X-Git-Url: https://git.librecmc.org/?a=blobdiff_plain;f=networking%2Fnslookup.c;h=45c218e6c615947ee010ce4bec6a9fc1694ce05d;hb=ed4393bdc7a4d3b1b59293a3393eb1d6953bac99;hp=8a820ce37cb4329cbd042d7f43c9db37a7a7ad72;hpb=3f5f24646656b761d2d50e57d778f41b13bffa11;p=oweals%2Fbusybox.git

diff --git a/networking/nslookup.c b/networking/nslookup.c
index 8a820ce37..45c218e6c 100644
--- a/networking/nslookup.c
+++ b/networking/nslookup.c
@@ -8,8 +8,31 @@
  * Correct default name server display and explicit name server option
  * added by Ben Zeckel <bzeckel@hmc.edu> June 2001
  *
- * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
+ * Licensed under GPLv2 or later, see file LICENSE in this source tree.
  */
+//config:config NSLOOKUP
+//config:	bool "nslookup (4.5 kb)"
+//config:	default y
+//config:	help
+//config:	nslookup is a tool to query Internet name servers.
+
+//applet:IF_NSLOOKUP(APPLET(nslookup, BB_DIR_USR_BIN, BB_SUID_DROP))
+
+//kbuild:lib-$(CONFIG_NSLOOKUP) += nslookup.o
+
+//usage:#define nslookup_trivial_usage
+//usage:       "[HOST] [SERVER]"
+//usage:#define nslookup_full_usage "\n\n"
+//usage:       "Query the nameserver for the IP address of the given HOST\n"
+//usage:       "optionally using a specified DNS server"
+//usage:
+//usage:#define nslookup_example_usage
+//usage:       "$ nslookup localhost\n"
+//usage:       "Server:     default\n"
+//usage:       "Address:    default\n"
+//usage:       "\n"
+//usage:       "Name:       debian\n"
+//usage:       "Address:    127.0.0.1\n"
 
 #include <resolv.h>
 #include "libbb.h"
@@ -66,7 +89,7 @@ static int print_host(const char *hostname, const char *header)
 	// hint.ai_flags = AI_CANONNAME;
 	rc = getaddrinfo(hostname, NULL /*service*/, &hint, &result);
 
-	if (!rc) {
+	if (rc == 0) {
 		struct addrinfo *cur = result;
 		unsigned cnt = 0;
 
@@ -94,7 +117,7 @@ static int print_host(const char *hostname, const char *header)
 		bb_error_msg("can't resolve '%s'", hostname);
 #endif
 	}
-	if (ENABLE_FEATURE_CLEAN_UP)
+	if (ENABLE_FEATURE_CLEAN_UP && result)
 		freeaddrinfo(result);
 	return (rc != 0);
 }
@@ -124,6 +147,9 @@ static void set_default_dns(const char *server)
 {
 	len_and_sockaddr *lsa;
 
+	if (!server)
+		return;
+
 	/* NB: this works even with, say, "[::1]:5353"! :) */
 	lsa = xhost2sockaddr(server, 53);
 
@@ -133,14 +159,19 @@ static void set_default_dns(const char *server)
 		_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) {
+	/* 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
 }
 
@@ -162,9 +193,17 @@ int nslookup_main(int argc, char **argv)
 	/* (but it also says "may be enabled in /etc/resolv.conf") */
 	/*_res.options |= RES_USE_INET6;*/
 
-	if (argv[2])
-		set_default_dns(argv[2]);
+	set_default_dns(argv[2]);
 
 	server_print();
+
+	/* getaddrinfo and friends are free to request a resolver
+	 * reinitialization. Just in case, set_default_dns() again
+	 * after getaddrinfo (in server_print). This reportedly helps
+	 * with bug 675 "nslookup does not properly use second argument"
+	 * at least on Debian Wheezy and Openwrt AA (eglibc based).
+	 */
+	set_default_dns(argv[2]);
+
 	return print_host(argv[1], "Name:");
 }