gbproxy: Add VTY parameter: link stored-msgs-max-length

It was discovered in some prod setups that some TLLIs can maintain quite
long queues of msgb in case its IMSI is not acquired and the tlli is not
pruned due to link-list max-{age,length} being set to 0. As a result,
the osmo-gpbroxy steadly increases the list size of maintained TLLIs, and
some TLLI was found without IMSI catching already 1211 msgb.

Let's allow setting a maxiumum length for the queue storing those msgb
in a per TLLI base. If the limit is reached, oldest msgb are removed
before adding a new one.

Depends: libosmocore Change-Id I33b501e89a8f29e4aa121696bcbb13d4b83db40f

Related: SYS#4297

Change-Id: I4473be8604f80302df03ffdd5a13280dc072f824

3 files changed, 59 insertions, 8 deletions

diff --git a/include/osmocom/sgsn/gb_proxy.h b/include/osmocom/sgsn/gb_proxy.h
index 70de3d715..16082fcde 100644
--- a/include/osmocom/sgsn/gb_proxy.h
+++ b/include/osmocom/sgsn/gb_proxy.h
@@ -105,8 +105,12 @@ struct gbproxy_config {
 	struct osmo_plmn_id core_plmn;
 	uint8_t* core_apn;
 	size_t core_apn_size;
+	/* If !0, Max age to consider a struct gbproxy_link_info as stale */
 	int tlli_max_age;
+	/* If !0, Max len of gbproxy_peer->list (list of struct gbproxy_link_info) */
 	int tlli_max_len;
+	/* If !0, Max len of gbproxy_link_info->stored_msgs (list of msgb) */
+	uint32_t stored_msgs_max_len;
 
 	/* Experimental config */
 	int patch_ptmsi;
@@ -171,6 +175,7 @@ struct gbproxy_link_info {
 
 	int imsi_acq_pending;
 	struct llist_head stored_msgs;
+	uint32_t stored_msgs_len;
 	unsigned vu_gen_tx_bss;
 
 	int is_deregistered;
diff --git a/src/gprs/gb_proxy.c b/src/gprs/gb_proxy.c
index f834ed3e6..8bb67895e 100644
--- a/src/gprs/gb_proxy.c
+++ b/src/gprs/gb_proxy.c
@@ -338,7 +338,8 @@ static int gbproxy_flush_stored_messages(struct gbproxy_peer *peer,
 	     msgb_nsei(msg));
 
 	/* Patch and flush stored messages towards the SGSN */
-	while ((stored_msg = msgb_dequeue(&link_info->stored_msgs))) {
+	while ((stored_msg = msgb_dequeue_count(&link_info->stored_msgs,
+						&link_info->stored_msgs_len))) {
 		struct gprs_gb_parse_context tmp_parse_ctx = {0};
 		tmp_parse_ctx.to_bss = 0;
 		tmp_parse_ctx.peer_nsei = msgb_nsei(stored_msg);
@@ -492,6 +493,24 @@ static int gbproxy_imsi_acquisition(struct gbproxy_peer *peer,
 
 	/* The message cannot be processed since the IMSI is still missing */
 
+	/* If queue is getting too large, drop oldest msgb before adding new one */
+	if (peer->cfg->stored_msgs_max_len > 0) {
+		int exceeded_max_len = link_info->stored_msgs_len
+				   + 1 - peer->cfg->stored_msgs_max_len;
+
+		for (; exceeded_max_len > 0; exceeded_max_len--) {
+			struct msgb *msgb_drop;
+			msgb_drop = msgb_dequeue_count(&link_info->stored_msgs,
+						       &link_info->stored_msgs_len);
+			LOGP(DLLC, LOGL_INFO,
+			     "NSEI=%d(BSS) Dropping stored msgb from list "
+			     "(!acq imsi, length %d, max_len exceeded)\n",
+			     msgb_nsei(msgb_drop), link_info->stored_msgs_len);
+
+			msgb_free(msgb_drop);
+		}
+	}
+
 	/* Enqueue unpatched messages */
 	LOGP(DLLC, LOGL_INFO,
 	     "NSEI=%d(BSS) IMSI acquisition in progress, "
@@ -500,7 +519,8 @@ static int gbproxy_imsi_acquisition(struct gbproxy_peer *peer,
 	     parse_ctx->llc_msg_name ? parse_ctx->llc_msg_name : "BSSGP");
 
 	stored_msg = bssgp_msgb_copy(msg, "process_bssgp_ul");
-	msgb_enqueue(&link_info->stored_msgs, stored_msg);
+	msgb_enqueue_count(&link_info->stored_msgs, stored_msg,
+			   &link_info->stored_msgs_len);
 
 	if (!link_info->imsi_acq_pending) {
 		LOGP(DLLC, LOGL_INFO,
diff --git a/src/gprs/gb_proxy_vty.c b/src/gprs/gb_proxy_vty.c
index cd10abfda..d74335556 100644
--- a/src/gprs/gb_proxy_vty.c
+++ b/src/gprs/gb_proxy_vty.c
@@ -23,6 +23,7 @@
 #include <arpa/inet.h>
 #include <string.h>
 #include <time.h>
+#include <inttypes.h>
 
