libipt: update sync offset at PSB

We currently update the sync offset only at explicit synchronization
requests, not while we are processing PSB during decode.

We used to start backward synchronization at the previous synchronization
point, so we couldn't update the sync offset during decode.  This changed
already some time ago to start at the current position.

Update the sync offset at PSB during decode.  This allows re-synchronizing
at the current PSB segment using

    pt_*_get_sync_offset()

followed by

    ps_*_sync_set()

Signed-off-by: Markus Metzger <[email protected]>

Author: markus-metzger

libipt/src/pt_packet_decoder.c

@@ -266,15 +266,19 @@ static int pt_pkt_decode_pad(struct pt_packet_decoder *decoder,
 static int pt_pkt_decode_psb(struct pt_packet_decoder *decoder,
 			     struct pt_packet *packet)
 {
+	const uint8_t *pos;
 	int size;
 
 	if (!decoder)
 		return -pte_internal;
 
-	size = pt_pkt_read_psb(decoder->pos, &decoder->config);
+	pos = decoder->pos;
+	size = pt_pkt_read_psb(pos, &decoder->config);
 	if (size < 0)
 		return size;
 
+	decoder->sync = pos;
+
 	packet->type = ppt_psb;
 	packet->size = (uint8_t) size;