+/*
+ * Set the `frozen' flag on a socket. A frozen socket is one in
+ * which all READABLE notifications are ignored, so that data is
+ * not accepted from the peer until the socket is unfrozen. This
+ * exists for two purposes:
+ *
+ * - Port forwarding: when a local listening port receives a
+ * connection, we do not want to receive data from the new
+ * socket until we have somewhere to send it. Hence, we freeze
+ * the socket until its associated SSH channel is ready; then we
+ * unfreeze it and pending data is delivered.
+ *
+ * - Socket buffering: if an SSH channel (or the whole connection)
+ * backs up or presents a zero window, we must freeze the
+ * associated local socket in order to avoid unbounded buffer
+ * growth.
+ */
+#define sk_set_frozen(s, is_frozen) (((*s)->set_frozen) (s, is_frozen))
+
+/*
+ * Return a (dynamically allocated) string giving some information
+ * about the other end of the socket, suitable for putting in log
+ * files. May be NULL if nothing is available at all.
+ */
+#define sk_peer_info(s) (((*s)->peer_info) (s))
+
+/*
+ * Simple wrapper on getservbyname(), needed by ssh.c. Returns the
+ * port number, in host byte order (suitable for printf and so on).
+ * Returns 0 on failure. Any platform not supporting getservbyname
+ * can just return 0 - this function is not required to handle
+ * numeric port specifications.
+ */
+int net_service_lookup(char *service);
+
+/*
+ * Look up the local hostname; return value needs freeing.
+ * May return NULL.
+ */
+char *get_hostname(void);
+
+/*
+ * Trivial socket implementation which just stores an error. Found in
+ * errsock.c.
+ */
+Socket new_error_socket(const char *errmsg, Plug plug);