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-rw-r--r--wiretap/mp2t.c434
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diff --git a/wiretap/mp2t.c b/wiretap/mp2t.c
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+/* mp2t.c
+ *
+ * ISO/IEC 13818-1 MPEG2-TS file format decoder for the Wiretap library.
+ * Written by Weston Schmidt <weston_schmidt@alumni.purdue.edu>
+ * Copyright 2012 Weston Schmidt
+ *
+ * Wiretap Library
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "config.h"
+
+#include <sys/types.h>
+
+#ifdef HAVE_UNISTD_H
+#include <unistd.h>
+#endif
+
+#include "mp2t.h"
+
+#include "wtap-int.h"
+#include <wsutil/buffer.h>
+#include "file_wrappers.h"
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+
+#define MP2T_SYNC_BYTE 0x47
+#define MP2T_SIZE 188
+#define MP2T_QAM64_BITRATE 26970350 /* bits per second */
+#define MP2T_PCR_CLOCK 27000000 /* cycles per second - 27MHz */
+
+/* we try to detect trailing data up to 40 bytes after each packet */
+#define TRAILER_LEN_MAX 40
+
+/* number of consecutive packets we must read to decide that a file
+ is actually an mpeg2 ts */
+#define SYNC_STEPS 10
+
+
+typedef struct {
+ guint32 start_offset;
+ guint64 bitrate;
+ /* length of trailing data (e.g. FEC) that's appended after each packet */
+ guint8 trailer_len;
+} mp2t_filetype_t;
+
+static int mp2t_file_type_subtype = -1;
+
+void register_mp2t(void);
+
+static gboolean
+mp2t_read_packet(mp2t_filetype_t *mp2t, FILE_T fh, gint64 offset,
+ wtap_rec *rec, Buffer *buf, int *err,
+ gchar **err_info)
+{
+ guint64 tmp;
+
+ /*
+ * MP2T_SIZE will always be less than WTAP_MAX_PACKET_SIZE_STANDARD, so
+ * we don't have to worry about the packet being too big.
+ */
+ ws_buffer_assure_space(buf, MP2T_SIZE);
+ if (!wtap_read_bytes_or_eof(fh, ws_buffer_start_ptr(buf), MP2T_SIZE, err, err_info))
+ return FALSE;
+
+ rec->rec_type = REC_TYPE_PACKET;
+ rec->block = wtap_block_create(WTAP_BLOCK_PACKET);
+
+ /* XXX - relative, not absolute, time stamps */
+ rec->presence_flags = WTAP_HAS_TS;
+
+ /*
+ * Every packet in an MPEG2-TS stream is has a fixed size of
+ * MP2T_SIZE plus the number of trailer bytes.
+ *
+ * We assume that the bits in the transport stream are supplied at
+ * a constant rate; is that guaranteed by all media that use
+ * MPEG2-TS? If so, the time offset, from the beginning of the
+ * stream, of a given packet is the packet offset, in bits, divided
+ * by the bitrate.
+ *
+ * It would be really cool to be able to configure the bitrate, in
+ * case our attempt to guess it from the PCRs of one of the programs
+ * doesn't get the right answer.
