gsm0808: Introduce Osmocom extensions to announce Osmux support
IE GSM0808_IE_OSMO_OSMUX_SUPPORT (T, 1 byte) is sent in AoIP appended to
BSSMAP RESET in order to announce the peer that its MGW supports handling
Osmux streams upon call set up.
IE GSM0808_IE_OSMO_OSMUX_CID (TV, T 1 byte & V 1 byte) is sent in AoIP
during call set up:
* MSC->BSC Assignment Request
* BSC->MSC Assignemnt Complete
The 1 byte value contains the local Osmux CID, aka the recvCID aka CID where the
peer sending the Assign Req/Compl will look for Osmux frames on that
call. Hence, the peer receiving this CID value must use it to send Osmux
frames for that call.
As a result, a given call leg BSC<->MSC can have one different Osmux CID
per direction. For example:
* MS => MGW_BSC ==CID 0==> MGW_MSC
* MS <= MGW_BSC <=CID 1=== MGW_MSC
This allows for setups with 256 call legs per BSC on scenarios where NAT
is not a problem, where MSC can have a pool of 256 CID per MGW_BSC (or
remote peer).
Related: OS#2551
Change-Id: I28f83e2e32b9533c99e65ccc1562900ac2aec74e
diff --git a/include/osmocom/gsm/gsm0808_utils.h b/include/osmocom/gsm/gsm0808_utils.h
index 3a7beb7..9cfaea6 100644
--- a/include/osmocom/gsm/gsm0808_utils.h
+++ b/include/osmocom/gsm/gsm0808_utils.h
@@ -100,6 +100,7 @@
const struct sockaddr_storage *ss);
int gsm0808_dec_aoip_trasp_addr(struct sockaddr_storage *ss,
const uint8_t *elem, uint8_t len);
+int gsm0808_dec_osmux_cid(uint8_t *cid, const uint8_t *elem, uint8_t len);
uint8_t gsm0808_enc_lcls(struct msgb *msg, const struct osmo_lcls *lcls);
int gsm0808_dec_lcls(struct osmo_lcls *lcls, const struct tlv_parsed *tp);