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lchan_rtp_fsm: Deferr IPACC MDCX after BTS side MGCP MDCX 

This is needed to be able to force MGW to provide an IPv4 address during
MDCX, since IPACC protocol on the BTS side only supports IPv4, but one
may need IPv6 side at the same time on the core side.
By moving the IPACC MDCX request to a later step, the BSC gains
knowledge of the local address on each side (BTS, MGW), and if they
don't match (ie. BTS uses IPv4 and MGW uses IPv6), it can then get MGW
to offer an IPv4 address during MGCP MDCX containing the BTS IPv4
address. At that point, the MGW can see the mismatch and provide an IPv4
address in the MGCP MDCX ACK, which can then finally be communicated to
the BTS during IPACC MDCX phase.

Previous order:
BSC -> MGW: CRCX
BSC <- MGW: CRCX ACK		(get MGW local IP addr)
BSC -> BTS: IPACC CRCX
BSC <- BTS: IPACC CRCX ACK 	(get BTS local IP addr)
BSC -> BTS: IPACC MDCX 		(set MGW IP addr)
BSC <- BTS: IPACC MDCX ACK
BSC -> MGW: MDCX 		(set BTS IP addr)
BSC <- MGW: MDCX ACK

New order:
BSC -> MGW: CRCX
BSC <- MGW: CRCX ACK 		(get MGCP local IPv6 addr)
BSC -> BTS: IPACC CRCX
BSC <- BTS: IPACC CRCX ACK 	(get BTS local IPv4 addr)
BSC -> MGW: MDCX 		(set BTS IPv4 addr)
BSC <- MGW: MDCX ACK 		(here MGW changes its local addr to IPv4)
BSC -> BTS: IPACC MDCX 		(set MGW IPv4 addr)
BSC <- BTS: IPACC MDCX ACK

Change-Id: I4de5ea5c94c1482c9cb0b6386997a942edc60e32
This commit is contained in:
Pau Espin 2020-09-02 18:40:43 +02:00
parent 422b751ac8
commit f087c1ebd4
3 changed files with 36 additions and 35 deletions
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7
doc/lchan-rtp-fsm.dot
View File

@ -1,7 +1,7 @@
digraph G {
rankdir=TB
labelloc=t; label="lchan RTP FSM"
lchan [label="lchan\nFSM",shape=box3d]
lchan2 [label="lchan\nFSM",shape=box3d]
ho_as [label="Handover or Assignment FSM",shape=box3d]
@ -23,14 +23,15 @@ labelloc=t; label="lchan RTP FSM"
lchan -> WAIT_LCHAN_READY [label="LCHAN_RTP_EV_LCHAN_READY",style=dashed]
WAIT_LCHAN_READY -> WAIT_IPACC_CRCX_ACK [label="IPACC BTS"]
WAIT_LCHAN_READY -> WAIT_READY_TO_SWITCH_RTP
WAIT_IPACC_CRCX_ACK -> WAIT_IPACC_MDCX_ACK
WAIT_IPACC_MDCX_ACK -> WAIT_READY_TO_SWITCH_RTP
WAIT_IPACC_CRCX_ACK -> WAIT_READY_TO_SWITCH_RTP
invisible -> ho [label="HO DETECT",style=dashed]
ho -> WAIT_READY_TO_SWITCH_RTP [label="LCHAN_RTP_EV_READY_TO_SWITCH",style=dashed]
WAIT_READY_TO_SWITCH_RTP -> WAIT_MGW_ENDPOINT_CONFIGURED
WAIT_MGW_ENDPOINT_CONFIGURED -> mgwep [label="MDCX",style=dashed]
mgwep -> WAIT_MGW_ENDPOINT_CONFIGURED [label="LCHAN_RTP_EV_\nMGW_ENDPOINT_\nCONFIGURED",style=dashed]
WAIT_MGW_ENDPOINT_CONFIGURED -> WAIT_IPACC_MDCX_ACK [label="IPACC BTS"]
WAIT_MGW_ENDPOINT_CONFIGURED -> RTP_READY
WAIT_IPACC_MDCX_ACK -> RTP_READY
RTP_READY -> lchan2 [label="LCHAN_EV_\nRTP_READY",style=dashed]
RTP_READY -> RTP_ESTABLISHED
lchan2 -> RTP_ESTABLISHED [label="LCHAN_RTP_EV_\nRELEASE",style=dashed]