+ */
+ tmp = ((guint64)(offset - mp2t->start_offset) * 8); /* offset, in bits */
+ rec->ts.secs = (time_t)(tmp / mp2t->bitrate);
+ rec->ts.nsecs = (int)((tmp % mp2t->bitrate) * 1000000000 / mp2t->bitrate);
+
+ rec->rec_header.packet_header.caplen = MP2T_SIZE;
+ rec->rec_header.packet_header.len = MP2T_SIZE;
+
+ return TRUE;
+}
+
+static gboolean
+mp2t_read(wtap *wth, wtap_rec *rec, Buffer *buf, int *err,
+ gchar **err_info, gint64 *data_offset)
+{
+ mp2t_filetype_t *mp2t;
+
+ mp2t = (mp2t_filetype_t*) wth->priv;
+
+ *data_offset = file_tell(wth->fh);
+
+ if (!mp2t_read_packet(mp2t, wth->fh, *data_offset, rec, buf, err,
+ err_info)) {
+ return FALSE;
+ }
+
+ /* if there's a trailer, skip it and go to the start of the next packet */
+ if (mp2t->trailer_len!=0) {
+ if (!wtap_read_bytes(wth->fh, NULL, mp2t->trailer_len, err, err_info)) {
+ return FALSE;
+ }
+ }
+
+ return TRUE;
+}
+
+static gboolean
+mp2t_seek_read(wtap *wth, gint64 seek_off, wtap_rec *rec,
+ Buffer *buf, int *err, gchar **err_info)
+{
+ mp2t_filetype_t *mp2t;
+
+ if (-1 == file_seek(wth->random_fh, seek_off, SEEK_SET, err)) {
+ return FALSE;
+ }
+
+ mp2t = (mp2t_filetype_t*) wth->priv;
+
+ if (!mp2t_read_packet(mp2t, wth->random_fh, seek_off, rec, buf,
+ err, err_info)) {
+ if (*err == 0)
+ *err = WTAP_ERR_SHORT_READ;
+ return FALSE;
+ }
+ return TRUE;
+}
+
+static guint64
+mp2t_read_pcr(guint8 *buffer)
+{
+ guint64 base;
+ guint64 ext;
+
+ base = pntoh40(buffer);
+ base >>= 7;
+
+ ext = pntoh16(&buffer[4]);
+ ext &= 0x01ff;
+
+ return (base * 300 + ext);
+}
+
+static gboolean
+mp2t_find_next_pcr(wtap *wth, guint8 trailer_len,
+ int *err, gchar **err_info, guint32 *idx, guint64 *pcr, guint16 *pid)
+{
+ guint8 buffer[MP2T_SIZE+TRAILER_LEN_MAX];
+ gboolean found;
+ guint8 afc;
+ guint timeout = 0;
+
+ found = FALSE;
+ while (FALSE == found && timeout++ < SYNC_STEPS * SYNC_STEPS) {
+ (*idx)++;
+ if (!wtap_read_bytes_or_eof(
+ wth->fh, buffer, MP2T_SIZE+trailer_len, err, err_info)) {
+ /* Read error, short read, or EOF */
+ return FALSE;
+ }
+
+ if (MP2T_SYNC_BYTE != buffer[0]) {
+ continue;
+ }
+
+ /* Read out the AFC value. */
+ afc = 3 & (buffer[3] >> 4);
+ if (afc < 2) {
+ continue;
+ }
+
+ /* Check the length. */
+ if (buffer[4] < 7) {
+ continue;
+ }
+
+ /* Check that there is the PCR flag. */
+ if (0x10 != (0x10 & buffer[5])) {
+ continue;
+ }
+
+ /* We have a PCR value! */
+ *pcr = mp2t_read_pcr(&buffer[6]);
+ *pid = 0x01ff & pntoh16(&buffer[1]);
+ found = TRUE;
+ }
+
+ return found;
+}
+
+static wtap_open_return_val
+mp2t_bits_per_second(wtap *wth, guint32 first, guint8 trailer_len,
+ guint64 *bitrate, int *err, gchar **err_info)
+{
+ guint32 pn1, pn2;
+ guint64 pcr1, pcr2;
+ guint16 pid1, pid2;
+ guint32 idx;
+ guint64 pcr_delta, bits_passed;
+
+ /* Find the first PCR + PID.
+ * Then find another PCR in that PID.
+ * Take the difference and that's our bitrate.
+ * All the different PCRs in different PIDs 'should' be the same.
+ *
+ * XXX - is this assuming that the time stamps in the PCRs correspond
+ * to the time scale of the underlying transport stream?
+ */
+ idx = first;
+
+ if (!mp2t_find_next_pcr(wth, trailer_len, err, err_info, &idx, &pcr1, &pid1)) {
+ /* Read error, short read, or EOF */
+ if (*err == WTAP_ERR_SHORT_READ)
+ return WTAP_OPEN_NOT_MINE; /* not a full frame */
+ if (*err != 0)
+ return WTAP_OPEN_ERROR;
+
+ /* We don't have any PCRs, so we can't guess the bit rate.
