Avoid DNS reverse resolution for server names (take 3)

A NFS client should be able to work properly even if the DNS Reverse
record for the server is not set. This means a DNS lookup should not be
done on server names at are passed to GSSAPI. This patch changes the default
behavior to no longer do those types of lookups

This change default behavior could negatively impact some current
environments, so the -D option is also being added that will re-enable
the DNS reverse looks on server names, which are passed to GSSAPI.

Signed-off-by: Simo Sorce <simo@redhat.com>
Signed-off-by: Steve Dickson <steved@redhat.com>

1 files changed, 27 insertions, 4 deletions

diff --git a/utils/gssd/gssd_proc.c b/utils/gssd/gssd_proc.c
index 2280088..af1844c 100644
--- a/utils/gssd/gssd_proc.c
+++ b/utils/gssd/gssd_proc.c
@@ -67,6 +67,7 @@
 #include <errno.h>
 #include <gssapi/gssapi.h>
 #include <netdb.h>
+#include <ctype.h>
 
 #include "gssd.h"
 #include "err_util.h"
@@ -107,6 +108,9 @@ struct pollfd * pollarray;
 
 unsigned long pollsize;  /* the size of pollaray (in pollfd's) */
 
+/* Avoid DNS reverse lookups on server names */
+int avoid_dns = 1;
+
 /*
  * convert a presentation address string to a sockaddr_storage struct. Returns
  * true on success or false on failure.
@@ -165,12 +169,31 @@ addrstr_to_sockaddr(struct sockaddr *sa, const char *node, const char *port)
  * convert a sockaddr to a hostname
  */
 static char *
-sockaddr_to_hostname(const struct sockaddr *sa, const char *addr)
+get_servername(const char *name, const struct sockaddr *sa, const char *addr)
 {
 	socklen_t		addrlen;
 	int			err;
 	char			*hostname;
 	char			hbuf[NI_MAXHOST];
+	unsigned char		buf[sizeof(struct in6_addr)];
+	int			servername = 0;
+
+	if (avoid_dns) {
+		/*
+		 * Determine if this is a server name, or an IP address.
+		 * If it is an IP address, do the DNS lookup otherwise
+		 * skip the DNS lookup.
+		 */
+		servername = 0;
+		if (strchr(name, '.') && inet_pton(AF_INET, name, buf) == 1)
+			servername = 1; /* IPv4 */
+		else if (strchr(name, ':') && inet_pton(AF_INET6, name, buf) == 1)
+			servername = 1; /* or IPv6 */
+
+		if (servername) {
+			return strdup(name);
+		}
+	}
 
 	switch (sa->sa_family) {
 	case AF_INET:
@@ -208,7 +231,7 @@ read_service_info(char *info_file_name, char **servicename, char **servername,
 		  struct sockaddr *addr) {
 #define INFOBUFLEN 256
 	char		buf[INFOBUFLEN + 1];
-	static char	dummy[128];
+	static char	server[128];
 	int		nbytes;
 	static char	service[128];
 	static char	address[128];
@@ -236,7 +259,7 @@ read_service_info(char *info_file_name, char **servicename, char **servername,
 		   "service: %127s %15s version %15s\n"
 		   "address: %127s\n"
 		   "protocol: %15s\n",
-		   dummy,
+		   server,
 		   service, program, version,
 		   address,
 		   protoname);
@@ -258,7 +281,7 @@ read_service_info(char *info_file_name, char **servicename, char **servername,
 	if (!addrstr_to_sockaddr(addr, address, port))
 		goto fail;
 
-	*servername = sockaddr_to_hostname(addr, address);
+	*servername = get_servername(server, addr, address);
 	if (*servername == NULL)
 		goto fail;