10
doc/lchan.msc
View File

@ -68,10 +68,6 @@ msc {
ms <= rtp [label="IPACC CRCX"];
...;
ms => rtp [label="IPACC CRCX ACK (BTS RTP port info)"];
rtp abox rtp [label="LCHAN_RTP_ST_WAIT_IPACC_MDCX_ACK"];
ms <= rtp [label="IPACC MDCX (MGW RTP port info)"];
...;
ms => rtp [label="IPACC MDCX ACK"];
--- [label="END ip.access style BTS"];
|||;
rtp box rtp [label="lchan_rtp_fsm_switch_rtp()"];
@ -91,6 +87,12 @@ msc {
...;
mgwep rbox mgwep [label="MGCP: MDCX OK"];
rtp <- mgwep [label="LCHAN_RTP_EV_MGW_ENDPOINT_CONFIGURED"];
--- [label="IF ip.access style BTS"];
rtp abox rtp [label="LCHAN_RTP_ST_WAIT_IPACC_MDCX_ACK"];
ms <= rtp [label="IPACC MDCX (MGW RTP port info)"];
...;
ms => rtp [label="IPACC MDCX ACK"];
--- [label="END ip.access style BTS"];
rtp abox rtp [label="LCHAN_RTP_ST_READY"];
lchan <- rtp [label="LCHAN_EV_RTP_READY"];
rtp note rtp [label="RTP FSM stays ready for Rollback until final establish event"];

