osmo-sgsn: ping GGSN periodically and check for restart counter

Before this commit, echo req/rsp logic was implemented in libgtp but
never used in osmo-sgsn.

This commit adds a timer which periodically sends a GTP ECHO Request to
every GGSN if there's at least one pdpd context associated with it. This
way by checking the restart counter in the ECHO Reply it can be known if
the GGSN was restarted. In this case, logic already present in osmo-sgsn
will terminate all pdp contexts associated with that GGSN.

Change-Id: I9d714726785407859f26bbef052cd0efc28e8dae

3 files changed, 53 insertions, 2 deletions

diff --git a/src/gprs/gprs_sgsn.c b/src/gprs/gprs_sgsn.c
index a58e504c5..55ce09616 100644
--- a/src/gprs/gprs_sgsn.c
+++ b/src/gprs/gprs_sgsn.c
@@ -411,7 +411,7 @@ struct sgsn_pdp_ctx *sgsn_pdp_ctx_alloc(struct sgsn_mm_ctx *mm,
 		return NULL;
 	}
 	llist_add(&pdp->list, &mm->pdp_list);
-	llist_add(&pdp->ggsn_list, &ggsn->pdp_list);
+	sgsn_ggsn_ctx_add_pdp(pdp->ggsn, pdp);
 	llist_add(&pdp->g_list, &sgsn_pdp_ctxts);
 
 	return pdp;
@@ -466,7 +466,7 @@ void sgsn_pdp_ctx_free(struct sgsn_pdp_ctx *pdp)
 	if (pdp->mm)
 		llist_del(&pdp->list);
 	if (pdp->ggsn)
-		llist_del(&pdp->ggsn_list);
+		sgsn_ggsn_ctx_remove_pdp(pdp->ggsn, pdp);
 	llist_del(&pdp->g_list);
 
 	/* _if_ we still have a library handle, at least set it to NULL
@@ -487,6 +487,12 @@ void sgsn_pdp_ctx_free(struct sgsn_pdp_ctx *pdp)
 }
 
 /* GGSN contexts */
+static void echo_timer_cb(void *data)
+{
+	struct sgsn_ggsn_ctx *ggc = (struct sgsn_ggsn_ctx *) data;
+	sgsn_ggsn_echo_req(ggc);
+	osmo_timer_schedule(&ggc->echo_timer, ggc->echo_interval, 0);
+}
 
 struct sgsn_ggsn_ctx *sgsn_ggsn_ctx_alloc(uint32_t id)
 {
@@ -499,9 +505,11 @@ struct sgsn_ggsn_ctx *sgsn_ggsn_ctx_alloc(uint32_t id)
 	ggc->id = id;
 	ggc->gtp_version = 1;
 	ggc->remote_restart_ctr = -1;
+	ggc->echo_interval = -1;
 	/* if we are called from config file parse, this gsn doesn't exist yet */
 	ggc->gsn = sgsn->gsn;
 	INIT_LLIST_HEAD(&ggc->pdp_list);
+	osmo_timer_setup(&ggc->echo_timer, echo_timer_cb, ggc);
 	llist_add(&ggc->list, &sgsn_ggsn_ctxts);
 
 	return ggc;
@@ -722,6 +730,19 @@ int sgsn_ggsn_ctx_drop_all_pdp(struct sgsn_ggsn_ctx *ggsn)
 	return num;
 }
 
+void sgsn_ggsn_ctx_add_pdp(struct sgsn_ggsn_ctx *ggc, struct sgsn_pdp_ctx *pdp)
+{
+	if (llist_empty(&ggc->pdp_list) && ggc->echo_interval > 0)
+		osmo_timer_schedule(&ggc->echo_timer, ggc->echo_interval, 0);
+	llist_add(&pdp->ggsn_list, &ggc->pdp_list);
+}
+void sgsn_ggsn_ctx_remove_pdp(struct sgsn_ggsn_ctx *ggc, struct sgsn_pdp_ctx *pdp)
+{
+	llist_del(&pdp->ggsn_list);
+	if (llist_empty(&ggc->pdp_list) && osmo_timer_pending(&ggc->echo_timer))
+		osmo_timer_del(&ggc->echo_timer);
+}
+
 void sgsn_update_subscriber_data(struct sgsn_mm_ctx *mmctx)
 {
 	OSMO_ASSERT(mmctx != NULL);
diff --git a/src/gprs/sgsn_libgtp.c b/src/gprs/sgsn_libgtp.c
index 2da8c4a74..88cea5d4a 100644
--- a/src/gprs/sgsn_libgtp.c
+++ b/src/gprs/sgsn_libgtp.c
@@ -460,6 +460,11 @@ void sgsn_pdp_upd_gtp_u(struct sgsn_pdp_ctx *pdp, void *addr, size_t alen)
 	gtp_update_context(pdp->ggsn->gsn, pdp->lib, pdp, &pdp->lib->hisaddr0);
 }
 
