osmux: add osmux circuit ID management and resolve NAT problems
This patch includes several osmux fixes that are interdependent:
1) This adds Osmux circuit ID, this is allocated from the bsc-nat. This
announces the circuit ID in the CRCX MGCP message. This aims to resolve
the lack of uniqueness due to the use of endp->ci, which is local to
the bsc. This ID is notified via X-Osmux: NUM where NUM is the osmux
circuit ID.
2) The dummy load routines are now used to setup osmux both in bsc and
bsc-nat to resolve source port NAT issues as suggested by Holger. The
source port that is used from the bsc is not known until the first
voice message is sent to the bsc-nat, therefore enabling osmux from
the MGCP plane breaks when a different source port is used.
3) Add refcnt to struct osmux_handle, several endpoints can be using the
same input RTP osmux handle to perform the batching. Remove it from the
osmux handle list once nobody is using it anymore to clean it up.
4) Add a simple Osmux state-machine with three states. The initial state
is disabled, then if the bsc-nat requests Osmux, both sides enters
activating. The final enabled state is reached once the bsc-nat sees
the dummy load message that tells what source port is used by the bsc.
5) The osmux input handle (which transforms RTP messages to one Osmux batch)
is now permanently attached to the endpoint when Osmux is set up from the
dummy load path, so we skip a lookup for each message. This simplifies
osmux_xfrm_to_osmux().
After this patch, the workflow to setup Osmux is the following:
bsc bsc-nat
| |
|<------ CRCX ----------|
| X-Osmux: 3 | (where 3 is the Osmux circuit ID
| | that the bsc-nat has allocated)
|------- resp --------->|
| X-Osmux: 3 | (the bsc confirm that it can
| | use Osmux).
. .
| |
setup osmux |----- dummy load ----->| setup osmux
| Osmux CID: 3 |
In two steps:
1st) Allocate the Osmux Circuit ID (CID): The bsc-nat allocates an unique
Osmux CID that is notified to the bsc through the 'X-Osmux:' extension.
The bsc-nat annotates this circuit ID in the endpoint object. The bsc
replies back with the 'X-Osmux:' to confirm that it agrees to use Osmux.
If the bsc doesn't want to use Osmux, it doesn't include the extension
so the bsc-nat knows that it has to use to RTP.
2nd) The dummy load is used to convey the Osmux CID. This needs to happen
at this stage since the bsc-nat needs to know what source port the bsc
uses to get this working since the bsc may use a different source
port due to NAT. Unfortunately, this can't be done from the MGCP signal
plane since the real source port is not known that the bsc uses is not
known.
This patch also reverts the MDCX handling until it is clear that we need
this special handling for this case.
diff --git a/openbsc/src/osmo-bsc_nat/bsc_mgcp_utils.c b/openbsc/src/osmo-bsc_nat/bsc_mgcp_utils.c
index 15c4767..606ac92 100644
--- a/openbsc/src/osmo-bsc_nat/bsc_mgcp_utils.c
+++ b/openbsc/src/osmo-bsc_nat/bsc_mgcp_utils.c
