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Merge "main/udptl.c: correctly handle udptl sequence wrap around"

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George Joseph
2019-08-06 09:48:01 -05:00
committed by Gerrit Code Review
parent 86452c9fa4 084901d548
commit 97fd008562
1 changed files with 18 additions and 0 deletions
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18
main/udptl.c
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@@ -405,6 +405,24 @@ static int udptl_rx_packet(struct ast_udptl *s, uint8_t *buf, unsigned int len)
seq_no = (buf[0] << 8) | buf[1];
ptr += 2;
/* UDPTL sequence numbers are 16 bit so after 0xFFFF comes
0 which breaks all packet recovery logic. To fix this
if we see that next expected packet (rx_seq_no) is close
to or beyond the wrap around limit & the received packet
is still near zero, then we 'unwrap' the received seqno
so it has the value it would have had. After a 16
packet grace period (there shouldn't be more than
that many recovery packets) we wrap the expected
sequence number around and things can return back
to normal */
if (seq_no < 0x000F && s->rx_seq_no > 0xFFF0) {
/* received seq_no has wrapped adjust it */
seq_no += 0x10000;
} else {
/* otherwise make sure expected rx_seq_no is properly wrapped */
s->rx_seq_no &= 0xFFFF;
}
/* Break out the primary packet */
if ((stat1 = decode_open_type(buf, len, &ptr, &ifp, &ifp_len)) != 0)
return -1;