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/* packet-applemidi.c
* Routines for dissection of Apple network-midi session establishment.
* Copyright 2006-2012, Tobias Erichsen <t.erichsen@gmx.de>
*
* Wireshark - Network traffic analyzer
* By Gerald Combs <gerald@wireshark.org>
* Copyright 1998 Gerald Combs
*
* Copied from packet-data.c, README.developer, and various other files.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*
*
* Apple network-midi session establishment is a lightweight protocol for
* providing a simple session establishment for MIDI-data sent in the form
* of RTP-MIDI (RFC 4695 / 6295). Peers recognize each other using the
* Apple Bonjour scheme with the service-name "_apple-midi._udp", establish
* a connection using AppleMIDI (no official name, just an abbreviation)
* and then send payload using RTP-MIDI. The implementation of this
* dissector is based on the Apple implementation summary from May 6th, 2005
* and the extension from August 13th, 2010.
*
* 2010-11-29
* - initial version of dissector
* 2012-02-24
* - implemented dynamic payloadtype support to automatically punt
* the decoding to the RTP-MIDI dissector via the RTP dissector
* - added new bitrate receive limit feature
*
* Here are some links:
*
* http://www.cs.berkeley.edu/~lazzaro/rtpmidi/
* http://www.faqs.org/rfcs/rfc4695.html
* http://www.faqs.org/rfcs/rfc6295.html
*/
#include "config.h"
#include <epan/packet.h>
#include <epan/conversation.h>
#include "packet-rtp.h"
void proto_register_applemidi(void);
void proto_reg_handoff_applemidi(void);
/* Definitions for protocol name during dissector-register */
#define APPLEMIDI_DISSECTOR_NAME "Apple Network-MIDI Session Protocol"
#define APPLEMIDI_DISSECTOR_SHORTNAME "AppleMIDI"
#define APPLEMIDI_DISSECTOR_ABBREVIATION "applemidi"
/* Signature "Magic Value" for Apple network MIDI session establishment */
#define APPLEMIDI_PROTOCOL_SIGNATURE 0xffff
/* Apple network MIDI valid commands */
#define APPLEMIDI_COMMAND_INVITATION 0x494e /* "IN" */
#define APPLEMIDI_COMMAND_INVITATION_REJECTED 0x4e4f /* "NO" */
#define APLLEMIDI_COMMAND_INVITATION_ACCEPTED 0x4f4b /* "OK" */
#define APPLEMIDI_COMMAND_ENDSESSION 0x4259 /* "BY" */
#define APPLEMIDI_COMMAND_SYNCHRONIZATION 0x434b /* "CK" */
#define APPLEMIDI_COMMAND_RECEIVER_FEEDBACK 0x5253 /* "RS" */
#define APPLEMIDI_COMMAND_BITRATE_RECEIVE_LIMIT 0x524c /* "RL" */
static int hf_applemidi_signature = -1;
static int hf_applemidi_command = -1;
static int hf_applemidi_protocol_version = -1;
static int hf_applemidi_token = -1;
static int hf_applemidi_ssrc = -1;
static int hf_applemidi_name = -1;
static int hf_applemidi_count = -1;
static int hf_applemidi_padding = -1;
static int hf_applemidi_timestamp1 = -1;
static int hf_applemidi_timestamp2 = -1;
static int hf_applemidi_timestamp3 = -1;
static int hf_applemidi_sequence_num = -1;
static int hf_applemidi_rtp_sequence_num = -1;
static int hf_applemidi_rtp_bitrate_limit = -1;
static int hf_applemidi_unknown_data = -1;
static gint ett_applemidi = -1;
static gint ett_applemidi_seq_num = -1;
static const value_string applemidi_commands[] = {
{ APPLEMIDI_COMMAND_INVITATION, "Invitation" },
{ APPLEMIDI_COMMAND_INVITATION_REJECTED, "Invitation Rejected" },
{ APLLEMIDI_COMMAND_INVITATION_ACCEPTED, "Invitation Accepted" },
{ APPLEMIDI_COMMAND_ENDSESSION, "End Session" },
{ APPLEMIDI_COMMAND_SYNCHRONIZATION, "Synchronization" },
{ APPLEMIDI_COMMAND_RECEIVER_FEEDBACK, "Receiver Feedback" },
{ APPLEMIDI_COMMAND_BITRATE_RECEIVE_LIMIT, "Bitrate Receive Limit" },
{ 0, NULL },
};
static int proto_applemidi = -1;
static dissector_handle_t applemidi_handle;
static dissector_handle_t rtp_handle;
