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Mkae the handling of non-full-frame time stamps match RFC 5456.

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At least as I read RFC 5456:

	1) non-full-frame time stamps should have high-order bits from
	   the time stamp of the last full frame ORed into it;

	2) "mini voice packets" have a 16-bit time stamp and "mini video
	   packets" have a 15-bit time stamp;

so adjust the non-full-frame time stamps in that fashion rather than by
adding 32768 until the value looks OK - and don't adjust full-frame time
stamps at all.

Change-Id: I20873a633a99415ac73a7e6baf087e5ec62a4905
Reviewed-on: https://code.wireshark.org/review/28555
Reviewed-by: Guy Harris <guy@alum.mit.edu>
This commit is contained in:
Guy Harris 2018-07-01 10:32:39 -07:00
parent 17a39db773
commit 5c6f2e8882
1 changed files with 91 additions and 34 deletions
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125
epan/dissectors/packet-iax2.c
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@ -177,7 +177,6 @@ static expert_field ei_iax_too_many_transfers = EI_INIT;
static expert_field ei_iax_circuit_id_conflict = EI_INIT;
static expert_field ei_iax_peer_address_unsupported = EI_INIT;
static expert_field ei_iax_invalid_len = EI_INIT;
static expert_field ei_iax_invalid_ts = EI_INIT;
static dissector_handle_t iax2_handle;
@ -726,6 +725,9 @@ typedef struct iax_call_data {
/* the absolute start time of the call */
nstime_t start_time;
/* time stamp from last full frame, in the first pass */
guint32 last_full_frame_ts;
iax_call_dirdata dirdata[2];
} iax_call_data;
@ -1014,6 +1016,7 @@ static iax_call_data *iax_new_call( packet_info *pinfo,
call -> n_reverse_circuit_ids = 0;
call -> subdissector = NULL;
call -> start_time = pinfo->abs_ts;
call -> last_full_frame_ts = 0;
nstime_delta(&call -> start_time, &call -> start_time, &millisecond);
init_dir_data(&call->dirdata[0]);
init_dir_data(&call->dirdata[1]);
@ -1551,11 +1554,10 @@ static guint32 dissect_iax2_command(tvbuff_t *tvb, guint32 offset,
return offset;
}
#define MAX_SECS_DIFF 60 /* Arbitrary. Needs to be within loop bounds below. */
static void iax2_add_ts_fields(packet_info *pinfo, proto_tree *iax2_tree, tvbuff_t *tvb, iax_packet_data *iax_packet, guint16 shortts)
static void iax2_add_ts_fields(packet_info *pinfo, proto_tree *iax2_tree, tvbuff_t *tvb, iax_packet_data *iax_packet, packet_type type, guint32 relts)
{
guint longts =shortts;
nstime_t ts;
guint32 full_relts = relts;
nstime_t lateness;
proto_item *item;
if (iax_packet->call_data == NULL) {
@ -1564,38 +1566,94 @@ static void iax2_add_ts_fields(packet_info *pinfo, proto_tree *iax2_tree, tvbuff
}
if (iax_packet->abstime.secs == -1) {
time_t start_secs = iax_packet->call_data->start_time.secs;
time_t abs_secs = start_secs + longts/1000;
nstime_t rel;
if (pinfo->abs_ts.secs - abs_secs > MAX_SECS_DIFF) {
proto_tree_add_expert(iax2_tree, pinfo, &ei_iax_invalid_ts, tvb, 0, 0);
} else {
/* deal with short timestamps by assuming that packets are never more than
* 16 seconds late */
/* XXX Use arithmetic here instead of a loop? */
while(abs_secs < pinfo->abs_ts.secs - 16) {
longts += 32768;
