ntpd: remove dynamic dns resolution code, too complex. -69 bytes

[oweals/busybox.git] / networking / nslookup.c

diff --git a/networking/nslookup.c b/networking/nslookup.c
index 0036d0d17366749208afdbf5496bce2c30d9d7c6..26287114caee6b83c1c01de0633048979872a329 100644 (file)
--- a/networking/nslookup.c
+++ b/networking/nslookup.c
@@ -15,8 +15,11 @@
 #include "libbb.h"
 
 /*
- *  I'm only implementing non-interactive mode;
- *  I totally forgot nslookup even had an interactive mode.
+ * I'm only implementing non-interactive mode;
+ * I totally forgot nslookup even had an interactive mode.
+ *
+ * This applet is the only user of res_init(). Without it,
+ * you may avoid pulling in _res global from libc.
  */
 
 /* Examples of 'standard' nslookup output
@@ -51,7 +54,6 @@ static int print_host(const char *hostname, const char *header)
 {
        /* We can't use xhost2sockaddr() - we want to get ALL addresses,
         * not just one */
-
        struct addrinfo *result = NULL;
        int rc;
        struct addrinfo hint;
@@ -69,7 +71,7 @@ static int print_host(const char *hostname, const char *header)
                unsigned cnt = 0;
 
                printf("%-10s %s\n", header, hostname);
-               // printf("%s\n", cur->ai_canonname); ?
+               // puts(cur->ai_canonname); ?
                while (cur) {
                        char *dotted, *revhost;
                        dotted = xmalloc_sockaddr2dotted_noport(cur->ai_addr);
@@ -101,33 +103,53 @@ 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);
-       puts("");
+       bb_putchar('\n');
 }
 
 /* alter the global _res nameserver structure to use
-   an explicit dns server instead of what is in /etc/resolv.h */
-static void set_default_dns(char *server)
+   an explicit dns server instead of what is in /etc/resolv.conf */
+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
+       /* Hoped libc can cope with IPv4 address there too.
+        * No such luck, glibc 2.4 segfaults even with IPv6,
+        * maybe I misunderstand how to make glibc use IPv6 addr?
+        * (uclibc 0.9.31+ should work) */
+       if (lsa->u.sa.sa_family == AF_INET6) {
+               // glibc neither SEGVs nor sends any dgrams with this
+               // (strace shows no socket ops):
+               //_res.nscount = 0;
+               _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);
+int nslookup_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int nslookup_main(int argc, char **argv)
 {
        /* We allow 1 or 2 arguments.
@@ -135,18 +157,17 @@ int nslookup_main(int argc, char **argv)
         * optional DNS server with which to do the lookup.
         * More than 3 arguments is an error to follow the pattern of the
         * standard nslookup */
-
-       if (argc < 2 || *argv[1] == '-' || argc > 3)
+       if (!argv[1] || argv[1][0] == '-' || argc > 3)
                bb_show_usage();
 
        /* initialize DNS structure _res used in printing the default
         * name server and in the explicit name server option feature. */
        res_init();
        /* rfc2133 says this enables IPv6 lookups */
-       /* (but it also says "may be enabled in /etc/resolv.conf|) */
+       /* (but it also says "may be enabled in /etc/resolv.conf") */
        /*_res.options |= RES_USE_INET6;*/
 
-       if (argc == 3)
+       if (argv[2])
                set_default_dns(argv[2]);
 
        server_print();