+void sgsn_ggsn_echo_req(struct sgsn_ggsn_ctx *ggc)
+{
+	gtp_echo_req(ggc->gsn, ggc->gtp_version, NULL, &ggc->remote_addr);
+}
+
 #ifdef BUILD_IU
 /* Callback for RAB assignment response */
 int sgsn_ranap_rab_ass_resp(struct sgsn_mm_ctx *ctx, RANAP_RAB_SetupOrModifiedItemIEs_t *setup_ies)
diff --git a/src/gprs/sgsn_vty.c b/src/gprs/sgsn_vty.c
index 07d4293db..9f9332c32 100644
--- a/src/gprs/sgsn_vty.c
+++ b/src/gprs/sgsn_vty.c
@@ -23,6 +23,7 @@
 #include <netinet/in.h>
 #include <arpa/inet.h>
 #include <time.h>
+#include <inttypes.h>
 
 #include <osmocom/core/talloc.h>
 #include <osmocom/core/utils.h>
@@ -181,6 +182,9 @@ static int config_write_sgsn(struct vty *vty)
 			inet_ntoa(gctx->remote_addr), VTY_NEWLINE);
 		vty_out(vty, " ggsn %u gtp-version %u%s", gctx->id,
 			gctx->gtp_version, VTY_NEWLINE);
+		if (gctx->echo_interval != -1)
+			vty_out(vty, " ggsn %u echo-interval %"PRId32"%s",
+				gctx->id, gctx->echo_interval, VTY_NEWLINE);
 	}
 
 	if (sgsn->cfg.dynamic_lookup)
@@ -356,6 +360,26 @@ DEFUN(cfg_ggsn_gtp_version, cfg_ggsn_gtp_version_cmd,
 	return CMD_SUCCESS;
 }
 
+/* Seee 3GPP TS 29.060 section 7.2.1 */
+DEFUN(cfg_ggsn_echo_interval, cfg_ggsn_echo_interval_cmd,
+	"ggsn <0-255> echo-interval <1-36000>",
+	GGSN_STR "GGSN Number\n"
+	"Send an echo request to this static GGSN every interval.\n"
+	"Interval between echo requests in seconds.\n")
+{
+	uint32_t id = atoi(argv[0]);
+	struct sgsn_ggsn_ctx *ggc = sgsn_ggsn_ctx_find_alloc(id);
+
+	ggc->echo_interval = atoi(argv[1]);
+
+	if (ggc->echo_interval < 60)
+		vty_out(vty, "%% 3GPP TS 29.060 section states inteval should " \
+			     "not be lower than 60 seconds, use this value for " \
+			     "testing purposes only!%s", VTY_NEWLINE);
+
+	return CMD_SUCCESS;
+}
+
 DEFUN(cfg_ggsn_dynamic_lookup, cfg_ggsn_dynamic_lookup_cmd,
 	"ggsn dynamic",
 	GGSN_STR
@@ -1277,6 +1301,7 @@ int sgsn_vty_init(struct sgsn_config *cfg)
 	install_element(SGSN_NODE, &cfg_ggsn_remote_ip_cmd);
 	//install_element(SGSN_NODE, &cfg_ggsn_remote_port_cmd);
 	install_element(SGSN_NODE, &cfg_ggsn_gtp_version_cmd);
+	install_element(SGSN_NODE, &cfg_ggsn_echo_interval_cmd);
 	install_element(SGSN_NODE, &cfg_imsi_acl_cmd);
 	install_element(SGSN_NODE, &cfg_auth_policy_cmd);
 	install_element(SGSN_NODE, &cfg_encrypt_cmd);