abs_secs = start_secs + longts/1000;
}
switch (type) {
case IAX2_MINI_VOICE_PACKET:
/* RFC 5456 says
*
* Abbreviated 'Mini Frames' are normally used for audio and
* video; however, each time the time-stamp is a multiple of
* 32,768 (0x8000 hex), a standard or 'Full Frame' MUST be sent.
*
* and, for what it later calls "Mini Frames", by which it means
* what we're calling "mini voice packets", it says:
*
* Mini frames carry a 16-bit time-stamp, which is the lower 16 bits
* of the transmitting peer's full 32-bit time-stamp for the call.
* The time-stamp allows synchronization of incoming frames so that
* they MAY be processed in chronological order instead of the
* (possibly different) order in which they are received. The 16-bit
* time-stamp wraps after 65.536 seconds, at which point a full frame
* SHOULD be sent to notify the remote peer that its time-stamp has
* been reset. A call MUST continue to send mini frames starting
* with time-stamp 0 even if acknowledgment of the resynchronization
* is not received.
*
* *If* we see all the full frames, that means we *should* be able
* to convert the 16-bit time stamp to a full 32-bit time stamp by
* ORing the upper 16 bits of the last full frame time stamp we saw
* in above the 16-bit time stamp.
*
* XXX - what, if anything, should we do about full frames we've
* missed? */
full_relts = (iax_packet->call_data->last_full_frame_ts & 0xFFFF0000) | relts;
break;
case IAX2_FULL_PACKET:
case IAX2_TRUNK_PACKET:
/* Timestamps have the full 32 bits of the timestamp.
* Save it, to add to the mini-packet time stamps.
*
* XXX - that's a maximum of 4294967296 milliseconds
* or about 4294967 seconds or about 49 days.
* Do we need to worry about that overflowing? */
full_relts = relts;
iax_packet->call_data->last_full_frame_ts = full_relts;
break;
case IAX2_MINI_VIDEO_PACKET:
/* See the comment above in the IAX2_MINI_VOICE_PACKET case.
* Note also that RFC 5456 says, in section 8.1.3.1 "Meta Video
* Frames", which covers what we're calling "mini video packets":
*
* Meta video frames carry a 16-bit time-stamp, which is the lower 16
* bits of the transmitting peer's full 32-bit time-stamp for the
* call. When this time-stamp wraps, a Full Frame SHOULD be sent to
* notify the remote peer that the time-stamp has been reset to 0.
*
* *but* it also shows the uppermost bit of that time stamp as "?",
* with a 15-bit time stamp, in the ASCII-art packet diagram after
* it. dissect_minivideopacket() says "bit 15 of the ts is used to
* represent the rtp 'marker' bit"; presumably that's what's going
* on, but the RFC doesn't say that.
*
* So we assume that the time stamp is only 15 bits, and that the
* upper *17* bits of the last full frame's time stamp need to be
* ORed in above the 15 bits of time stamp.
*
* XXX - do we need to worry about overflows or missed packets
* with full timestamps? */
full_relts = (iax_packet->call_data->last_full_frame_ts & 0xFFFF8000) | relts;
break;
}
iax_packet->abstime.secs=abs_secs;
iax_packet->abstime.nsecs=iax_packet->call_data->start_time.nsecs + (longts % 1000) * 1000000;
if (iax_packet->abstime.nsecs >= 1000000000) {
iax_packet->abstime.nsecs -= 1000000000;
