Support Neighbor Address Resolution over PCUIF IPA multiplex

While NACC was initially developed, it became clear there was need for
a way to interact PCU<->BSC in order resolve ARFCN+BSIC into CGI-PS
for later RIM usage.
Hence, this resolution was first (until today) implemented using an out
of bands RPC system using the CTRL interface, which required specific
config to be written and matches in osmo-pcu and osmo-bsc VTY (ip+port
of the CTRL interface to use).
However, this has several shortcomings:
* As explained above, specific configuration is required
* Since recently, we do support BSC redundancy in osmo-bts. Hence the BTS
  may switch to a BSC other than first one. If that happened, that'd mean
  the CTRL interface would still point to the initially configured one,
  which may not be the same currently serving the PCU.

During recent development of ANR related features, a similar need for
PCU<->BSC was required, but this time it was decided to extend the IPA
multiplex of the Abis OML connection to pass PCUIF messages,
transparently forwarded to each side by the BTS.
This has the advantage that connection PCU<->BTS is handled by BTS and
both sides send messages transparently.

Let's switch by default to using this new interface, while still
maintaing the old way for a while (announcing them as deprecated) to
avoid breaking existing deployments until they are upgraded to new
versions of osmo-pcu and osmo-bsc.

Change-Id: I9073a121564503f483c84263ac72476041e47c03
Related: SYS#4971

3 files changed, 128 insertions, 42 deletions

diff --git a/src/osmo-bsc/abis_osmo.c b/src/osmo-bsc/abis_osmo.c
index 39caac6df..48774b4e8 100644
--- a/src/osmo-bsc/abis_osmo.c
+++ b/src/osmo-bsc/abis_osmo.c
@@ -32,6 +32,7 @@
 #include <osmocom/bsc/debug.h>
 #include <osmocom/bsc/bts.h>
 #include <osmocom/bsc/pcuif_proto.h>
+#include <osmocom/bsc/neighbor_ident.h>
 
 #define OM_HEADROOM_SIZE	128
 
@@ -40,7 +41,6 @@
 ///////////////////////////////////////
 #define PCUIF_HDR_SIZE ( sizeof(struct gsm_pcu_if) - sizeof(((struct gsm_pcu_if *)0)->u) )
 
-#if 0
 static struct msgb *abis_osmo_pcu_msgb_alloc(uint8_t msg_type, uint8_t bts_nr, size_t extra_size)
 {
 	struct msgb *msg;
@@ -62,7 +62,65 @@ static int abis_osmo_pcu_sendmsg(struct gsm_bts *bts, struct msgb *msg)
 	ipa_prepend_header_ext(msg, IPAC_PROTO_EXT_PCU);
 	return abis_osmo_sendmsg(bts, msg);
 }
-#endif
+
+static int abis_osmo_pcu_tx_neigh_addr_cnf(struct gsm_bts *bts, const struct gsm_pcu_if_neigh_addr_req *naddr_req,
+				    uint8_t err_code, const struct osmo_cell_global_id_ps *cgi_ps)
+{
+	struct msgb *msg = abis_osmo_pcu_msgb_alloc(PCU_IF_MSG_CONTAINER, bts->bts_nr, sizeof(struct gsm_pcu_if_neigh_addr_cnf));
+	struct gsm_pcu_if *pcu_prim = (struct gsm_pcu_if *) msgb_data(msg);
+	struct gsm_pcu_if_neigh_addr_cnf *naddr_cnf = (struct gsm_pcu_if_neigh_addr_cnf *)&pcu_prim->u.container.data[0];
+
+	msgb_put(msg, sizeof(pcu_prim->u.container) + sizeof(struct gsm_pcu_if_neigh_addr_cnf));
+	pcu_prim->u.container.msg_type = PCU_IF_MSG_NEIGH_ADDR_CNF;
+	osmo_store16be(sizeof(struct gsm_pcu_if_neigh_addr_cnf), &pcu_prim->u.container.length);
+
+	naddr_cnf->orig_req = *naddr_req;
+	naddr_cnf->err_code = err_code;
+	if (err_code == 0) {
+		osmo_store16be(cgi_ps->rai.lac.plmn.mcc, &naddr_cnf->cgi_ps.mcc);
+		osmo_store16be(cgi_ps->rai.lac.plmn.mnc, &naddr_cnf->cgi_ps.mnc);
+		naddr_cnf->cgi_ps.mnc_3_digits = cgi_ps->rai.lac.plmn.mnc_3_digits;
+		osmo_store16be(cgi_ps->rai.lac.lac, &naddr_cnf->cgi_ps.lac);
+		naddr_cnf->cgi_ps.rac = cgi_ps->rai.rac;
+		osmo_store16be(cgi_ps->cell_identity, &naddr_cnf->cgi_ps.cell_identity);
+	}
+
+	return abis_osmo_pcu_sendmsg(bts, msg);
+}
+
+static int rcvmsg_pcu_neigh_addr_req(struct gsm_bts *bts, const struct gsm_pcu_if_neigh_addr_req *naddr_req)
+{
+
+	struct cell_ab ab;
+	uint16_t local_lac, local_ci;
+	struct osmo_cell_global_id_ps cgi_ps;
+	int rc;
+
+	local_lac = osmo_load16be(&naddr_req->local_lac);
+	local_ci = osmo_load16be(&naddr_req->local_ci);
+	ab = (struct cell_ab){
+		.arfcn = osmo_load16be(&naddr_req->tgt_arfcn),
+		.bsic = naddr_req->tgt_bsic,
+	};
+
+	LOGP(DNM, LOGL_INFO, "(bts=%d) Rx Neighbor Address Resolution Req (ARFCN=%u,BSIC=%u) from (LAC=%u,CI=%u)\n",
+	     bts->nr, ab.arfcn, ab.bsic, local_lac, local_ci);
+
+	if (!cell_ab_valid(&ab)) {
+		rc = 2;
+		goto do_fail;
+	}
+
+	if (neighbor_address_resolution(bts->network, &ab, local_lac, local_ci, &cgi_ps) < 0) {
+		rc = 1;
+		goto do_fail;
+	}
+	return abis_osmo_pcu_tx_neigh_addr_cnf(bts, naddr_req, 0, &cgi_ps);
+
+do_fail:
+	return abis_osmo_pcu_tx_neigh_addr_cnf(bts, naddr_req, rc, NULL);
+}
+
 