@@ -50,6 +50,8 @@
#include <openbsc/ipaccess.h>
#include <openbsc/mgcp.h>
#include <openbsc/mgcp_internal.h>
+#include <openbsc/osmux.h>
+
#include <osmocom/ctrl/control_cmd.h>
#include <osmocom/sccp/sccp.h>
@@ -262,13 +264,12 @@
int len;
len = snprintf(buf, sizeof(buf),
- "MDCX 23 %x@mgw MGCP 1.0%s\r\n"
+ "MDCX 23 %x@mgw MGCP 1.0\r\n"
"Z: noanswer\r\n"
"\r\n"
"c=IN IP4 %s\r\n"
"m=audio %d RTP/AVP 255\r\n",
- port, bsc->cfg->osmux ? "\nX-Osmux: on" : "",
- bsc->nat->mgcp_cfg->source_addr,
+ port, bsc->nat->mgcp_cfg->source_addr,
endp->bts_end.local_port);
if (len < 0) {
LOGP(DMGCP, LOGL_ERROR, "snprintf for MDCX failed.\n");
@@ -505,6 +506,7 @@
struct nat_sccp_connection *sccp;
struct mgcp_endpoint *mgcp_endp;
struct msgb *bsc_msg;
+ int osmux_cid = -1;
nat = tcfg->cfg->data;
bsc_endp = &nat->bsc_endpoints[endpoint];
@@ -541,11 +543,15 @@
}
}
+ /* Allocate a Osmux circuit ID */
+ if (state == MGCP_ENDP_CRCX &&
+ nat->mgcp_cfg->osmux && sccp->bsc->cfg->osmux)
+ osmux_cid = osmux_get_cid();
+
/* we need to generate a new and patched message */
bsc_msg = bsc_mgcp_rewrite((char *) nat->mgcp_msg, nat->mgcp_length,
sccp->bsc_endp, nat->mgcp_cfg->source_addr,
- mgcp_endp->bts_end.local_port,
- nat->mgcp_cfg->osmux ? sccp->bsc->cfg->osmux : 0,
+ mgcp_endp->bts_end.local_port, osmux_cid,
&mgcp_endp->net_end.payload_type);
if (!bsc_msg) {
LOGP(DMGCP, LOGL_ERROR, "Failed to patch the msg.\n");
@@ -560,14 +566,14 @@
/* we need to update some bits */
if (state == MGCP_ENDP_CRCX) {
struct sockaddr_in sock;
- struct mgcp_endpoint *endp = &nat->mgcp_cfg->trunk.endpoints[endpoint];
- if (nat->mgcp_cfg->osmux ? sccp->bsc->cfg->osmux : 0) {
- if (osmux_enable_endpoint(endp, OSMUX_ROLE_BSC_NAT) < 0) {
- LOGP(DMGCP, LOGL_ERROR,
- "Could not activate osmux in endpoint %d\n",
- ENDPOINT_NUMBER(endp));
- }
+ /* Annotate the allocated Osmux CID until the bsc confirms that
+ * it agrees to use Osmux for this voice flow.
+ */
+ if (osmux_cid >= 0 &&
+ mgcp_endp->osmux.state != OSMUX_STATE_ENABLED) {
+ mgcp_endp->osmux.state = OSMUX_STATE_ACTIVATING;
+ mgcp_endp->osmux.cid = osmux_cid;
}
socklen_t len = sizeof(sock);
@@ -586,6 +592,11 @@
/* we will free the endpoint now and send a DLCX to the BSC */
msgb_free(bsc_msg);
bsc_mgcp_dlcx(sccp);
+
+ /* libmgcp clears the MGCP endpoint for us */
+ if (mgcp_endp->osmux.state == OSMUX_STATE_ENABLED)
+ osmux_put_cid(mgcp_endp->osmux.cid);
+
return MGCP_POLICY_CONT;
} else {
bsc_write(sccp->bsc, bsc_msg, IPAC_PROTO_MGCP_OLD);
@@ -624,6 +635,42 @@
mgcp_release_endp(endp);
}
+static void bsc_mgcp_osmux_confirm(struct mgcp_endpoint *endp, const char *str)
+{
+ unsigned int osmux_cid;
+ char *res;
+
+ res = strstr(str, "X-Osmux: ");
+ if (!res) {
+ LOGP(DMGCP, LOGL_INFO,
+ "BSC doesn't want to use Osmux, failing back to RTP\n");
+ goto err;
+ }
+
+ if (sscanf(res, "X-Osmux: %u", &osmux_cid) != 1) {
+ LOGP(DMGCP, LOGL_ERROR, "Failed to parse Osmux CID '%s'\n",
+ str);
+ goto err;
+ }
+
