nat: Attempt to make MGCP forwarding more robust

When not being able to allocate the msgb for the forwarded data
there is no point in keeping and preparing the transaction. So
we can move the msg creation a bit up and only do the allocations
after having done the msgb allocation.

When receiving a DLCX we will now delete the endpoint right away. This
means when a BSS does not respond to the DLCX our endpoint will not
be blocked. E.g. this could happen when the MGCP is restarting or
in similiar conditions. When the BSS is not responding we move the
burden up the chain to the CallAgent. We have to still keep track
of the transaction id and the bsc pointer to keep the mgcp forward
routine working.

1 files changed, 27 insertions, 17 deletions

diff --git a/openbsc/src/nat/bsc_mgcp_utils.c b/openbsc/src/nat/bsc_mgcp_utils.c
index 2dbf1fd00..435c8584b 100644
--- a/openbsc/src/nat/bsc_mgcp_utils.c
+++ b/openbsc/src/nat/bsc_mgcp_utils.c
@@ -148,9 +148,18 @@ int bsc_mgcp_policy_cb(struct mgcp_config *cfg, int endpoint, int state, const c
 		talloc_free(bsc_endp->transaction_id);
 	}
 
+	/* we need to generate a new and patched message */
+	bsc_msg = bsc_mgcp_rewrite((char *) nat->mgcp_msg, nat->mgcp_length,
+				   nat->mgcp_cfg->source_addr, mgcp_endp->rtp_port);
+	if (!bsc_msg) {
+		LOGP(DMGCP, LOGL_ERROR, "Failed to patch the msg.\n");
+		return MGCP_POLICY_CONT;
+	}
+
+
 	bsc_endp->transaction_id = talloc_strdup(nat, transaction_id);
 	bsc_endp->bsc = bsc_con;
-	bsc_endp->pending_delete = state == MGCP_ENDP_DLCX;
+	bsc_endp->pending_delete = 0;
 
 	/* we need to update some bits */
 	if (state == MGCP_ENDP_CRCX) {
@@ -162,14 +171,10 @@ int bsc_mgcp_policy_cb(struct mgcp_config *cfg, int endpoint, int state, const c
 		} else {
 			mgcp_endp->bts = sock.sin_addr;
 		}
-	}
-
-	/* we need to generate a new and patched message */
-	bsc_msg = bsc_mgcp_rewrite((char *) nat->mgcp_msg, nat->mgcp_length,
-				   nat->mgcp_cfg->source_addr, mgcp_endp->rtp_port);
-	if (!bsc_msg) {
-		LOGP(DMGCP, LOGL_ERROR, "Failed to patch the msg.\n");
-		return MGCP_POLICY_CONT;
+	} else if (state == MGCP_ENDP_DLCX) {
+		/* we will free the endpoint now in case the BSS does not respond */
+		bsc_endp->pending_delete = 1;
+		mgcp_free_endp(mgcp_endp);
 	}
 
 	bsc_write_mgcp_msg(bsc_con, bsc_msg);
@@ -223,21 +228,26 @@ void bsc_mgcp_forward(struct bsc_connection *bsc, struct msgb *msg)
 		return;
 	}
 
+	/* make it point to our endpoint if it was not deleted */
+	if (bsc_endp->pending_delete) {
+		bsc_endp->bsc = NULL;
+		bsc_endp->pending_delete = 0;
+	} else {
+		endp->ci = bsc_mgcp_extract_ci((const char *) msg->l2h);
+	}
+
 	/* free some stuff */
 	talloc_free(bsc_endp->transaction_id);
 	bsc_endp->transaction_id = NULL;
 
-	/* make it point to our endpoint */
-	endp->ci = bsc_mgcp_extract_ci((const char *) msg->l2h);
+	/*
+	 * rewrite the information. In case the endpoint was deleted
+	 * there should be nothing for us to rewrite so putting endp->rtp_port
+	 * with the value of 0 should be no problem.
+	 */
 	output = bsc_mgcp_rewrite((char * ) msg->l2h, msgb_l2len(msg),
 				  bsc->nat->mgcp_cfg->source_addr, endp->rtp_port);
 
-	if (bsc_endp->pending_delete) {
-		mgcp_free_endp(endp);
-		bsc_endp->bsc = NULL;
-		bsc_endp->pending_delete = 0;
-	}
-
 	if (!output) {
 		LOGP(DMGCP, LOGL_ERROR, "Failed to rewrite MGCP msg.\n");
 		return;