net: Cherry-pick DHCP/DNS improvements

drivers/modem/hl7800.c

@@ -1966,7 +1966,8 @@ static void dns_work_cb(struct k_work *work)
 			}
 		} else {
 			LOG_DBG("Reconfiguring DNS resolver");
-			ret = dns_resolve_reconfigure(dnsCtx, (const char **)dns_servers_str, NULL);
+			ret = dns_resolve_reconfigure(dnsCtx, (const char **)dns_servers_str, NULL,
+						      DNS_SOURCE_MANUAL);
 			if (ret < 0) {
 				LOG_ERR("dns_resolve_reconfigure fail (%d)", ret);
 				retry = true;

drivers/wifi/esp_at/esp.c

@@ -490,18 +490,24 @@
 	struct dns_resolve_context *dnsctx;
 	struct sockaddr_in *addrs = data->dns_addresses;
 	const struct sockaddr *dns_servers[ESP_MAX_DNS + 1] = {};
+	int interfaces[ESP_MAX_DNS];
 	size_t i;
-	int err;
+	int err, ifindex;
+
+	ifindex = net_if_get_by_ifindex(data->net_iface);
 
 	for (i = 0; i < ESP_MAX_DNS; i++) {
 		if (!addrs[i].sin_addr.s_addr) {
 			break;
 		}
 		dns_servers[i] = (struct sockaddr *) &addrs[i];
+		interfaces[i] = ifindex;
 	}
 
 	dnsctx = dns_resolve_get_default();
-	err = dns_resolve_reconfigure(dnsctx, NULL, dns_servers);
+	err = dns_resolve_reconfigure_with_interfaces(dnsctx, NULL, dns_servers,
+						      interfaces,
+						      DNS_SOURCE_MANUAL);
 	if (err) {
 		LOG_ERR("Could not set DNS servers: %d", err);
 	}

include/zephyr/net/dns_resolve.h

@@ -42,6 +42,24 @@
 	DNS_QUERY_TYPE_AAAA = 28
 };
 
+/**
+ * Entity that added the DNS server.
+ */
+enum dns_server_source {
+	/** Source is unknown */
+	DNS_SOURCE_UNKNOWN = 0,
+	/** Server information is added manually, for example by an application */
+	DNS_SOURCE_MANUAL,
+	/** Server information is from DHCPv4 server */
+	DNS_SOURCE_DHCPV4,
+	/** Server information is from DHCPv6 server */
+	DNS_SOURCE_DHCPV6,
+	/** Server information is from IPv6 SLAAC (router advertisement) */
+	DNS_SOURCE_IPV6_RA,
+	/** Server information is from PPP */
+	DNS_SOURCE_PPP,
+};
+
 /** Max size of the resolved name. */
 #ifndef DNS_MAX_NAME_SIZE
 #define DNS_MAX_NAME_SIZE 20
@@ -320,6 +338,7 @@
 /** @cond INTERNAL_HIDDEN */
 
 enum dns_resolve_context_state {
+	DNS_RESOLVE_CONTEXT_UNINITIALIZED = 0,
 	DNS_RESOLVE_CONTEXT_ACTIVE,
 	DNS_RESOLVE_CONTEXT_DEACTIVATING,
 	DNS_RESOLVE_CONTEXT_INACTIVE,
@@ -344,6 +363,9 @@
 		 */
 		int if_index;
 
+		/** Source of the DNS server, e.g., manual, DHCPv4/6, etc. */
+		enum dns_server_source source;
+
 		/** Is this server mDNS one */
 		uint8_t is_mdns : 1;
 