 static int rcvmsg_pcu_container(struct gsm_bts *bts, struct gsm_pcu_if_container *container, size_t container_len)
 {
@@ -79,6 +137,13 @@ static int rcvmsg_pcu_container(struct gsm_bts *bts, struct gsm_pcu_if_container
 	     bts->nr, container->msg_type);
 
 	switch (container->msg_type) {
+	case PCU_IF_MSG_NEIGH_ADDR_REQ:
+		if (data_length < sizeof(struct gsm_pcu_if_neigh_addr_req)) {
+			LOGP(DNM, LOGL_ERROR, "ABIS_OSMO_PCU CONTAINER ANR_CNF message too short\n");
+			return -EINVAL;
+		}
+		rc = rcvmsg_pcu_neigh_addr_req(bts, (struct gsm_pcu_if_neigh_addr_req *)&container->data);
+		break;
 	default:
 		LOGP(DNM, LOGL_NOTICE, "(bts=%d) Rx ABIS_OSMO_PCU unexpected msg type (%u) inside container!\n",
 		     bts->nr, container->msg_type);
diff --git a/src/osmo-bsc/neighbor_ident.c b/src/osmo-bsc/neighbor_ident.c
index 6e706258d..c66d3ac55 100644
--- a/src/osmo-bsc/neighbor_ident.c
+++ b/src/osmo-bsc/neighbor_ident.c
@@ -366,47 +366,17 @@ static int gsm_bts_get_cgi_ps(const struct gsm_bts *bts, struct osmo_cell_global
 	return 0;
 }
 
-static int get_neighbor_resolve_cgi_ps_from_lac_ci(struct ctrl_cmd *cmd, void *data)
+/* Attempt resolution of cgi_ps from ARFCN+BSIC of neighbor from BTS identified by LAC+CI */
+int neighbor_address_resolution(const struct gsm_network *net, const struct cell_ab *ab,
+				uint16_t lac, uint16_t cell_id,
+				struct osmo_cell_global_id_ps *res_cgi_ps)
 {
-	struct gsm_network *net = (struct gsm_network *)data;
 	struct gsm_bts *bts_tmp, *bts_found = NULL;
-	char *tmp = NULL, *tok, *saveptr;
-	struct cell_ab ab;
-	unsigned lac, cell_id;
 	struct osmo_cell_global_id_ps local_cgi_ps;
 	const struct osmo_cell_global_id_ps *cgi_ps = NULL;
 	struct gsm_bts *local_neighbor = NULL;
 	struct gsm0808_cell_id_list2 remote_neighbors = { 0 };
 
-	if (!cmd->variable)
-		goto fmt_err;
-
-	tmp = talloc_strdup(cmd, cmd->variable);
-	if (!tmp) {
-		cmd->reply = "OOM";
-		return CTRL_CMD_ERROR;
-	}
-
-	if (!(tok = strtok_r(tmp, ".", &saveptr)))
-		goto fmt_err;
-	OSMO_ASSERT(strcmp(tok, "neighbor_resolve_cgi_ps_from_lac_ci") == 0);
-
-	if (!(tok = strtok_r(NULL, ".", &saveptr)))
-		goto fmt_err;
-	lac = atoi(tok);
-
-	if (!(tok = strtok_r(NULL, ".", &saveptr)))
-		goto fmt_err;
-	cell_id = atoi(tok);
-
-	if (!(tok = strtok_r(NULL, ".", &saveptr)))
-		goto fmt_err;
-	ab.arfcn = atoi(tok);
-
-	if (!(tok = strtok_r(NULL, "\0", &saveptr)))
-		goto fmt_err;
-	ab.bsic = atoi(tok);
-
 	llist_for_each_entry(bts_tmp, &net->bts_list, list) {
 		if (bts_tmp->location_area_code != lac)
 			continue;
@@ -420,12 +390,9 @@ static int get_neighbor_resolve_cgi_ps_from_lac_ci(struct ctrl_cmd *cmd, void *d
 		goto notfound_err;
 
