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mgcp: Calculate the wrap around as of Appendix A in RFC 3550 

This is missing the probation and the dealing with a remote
restart. For the remote restart we will simply write a log
statement as this is unlikely to happen during a call or if
it does happen the call will be taken down by the BSC anyway.
This commit is contained in:
Holger Hans Peter Freyther 2012-10-22 17:30:12 +02:00
parent 1e85af661c
commit 769912c9e9
2 changed files with 21 additions and 1 deletions
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1
openbsc/include/openbsc/mgcp_internal.h
View File

@ -50,6 +50,7 @@ struct mgcp_rtp_state {
uint16_t base_seq;
uint16_t max_seq;
int seq_offset;
int cycles;
uint32_t last_timestamp;
int32_t timestamp_offset;

21
openbsc/src/libmgcp/mgcp_network.c
View File

@ -73,6 +73,10 @@ struct rtp_hdr {
uint32_t ssrc;
} __attribute__((packed));
#define RTP_SEQ_MOD (1 << 16)
#define RTP_MAX_DROPOUT 3000
#define RTP_MAX_MISORDER 100
enum {
DEST_NETWORK = 0,
@ -116,7 +120,7 @@ int mgcp_send_dummy(struct mgcp_endpoint *endp)
static void patch_and_count(struct mgcp_endpoint *endp, struct mgcp_rtp_state *state,
int payload, struct sockaddr_in *addr, char *data, int len)
{
uint16_t seq;
uint16_t seq, udelta;
uint32_t timestamp;
struct rtp_hdr *rtp_hdr;
@ -154,6 +158,21 @@ static void patch_and_count(struct mgcp_endpoint *endp, struct mgcp_rtp_state *s
rtp_hdr->timestamp = htonl(timestamp);
}
/*
* The below takes the shape of the validation from Appendix A. Check
* if there is something weird with the sequence number, otherwise check
* for a wrap around in the sequence number.
*/
udelta = seq - state->max_seq;
if (udelta < RTP_MAX_DROPOUT) {
if (seq < state->max_seq)
state->cycles += RTP_SEQ_MOD;
} else if (udelta <= RTP_SEQ_MOD + RTP_MAX_MISORDER) {
LOGP(DMGCP, LOGL_NOTICE,
"RTP seqno made a very large jump on 0x%x delta: %u\n",
ENDPOINT_NUMBER(endp), udelta);
}
state->max_seq = seq;
state->last_timestamp = timestamp;