net: Do not try to parse empty IP address string

If the IP address string is empty, then it is no use trying
to parse it. This was seen when handling DNS server strings when
user has made a mistake and defined the DNS server addresses
incorrectly.

Signed-off-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>

subsys/net/ip/utils.c

@@ -683,6 +683,15 @@ bool net_ipaddr_parse(const char *str, size_t str_len, struct sockaddr *addr)
 {
 	int i, count;
 
+	if (!str || str_len == 0) {
+		return false;
+	}
+
+	/* We cannot accept empty string here */
+	if (*str == '\0') {
+		return false;
+	}
+
 	if (*str == '[') {
 #if defined(CONFIG_NET_IPV6)
 		return parse_ipv6(str, str_len, addr, true);