+ if (endp->osmux.cid != osmux_cid) {
+ LOGP(DMGCP, LOGL_INFO,
+ "BSC sent us wrong CID %u, we expected %u",
+ osmux_cid, endp->osmux.cid);
+ goto err;
+ }
+
+ LOGP(DMGCP, LOGL_NOTICE, "bsc accepted to use Osmux (cid=%u)\n",
+ osmux_cid);
+ return;
+err:
+ LOGP(DMGCP, LOGL_NOTICE, "bsc didn't accept to use Osmux (cid=%u)\n",
+ osmux_cid);
+ osmux_put_cid(endp->osmux.cid);
+ endp->osmux.cid = -1;
+ endp->osmux.state = OSMUX_STATE_DISABLED;
+}
+
/*
* We have received a msg from the BSC. We will see if we know
* this transaction and if it belongs to the BSC. Then we will
@@ -685,6 +732,9 @@
return;
}
+ if (endp->osmux.state == OSMUX_STATE_ACTIVATING)
+ bsc_mgcp_osmux_confirm(endp, (const char *) msg->l2h);
+
/* free some stuff */
talloc_free(bsc_endp->transaction_id);
bsc_endp->transaction_id = NULL;
@@ -697,8 +747,7 @@
*/
output = bsc_mgcp_rewrite((char * ) msg->l2h, msgb_l2len(msg), -1,
bsc->nat->mgcp_cfg->source_addr,
- endp->net_end.local_port,
- bsc->nat->mgcp_cfg->osmux ? bsc_endp->bsc->cfg->osmux : 0,
+ endp->net_end.local_port, -1,
&endp->bts_end.payload_type);
if (!output) {
LOGP(DMGCP, LOGL_ERROR, "Failed to rewrite MGCP msg.\n");
@@ -738,11 +787,12 @@
* Create a new MGCPCommand based on the input and endpoint from a message
*/
static void patch_mgcp(struct msgb *output, const char *op, const char *tok,
- int endp, int len, int cr, int osmux)
+ int endp, int len, int cr, int osmux_cid)
{
int slen;
int ret;
char buf[40];
+ char osmux_extension[strlen("X-Osmux: 255")];
buf[0] = buf[39] = '\0';
ret = sscanf(tok, "%*s %s", buf);
@@ -752,15 +802,19 @@
return;
}
+ if (osmux_cid >= 0)
+ sprintf(osmux_extension, "\nX-Osmux: %u", osmux_cid);
+ else
+ osmux_extension[0] = '\0';
+
slen = sprintf((char *) output->l3h, "%s %s %x@mgw MGCP 1.0%s%s",
- op, buf, endp, osmux ? "\nX-Osmux: on" : "",
- cr ? "\r\n" : "\n");
+ op, buf, endp, osmux_extension, cr ? "\r\n" : "\n");
output->l3h = msgb_put(output, slen);
}
/* we need to replace some strings... */
struct msgb *bsc_mgcp_rewrite(char *input, int length, int endpoint,
- const char *ip, int port, int osmux,
+ const char *ip, int port, int osmux_cid,
int *payload_type)
{
static const char crcx_str[] = "CRCX ";
@@ -799,11 +853,11 @@
cr = len > 0 && token[len - 1] == '\r';
if (strncmp(crcx_str, token, (sizeof crcx_str) - 1) == 0) {
- patch_mgcp(output, "CRCX", token, endpoint, len, cr, osmux);
+ patch_mgcp(output, "CRCX", token, endpoint, len, cr, osmux_cid);
} else if (strncmp(dlcx_str, token, (sizeof dlcx_str) - 1) == 0) {
- patch_mgcp(output, "DLCX", token, endpoint, len, cr, 0);
+ patch_mgcp(output, "DLCX", token, endpoint, len, cr, -1);
} else if (strncmp(mdcx_str, token, (sizeof mdcx_str) - 1) == 0) {
- patch_mgcp(output, "MDCX", token, endpoint, len, cr, osmux);
+ patch_mgcp(output, "MDCX", token, endpoint, len, cr, -1);
} else if (strncmp(ip_str, token, (sizeof ip_str) - 1) == 0) {
output->l3h = msgb_put(output, strlen(ip_str));
memcpy(output->l3h, ip_str, strlen(ip_str));