static const char applemidi_unknown_command[] = "unknown command: 0x%04x";
static void
dissect_applemidi_common( tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, guint16 command ) {
proto_item *ti;
guint16 seq_num;
guint8 count;
guint8 *name;
gint offset = 0;
gint len;
gint string_size;
proto_tree *applemidi_tree;
proto_tree *applemidi_tree_seq_num;
col_set_str( pinfo->cinfo, COL_PROTOCOL, APPLEMIDI_DISSECTOR_SHORTNAME );
col_add_fstr( pinfo->cinfo, COL_INFO, "%s", val_to_str( command, applemidi_commands, applemidi_unknown_command ) );
ti = proto_tree_add_item( tree, proto_applemidi, tvb, 0, -1, ENC_NA );
applemidi_tree = proto_item_add_subtree( ti, ett_applemidi );
proto_tree_add_item( applemidi_tree, hf_applemidi_signature, tvb, offset, 2, ENC_BIG_ENDIAN );
offset += 2;
proto_tree_add_item( applemidi_tree, hf_applemidi_command, tvb, offset, 2, ENC_BIG_ENDIAN );
offset += 2;
/* the format of packets for "IN", "NO", "OK" and "BY" is identical and contains
* the protocol version, a random number generated by the initiator of the session,
* the SSRC that is used by the respective sides RTP-entity and optionally the
* name of the participant */
if ( ( APPLEMIDI_COMMAND_INVITATION == command ) ||
( APPLEMIDI_COMMAND_INVITATION_REJECTED == command ) ||
( APLLEMIDI_COMMAND_INVITATION_ACCEPTED == command ) ||
( APPLEMIDI_COMMAND_ENDSESSION == command ) ) {
proto_tree_add_item( applemidi_tree, hf_applemidi_protocol_version, tvb, offset, 4, ENC_BIG_ENDIAN );
offset += 4;
proto_tree_add_item( applemidi_tree, hf_applemidi_token, tvb, offset, 4, ENC_BIG_ENDIAN );
offset += 4;
proto_tree_add_item( applemidi_tree, hf_applemidi_ssrc, tvb, offset, 4, ENC_BIG_ENDIAN );
offset += 4;
len = tvb_reported_length(tvb) - offset;
/* Name is optional */
if ( len > 0 ) {
name = tvb_get_string_enc( wmem_packet_scope(), tvb, offset, len, ENC_UTF_8|ENC_NA );
string_size = (gint)( strlen( name ) + 1 );
proto_tree_add_item( applemidi_tree, hf_applemidi_name, tvb, offset, string_size, ENC_UTF_8|ENC_NA );
col_append_fstr( pinfo->cinfo, COL_INFO, ": peer = \"%s\"", name );
offset += string_size;
}
/* the synchronization packet contains three 64bit timestamps, and a value to define how
* many of the timestamps transmitted are valid */
} else if ( APPLEMIDI_COMMAND_SYNCHRONIZATION == command ) {
proto_tree_add_item( applemidi_tree, hf_applemidi_ssrc, tvb, offset, 4, ENC_BIG_ENDIAN );
offset += 4;
count = tvb_get_guint8( tvb, offset );
proto_tree_add_item( applemidi_tree, hf_applemidi_count, tvb, offset, 1, ENC_BIG_ENDIAN );
col_append_fstr( pinfo->cinfo, COL_INFO, ": count = %u", count );
offset += 1;
proto_tree_add_item( applemidi_tree, hf_applemidi_padding, tvb, offset, 3, ENC_BIG_ENDIAN );
offset += 3;
proto_tree_add_item( applemidi_tree, hf_applemidi_timestamp1, tvb, offset, 8, ENC_BIG_ENDIAN );
offset += 8;
proto_tree_add_item( applemidi_tree, hf_applemidi_timestamp2, tvb, offset, 8, ENC_BIG_ENDIAN );
offset += 8;
proto_tree_add_item( applemidi_tree, hf_applemidi_timestamp3, tvb, offset, 8, ENC_BIG_ENDIAN );
offset += 8;
/* With the receiver feedback packet, the recipient can tell the sender up to what sequence
* number in the RTP-stream the packets have been received; this can be used to shorten the
* recovery-journal-section in the RTP-session */
} else if ( APPLEMIDI_COMMAND_RECEIVER_FEEDBACK == command ) {
proto_tree_add_item( applemidi_tree, hf_applemidi_ssrc, tvb, offset, 4, ENC_BIG_ENDIAN );
offset += 4;
ti = proto_tree_add_item( applemidi_tree, hf_applemidi_sequence_num, tvb, offset, 4, ENC_BIG_ENDIAN );
/* Apple includes a 32bit sequence-number, but the RTP-packet only specifies 16bit.
