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

1 files changed, 57 insertions, 40 deletions

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;