+#ifdef HAVE_GETIFADDRS
+
+#include <ifaddrs.h>
+#include <time.h>
+
+/**
+ * from_local - determine whether request comes from the local system
+ * @sap: pointer to socket address to check
+ *
+ * With virtual hosting, each hardware network interface can have
+ * multiple network addresses. On such machines the number of machine
+ * addresses can be surprisingly large.
+ *
+ * We also expect the local network configuration to change over time,
+ * so call getifaddrs(3) more than once, but not too often.
+ *
+ * Returns TRUE if the sockaddr contains an address of one of the local
+ * network interfaces. Otherwise FALSE is returned.
+ */
+int
+from_local(const struct sockaddr *sap)
+{
+ static struct ifaddrs *ifaddr = NULL;
+ static time_t last_update = 0;
+ struct ifaddrs *ifa;
+ unsigned int count;
+ time_t now;
+
+ if (time(&now) == ((time_t)-1)) {
+ xlog(L_ERROR, "%s: time(2): %m", __func__);
+
+ /* If we don't know what time it is, use the
+ * existing ifaddr list, if one exists */
+ now = last_update;
+ if (ifaddr == NULL)
+ now++;
+ }
+ if (now != last_update) {
+ xlog(D_GENERAL, "%s: updating local if addr list", __func__);
+
+ if (ifaddr)
+ freeifaddrs(ifaddr);
+
+ if (getifaddrs(&ifaddr) == -1) {
+ xlog(L_ERROR, "%s: getifaddrs(3): %m", __func__);
+ return FALSE;
+ }
+
+ last_update = now;
+ }
+
+ count = 0;
+ for (ifa = ifaddr; ifa; ifa = ifa->ifa_next) {
+ if ((ifa->ifa_flags & IFF_UP) &&
+ nfs_compare_sockaddr(sap, ifa->ifa_addr)) {
+ xlog(D_GENERAL, "%s: incoming address matches "
+ "local interface address", __func__);
+ return TRUE;
+ } else
+ count++;
+ }
+
+ xlog(D_GENERAL, "%s: checked %u local if addrs; "
+ "incoming address not found", __func__, count);
+ return FALSE;
+}
+
+#else /* !HAVE_GETIFADDRS */
+