* this subtree and subitem are added to be able to associate the sequence-number
* here easier with the one specified in the corresponding RTP-packet */
applemidi_tree_seq_num = proto_item_add_subtree( ti, ett_applemidi_seq_num );
seq_num = tvb_get_ntohs( tvb, offset );
proto_tree_add_uint( applemidi_tree_seq_num, hf_applemidi_rtp_sequence_num, tvb, offset, 2, seq_num );
offset += 4;
col_append_fstr( pinfo->cinfo, COL_INFO, ": seq = %u", seq_num );
/* With the bitrate receive limit packet, the recipient can tell the sender to limit
the transmission to a certain bitrate. This is important if the peer is a gateway
to a hardware-device that only supports a certain speed. Like the MIDI 1.0 DIN-cable
MIDI-implementation which is limited to 31250. */
} else if ( APPLEMIDI_COMMAND_BITRATE_RECEIVE_LIMIT == command ) {
proto_tree_add_item( applemidi_tree, hf_applemidi_ssrc, tvb, offset, 4, ENC_BIG_ENDIAN );
offset += 4;
proto_tree_add_item( applemidi_tree, hf_applemidi_rtp_bitrate_limit,
tvb, offset, 4, ENC_BIG_ENDIAN );
offset += 4;
}
/* If there is any remaining data (possibly because an unknown command was encountered),
* we just dump it here */
len = tvb_reported_length_remaining( tvb, offset );
if ( len > 0 ) {
proto_tree_add_item( applemidi_tree, hf_applemidi_unknown_data, tvb, offset, len, ENC_NA );
}
}
static gboolean
test_applemidi(tvbuff_t *tvb, guint16 *command_p, gboolean conversation_established ) {
*command_p = 0xffff;
/* An applemidi session protocol UDP-packet must start with the "magic value" of 0xffff ... */
if ( APPLEMIDI_PROTOCOL_SIGNATURE != tvb_get_ntohs( tvb, 0 ) )
return FALSE;
*command_p = tvb_get_ntohs( tvb, 2 );
/* If the conversation is establised (one prior packet with a valid known command)
* we won't check the commands anymore - this way we still show new commands
* Apple might introduce as "unknown" instead of punting to RTP-dissector */
if ( conversation_established ) {
return TRUE;
}
/* ... followed by packet-command: "IN", "NO", "OK", "BY", "CK" and "RS" and "RL" */
if ( ( APPLEMIDI_COMMAND_INVITATION == *command_p ) ||
( APPLEMIDI_COMMAND_INVITATION_REJECTED == *command_p ) ||
( APLLEMIDI_COMMAND_INVITATION_ACCEPTED == *command_p ) ||
( APPLEMIDI_COMMAND_ENDSESSION == *command_p ) ||
( APPLEMIDI_COMMAND_SYNCHRONIZATION == *command_p ) ||
( APPLEMIDI_COMMAND_RECEIVER_FEEDBACK == *command_p ) ||
( APPLEMIDI_COMMAND_BITRATE_RECEIVE_LIMIT == *command_p ) )
return TRUE;
return FALSE;
}
/* dissect_applemidi() is called when a packet is seen from a previously identified applemidi conversation */
/* If the packet isn't a valid applemidi packet, assume it's an RTP-MIDI packet. */
static int
dissect_applemidi( tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_ ) {
guint16 command;
if ( test_applemidi( tvb, &command, TRUE ) )
dissect_applemidi_common( tvb, pinfo, tree, command );
else
call_dissector( rtp_handle, tvb, pinfo, tree );
return tvb_captured_length(tvb);
}
static gboolean
dissect_applemidi_heur( tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_ ) {
guint16 command;
conversation_t *p_conv;
rtp_dyn_payload_t *rtp_dyn_payload;
if ( tvb_captured_length( tvb ) < 4)
return FALSE; /* not enough bytes to check */
if ( !test_applemidi( tvb, &command, FALSE ) ) {
return FALSE;
}
/* set dynamic payload-type 97 which is used by Apple for their RTP-MIDI implementation for this
address/port-tuple to cause RTP-dissector to call the RTP-MIDI-dissector for payload-decoding */
rtp_dyn_payload = rtp_dyn_payload_new();
rtp_dyn_payload_insert(rtp_dyn_payload, 97, "rtp-midi", 10000);