+ * Default to something reasonable.
+ */
+ *bitrate = MP2T_QAM64_BITRATE;
+ return WTAP_OPEN_MINE;
+ }
+
+ pn1 = idx;
+ pn2 = pn1;
+
+ while (pn1 == pn2) {
+ if (!mp2t_find_next_pcr(wth, trailer_len, err, err_info, &idx, &pcr2, &pid2)) {
+ /* Read error, short read, or EOF */
+ if (*err == WTAP_ERR_SHORT_READ)
+ return WTAP_OPEN_NOT_MINE; /* not a full frame */
+ if (*err != 0)
+ return WTAP_OPEN_ERROR;
+
+ /* We don't have two PCRs for the same PID, so we can't guess
+ * the bit rate.
+ * Default to something reasonable.
+ */
+ *bitrate = MP2T_QAM64_BITRATE;
+ return WTAP_OPEN_MINE;
+ }
+
+ if (pid1 == pid2) {
+ pn2 = idx;
+ }
+ }
+
+ if (pcr2 <= pcr1) {
+ /* The PCRs for that PID didn't go forward; treat that as an
+ * indication that this isn't an MPEG-2 TS.
+ */
+ return WTAP_OPEN_NOT_MINE;
+ }
+ pcr_delta = pcr2 - pcr1;
+ /* cast one of the factors to guint64
+ otherwise, the multiplication would use guint32 and could
+ overflow before the result is assigned to the guint64 bits_passed */
+ bits_passed = (guint64)MP2T_SIZE * (pn2 - pn1) * 8;
+
+ *bitrate = ((MP2T_PCR_CLOCK * bits_passed) / pcr_delta);
+ if (*bitrate == 0) {
+ /* pcr_delta < MP2T_PCR_CLOCK * bits_passed (pn2 != pn1,
+ * as that's the test for the loop above, so bits_passed
+ * is non-zero).
+ *
+ * That will produce a fractional bitrate, which turns
+ * into zero, causing a zero divide later.
+ *
+ * XXX - should we report this as "not ours"? A bitrate
+ * of less than 1 bit per second is not very useful for any
+ * form of audio/video, so presumably that's unlikely to
+ * be an MP2T file.
+ */
+ return WTAP_OPEN_ERROR;
+ }
+ return WTAP_OPEN_MINE;
+}
+
+wtap_open_return_val
+mp2t_open(wtap *wth, int *err, gchar **err_info)
+{
+ guint8 buffer[MP2T_SIZE+TRAILER_LEN_MAX];
+ guint8 trailer_len = 0;
+ guint sync_steps = 0;
+ guint i;
+ guint32 first = 0;
+ mp2t_filetype_t *mp2t;
+ wtap_open_return_val status;
+ guint64 bitrate;
+
+
+ if (!wtap_read_bytes(wth->fh, buffer, MP2T_SIZE, err, err_info)) {
+ if (*err != WTAP_ERR_SHORT_READ)
+ return WTAP_OPEN_ERROR;
+ return WTAP_OPEN_NOT_MINE;
+ }
+
+ for (i = 0; i < MP2T_SIZE; i++) {
+ if (MP2T_SYNC_BYTE == buffer[i]) {
+ first = i;
+ goto found;
+ }
+ }
+ /*
+ * No sync bytes found, so not an MPEG-2 Transport Stream file.