iax_packet->abstime.secs ++;
}
/* Convert the full relative time stamp to an nstime_t */
rel.secs = full_relts / 1000;
rel.nsecs = (full_relts % 1000) * 1000000;
/* Add it to the start time to get the absolute time. */
nstime_sum(&iax_packet->abstime, &iax_packet->call_data->start_time, &rel);
}
iax2_info->timestamp = longts;
iax2_info->timestamp = relts; /* raw time stamp; nobody uses it */
if (iax2_tree) {
item = proto_tree_add_time(iax2_tree, hf_iax2_absts, tvb, 0, 0, &iax_packet->abstime);
PROTO_ITEM_SET_GENERATED(item);
ts = pinfo->abs_ts;
nstime_delta(&ts, &ts, &iax_packet->abstime);
nstime_delta(&lateness, &pinfo->abs_ts, &iax_packet->abstime);
item = proto_tree_add_time(iax2_tree, hf_iax2_lateness, tvb, 0, 0, &ts);
item = proto_tree_add_time(iax2_tree, hf_iax2_lateness, tvb, 0, 0, &lateness);
PROTO_ITEM_SET_GENERATED(item);
}
}
@ -1669,7 +1727,7 @@ dissect_fullpacket(tvbuff_t *tvb, guint32 offset,
}
proto_tree_add_uint(iax2_tree, hf_iax2_ts, tvb, offset+2, 4, ts);
iax2_add_ts_fields(pinfo, iax2_tree, tvb, iax_packet, (guint16)ts);
iax2_add_ts_fields(pinfo, iax2_tree, tvb, iax_packet, IAX2_FULL_PACKET, ts);
proto_tree_add_item(iax2_tree, hf_iax2_oseqno, tvb, offset+6, 1,
ENC_BIG_ENDIAN);
@ -1682,7 +1740,7 @@ dissect_fullpacket(tvbuff_t *tvb, guint32 offset,
/* add the type-specific subtree */
packet_type_tree = proto_item_add_subtree(packet_type_base, ett_iax2_type);
} else {
iax2_add_ts_fields(pinfo, iax2_tree, tvb, iax_packet, (guint16)ts);
iax2_add_ts_fields(pinfo, iax2_tree, tvb, iax_packet, IAX2_FULL_PACKET, ts);
}
@ -1886,10 +1944,10 @@ static guint32 dissect_minivideopacket(tvbuff_t *tvb, guint32 offset,
}
proto_tree_add_item(iax2_tree, hf_iax2_minividts, tvb, offset, 2, ENC_BIG_ENDIAN);
iax2_add_ts_fields(pinfo, iax2_tree, tvb, iax_packet, (guint16)ts);
iax2_add_ts_fields(pinfo, iax2_tree, tvb, iax_packet, IAX2_MINI_VIDEO_PACKET, ts);
proto_tree_add_item(iax2_tree, hf_iax2_minividmarker, tvb, offset, 2, ENC_BIG_ENDIAN);
} else {
iax2_add_ts_fields(pinfo, iax2_tree, tvb, iax_packet, (guint16)ts);
iax2_add_ts_fields(pinfo, iax2_tree, tvb, iax_packet, IAX2_MINI_VIDEO_PACKET, ts);
}
offset += 2;
@ -1928,9 +1986,9 @@ static guint32 dissect_minipacket(tvbuff_t *tvb, guint32 offset, guint16 scallno
}
proto_tree_add_uint(iax2_tree, hf_iax2_minits, tvb, offset, 2, ts);
iax2_add_ts_fields(pinfo, iax2_tree, tvb, iax_packet, (guint16)ts);
iax2_add_ts_fields(pinfo, iax2_tree, tvb, iax_packet, IAX2_MINI_VOICE_PACKET, ts);
} else {
iax2_add_ts_fields(pinfo, iax2_tree, tvb, iax_packet, (guint16)ts);
iax2_add_ts_fields(pinfo, iax2_tree, tvb, iax_packet, IAX2_MINI_VOICE_PACKET, ts);
}
@ -3173,7 +3231,6 @@ proto_register_iax2(void)
{ &ei_iax_circuit_id_conflict, { "iax2.circuit_id_conflict", PI_PROTOCOL, PI_WARN, "Circuit ID conflict", EXPFILL }},
{ &ei_iax_peer_address_unsupported, { "iax2.peer_address_unsupported", PI_PROTOCOL, PI_WARN, "Peer address unsupported", EXPFILL }},
{ &ei_iax_invalid_len, { "iax2.invalid_len", PI_PROTOCOL, PI_WARN, "Invalid length", EXPFILL }},
{ &ei_iax_invalid_ts, { "iax2.invalid_ts", PI_PROTOCOL, PI_WARN, "Invalid timestamp", EXPFILL }}
};
expert_module_t* expert_iax;