 #include <osmocom/core/talloc.h>
 #include <osmocom/core/rate_ctr.h>
@@ -128,6 +129,9 @@ static int config_write_gbproxy(struct vty *vty)
 	vty_out(vty, " link-list keep-mode %s%s",
 		get_value_string(keep_modes, g_cfg->keep_link_infos),
 		VTY_NEWLINE);
+	if (g_cfg->stored_msgs_max_len > 0)
+		vty_out(vty, " link stored-msgs-max-length %"PRIu32"%s",
+			g_cfg->stored_msgs_max_len, VTY_NEWLINE);
 
 
 	return CMD_SUCCESS;
@@ -402,6 +406,7 @@ DEFUN(cfg_gbproxy_no_secondary_sgsn,
 }
 
 #define GBPROXY_LINK_LIST_STR "Set TLLI list parameters\n"
+#define GBPROXY_LINK_STR "Set TLLI parameters\n"
 #define GBPROXY_MAX_AGE_STR "Limit maximum age\n"
 
 DEFUN(cfg_gbproxy_link_list_max_age,
@@ -464,6 +469,27 @@ DEFUN(cfg_gbproxy_link_list_keep_mode,
 	return CMD_SUCCESS;
 }
 
+DEFUN(cfg_gbproxy_link_stored_msgs_max_len,
+      cfg_gbproxy_link_stored_msgs_max_len_cmd,
+      "link stored-msgs-max-length <1-99999>",
+      GBPROXY_LINK_STR GBPROXY_MAX_LEN_STR
+      "Maximum number of msgb stored in the logical link waiting to acquire its IMSI\n")
+{
+	g_cfg->stored_msgs_max_len = (uint32_t) atoi(argv[0]);
+
+	return CMD_SUCCESS;
+}
+
+DEFUN(cfg_gbproxy_link_no_stored_msgs_max_len,
+      cfg_gbproxy_link_no_stored_msgs_max_len_cmd,
+      "no link stored-msgs-max-length",
+      NO_STR GBPROXY_LINK_STR GBPROXY_MAX_LEN_STR)
+{
+	g_cfg->stored_msgs_max_len = 0;
+
+	return CMD_SUCCESS;
+}
+
 
 DEFUN(show_gbproxy, show_gbproxy_cmd, "show gbproxy [stats]",
        SHOW_STR "Display information about the Gb proxy\n" "Show statistics\n")
@@ -502,10 +528,6 @@ DEFUN(show_gbproxy_links, show_gbproxy_links_cmd, "show gbproxy links",
 
 		llist_for_each_entry(link_info, &state->logical_links, list) {
 			time_t age = now - link_info->timestamp;
-			int stored_msgs = 0;
-			struct llist_head *iter;
-			llist_for_each(iter, &link_info->stored_msgs)
-				stored_msgs++;
 
 			if (link_info->imsi > 0) {
 				snprintf(mi_buf, sizeof(mi_buf), "(invalid)");
@@ -518,8 +540,10 @@ DEFUN(show_gbproxy_links, show_gbproxy_links_cmd, "show gbproxy links",
 			vty_out(vty, "  TLLI %08x, IMSI %s, AGE %d",
 				link_info->tlli.current, mi_buf, (int)age);
 
-			if (stored_msgs)
-				vty_out(vty, ", STORED %d", stored_msgs);
+			if (link_info->stored_msgs_len)
+				vty_out(vty, ", STORED %"PRIu32"/%"PRIu32,
+					link_info->stored_msgs_len,
+					g_cfg->stored_msgs_max_len);
 
 			if (g_cfg->route_to_sgsn2)
 				vty_out(vty, ", SGSN NSEI %d",
@@ -825,6 +849,7 @@ int gbproxy_vty_init(void)
 	install_element(GBPROXY_NODE, &cfg_gbproxy_link_list_max_age_cmd);
 	install_element(GBPROXY_NODE, &cfg_gbproxy_link_list_max_len_cmd);
 	install_element(GBPROXY_NODE, &cfg_gbproxy_link_list_keep_mode_cmd);
+	install_element(GBPROXY_NODE, &cfg_gbproxy_link_stored_msgs_max_len_cmd);
 	install_element(GBPROXY_NODE, &cfg_gbproxy_no_core_mcc_cmd);
 	install_element(GBPROXY_NODE, &cfg_gbproxy_no_core_mnc_cmd);
 	install_element(GBPROXY_NODE, &cfg_gbproxy_no_match_imsi_cmd);
@@ -834,6 +859,7 @@ int gbproxy_vty_init(void)
 	install_element(GBPROXY_NODE, &cfg_gbproxy_no_acquire_imsi_cmd);
 	install_element(GBPROXY_NODE, &cfg_gbproxy_link_list_no_max_age_cmd);
 	install_element(GBPROXY_NODE, &cfg_gbproxy_link_list_no_max_len_cmd);
+	install_element(GBPROXY_NODE, &cfg_gbproxy_link_no_stored_msgs_max_len_cmd);
 
 	/* broken or deprecated to allow an upgrade path */
 	install_element(GBPROXY_NODE, &cfg_gbproxy_broken_apn_match_cmd);