+
+/**
+ * nfs_callback_address - acquire our local network address
+ * @sap: pointer to address of remote
+ * @sap_len: length of address
+ * @buf: pointer to buffer to be filled in with local network address
+ * @buflen: IN: length of buffer to fill in; OUT: length of filled-in address
+ *
+ * Discover a network address that an NFSv4 server can use to call us back.
+ * On multi-homed clients, this address depends on which NIC we use to
+ * route requests to the server.
+ *
+ * Returns 1 and fills in @buf if an unambiguous local address is
+ * available; returns 1 and fills in an appropriate ANYADDR address
+ * if a local address isn't available; otherwise, returns zero.
+ */
+int nfs_callback_address(const struct sockaddr *sap, const socklen_t salen,
+ struct sockaddr *buf, socklen_t *buflen)
+{
+ struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)buf;
+
+ if (nfs_ca_sockname(sap, salen, buf, buflen) == 0)
+ if (nfs_ca_gai(sap, salen, buf, buflen) == 0)
+ goto out_failed;
+
+ /*
+ * The server can't use an interface ID that was generated
+ * here on the client, so always clear sin6_scope_id.
+ */
+ if (sin6->sin6_family == AF_INET6)
+ sin6->sin6_scope_id = 0;
+
+ return 1;
+
+out_failed:
+ *buflen = 0;
+ if (verbose)
+ nfs_error(_("%s: failed to construct callback address"));
+ return 0;
+
+}