54
src/osmo-bsc/lchan_rtp_fsm.c
View File

@ -301,10 +301,7 @@ static void lchan_rtp_fsm_wait_ipacc_crcx_ack(struct osmo_fsm_inst *fi, uint32_t
switch (event) {
case LCHAN_RTP_EV_IPACC_CRCX_ACK:
/* the CRCX ACK parsing has already noted the RTP port information at
* lchan->abis_ip.bound_*, see ipac_parse_rtp(). We'll use that in
* lchan_rtp_fsm_wait_mgw_endpoint_configured_onenter(). */
lchan_rtp_fsm_state_chg(LCHAN_RTP_ST_WAIT_IPACC_MDCX_ACK);
lchan_rtp_fsm_switch_rtp(fi);
return;
case LCHAN_RTP_EV_IPACC_CRCX_NACK:
@ -366,21 +363,16 @@ static void lchan_rtp_fsm_wait_ipacc_mdcx_ack_onenter(struct osmo_fsm_inst *fi,
static void lchan_rtp_fsm_wait_ipacc_mdcx_ack(struct osmo_fsm_inst *fi, uint32_t event, void *data)
{
struct gsm_lchan *lchan = lchan_rtp_fi_lchan(fi);
switch (event) {
case LCHAN_RTP_EV_IPACC_MDCX_ACK:
lchan_rtp_fsm_switch_rtp(fi);
lchan_rtp_fsm_state_chg(LCHAN_RTP_ST_READY);
return;
case LCHAN_RTP_EV_IPACC_MDCX_NACK:
lchan_rtp_fail("Received NACK on IPACC MDCX");
return;
case LCHAN_RTP_EV_READY_TO_SWITCH_RTP:
lchan->activate.info.wait_before_switching_rtp = false;
return;
case LCHAN_RTP_EV_RELEASE:
case LCHAN_RTP_EV_ROLLBACK:
osmo_fsm_inst_term(fi, OSMO_FSM_TERM_REQUEST, 0);
@ -480,10 +472,15 @@ static void lchan_rtp_fsm_wait_mgw_endpoint_configured_onenter(struct osmo_fsm_i
static void lchan_rtp_fsm_wait_mgw_endpoint_configured(struct osmo_fsm_inst *fi, uint32_t event, void *data)
{
switch (event) {
struct gsm_lchan *lchan = lchan_rtp_fi_lchan(fi);
switch (event) {
case LCHAN_RTP_EV_MGW_ENDPOINT_CONFIGURED:
lchan_rtp_fsm_state_chg(LCHAN_RTP_ST_READY);
if (is_ipaccess_bts(lchan->ts->trx->bts))
lchan_rtp_fsm_state_chg(LCHAN_RTP_ST_WAIT_IPACC_MDCX_ACK);
else {
lchan_rtp_fsm_state_chg(LCHAN_RTP_ST_READY);
}
return;
case LCHAN_RTP_EV_MGW_ENDPOINT_ERROR:
@ -651,24 +648,9 @@ static const struct osmo_fsm_state lchan_rtp_fsm_states[] = {
| S(LCHAN_RTP_EV_RELEASE)
| S(LCHAN_RTP_EV_ROLLBACK)
,
.out_state_mask = 0
| S(LCHAN_RTP_ST_WAIT_IPACC_MDCX_ACK)
,
},
[LCHAN_RTP_ST_WAIT_IPACC_MDCX_ACK] = {
.name = "WAIT_IPACC_MDCX_ACK",
.onenter = lchan_rtp_fsm_wait_ipacc_mdcx_ack_onenter,
.action = lchan_rtp_fsm_wait_ipacc_mdcx_ack,
.in_event_mask = 0
| S(LCHAN_RTP_EV_READY_TO_SWITCH_RTP)
| S(LCHAN_RTP_EV_IPACC_MDCX_ACK)
| S(LCHAN_RTP_EV_IPACC_MDCX_NACK)
| S(LCHAN_RTP_EV_RELEASE)
| S(LCHAN_RTP_EV_ROLLBACK)
,
.out_state_mask = 0
| S(LCHAN_RTP_ST_WAIT_READY_TO_SWITCH_RTP)
| S(LCHAN_RTP_ST_WAIT_MGW_ENDPOINT_CONFIGURED)
| S(LCHAN_RTP_ST_WAIT_MGW_ENDPOINT_CONFIGURED) /*old: LCHAN_RTP_ST_WAIT_IPACC_MDCX_ACK*/
,
},
[LCHAN_RTP_ST_WAIT_READY_TO_SWITCH_RTP] = {
@ -693,6 +675,22 @@ static const struct osmo_fsm_state lchan_rtp_fsm_states[] = {
| S(LCHAN_RTP_EV_RELEASE)
| S(LCHAN_RTP_EV_ROLLBACK)
,
.out_state_mask = 0
| S(LCHAN_RTP_ST_WAIT_IPACC_MDCX_ACK)
| S(LCHAN_RTP_ST_READY)
| S(LCHAN_RTP_ST_ROLLBACK)
,
},
[LCHAN_RTP_ST_WAIT_IPACC_MDCX_ACK] = {
.name = "WAIT_IPACC_MDCX_ACK",
.onenter = lchan_rtp_fsm_wait_ipacc_mdcx_ack_onenter,
.action = lchan_rtp_fsm_wait_ipacc_mdcx_ack,
.in_event_mask = 0
| S(LCHAN_RTP_EV_IPACC_MDCX_ACK)
| S(LCHAN_RTP_EV_IPACC_MDCX_NACK)
| S(LCHAN_RTP_EV_RELEASE)
| S(LCHAN_RTP_EV_ROLLBACK)
,
.out_state_mask = 0
| S(LCHAN_RTP_ST_READY)
| S(LCHAN_RTP_ST_ROLLBACK)