xua: Implement SNM availability/unavailability messaging

M3UA and SUA have one sub-protocol called [S]SNM, through which the
SG informs the ASP about certain destinations (point codes) becoming
available (DAVA) or unavailable (DUNA) in the SS7 network.

This patch adds support for
* generating DAVA/DUAN on a SGP when the AS FSM changes to/from AS-ACTIVE
* receiving DAVA/DUNA on an ASP and informing other "SG role" AS/ASP
* processing DAUD from ASP received by SG, generating relate DAVA/DUNA
  responses

Related: OS#2623
Change-Id: Id92be4691b0fd77598a6edb642c028bbd8c5b623

1 files changed, 211 insertions, 0 deletions

diff --git a/src/xua_snm.c b/src/xua_snm.c
new file mode 100644
index 0000000..c4dffbb
--- /dev/null
+++ b/src/xua_snm.c
@@ -0,0 +1,211 @@
+/* M3UA/SUA [S]SNM Handling */
+
+/* (C) 2021 by Harald Welte <laforge@gnumonks.org>
+ * All Rights Reserved
+ *
+ * SPDX-License-Identifier: GPL-2.0+
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include <stdint.h>
+
+#include <osmocom/core/utils.h>
+#include <osmocom/core/talloc.h>
+#include <osmocom/core/linuxlist.h>
+
+#include <osmocom/sigtran/osmo_ss7.h>
+#include <osmocom/sigtran/protocol/m3ua.h>
+#include <osmocom/sigtran/protocol/sua.h>
+
+#include "xua_internal.h"
+
+/* we can share this code between M3UA and SUA as the below conditions are true */
+osmo_static_assert(M3UA_SNM_DUNA == SUA_SNM_DUNA, _sa_duna);
+osmo_static_assert(M3UA_SNM_DAVA == SUA_SNM_DAVA, _sa_dava);
+osmo_static_assert(M3UA_SNM_DAUD == SUA_SNM_DAUD, _sa_dava);
+osmo_static_assert(M3UA_IEI_AFFECTED_PC == SUA_IEI_AFFECTED_PC, _sa_aff_pc);
+osmo_static_assert(M3UA_IEI_ROUTE_CTX == SUA_IEI_ROUTE_CTX, _sa_rctx);
+osmo_static_assert(M3UA_IEI_INFO_STRING == SUA_IEI_INFO_STRING, _sa_inf_str);
+
+static const char *format_affected_pcs_c(void *ctx, const struct osmo_ss7_instance *s7i,
+					 const struct xua_msg_part *ie_aff_pc)
+{
+	const uint32_t *aff_pc = (const uint32_t *) ie_aff_pc->dat;
+	unsigned int num_aff_pc = ie_aff_pc->len / sizeof(uint32_t);
+	char *out = talloc_strdup(ctx, "");
+	int i;
+
+	for (i = 0; i < num_aff_pc; i++) {
+		uint32_t _aff_pc = ntohl(aff_pc[i]);
+		uint32_t pc = _aff_pc & 0xffffff;
+		uint8_t mask = _aff_pc >> 24;
+
+		/* append point code + mask */
+		out = talloc_asprintf_append(out, "%s%s/%u, ", i == 0 ? "" : ", ",
+					     osmo_ss7_pointcode_print(s7i, pc), mask);
+	}
+	return out;
+}
+
+/* obtain all routing contexts (in network byte order) that exist within the given ASP */
+static unsigned int get_all_rctx_for_asp(uint32_t *rctx, unsigned int rctx_size,
+					 struct osmo_ss7_asp *asp, struct osmo_ss7_as *excl_as)
+{
+	unsigned int count = 0;
+	struct osmo_ss7_as *as;
+
+	llist_for_each_entry(as, &asp->inst->as_list, list) {
+		if (as == excl_as)
+			continue;
+		if (!osmo_ss7_as_has_asp(as, asp))
+			continue;
+		if (as->cfg.routing_key.context == 0)
+			continue;
+		if (count >= rctx_size)
+			break;
+		rctx[count] = htonl(as->cfg.routing_key.context);
+		count++;
+	}
+	return count;
+}
+
+static void xua_tx_snm_available(struct osmo_ss7_asp *asp, const uint32_t *rctx, unsigned int num_rctx,
+				 const uint32_t *aff_pc, unsigned int num_aff_pc,
+				 const char *info_str, bool available)
+{
+	switch (asp->cfg.proto) {
+	case OSMO_SS7_ASP_PROT_M3UA:
+		m3ua_tx_snm_available(asp, rctx, num_rctx, aff_pc, num_aff_pc, info_str, available);
+		break;
+	case OSMO_SS7_ASP_PROT_SUA:
+		sua_tx_snm_available(asp, rctx, num_rctx, aff_pc, num_aff_pc, NULL, NULL, info_str, available);
+		break;
+	default:
+		break;
+	}
+}
+
+/* advertise availability of point codes (with masks) */
+void xua_snm_pc_available(struct osmo_ss7_as *as, const uint32_t *aff_pc,
+			  unsigned int num_aff_pc, const char *info_str, bool available)
+{
+	struct osmo_ss7_instance *s7i = as->inst;
+	struct osmo_ss7_asp *asp;
+	uint32_t rctx[32];
+	unsigned int num_rctx;
