net: introduce CONFIG_DNS

Introduce the DNS Kconfig symbol so that various network commands may
use host names without the dns command (CMD_DNS) being selected.

Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org>
CC: E Shattow <e@freeshell.de>

net/Kconfig

@@ -244,11 +244,17 @@ config NET_RANDOM_ETHADDR
 	  generated. It will be saved to the appropriate environment variable,
 	  too.
 
+config DNS
+	bool "Enable DNS resolutions"
+	select PROT_DNS_LWIP if NET_LWIP
+	help
+	  Selecting this will allow the network stack to use server names
+	  in addition to IP addresses.
+
 config WGET
 	bool "Enable wget"
 	select PROT_TCP if NET
 	select PROT_TCP_LWIP if NET_LWIP
-	select PROT_DNS_LWIP if NET_LWIP
 	help
 	  Selecting this will enable wget, an interface to send HTTP requests
 	  via the network stack.

net/Makefile

@@ -10,7 +10,7 @@ ifeq ($(CONFIG_NET),y)
 obj-$(CONFIG_NET)      += arp.o
 obj-$(CONFIG_CMD_BOOTP) += bootp.o
 obj-$(CONFIG_CMD_CDP)  += cdp.o
-obj-$(CONFIG_CMD_DNS)  += dns.o
+obj-$(CONFIG_DNS)  += dns.o
 obj-$(CONFIG_CMD_LINK_LOCAL) += link_local.o
 obj-$(CONFIG_IPV6)     += ndisc.o
 obj-$(CONFIG_$(PHASE_)DM_ETH) += net.o

net/lwip/Makefile

@@ -2,6 +2,7 @@ ccflags-y += -I$(srctree)/lib/lwip/lwip/src/include -I$(srctree)/lib/lwip/u-boot
 
 obj-$(CONFIG_$(PHASE_)DM_ETH) += net-lwip.o
 obj-$(CONFIG_CMD_DHCP) += dhcp.o
+obj-$(CONFIG_DNS) += dns.o
 obj-$(CONFIG_LWIP_ICMP_SHOW_UNREACH) += icmp_unreach.o
 obj-$(CONFIG_CMD_TFTPBOOT) += tftp.o
 obj-$(CONFIG_WGET) += wget.o

net/lwip/dns.c

@@ -0,0 +1,113 @@
+// SPDX-License-Identifier: GPL-2.0+
+/* Copyright (C) 2024 Linaro Ltd. */
+
+#include <command.h>
+#include <console.h>
+#include <env.h>
+#include <lwip/dns.h>
+#include <lwip/timeouts.h>
+#include <net.h>
+#include <time.h>
+
+#define DNS_RESEND_MS 1000
+#define DNS_TIMEOUT_MS 10000
+
+struct dns_cb_arg {
+	ip_addr_t host_ipaddr;
+	const char *var;
+	bool done;
+};
+
+static void do_dns_tmr(void *arg)
+{
+	dns_tmr();
+}
+
+static void dns_cb(const char *name, const ip_addr_t *ipaddr, void *arg)
+{
+	struct dns_cb_arg *dns_cb_arg = arg;
+	char *ipstr = ip4addr_ntoa(ipaddr);
+
+	dns_cb_arg->done = true;
+
+	if (!ipaddr) {
+		printf("DNS: host not found\n");
+		dns_cb_arg->host_ipaddr.addr = 0;
+		return;
+	}
+
+	dns_cb_arg->host_ipaddr.addr = ipaddr->addr;
+
+	if (dns_cb_arg->var)
+		env_set(dns_cb_arg->var, ipstr);
+}
+
+static int dns_loop(struct udevice *udev, const char *name, const char *var)
+{
+	struct dns_cb_arg dns_cb_arg = { };
+	struct netif *netif;
+	ip_addr_t ipaddr;
+	ulong start;
+	int ret;
+
+	dns_cb_arg.var = var;
+
+	netif = net_lwip_new_netif(udev);
+	if (!netif)
+		return CMD_RET_FAILURE;
+
+	if (net_lwip_dns_init()) {
+		net_lwip_remove_netif(netif);
+		return CMD_RET_FAILURE;
+	}
+
+	dns_cb_arg.done = false;
+
+	ret = dns_gethostbyname(name, &ipaddr, dns_cb, &dns_cb_arg);
+
+	if (ret == ERR_OK) {
+		dns_cb(name, &ipaddr, &dns_cb_arg);
+	} else if (ret == ERR_INPROGRESS) {
+		start = get_timer(0);
+		sys_timeout(DNS_RESEND_MS, do_dns_tmr, NULL);
+		do {
+			net_lwip_rx(udev, netif);
+			if (dns_cb_arg.done)
+				break;
+			if (ctrlc()) {
+				printf("\nAbort\n");
+				break;
+			}
+		} while (get_timer(start) < DNS_TIMEOUT_MS);
+		sys_untimeout(do_dns_tmr, NULL);
+	}
+
+	net_lwip_remove_netif(netif);
+
+	if (dns_cb_arg.done && dns_cb_arg.host_ipaddr.addr != 0) {
+		if (!var)
+			printf("%s\n", ipaddr_ntoa(&ipaddr));
+		return CMD_RET_SUCCESS;
+	}
+
+	return CMD_RET_FAILURE;
+}
+
+int do_dns(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[])
+{
+	char *name;
+	char *var = NULL;
+
+	if (argc == 1 || argc > 3)
+		return CMD_RET_USAGE;
+
+	name = argv[1];
+
+	if (argc == 3)
+		var = argv[2];
+
+	if (net_lwip_eth_start() < 0)
+		return CMD_RET_FAILURE;
+
+	return dns_loop(eth_get_dev(), name, var);
+}

