net: dns: return error codes

The resolv() function used to return the IP address. When net_udp_new()
fails we return an error code though which the callers of resolv() take
as an IP address. This is wrong of course and we could return 0 in this
case. Instead we return an error code and pass the resolved IP as a
pointer which allows us to return proper error codes.

This patch also adds error messages and error returns to the various
callers of resolv() which used to just continue with a zero IP and
let the user figure out what went wrong.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

5 files changed, 35 insertions, 23 deletions

diff --git a/net/dhcp.c b/net/dhcp.c
index 79aa75d878..670a6a6422 100644
--- a/net/dhcp.c
+++ b/net/dhcp.c
@@ -562,6 +562,8 @@ out:
 
 int dhcp_set_result(struct eth_device *edev, struct dhcp_result *res)
 {
+	int ret;
+
 	net_set_ip(edev, res->ip);
 	net_set_netmask(edev, res->netmask);
 	net_set_gateway(res->gateway);
@@ -580,8 +582,8 @@ int dhcp_set_result(struct eth_device *edev, struct dhcp_result *res)
 	if (res->tftp_server_name) {
 		IPaddr_t ip;
 
-		ip = resolv(res->tftp_server_name);
-		if (ip)
+		ret = resolv(res->tftp_server_name, &ip);
+		if (!ret)
 			net_set_serverip_empty(ip);
 	} else if (res->serverip) {
 		net_set_serverip_empty(res->serverip);
diff --git a/net/dns.c b/net/dns.c
index a3a3b94145..4516235df2 100644
--- a/net/dns.c
+++ b/net/dns.c
@@ -201,26 +201,27 @@ static void dns_handler(void *ctx, char *packet, unsigned len)
 		net_eth_to_udplen(packet));
 }
 
-IPaddr_t resolv(const char *host)
+int resolv(const char *host, IPaddr_t *ip)
 {
-	IPaddr_t ip;
+	IPaddr_t nameserver;
 
-	if (!string_to_ip(host, &ip))
-		return ip;
+	if (!string_to_ip(host, ip))
+		return 0;
 
 	dns_ip = 0;
+	*ip = 0;
 
 	dns_state = STATE_INIT;
 
-	ip = net_get_nameserver();
-	if (!ip) {
+	nameserver = net_get_nameserver();
+	if (!nameserver) {
 		pr_err("no nameserver specified in $net.nameserver\n");
 		return 0;
 	}
 
-	pr_debug("resolving host %s via nameserver %pI4\n", host, &ip);
+	pr_debug("resolving host %s via nameserver %pI4\n", host, &nameserver);
 
-	dns_con = net_udp_new(ip, DNS_PORT, dns_handler, NULL);
+	dns_con = net_udp_new(nameserver, DNS_PORT, dns_handler, NULL);
 	if (IS_ERR(dns_con))
 		return PTR_ERR(dns_con);
 	dns_timer_start = get_time_ns();
@@ -240,25 +241,32 @@ IPaddr_t resolv(const char *host)
 
 	net_unregister(dns_con);
 
-	pr_debug("host %s is at %pI4\n", host, &dns_ip);
+	if (dns_ip) {
+		pr_debug("host %s is at %pI4\n", host, &dns_ip);
+	} else {
+		pr_debug("host %s not found\n", host);
+		return -ENOENT;
+	}
+
+	*ip = dns_ip;
 
-	return dns_ip;
+	return 0;
 }
 
 #ifdef CONFIG_CMD_HOST
 static int do_host(int argc, char *argv[])
 {
 	IPaddr_t ip;
+	int ret;
 
 	if (argc != 2)
 		return COMMAND_ERROR_USAGE;
 
-	ip = resolv(argv[1]);
-	if (!ip)
+	ret = resolv(argv[1], &ip);
+	if (ret)
 		printf("unknown host %s\n", argv[1]);
-	else {
+	else
 		printf("%s is at %pI4\n", argv[1], &ip);
-	}
 
 	return 0;
 }
diff --git a/net/net.c b/net/net.c
index 63f42fa5cc..f1a7df0298 100644
--- a/net/net.c
+++ b/net/net.c
@@ -107,7 +107,9 @@ IPaddr_t getenv_ip(const char *name)
 	if (!string_to_ip(var, &ip))
 		return ip;
 
-	return resolv((char*)var);
+	resolv(var, &ip);
+
+	return ip;
 }
 
 int setenv_ip(const char *name, IPaddr_t ip)
diff --git a/net/ping.c b/net/ping.c
index b5926280e0..a71f59a805 100644
--- a/net/ping.c
+++ b/net/ping.c
@@ -61,9 +61,9 @@ static int do_ping(int argc, char *argv[])
 	if (argc < 2)
 		return COMMAND_ERROR_USAGE;
 
-	net_ping_ip = resolv(argv[1]);
-	if (!net_ping_ip) {
-		printf("unknown host %s\n", argv[1]);
+	ret = resolv(argv[1], &net_ping_ip);
+	if (ret) {
+		printf("Cannot resolve \"%s\": %s\n", argv[1], strerror(-ret));
 		return 1;
 	}
 
diff --git a/net/sntp.c b/net/sntp.c
index 577c859616..b4e6d6439c 100644
--- a/net/sntp.c
+++ b/net/sntp.c
@@ -120,9 +120,9 @@ s64 sntp(const char *server)
 	if (!server)
 		return -EINVAL;
 
-	net_sntp_ip = resolv(server);
-	if (!net_sntp_ip) {
-		printf("unknown host %s\n", server);
+	ret = resolv(server, &net_sntp_ip);
+	if (ret) {
+		printf("Cannot resolve \"%s\": %s\n", server, strerror(-ret));;
 		return 1;
 	}