+
+	llist_for_each_entry(asp, &s7i->asp_list, list) {
+		/* SSNM is only permitted for ASPs in ACTIVE state */
+		if (!osmo_ss7_asp_active(asp))
+			continue;
+
+		/* only send DAVA/DUNA if we locally are the SG and the remote is ASP */
+		if (asp->cfg.role != OSMO_SS7_ASP_ROLE_SG)
+			continue;
+
+		num_rctx = get_all_rctx_for_asp(rctx, ARRAY_SIZE(rctx), asp, as);
+		/* this can happen if the given ASP is only in the AS that reports the change,
+		 * which shall be excluded */
+		if (num_rctx == 0)
+			continue;
+		xua_tx_snm_available(asp, rctx, num_rctx, aff_pc, num_aff_pc, info_str, available);
+	}
+}
+
+/* receive DAUD from ASP; pc is 'affected PC' IE with mask in network byte order! */
+void xua_snm_rx_daud(struct osmo_ss7_asp *asp, struct xua_msg *xua)
+{
+	struct xua_msg_part *ie_aff_pc = xua_msg_find_tag(xua, M3UA_IEI_AFFECTED_PC);
+	const char *info_str = xua_msg_get_str(xua, M3UA_IEI_INFO_STRING);
+	struct osmo_ss7_instance *s7i = asp->inst;
+	unsigned int num_aff_pc;
+	unsigned int num_rctx;
+	const uint32_t *aff_pc;
+	uint32_t rctx[32];
+	int log_ss = osmo_ss7_asp_get_log_subsys(asp);
+	int i;
+
+	OSMO_ASSERT(ie_aff_pc);
+	aff_pc = (const uint32_t *) ie_aff_pc->dat;
+	num_aff_pc = ie_aff_pc->len / sizeof(uint32_t);
+
+	num_rctx = get_all_rctx_for_asp(rctx, ARRAY_SIZE(rctx), asp, NULL);
+
+	LOGPASP(asp, log_ss, LOGL_INFO, "Rx DAUD(%s) for %s\n", info_str ? info_str : "",
+		format_affected_pcs_c(xua, asp->inst, ie_aff_pc));
+
+	/* iterate over list of point codes, generate DAVA/DUPU */
+	for (i = 0; i < num_aff_pc; i++) {
+		uint32_t _aff_pc = ntohl(aff_pc[i]);
+		uint32_t pc = _aff_pc & 0xffffff;
+		uint8_t mask = _aff_pc >> 24;
+		bool is_available = false;
+
+		if (mask == 0) {
+			/* one single point code */
+
+			/* FIXME: don't just check for a route; but also check if the route is "active" */
+			if (osmo_ss7_route_lookup(s7i, pc))
+				is_available = true;
+
+			xua_tx_snm_available(asp, rctx, num_rctx, &aff_pc[i], 1, "Response to DAUD",
+					     is_available);
+		} else {
+			/* TODO: wildcard match */
+			LOGPASP(asp, log_ss, LOGL_NOTICE, "DAUD with wildcard match not supported yet\n");
+		}
+	}
+}
+
+/* an incoming xUA DUNA was received from a remote SG */
+void xua_snm_rx_duna(struct osmo_ss7_asp *asp, struct osmo_ss7_as *as, struct xua_msg *xua)
+{
+	struct xua_msg_part *ie_aff_pc = xua_msg_find_tag(xua, M3UA_IEI_AFFECTED_PC);
+	const char *info_str = xua_msg_get_str(xua, M3UA_IEI_INFO_STRING);
+	/* TODO: should our processing depend on the RCTX included? I somehow don't think so */
+	//struct xua_msg_part *ie_rctx = xua_msg_find_tag(xua, M3UA_IEI_ROUTE_CTX);
+	int log_ss = osmo_ss7_asp_get_log_subsys(asp);
+
+	OSMO_ASSERT(ie_aff_pc);
+
+	if (asp->cfg.role != OSMO_SS7_ASP_ROLE_ASP)
+		return;
+
+	LOGPASP(asp, log_ss, LOGL_NOTICE, "Rx DUNA(%s) for %s\n", info_str ? info_str : "",
+		format_affected_pcs_c(xua, asp->inst, ie_aff_pc));
+
+	xua_snm_pc_available(as, (const uint32_t *)ie_aff_pc->dat, ie_aff_pc->len/4, info_str, false);
+}
+
+/* an incoming xUA DAVA was received from a remote SG */
+void xua_snm_rx_dava(struct osmo_ss7_asp *asp, struct osmo_ss7_as *as, struct xua_msg *xua)
+{
+	struct xua_msg_part *ie_aff_pc = xua_msg_find_tag(xua, M3UA_IEI_AFFECTED_PC);
+	const char *info_str = xua_msg_get_str(xua, M3UA_IEI_INFO_STRING);
+	/* TODO: should our processing depend on the RCTX included? I somehow don't think so */
+	//struct xua_msg_part *ie_rctx = xua_msg_find_tag(xua, M3UA_IEI_ROUTE_CTX);
+	int log_ss = osmo_ss7_asp_get_log_subsys(asp);
+
+	OSMO_ASSERT(ie_aff_pc);
+
+	if (asp->cfg.role != OSMO_SS7_ASP_ROLE_ASP)
+		return;
+
+	LOGPASP(asp, log_ss, LOGL_NOTICE, "Rx DAVA(%s) for %s\n", info_str ? info_str : "",
+		format_affected_pcs_c(xua, asp->inst, ie_aff_pc));
+
+	xua_snm_pc_available(as, (const uint32_t *)ie_aff_pc->dat, ie_aff_pc->len/4, info_str, true);
+}