@@ -517,12 +539,65 @@
  * @param servers_sa DNS server addresses as struct sockaddr. The array
  * is NULL terminated. Port numbers are optional in struct sockaddr, the
  * default will be used if set to 0.
+ * @param source Source of the DNS servers, e.g., manual, DHCPv4/6, etc.
  *
  * @return 0 if ok, <0 if error.
  */
 int dns_resolve_reconfigure(struct dns_resolve_context *ctx,
 			    const char *servers_str[],
-			    const struct sockaddr *servers_sa[]);
+			    const struct sockaddr *servers_sa[],
+			    enum dns_server_source source);
+
+/**
+ * @brief Reconfigure DNS resolving context with new server list and
+ *        allowing servers to be specified to a specific network interface.
+ *
+ * @param ctx DNS context
+ * @param servers_str DNS server addresses using textual strings. The
+ *        array is NULL terminated. The port number can be given in the string.
+ *        Syntax for the server addresses with or without port numbers:
+ *           IPv4        : 10.0.9.1
+ *           IPv4 + port : 10.0.9.1:5353
+ *           IPv6        : 2001:db8::22:42
+ *           IPv6 + port : [2001:db8::22:42]:5353
+ * @param servers_sa DNS server addresses as struct sockaddr. The array
+ *        is NULL terminated. Port numbers are optional in struct sockaddr, the
+ *        default will be used if set to 0.
+ * @param interfaces Network interfaces to which the DNS servers are bound.
+ *        This is an array of network interface indices. The array must be
+ *        the same length as the servers_str and servers_sa arrays.
+ * @param source Source of the DNS servers, e.g., manual, DHCPv4/6, etc.
+ *
+ * @return 0 if ok, <0 if error.
+ */
+int dns_resolve_reconfigure_with_interfaces(struct dns_resolve_context *ctx,
+					    const char *servers_str[],
+					    const struct sockaddr *servers_sa[],
+					    int interfaces[],
+					    enum dns_server_source source);
+
+/**
+ * @brief Remove servers from the DNS resolving context.
+ *
+ * @param ctx DNS context
+ * @param if_index Network interface from which the DNS servers are removed.
+ *
+ * @return 0 if ok, <0 if error.
+ */
+int dns_resolve_remove(struct dns_resolve_context *ctx, int if_index);
+
+/**
+ * @brief Remove servers from the DNS resolving context that were added by
+ *        a specific source.
+ *
+ * @param ctx DNS context
+ * @param if_index Network interface from which the DNS servers are removed.
+ * @param source Source of the DNS servers, e.g., manual, DHCPv4/6, etc.
+ *
+ * @return 0 if ok, <0 if error.
+ */
+int dns_resolve_remove_source(struct dns_resolve_context *ctx, int if_index,
+			      enum dns_server_source source);
 
 /**
  * @brief Cancel a pending DNS query.
@@ -664,6 +739,15 @@
 
 /** @cond INTERNAL_HIDDEN */
 
+/**
+ * @brief Get string representation of the DNS server source.
+ *
+ * @param source Source of the DNS server.
+ *
+ * @return String representation of the DNS server source.
+ */
+const char *dns_get_source_str(enum dns_server_source source);
+
 /**
  * @brief Initialize DNS subsystem.
  */

subsys/net/ip/Kconfig.stack

@@ -17,6 +17,7 @@ config NET_TX_STACK_SIZE
 
 config NET_RX_STACK_SIZE
 	int "RX thread stack size"
+	default 1792 if DNS_RESOLVER
 	default 1500
 	help
 	  Set the RX thread stack size in bytes. The RX thread is waiting

subsys/net/ip/ipv6_nbr.c

@@ -2469,7 +2469,10 @@
 	const struct sockaddr *dns_servers[] = {
 		(struct sockaddr *)&dns, NULL
 	};
+	int interfaces[] = {
+		net_if_get_by_iface(net_pkt_iface(pkt))
+	};
 	size_t rdnss_size;
 	int ret;
 
 	rdnss = (struct net_icmpv6_nd_opt_rdnss *) net_pkt_get_data(pkt, &rdnss_access);
@@ -2505,7 +2508,9 @@
 
 	/* TODO: Handle lifetime. */
 	ctx = dns_resolve_get_default();
-	ret = dns_resolve_reconfigure(ctx, NULL, dns_servers);
+	ret = dns_resolve_reconfigure_with_interfaces(ctx, NULL, dns_servers,
+						      interfaces,
+						      DNS_SOURCE_IPV6_RA);
 	if (ret < 0) {
 		NET_DBG("Failed to set RDNSS resolve address: %d", ret);
 	}

subsys/net/l2/ppp/ipcp.c

@@ -362,7 +362,9 @@
 		(struct sockaddr *) &dns2,
 		NULL
 	};
+	int ifindex = net_if_get_by_iface(ctx->iface);
+	int interfaces[2] = { ifindex, ifindex };
 	int ret;
 
 	if (!dns1.sin_addr.s_addr) {
 		return;
@@ -373,7 +375,9 @@
 	}
 
 	dnsctx = dns_resolve_get_default();
-	ret = dns_resolve_reconfigure(dnsctx, NULL, dns_servers);
+	ret = dns_resolve_reconfigure_with_interfaces(dnsctx, NULL, dns_servers,
+						      interfaces,
+						      DNS_SOURCE_PPP);
 	if (ret < 0) {
 		NET_ERR("Could not set DNS servers");
 		return;

subsys/net/lib/dhcpv4/Kconfig

@@ -96,6 +96,23 @@ config NET_DHCPV4_OPTION_PRINT_IGNORED
 	  received and ignored. If this is not set, then we print these as unknown
 	  options.
 