 	LOG_BTS(bts_found, DLINP, LOGL_DEBUG, "Resolving neighbor BTS %u -> %s\n", bts_found->nr,
-		cell_ab_to_str_c(OTC_SELECT, &ab));
-
-	if (!cell_ab_valid(&ab))
-		goto fmt_err;
+		cell_ab_to_str_c(OTC_SELECT, ab));
 
-	if (resolve_neighbors(&local_neighbor, &remote_neighbors, bts_found, &ab, true))
+	if (resolve_neighbors(&local_neighbor, &remote_neighbors, bts_found, ab, true))
 		goto notfound_err;
 
 	/* resolve_neighbors() returns either a local_neighbor or remote_neighbors.
@@ -448,7 +415,57 @@ static int get_neighbor_resolve_cgi_ps_from_lac_ci(struct ctrl_cmd *cmd, void *d
 	if (!cgi_ps)
 		goto notfound_err;
 
-	ctrl_cmd_reply_printf(cmd, "%s", osmo_cgi_ps_name(cgi_ps));
+	*res_cgi_ps = *cgi_ps;
+	return 0;
+
+notfound_err:
+	return -1;
+}
+
+static int get_neighbor_resolve_cgi_ps_from_lac_ci(struct ctrl_cmd *cmd, void *data)
+{
+	struct gsm_network *net = (struct gsm_network *)data;
+	char *tmp = NULL, *tok, *saveptr;
+	struct cell_ab ab;
+	unsigned int lac, cell_id;
+	struct osmo_cell_global_id_ps cgi_ps;
+
+	if (!cmd->variable)
+		goto fmt_err;
+
+	tmp = talloc_strdup(cmd, cmd->variable);
+	if (!tmp) {
+		cmd->reply = "OOM";
+		return CTRL_CMD_ERROR;
+	}
+
+	if (!(tok = strtok_r(tmp, ".", &saveptr)))
+		goto fmt_err;
+	OSMO_ASSERT(strcmp(tok, "neighbor_resolve_cgi_ps_from_lac_ci") == 0);
+
+	if (!(tok = strtok_r(NULL, ".", &saveptr)))
+		goto fmt_err;
+	lac = atoi(tok);
+
+	if (!(tok = strtok_r(NULL, ".", &saveptr)))
+		goto fmt_err;
+	cell_id = atoi(tok);
+
+	if (!(tok = strtok_r(NULL, ".", &saveptr)))
+		goto fmt_err;
+	ab.arfcn = atoi(tok);
+
+	if (!(tok = strtok_r(NULL, "\0", &saveptr)))
+		goto fmt_err;
+	ab.bsic = atoi(tok);
+
+	if (!cell_ab_valid(&ab))
+		goto fmt_err;
+
+	if (neighbor_address_resolution(net, &ab, lac, cell_id, &cgi_ps) < 0)
+		goto notfound_err;
+
+	ctrl_cmd_reply_printf(cmd, "%s", osmo_cgi_ps_name(&cgi_ps));
 	talloc_free(tmp);
 	return CTRL_CMD_REPLY;
 
diff --git a/src/osmo-bsc/neighbor_ident_vty.c b/src/osmo-bsc/neighbor_ident_vty.c
index b9160ec67..b500b34a4 100644
--- a/src/osmo-bsc/neighbor_ident_vty.c
+++ b/src/osmo-bsc/neighbor_ident_vty.c
@@ -481,6 +481,10 @@ DEFUN(cfg_neighbor_bind, cfg_neighbor_bind_cmd,
 	NEIGHBOR_DOC "Bind Neighbor Resolution Service (CTRL interface) to given ip and port\n"
 	IP_STR IPV6_STR "Port to bind the service to [defaults to 4248 if not provided]\n")
 {
+	vty_out(vty, "%% Warning: The CTRL interface for Neighbor Address Resolution is now deprecated."
+		"Upgrade osmo-pcu and drop the 'neighbor-resolution bind " VTY_IPV46_CMD " [<0-65535>]' VTY "
+		"option in order to let osmo-pcu use the new resoluton method using the PCUIF over IPA "
+		"multiplex, which will work out of the box without required configuration.%s", VTY_NEWLINE);
 	osmo_talloc_replace_string(bsc_gsmnet, &bsc_gsmnet->neigh_ctrl.addr, argv[0]);
 	if (argc > 1)
 		bsc_gsmnet->neigh_ctrl.port = atoi(argv[1]);