+ */
+ return WTAP_OPEN_NOT_MINE; /* wrong file type - not an mpeg2 ts file */
+
+found:
+ if (-1 == file_seek(wth->fh, first, SEEK_SET, err)) {
+ return WTAP_OPEN_ERROR;
+ }
+
+ /* read some packets and make sure they all start with a sync byte */
+ do {
+ if (!wtap_read_bytes(wth->fh, buffer, MP2T_SIZE+trailer_len, err, err_info)) {
+ if (*err != WTAP_ERR_SHORT_READ)
+ return WTAP_OPEN_ERROR; /* read error */
+ if(sync_steps<2) return WTAP_OPEN_NOT_MINE; /* wrong file type - not an mpeg2 ts file */
+ break; /* end of file, that's ok if we're still in sync */
+ }
+ if (buffer[0] == MP2T_SYNC_BYTE) {
+ sync_steps++;
+ }
+ else {
+ /* no sync byte found, check if trailing data is appended
+ and we have to increase the packet size */
+
+ /* if we've already detected a trailer field, we must remain in sync
+ another mismatch means we have no mpeg2 ts file */
+ if (trailer_len>0)
+ return WTAP_OPEN_NOT_MINE;
+
+ /* check if a trailer is appended to the packet */
+ for (i=0; i<TRAILER_LEN_MAX; i++) {
+ if (buffer[i] == MP2T_SYNC_BYTE) {
+ trailer_len = i;
+ if (-1 == file_seek(wth->fh, first, SEEK_SET, err)) {
+ return WTAP_OPEN_ERROR;
+ }
+ sync_steps = 0;
+ break;
+ }
+ }
+ /* no sync byte found in the vicinity, this is no mpeg2 ts file */
+ if (i==TRAILER_LEN_MAX)
+ return WTAP_OPEN_NOT_MINE;
+ }
+ } while (sync_steps < SYNC_STEPS);
+
+ if (-1 == file_seek(wth->fh, first, SEEK_SET, err)) {
+ return WTAP_OPEN_ERROR;
+ }
+
+ /* Ensure there is a valid bitrate */
+ status = mp2t_bits_per_second(wth, first, trailer_len,
+ &bitrate, err, err_info);
+ if (status != WTAP_OPEN_MINE) {
+ return status;
+ }
+
+ if (-1 == file_seek(wth->fh, first, SEEK_SET, err)) {
+ return WTAP_OPEN_ERROR;
+ }
+
+ wth->file_type_subtype = mp2t_file_type_subtype;
+ wth->file_encap = WTAP_ENCAP_MPEG_2_TS;
+ wth->file_tsprec = WTAP_TSPREC_NSEC;
+ wth->subtype_read = mp2t_read;
+ wth->subtype_seek_read = mp2t_seek_read;
+ wth->snapshot_length = 0;
+
+ mp2t = g_new(mp2t_filetype_t, 1);
+
+ wth->priv = mp2t;
+ mp2t->start_offset = first;
+ mp2t->trailer_len = trailer_len;
+ mp2t->bitrate = bitrate;
+
+ return WTAP_OPEN_MINE;
+}
+
+static const struct supported_block_type mp2t_blocks_supported[] = {
+ /*
+ * We support packet blocks, with no comments or other options.
+ */
+ { WTAP_BLOCK_PACKET, MULTIPLE_BLOCKS_SUPPORTED, NO_OPTIONS_SUPPORTED }
+};
+
+static const struct file_type_subtype_info mp2t_info = {
+ "MPEG2 transport stream", "mp2t", "mp2t", "ts;mpg",
+ FALSE, BLOCKS_SUPPORTED(mp2t_blocks_supported),
+ NULL, NULL, NULL
+};
+
+void register_mp2t(void)
+{
+ mp2t_file_type_subtype = wtap_register_file_type_subtype(&mp2t_info);
+
+ /*
+ * Register name for backwards compatibility with the
+ * wtap_filetypes table in Lua.
+ */
+ wtap_register_backwards_compatibility_lua_name("MPEG_2_TS",
+ mp2t_file_type_subtype);
+}
+
+/*
+ * Editor modelines - https://www.wireshark.org/tools/modelines.html
+ *
+ * Local variables:
+ * c-basic-offset: 4
+ * tab-width: 8
+ * indent-tabs-mode: nil
+ * End:
+ *
+ * vi: set shiftwidth=4 tabstop=8 expandtab:
+ * :indentSize=4:tabSize=8:noTabs=true:
+ */
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