rtp_add_address( pinfo, &pinfo->src, pinfo->srcport, 0, APPLEMIDI_DISSECTOR_SHORTNAME,
pinfo->num, FALSE, rtp_dyn_payload);
/* call dissect_applemidi() from now on for UDP packets on this "connection"
it is important to do this step after calling rtp_add_address, otherwise
all further packets will go directly to the RTP-dissector! */
p_conv = find_or_create_conversation(pinfo);
conversation_set_dissector( p_conv, applemidi_handle );
/* punt to actual decoding */
dissect_applemidi_common( tvb, pinfo, tree, command );
return TRUE;
}
void
proto_register_applemidi( void )
{
static hf_register_info hf[] = {
{
&hf_applemidi_signature,
{
"Signature",
"applemidi.signature",
FT_UINT16,
BASE_HEX,
NULL,
0x0,
NULL, HFILL
}
},
{
&hf_applemidi_command,
{
"Command",
"applemidi.command",
FT_UINT16,
BASE_HEX,
VALS( applemidi_commands ),
0x0,
NULL, HFILL
}
},
{
&hf_applemidi_protocol_version,
{
"Protocol Version",
"applemidi.protocol_version",
FT_UINT32,
BASE_DEC,
NULL,
0x0,
NULL, HFILL
}
},
{
&hf_applemidi_token,
{
"Initiator Token",
"applemidi.initiator_token",
FT_UINT32,
BASE_HEX,
NULL,
0x0,
NULL, HFILL
}
},
{
&hf_applemidi_ssrc,
{
"Sender SSRC",
"applemidi.sender_ssrc",
FT_UINT32,
BASE_HEX,
NULL,
0x0,
NULL, HFILL
}
},
{
&hf_applemidi_name,
{
"Name",
"applemidi.name",
FT_STRING,
BASE_NONE,
NULL,
0x0,
NULL, HFILL
}
},
{
&hf_applemidi_count,
{
"Count",
"applemidi.count",
FT_UINT8,
BASE_DEC,
NULL,
0x0,
NULL, HFILL
}
},
{
&hf_applemidi_padding,
{
"Padding",
"applemidi.padding",
FT_UINT24,
BASE_HEX,
NULL,
0x0,
NULL, HFILL
}
},
{
&hf_applemidi_timestamp1,
{
"Timestamp 1",
"applemidi.timestamp1",
FT_UINT64,
BASE_HEX,
NULL,
0x0,
NULL, HFILL
}
},
{
&hf_applemidi_timestamp2,
{
"Timestamp 2",
"applemidi.timestamp2",
FT_UINT64,
BASE_HEX,
NULL,
0x0,
NULL, HFILL
}
},
{
&hf_applemidi_timestamp3,
{
"Timestamp 3",
"applemidi.timestamp3",
FT_UINT64,
BASE_HEX,
NULL,
0x0,
NULL, HFILL
}
},
{
&hf_applemidi_sequence_num,
{
"Sequence Number",
"applemidi.sequence_number",
FT_UINT32,
BASE_HEX,
NULL,
0x0,
NULL, HFILL
}
},
{
&hf_applemidi_rtp_sequence_num,
{
"RTP Sequence Number",
"applemidi.rtp_sequence_number",
FT_UINT16,
BASE_DEC,
NULL,
0x0,
NULL, HFILL
}
},
{
&hf_applemidi_rtp_bitrate_limit,
{
"Bitrate limit",
"applemidi.bitrate_limit",
FT_UINT32,
BASE_DEC,
NULL,
0x0,
NULL, HFILL
}
},
{
&hf_applemidi_unknown_data,
{
"Unknown Data",
"applemidi.unknown_data",
FT_BYTES,
BASE_NONE,
NULL,
0x00,
NULL, HFILL
}
},
};
static gint *ett[] = {
&ett_applemidi,
&ett_applemidi_seq_num
};
proto_applemidi = proto_register_protocol( APPLEMIDI_DISSECTOR_NAME,
APPLEMIDI_DISSECTOR_SHORTNAME,
APPLEMIDI_DISSECTOR_ABBREVIATION );
proto_register_field_array( proto_applemidi, hf, array_length( hf ) );
proto_register_subtree_array( ett, array_length( ett ) );
}
void
proto_reg_handoff_applemidi( void ) {
applemidi_handle = create_dissector_handle( dissect_applemidi, proto_applemidi );
/* If we cannot decode the data it will be RTP-MIDI since the Apple session protocol uses
* two ports: the control-port and the MIDI-port. On both ports an invitation is being sent.
* The second port is then used for the RTP-MIDI-data. So if we can't find valid AppleMidi
* packets, it will be most likely RTP-MIDI...
*/
rtp_handle = find_dissector_add_dependency( "rtp", proto_applemidi );
heur_dissector_add( "udp", dissect_applemidi_heur, "Apple MIDI over UDP", "applemidi_udp", proto_applemidi, HEURISTIC_ENABLE );
}
/*
* Editor modelines - http://www.wireshark.org/tools/modelines.html
*
* Local variables:
* c-basic-offset: 8
* tab-width: 8
* indent-tabs-mode: t
* End:
*
* vi: set shiftwidth=8 tabstop=8 noexpandtab:
* :indentSize=8:tabSize=8:noTabs=false:
*/