modem: hl7800: ensure net_if_down is triggered and not ignored

Trigger network dropped based on socket error notifications.
This debounces the network state and only triggers
the network interface to go down if the network
really drops or causes socket problems.
This will ensure upper networking stack layers can
cleanup broken sockets properly.

Debounce DNS resolver refresh.
Only trigger DNS resolver refresh if the DNS address changes.

Signed-off-by: Ryan Erickson <ryan.erickson@lairdconnect.com>

drivers/modem/hl7800.c

@@ -504,6 +504,8 @@ struct hl7800_iface_ctx {
 	enum mdm_hl7800_sleep sleep_state;
 	enum hl7800_lpm low_power_mode;
 	enum mdm_hl7800_network_state network_state;
+	bool network_dropped;
+	bool dns_ready;
 	enum net_operator_status operator_status;
 	struct tm local_time;
 	int32_t local_time_offset;
@@ -1831,7 +1833,7 @@ static void dns_work_cb(struct k_work *work)
 #endif
 						       NULL };
 
-	if (ictx.iface && net_if_is_up(ictx.iface)) {
+	if (ictx.iface && net_if_is_up(ictx.iface) && !ictx.dns_ready) {
 		/* set new DNS addr in DNS resolver */
 		LOG_DBG("Refresh DNS resolver");
 		dnsCtx = dns_resolve_get_default();
@@ -1841,6 +1843,7 @@ static void dns_work_cb(struct k_work *work)
 			LOG_ERR("dns_resolve_init fail (%d)", ret);
 			return;
 		}
+		ictx.dns_ready = true;
 	}
 #endif
 }
@@ -2021,7 +2024,13 @@ static bool on_cmd_atcmdinfo_ipaddr(struct net_buf **buf, uint16_t len)
 	/* store new dns */
 	addr_start = delims[4] + 1;
 	addr_len = delims[5] - addr_start;
+	strncpy(temp_addr_str, addr_start, addr_len);
+	temp_addr_str[addr_len] = 0;
 	if (is_ipv4) {
+		ret = strncmp(temp_addr_str, ictx.dns_v4_string, addr_len);
+		if (ret != 0) {
+			ictx.dns_ready = false;
+		}
 		strncpy(ictx.dns_v4_string, addr_start, addr_len);
 		ictx.dns_v4_string[addr_len] = 0;
 		ret = net_addr_pton(AF_INET, ictx.dns_v4_string, &ictx.dns_v4);
@@ -2029,6 +2038,10 @@ static bool on_cmd_atcmdinfo_ipaddr(struct net_buf **buf, uint16_t len)
 	}
 #ifdef CONFIG_NET_IPV6
 	else {
+		ret = strncmp(temp_addr_str, ictx.dns_v6_string, addr_len);
+		if (ret != 0) {
+			ictx.dns_ready = false;
+		}
 		/* store HL7800 formatted IPv6 DNS string temporarily */
 		strncpy(ictx.dns_v6_string, addr_start, addr_len);
 
@@ -3162,6 +3175,7 @@ static void iface_status_work_cb(struct k_work *work)
 {
 	int ret;
 	hl7800_lock();
+	enum mdm_hl7800_network_state state;
 
 	if (!ictx.initialized && ictx.restarting) {
 		LOG_DBG("Wait for driver init, process network state later");
@@ -3191,6 +3205,15 @@ static void iface_status_work_cb(struct k_work *work)
 
 	LOG_DBG("Updating network state...");
 
+	state = ictx.network_state;
+	/* Ensure we bring the network interface down and then re-check the current state */
+	if (ictx.network_dropped) {
+		ictx.network_dropped = false;
+		state = HL7800_OUT_OF_COVERAGE;
+		k_work_reschedule_for_queue(&hl7800_workq, &ictx.iface_status_work,
+					    IFACE_WORK_DELAY);
+	}
+
 	/* Query operator selection */
 	ret = send_at_cmd(NULL, "AT+COPS?", MDM_CMD_SEND_TIMEOUT, 0, false);
 	if (ret < 0) {
@@ -3198,7 +3221,7 @@ static void iface_status_work_cb(struct k_work *work)
 	}
 
 	/* bring iface up/down */
-	switch (ictx.network_state) {
+	switch (state) {
 	case HL7800_HOME_NETWORK:
 	case HL7800_ROAMING:
 		if (ictx.iface) {
@@ -3210,14 +3233,14 @@ static void iface_status_work_cb(struct k_work *work)
 	default:
 		if (ictx.iface && (ictx.low_power_mode != HL7800_LPM_PSM)) {
 			LOG_DBG("HL7800 iface DOWN");
+			ictx.dns_ready = false;
 			net_if_carrier_off(ictx.iface);
 		}
 		break;
 	}
 
 	if ((ictx.iface && !net_if_is_up(ictx.iface)) ||
-	    (ictx.low_power_mode == HL7800_LPM_PSM &&
+	    (ictx.low_power_mode == HL7800_LPM_PSM && state == HL7800_OUT_OF_COVERAGE)) {
-	     ictx.network_state == HL7800_OUT_OF_COVERAGE)) {
 		hl7800_stop_rssi_work();
 		notify_all_tcp_sockets_closed();
 	} else if (ictx.iface && net_if_is_up(ictx.iface)) {
@@ -3755,7 +3778,11 @@ static bool on_cmd_sock_notif(struct net_buf **buf, uint16_t len)
 
 	id = strtol(value, NULL, 10);
 	notif_val = strtol(delim + 1, NULL, 10);
-	LOG_DBG("+K**P_NOTIF: %d,%d", id, notif_val);
+	if (notif_val == HL7800_TCP_DISCON) {
+		LOG_DBG("+K**P_NOTIF: %d,%d", id, notif_val);
+	} else {
+		LOG_WRN("+K**P_NOTIF: %d,%d", id, notif_val);
+	}
 	sock = socket_from_id(id);
 	if (!sock) {
 		goto done;
@@ -3772,6 +3799,7 @@ static bool on_cmd_sock_notif(struct net_buf **buf, uint16_t len)
 		sock->error = -ENOTCONN;
 		break;
 	default:
+		ictx.network_dropped = true;
 		err = true;
 		sock->error = -EIO;
 		break;
@@ -3788,6 +3816,11 @@ static bool on_cmd_sock_notif(struct net_buf **buf, uint16_t len)
 		if (trigger_sem) {
 			k_sem_give(&sock->sock_send_sem);
 		}
+
+		if (ictx.network_dropped) {
+			k_work_reschedule_for_queue(&hl7800_workq, &ictx.iface_status_work,
+						    IFACE_WORK_DELAY);
+		}
 	}
 done:
 	return true;