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osmux: Proper encoding of osmux frames when when AMR FT changes 

The AMR FT (and hence payload content and size) may well change over the
lifetime of an RTP stream. Since all AMR payloads in an osmux batch
share the same FT (its joined payload is calculated based on
osmuxh->ctr*amr_bytes((osmuxh->amr_ft)), if a new RTP/AMR with a
different FT arrives we cannot simply append it to the current batch.
Instead, the current batch must be considered done and a new batch with
anew osmuxh header must be prepared for the resulting osmux frame to
send over UDP.

Before this patch, when a packet with a different AMR FT was submitted
for batching, it would be added in the same batch and decoding would
fail since the sizes of the batches would be wrong.

Related: SYS#5987
Change-Id: I25eb6ee54c898f575cc71ccfd6d190fe51d56dbe
This commit is contained in:
Pau Espin 2022-09-27 19:19:03 +02:00
parent f136c648fb
commit e36cbdf99e
1 changed files with 52 additions and 29 deletions
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81
src/osmux.c
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@ -398,23 +398,6 @@ static int osmux_batch_put(struct osmux_batch *batch,
return 0;
}
static int osmux_xfrm_encode_amr(struct osmux_batch *batch,
struct osmux_input_state *state)
{
uint32_t amr_len;
state->amrh = osmo_rtp_get_payload(state->rtph, state->msg, &amr_len);
if (state->amrh == NULL)
return -1;
state->amr_payload_len = amr_len - sizeof(struct amr_hdr);
if (osmux_batch_put(batch, state) < 0)
return -1;
return 0;
}
static void osmux_encode_dummy(struct osmux_batch *batch, uint8_t batch_factor,
struct osmux_input_state *state)
{
@ -457,6 +440,7 @@ static struct msgb *osmux_build_batch(struct osmux_batch *batch,
llist_for_each_entry(circuit, &batch->circuit_list, head) {
struct msgb *cur, *tmp;
int ctr = 0;
int prev_amr_ft;
if (circuit->dummy) {
struct osmux_input_state state = {
@ -473,6 +457,7 @@ static struct msgb *osmux_build_batch(struct osmux_batch *batch,
.out_msg = batch_msg,
.ccid = circuit->ccid,
};
uint32_t amr_len;
#ifdef DEBUG_MSG
char buf[4096];
@ -482,20 +467,31 @@ static struct msgb *osmux_build_batch(struct osmux_batch *batch,
#endif
state.rtph = osmo_rtp_get_hdr(cur);
if (state.rtph == NULL)
if (!state.rtph)
return NULL;
state.amrh = osmo_rtp_get_payload(state.rtph, state.msg, &amr_len);
if (!state.amrh)
return NULL;
state.amr_payload_len = amr_len - sizeof(struct amr_hdr);
if (ctr == 0) {
#ifdef DEBUG_MSG
LOGP(DLMUX, LOGL_DEBUG, "add osmux header\n");
LOGP(DLMUX, LOGL_DEBUG, "Add osmux header (First in batch)\n");
#endif
state.add_osmux_hdr = 1;
} else if (prev_amr_ft != state.amrh->ft) {
/* If AMR FT changed, we have to generate an extra batch osmux header: */
#ifdef DEBUG_MSG
LOGP(DLMUX, LOGL_DEBUG, "Add osmux header (New AMR FT)\n");
#endif
state.add_osmux_hdr = 1;
}
osmux_xfrm_encode_amr(batch, &state);
osmux_batch_put(batch, &state);
osmux_batch_dequeue(cur, circuit);
msgb_free(cur);
prev_amr_ft = state.amrh->ft;
ctr++;
msgb_free(cur);
batch->nmsgs--;
}
}
@ -536,16 +532,10 @@ static void osmux_batch_timer_expired(void *data)
osmux_xfrm_input_deliver(h);
}
static int osmux_rtp_amr_payload_len(struct msgb *msg, struct rtp_hdr *rtph)
static int osmux_rtp_amr_payload_len(struct amr_hdr *amrh, uint32_t amr_len)
{
struct amr_hdr *amrh;
unsigned int amr_len;
int amr_payload_len;
amrh = osmo_rtp_get_payload(rtph, msg, &amr_len);
if (amrh == NULL)
return -1;
if (!osmo_amr_ft_valid(amrh->ft))
return -1;
@ -561,6 +551,28 @@ static int osmux_rtp_amr_payload_len(struct msgb *msg, struct rtp_hdr *rtph)
return amr_payload_len;
}
/* Last stored AMR FT to be added in the current osmux batch. -1 if none stored yet */
static int osmux_circuit_get_last_stored_amr_ft(struct osmux_circuit *circuit)
{
struct msgb *last;
struct rtp_hdr *rtph;
struct amr_hdr *amrh;
uint32_t amr_len;
/* Have we seen any RTP packet in this batch before? */
if (llist_empty(&circuit->msg_list))
return -1;
OSMO_ASSERT(circuit->nmsgs > 0);
/* Get last RTP packet seen in this batch */
last = llist_entry(circuit->msg_list.prev, struct msgb, list);
rtph = osmo_rtp_get_hdr(last);
amrh = osmo_rtp_get_payload(rtph, last, &amr_len);
if (amrh == NULL)
return -1;
return amrh->ft;
}
/* returns: 1 if batch is full, 0 if batch still not full, negative on error. */
static int osmux_replay_lost_packets(struct osmux_circuit *circuit,
struct rtp_hdr *cur_rtph, int batch_factor)
@ -683,6 +695,8 @@ osmux_batch_add(struct osmux_batch *batch, uint32_t batch_factor, struct msgb *m
struct osmux_circuit *circuit;
struct msgb *cur;
int rc;
struct amr_hdr *amrh;
uint32_t amr_len;
circuit = osmux_batch_find_circuit(batch, ccid);
if (!circuit)
@ -693,7 +707,11 @@ osmux_batch_add(struct osmux_batch *batch, uint32_t batch_factor, struct msgb *m
circuit->dummy = 0;
batch->ndummy--;
}
amr_payload_len = osmux_rtp_amr_payload_len(msg, rtph);
amrh = osmo_rtp_get_payload(rtph, msg, &amr_len);
if (amrh == NULL)
return -1;
amr_payload_len = osmux_rtp_amr_payload_len(amrh, amr_len);
if (amr_payload_len < 0) {
LOGP(DLMUX, LOGL_NOTICE, "AMR payload invalid\n");
return -1;
@ -723,8 +741,13 @@ osmux_batch_add(struct osmux_batch *batch, uint32_t batch_factor, struct msgb *m
}
/* First check if there is room for this message in the batch */
/* First in batch comes after the batch header: */
if (circuit->nmsgs == 0)
bytes += sizeof(struct osmux_hdr);
/* If AMR FT changes in the middle of current batch a new header is
* required to adapt to size change: */
else if (osmux_circuit_get_last_stored_amr_ft(circuit) != amrh->ft)
bytes += sizeof(struct osmux_hdr);
bytes += amr_payload_len;
/* No room, sorry. You'll have to retry */