reviewed-on: https://code.wireshark.org/review/17724
Reviewed-by: Michael Mann <mmann78@netscape.net>
Have all dissector tables have a "supports Decode As" flag, which
defaults to FALSE, and which is set to TRUE if a register_decode_as()
refers to it.
When adding a dissector to a dissector table with a given key, only add
it for Decode As if the dissector table supports it.
For non-FT_STRING dissector tables, always check for multiple entries
for the same protocol with different dissectors, and report an error if
we found them.
This means there's no need for the creator of a dissector table to
specify whether duplicates of that sort should be allowed - we always do
the check when registering something for "Decode As" (in a non-FT_STRING
dissector table), and just don't bother registering anything for "Decode
As" if the dissector table doesn't support "Decode As", so there's no
check done for those dissector tables.
Change-Id: I4a1fdea3bddc2af27a65cfbca23edc99b26c0eed
Reviewed-on: https://code.wireshark.org/review/17402
Petri-Dish: Guy Harris <guy@alum.mit.edu>
Reviewed-by: Guy Harris <guy@alum.mit.edu>
gcp_analyze_msg() is called with a NULL tvb, remove h248_tvb and use tvb
instead.
Change-Id: I2cb4c3577817bbaa4ec50b2a5ef0ef296059e683
Reviewed-on: https://code.wireshark.org/review/17082
Petri-Dish: Anders Broman <a.broman58@gmail.com>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Anders Broman <a.broman58@gmail.com>
If an ASN.1 dissector is calling register_dissector for itself in its proto_register_xxx
function and then calling find_dissector for itself in its proto_reg_handoff_xxx
function then just create a static handle for that dissector and use the return
value of register_dissector, so the find isn't necessary.
Change-Id: I911bdadc2fb4259601c141b955e741a2369cc447
Reviewed-on: https://code.wireshark.org/review/16233
Reviewed-by: Michael Mann <mmann78@netscape.net>
Petri-Dish: Michael Mann <mmann78@netscape.net>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Anders Broman <a.broman58@gmail.com>
Rather than have a bitmask for each desired field, have a dissector
provide a list of structures that represent data that goes into
the PDU.
Change-Id: I125190cbaee489ebffb7d9f5d8bc6f3be2d06353
Reviewed-on: https://code.wireshark.org/review/16122
Petri-Dish: Michael Mann <mmann78@netscape.net>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Pascal Quantin <pascal.quantin@gmail.com>
The formatting of the address type is determined by a preference in
packet-mtp3.c, so just make MTP3 register the address type.
Use address_type_get_by_name in other dissectors (and export_pdu)
to use the address type.
Change-Id: Ifb32d7de27aeaa23cee8e803e25ffb3c905547b5
Reviewed-on: https://code.wireshark.org/review/15856
Petri-Dish: Michael Mann <mmann78@netscape.net>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Anders Broman <a.broman58@gmail.com>
The Gateway Control Protocol (Context Tracking) is used by both H248
and MEGACO, so the functionality was refactored to epan, but should
really be kept in the dissector directory to minimize (and eventually
completely remove) the epan directory's dependence on it.
Change-Id: I387b46aecde97234086bfdb7d8c546854fa301cd
Reviewed-on: https://code.wireshark.org/review/15798
Petri-Dish: Michael Mann <mmann78@netscape.net>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Michael Mann <mmann78@netscape.net>
Started by grepping call_dissector_with_data, call_dissector_only and call_dissector and traced the handles passed into them to a find_dissector within the dissector. Then replaced find_dissector with find_dissector_add_dependency and added the protocol id from the dissector.
"data" dissector was not considered to be a dependency.
Change-Id: I15d0d77301306587ef8e7af5876e74231816890d
Reviewed-on: https://code.wireshark.org/review/14509
Petri-Dish: Michael Mann <mmann78@netscape.net>
Reviewed-by: Michael Mann <mmann78@netscape.net>
This will make it easier to determine protocol dependencies.
Some LLC OUI dissector tables didn't have an associated protocol, so they were left without one (-1 used)
Change-Id: I6339f16476510ef3f393d6fb5d8946419bfb4b7d
Reviewed-on: https://code.wireshark.org/review/14446
Reviewed-by: Michael Mann <mmann78@netscape.net>
Guy Harris