nslookup: allow usage of IPv6 addresses or hostnames

 for DNS server name; allow for port specification.
 Tested to work: "nslookup google.com [::1]:5353"

diff --git a/networking/nslookup.c b/networking/nslookup.c
index 73ccb0dddbd68777d0d0859f6da1dc35588ab9fe..8a820ce37cb4329cbd042d7f43c9db37a7a7ad72 100644 (file)
--- a/networking/nslookup.c
+++ b/networking/nslookup.c
@@ -103,14 +103,15 @@ static int print_host(const char *hostname, const char *header)
 static void server_print(void)
 {
        char *server;
+       struct sockaddr *sa;
+
+#if ENABLE_FEATURE_IPV6
+       sa = (struct sockaddr*)_res._u._ext.nsaddrs[0];
+       if (!sa)
+#endif
+               sa = (struct sockaddr*)&_res.nsaddr_list[0];
+       server = xmalloc_sockaddr2dotted_noport(sa);
 
-       server = xmalloc_sockaddr2dotted_noport((struct sockaddr*)&_res.nsaddr_list[0]);
-       /* I honestly don't know what to do if DNS server has _IPv6 address_.
-        * Probably it is listed in
-        * _res._u._ext_.nsaddrs[MAXNS] (of type "struct sockaddr_in6*" each)
-        * but how to find out whether resolver uses
-        * _res.nsaddr_list[] or _res._u._ext_.nsaddrs[], or both?
-        * Looks like classic design from hell, BIND-grade. Hard to surpass. */
        print_host(server, "Server:");
        if (ENABLE_FEATURE_CLEAN_UP)
                free(server);
@@ -119,14 +120,28 @@ static void server_print(void)
 
 /* alter the global _res nameserver structure to use
    an explicit dns server instead of what is in /etc/resolv.conf */
-static void set_default_dns(char *server)
+static void set_default_dns(const char *server)
 {
-       struct in_addr server_in_addr;
+       len_and_sockaddr *lsa;
 
-       if (inet_pton(AF_INET, server, &server_in_addr) > 0) {
+       /* NB: this works even with, say, "[::1]:5353"! :) */
+       lsa = xhost2sockaddr(server, 53);
+
+       if (lsa->u.sa.sa_family == AF_INET) {
                _res.nscount = 1;
-               _res.nsaddr_list[0].sin_addr = server_in_addr;
+               /* struct copy */
+               _res.nsaddr_list[0] = lsa->u.sin;
        }
+#if ENABLE_FEATURE_IPV6
+// Hoping libc will handle an IPv4 address there too,
+// if it so happens that family is indeed AF_INET
+//     if (lsa->u.sa.sa_family == AF_INET6) {
+               _res._u._ext.nscount = 1;
+               /* store a pointer to part of malloc'ed lsa */
+               _res._u._ext.nsaddrs[0] = &lsa->u.sin6;
+               /* must not free(lsa)! */
+//     }
+#endif
 }
 
 int nslookup_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;