X-Git-Url: https://git.decadent.org.uk/gitweb/?p=nfs-utils.git;a=blobdiff_plain;f=support%2Fexport%2Fhostname.c;h=3957d80069c5510b9faa6e60a4c876d00573ace5;hp=299fe9937b4d03606dcbc14a749cae3bd7e057a7;hb=a980156c122e975cc185a6c41ef705f166a5765f;hpb=282284fac3c3fe20187f892e3ce15ac319c8acb7

diff --git a/support/export/hostname.c b/support/export/hostname.c
index 299fe99..3957d80 100644
--- a/support/export/hostname.c
+++ b/support/export/hostname.c
@@ -16,6 +16,7 @@
 #include <netinet/in.h>
 #include <arpa/inet.h>
 #include <stdlib.h>
+#include <xlog.h>
 #ifdef TEST
 #define xmalloc malloc
 #else
@@ -216,6 +217,56 @@ matchhostname (const char *h1, const char *h2)
   return status;
 }
 
+
+/* Map IP to hostname, and then map back to addr to make sure it is a
+ * reliable hostname 
+ */
+struct hostent *
+get_reliable_hostbyaddr(const char *addr, int len, int type)
+{
+	struct hostent *hp = NULL;
+
+	struct hostent *reverse;
+	struct hostent *forward;
+	char **sp;
+
+	reverse = gethostbyaddr (addr, len, type);
+	if (!reverse)
+		return NULL;
+
+	/* must make sure the hostent is authorative. */
+
+	reverse = hostent_dup (reverse);
+	forward = gethostbyname (reverse->h_name);
+
+	if (forward) {
+		/* now make sure the "addr" is in the list */
+		for (sp = forward->h_addr_list ; *sp ; sp++) {
+			if (memcmp (*sp, addr, forward->h_length) == 0)
+				break;
+		}
+
+		if (*sp) {
+			/* it's valid */
+			hp = hostent_dup (forward);
+		}
+		else {
+			/* it was a FAKE */
+			xlog (L_WARNING, "Fake hostname %s for %s - forward lookup doesn't match reverse",
+			      reverse->h_name, inet_ntoa(*(struct in_addr*)addr));
+		}
+	}
+	else {
+		/* never heard of it. misconfigured DNS? */
+		xlog (L_WARNING, "Fake hostname %s for %s - forward lookup doesn't exist",
+		      reverse->h_name, inet_ntoa(*(struct in_addr*)addr));
+	}
+
+	free (reverse);
+	return hp;
+}
+
+
 #ifdef TEST
 void
 print_host (struct hostent *hp)