net/lwip/net-lwip.c

@@ -147,7 +147,7 @@ static int get_udev_ipv4_info(struct udevice *dev, ip4_addr_t *ip,
  */
 int net_lwip_dns_init(void)
 {
-#if CONFIG_IS_ENABLED(CMD_DNS)
+#if CONFIG_IS_ENABLED(DNS)
 	bool has_server = false;
 	ip_addr_t ns;
 	char *nsenv;
@@ -364,7 +364,7 @@ int net_lwip_rx(struct udevice *udev, struct netif *netif)
  */
 int net_lwip_dns_resolve(char *name_or_ip, ip_addr_t *ip)
 {
-#if defined(CONFIG_CMD_DNS)
+#if defined(CONFIG_DNS)
 	char *var = "_dnsres";
 	char *argv[] = { "dns", name_or_ip, var, NULL };
 	int argc = ARRAY_SIZE(argv) - 1;
@@ -373,7 +373,7 @@ int net_lwip_dns_resolve(char *name_or_ip, ip_addr_t *ip)
 	if (ipaddr_aton(name_or_ip, ip))
 		return 0;
 
-#if defined(CONFIG_CMD_DNS)
+#if defined(CONFIG_DNS)
 	if (do_dns(NULL, 0, argc, argv) != CMD_RET_SUCCESS)
 		return -1;
 

net/net.c

@@ -114,7 +114,7 @@
 #include "bootp.h"
 #include "cdp.h"
 #include "dhcpv6.h"
-#if defined(CONFIG_CMD_DNS)
+#if defined(CONFIG_DNS)
 #include "dns.h"
 #endif
 #include "link_local.h"
@@ -287,7 +287,7 @@ static int on_vlan(const char *name, const char *value, enum env_op op,
 }
 U_BOOT_ENV_CALLBACK(vlan, on_vlan);
 
-#if defined(CONFIG_CMD_DNS)
+#if defined(CONFIG_DNS)
 static int on_dnsip(const char *name, const char *value, enum env_op op,
 	int flags)
 {
@@ -581,7 +581,7 @@ restart:
 			nc_start();
 			break;
 #endif
-#if defined(CONFIG_CMD_DNS)
+#if defined(CONFIG_DNS)
 		case DNS:
 			dns_start();
 			break;
@@ -1506,7 +1506,7 @@ static int net_check_prereq(enum proto_t protocol)
 		}
 		goto common;
 #endif
-#if defined(CONFIG_CMD_DNS)
+#if defined(CONFIG_DNS)
 	case DNS:
 		if (net_dns_server.s_addr == 0) {
 			puts("*** ERROR: DNS server address not given\n");
@@ -1539,7 +1539,7 @@ static int net_check_prereq(enum proto_t protocol)
 			return 1;
 		}
 #if	defined(CONFIG_CMD_PING) || \
-	defined(CONFIG_CMD_DNS) || defined(CONFIG_PROT_UDP)
+	defined(CONFIG_DNS) || defined(CONFIG_PROT_UDP)
 common:
 #endif
 		/* Fall through */

net/wget.c

@@ -393,7 +393,7 @@ int wget_do_request(ulong dst_addr, char *uri)
 	if (string_to_ip(host_name).s_addr) {
 		s = host_name;
 	} else {
-#if IS_ENABLED(CONFIG_CMD_DNS)
+#if IS_ENABLED(CONFIG_DNS)
 		net_dns_resolve = host_name;
 		net_dns_env_var = "httpserverip";
 		if (net_loop(DNS) < 0) {