[mp2t] use the correct file infomation for PCR detection

when we check for an mpeg2 transport stream, we're trying to detect an
initial offset before the first sync byte and the length of additional
data appended to each packet

use those values when we go through the file again and verify the PCR

Bug: 11749
Change-Id: Iab03cb271d23d38f850ca857b64ca47ba4501175
Reviewed-on: https://code.wireshark.org/review/12183
Reviewed-by: Michael Mann <mmann78@netscape.net>
(cherry picked from commit 6da516821d24b8857fe3a55703e517db0106d23c)
Reviewed-on: https://code.wireshark.org/review/12244
Reviewed-by: Martin Kaiser <wireshark@kaiser.cx>

1 files changed, 13 insertions, 7 deletions

diff --git a/wiretap/mp2t.c b/wiretap/mp2t.c
index ba626ed677..0a432d7031 100644
--- a/wiretap/mp2t.c
+++ b/wiretap/mp2t.c
@@ -165,7 +165,8 @@ mp2t_read_pcr(guint8 *buffer)
  * potentially scanning the entire file for a PCR?
  */
 static gboolean
-mp2t_find_next_pcr(wtap *wth, int *err, gchar **err_info, guint32 *idx, guint64 *pcr, guint16 *pid)
+mp2t_find_next_pcr(wtap *wth, guint8 trailer_len,
+        int *err, gchar **err_info, guint32 *idx, guint64 *pcr, guint16 *pid)
 {
     guint8 buffer[MP2T_SIZE];
     gboolean found;
@@ -174,7 +175,8 @@ mp2t_find_next_pcr(wtap *wth, int *err, gchar **err_info, guint32 *idx, guint64
     found = FALSE;
     while (FALSE == found) {
         (*idx)++;
-        if (!wtap_read_bytes_or_eof(wth->fh, buffer, MP2T_SIZE, err, err_info)) {
+        if (!wtap_read_bytes_or_eof(
+                    wth->fh, buffer, MP2T_SIZE+trailer_len, err, err_info)) {
             /* Read error, short read, or EOF */
             return FALSE;
         }
@@ -209,7 +211,8 @@ mp2t_find_next_pcr(wtap *wth, int *err, gchar **err_info, guint32 *idx, guint64
 }
 
 static wtap_open_return_val
-mp2t_bits_per_second(wtap *wth, guint64 *bitrate, int *err, gchar **err_info)
+mp2t_bits_per_second(wtap *wth, gint first, guint8 trailer_len,
+        guint64 *bitrate, int *err, gchar **err_info)
 {
     guint32 pn1, pn2;
     guint64 pcr1, pcr2;
@@ -226,9 +229,11 @@ mp2t_bits_per_second(wtap *wth, guint64 *bitrate, int *err, gchar **err_info)
      * to the time scale of the underlying transport stream?
      */
 
-    idx = 0;
+    if (first<0)
+        return WTAP_OPEN_ERROR;
+    idx = (guint32)first;
 
-    if (!mp2t_find_next_pcr(wth, err, err_info, &idx, &pcr1, &pid1)) {
+    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 */
@@ -246,7 +251,7 @@ mp2t_bits_per_second(wtap *wth, guint64 *bitrate, int *err, gchar **err_info)
     pn2 = pn1;
 
     while (pn1 == pn2) {
-        if (!mp2t_find_next_pcr(wth, err, err_info, &idx, &pcr2, &pid2)) {
+        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 */
@@ -355,7 +360,8 @@ mp2t_open(wtap *wth, int *err, gchar **err_info)
     }
 
     /* Ensure there is a valid bitrate */
-    status = mp2t_bits_per_second(wth, &bitrate, err, err_info);
+    status = mp2t_bits_per_second(wth, first, trailer_len,
+            &bitrate, err, err_info);
     if (status != WTAP_OPEN_MINE) {
         return status;
     }