net: lwip: add dns command

Add CMD_DNS when NET_LWIP is enabled to provide the dns command using
lwIP.

Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org>
Acked-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>

cmd/Kconfig

@@ -2027,11 +2027,6 @@ config CMD_SNTP
 	help
 	  Synchronize RTC via network
 
-config CMD_DNS
-	bool "dns"
-	help
-	  Lookup the IP of a hostname
-
 config CMD_LINK_LOCAL
 	bool "linklocal"
 	select LIB_RAND
@@ -2079,6 +2074,12 @@ config CMD_DHCP
 	help
 	  Boot image via network using DHCP/TFTP protocol
 
+config CMD_DNS
+	bool "dns"
+	select PROT_DNS_LWIP if NET_LWIP
+	help
+	  Lookup the IP of a hostname
+
 config CMD_MII
 	bool "mii"
 	imply CMD_MDIO

cmd/net-lwip.c

@@ -27,3 +27,11 @@ U_BOOT_CMD(
 	"[loadAddress] [[hostIPaddr:]bootfilename]"
 );
 #endif
+
+#if defined(CONFIG_CMD_DNS)
+U_BOOT_CMD(
+	dns,	3,	1,	do_dns,
+	"lookup the IP of a hostname",
+	"hostname [envvar]"
+);
+#endif

include/net-lwip.h

@@ -17,6 +17,7 @@ struct netif *net_lwip_get_netif(void);
 int net_lwip_rx(struct udevice *udev, struct netif *netif);
 
 int do_dhcp(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[]);
+int do_dns(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[]);
 int do_ping(struct cmd_tbl *cmdtp, int flag, int argc, char *const argv[]);
 
 #endif /* __NET_LWIP_H__ */

net/lwip/Makefile

@@ -2,5 +2,6 @@ ccflags-y += -I$(srctree)/lib/lwip/lwip/src/include -I$(srctree)/lib/lwip/u-boot
 
 obj-$(CONFIG_$(SPL_)DM_ETH) += net-lwip.o
 obj-$(CONFIG_CMD_DHCP) += dhcp.o
+obj-$(CONFIG_CMD_DNS) += dns.o
 obj-$(CONFIG_CMD_PING) += ping.o
 obj-$(CONFIG_CMD_TFTPBOOT) += tftp.o

net/lwip/dns.c

@@ -0,0 +1,127 @@
+// SPDX-License-Identifier: GPL-2.0+
+/* Copyright (C) 2024 Linaro Ltd. */
+
+#include <command.h>
+#include <console.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;
+	}
+
+	if (dns_cb_arg->var)
+		env_set(dns_cb_arg->var, ipstr);
+
+	printf("%s\n", ipstr);
+}
+
+static int dns_loop(struct udevice *udev, const char *name, const char *var)
+{
+	struct dns_cb_arg dns_cb_arg = { };
+	bool has_server = false;
+	struct netif *netif;
+	ip_addr_t ipaddr;
+	ip_addr_t ns;
+	ulong start;
+	char *nsenv;
+	int ret;
+
+	dns_cb_arg.var = var;
+
+	netif = net_lwip_new_netif(udev);
+	if (!netif)
+		return -1;
+
+	dns_init();
+
+	nsenv = env_get("dnsip");
+	if (nsenv && ipaddr_aton(nsenv, &ns)) {
+		dns_setserver(0, &ns);
+		has_server = true;
+	}
+
+	nsenv = env_get("dnsip2");
+	if (nsenv && ipaddr_aton(nsenv, &ns)) {
+		dns_setserver(1, &ns);
+		has_server = true;
+	}
+
+	if (!has_server) {
+		log_err("No valid name server (dnsip/dnsip2)\n");
+		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;
+			sys_check_timeouts();
+			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)
+		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];
+
+	eth_set_current();
+
+	return dns_loop(eth_get_dev(), name, var);
+}