+config NET_DHCPV4_DNS_SERVER_VIA_INTERFACE
+	bool "Make DNS servers specific to the network interface"
+	depends on NET_DHCPV4_OPTION_DNS_ADDRESS
+	default y
+	help
+	  If this is set, then if the system has multiple network interfaces
+	  and each has DHCP enabled, then assign DNS servers received from that
+	  network interface, to that specific interface.
+	  If this option is not set, then any interface can be used for all
+	  the configured DNS server addresses when doing DNS queries.
+	  Example: We receive DNS server 192.0.2.53 DHCPv4 option from Wi-Fi
+	  interface and DNS server 198.51.100.53 from Ethernet interface.
+	  When this option is set, the DNS resolver will use DNS server
+	  192.0.2.53 when sending DNS query to the Wi-Fi interface and DNS
+	  server 198.51.100.53 when sending DNS query to the Ethernet
+	  interface.
+
 endif # NET_DHCPV4
 
 config NET_DHCPV4_SERVER

subsys/net/lib/dhcpv4/dhcpv4.c

@@ -1171,7 +1171,27 @@
 			for (uint8_t i = 0; i < dns_servers_cnt; i++) {
 				dnses[i].sin_family = AF_INET;
 			}
-			status = dns_resolve_reconfigure(ctx, NULL, dns_servers);
+
+			if (IS_ENABLED(CONFIG_NET_DHCPV4_DNS_SERVER_VIA_INTERFACE)) {
+				/* If we are using the interface to resolve DNS servers,
+				 * we need to save the interface index.
+				 */
+				int ifindex = net_if_get_by_iface(iface);
+				int interfaces[MAX_DNS_SERVERS];
+
+				for (uint8_t i = 0; i < dns_servers_cnt; i++) {
+					interfaces[i] = ifindex;
+				}
+
+				status = dns_resolve_reconfigure_with_interfaces(ctx, NULL,
+										 dns_servers,
+										 interfaces,
+										 DNS_SOURCE_DHCPV4);
+			} else {
+				status = dns_resolve_reconfigure(ctx, NULL, dns_servers,
+								 DNS_SOURCE_DHCPV4);
+			}
+
 			if (status < 0) {
 				NET_DBG("options_dns, failed to set "
 					"resolve address: %d", status);
@@ -1650,6 +1670,17 @@
 			if (!net_if_ipv4_addr_rm(iface, &iface->config.dhcpv4.requested_ip)) {
 				NET_DBG("Failed to remove addr from iface");
 			}
+
+			/* Remove DNS servers as interface is gone. We only need to
+			 * do this for this interface. If using global setting, the
+			 * DNS servers are removed automatically when the interface
+			 * comes back up.
+			 */
+			if (IS_ENABLED(CONFIG_NET_DHCPV4_DNS_SERVER_VIA_INTERFACE)) {
+				dns_resolve_remove_source(dns_resolve_get_default(),
+							  net_if_get_by_iface(iface),
+							  DNS_SOURCE_DHCPV4);
+			}
 		}
 	} else if (mgmt_event == NET_EVENT_IF_UP) {
 		NET_DBG("Interface %p coming up", iface);
@@ -1914,6 +1945,12 @@
 		NET_DBG("state=%s",
 			net_dhcpv4_state_name(iface->config.dhcpv4.state));
 
+		if (IS_ENABLED(CONFIG_NET_DHCPV4_DNS_SERVER_VIA_INTERFACE)) {
+			dns_resolve_remove_source(dns_resolve_get_default(),
+						  net_if_get_by_iface(iface),
+						  DNS_SOURCE_DHCPV4);
+		}
+
 		sys_slist_find_and_remove(&dhcpv4_ifaces,
 					  &iface->config.dhcpv4.node);
 

subsys/net/lib/dhcpv6/Kconfig

@@ -31,6 +31,23 @@ config NET_DHCPV6_OPTION_DNS_ADDRESS
 	  option from the server, and if available, use obtained information
 	  to configure DNS resolver.
 
+config NET_DHCPV6_DNS_SERVER_VIA_INTERFACE
+	bool "Make DNS servers specific to the network interface"
+	depends on NET_DHCPV6_OPTION_DNS_ADDRESS
+	default y
+	help
+	  If this is set, then if the system has multiple network interfaces
+	  and each has DHCP enabled, then assign DNS servers received from that
+	  network interface, to that specific interface.
+	  If this option is not set, then any interface can be used for all
+	  the configured DNS server addresses when doing DNS queries.
+	  Example: We receive DNS server 2001:db8::1:53 DHCPv6 option from Wi-Fi
+	  interface and DNS server 2001:db8::2:53 from Ethernet interface.
+	  When this option is set, the DNS resolver will use DNS server
+	  2001:db8::1:53 when sending DNS query to the Wi-Fi interface and DNS
+	  server 2001:db8::2:53 when sending DNS query to the Ethernet
+	  interface.
+
 if NET_DHCPV6
 module = NET_DHCPV6
 module-dep = NET_LOG

subsys/net/lib/dhcpv6/dhcpv6.c

@@ -1412,7 +1412,27 @@
 	}
 
 	ctx = dns_resolve_get_default();
-	status = dns_resolve_reconfigure(ctx, NULL, dns_servers);
+
+	if (IS_ENABLED(CONFIG_NET_DHCPV6_DNS_SERVER_VIA_INTERFACE)) {
+		/* If we are using the interface to resolve DNS servers,
+		 * we need to save the interface index.
+		 */
+		int ifindex = net_if_get_by_iface(net_pkt_iface(pkt));
+		int interfaces[MAX_DNS_SERVERS];
+
+		for (uint8_t i = 0; i < server_count; i++) {
+			interfaces[i] = ifindex;
+		}
+
+		status = dns_resolve_reconfigure_with_interfaces(ctx, NULL,
+								 dns_servers,
+								 interfaces,
+								 DNS_SOURCE_DHCPV6);
+	} else {
+		status = dns_resolve_reconfigure(ctx, NULL, dns_servers,
+						 DNS_SOURCE_DHCPV6);
+	}
+
 	if (status < 0) {
 		NET_DBG("Failed to reconfigure DNS resolver from DHCPv6 "
 			"option: %d", status);
@@ -2199,6 +2219,17 @@
 	if (mgmt_event == NET_EVENT_IF_DOWN) {
 		NET_DBG("Interface %p going down", iface);
 		dhcpv6_set_timeout(iface, UINT64_MAX);
+
+		/* Remove DNS servers as interface is gone. We only need to
+		 * do this for this interface. If using global setting, the
+		 * DNS servers are removed automatically when the interface
+		 * comes back up.
+		 */
+		if (IS_ENABLED(CONFIG_NET_DHCPV6_DNS_SERVER_VIA_INTERFACE)) {
+			dns_resolve_remove_source(dns_resolve_get_default(),
+						  net_if_get_by_iface(iface),
+						  DNS_SOURCE_DHCPV6);
+		}
 	} else if (mgmt_event == NET_EVENT_IF_UP) {
 		NET_DBG("Interface %p coming up", iface);
 		dhcpv6_enter_state(iface, NET_DHCPV6_INIT);
@@ -2293,6 +2324,12 @@
 
 		(void)dhcpv6_enter_state(iface, NET_DHCPV6_DISABLED);
 
+		if (IS_ENABLED(CONFIG_NET_DHCPV6_DNS_SERVER_VIA_INTERFACE)) {
+			dns_resolve_remove_source(dns_resolve_get_default(),
+						  net_if_get_by_iface(iface),
+						  DNS_SOURCE_DHCPV6);
+		}
+
 		sys_slist_find_and_remove(&dhcpv6_ifaces,
 					  &iface->config.dhcpv6.node);
 

subsys/net/lib/dns/Kconfig

@@ -121,6 +121,19 @@ config DNS_SERVER5
 
 endif # DNS_SERVER_IP_ADDRESSES
 
+config DNS_RECONFIGURE_CLEANUP
+	bool "Cleanup old DNS server entries when reconfiguring"
+	help
+	  If calling dns_resolve_reconfigure() when new DNS servers
+	  are being set, for example if receiving new ones from DHCP server,
+	  remove the old entries before setting up the new ones.
+	  If you have only one network interface, then this can be enabled.
+	  If you have multiple network interfaces, then this should be disabled
+	  because the later configuration update would remove the entries
+	  set by the other network interface configuration.
+	  The previous default in Zephyr 4.1 or earlier was to have this enabled.
+	  The current default in Zephyr 4.2 is to disable this option.
+
 config DNS_NUM_CONCUR_QUERIES
 	int "Number of simultaneous DNS queries per one DNS context"
 	default 1