+ * While glibc doesn't define \p UNIX_PATH_MAX, it documents it has being
+ * limited to 108 bytes. On NetBSD it is only 104 bytes though. We trust \p
+ * UNIX_PATH_MAX if it is defined and use the size of the ->sun_path member
+ * otherwise. This should be safe everywhere.
+ */
+#ifndef UNIX_PATH_MAX
+#define UNIX_PATH_MAX (sizeof(((struct sockaddr_un *)0)->sun_path))
+#endif
+
+/* Userland defines for Linux DCCP support. */
+
+#ifndef IPPROTO_DCCP
+#define IPPROTO_DCCP 33 /**< IANA assigned value. */
+#endif
+
+#ifndef SOCK_DCCP
+#define SOCK_DCCP 6 /**< Linux socket type. */
+#endif
+
+#ifndef DCCP_SOCKOPT_RX_CCID
+/** Per-connection CCID support (set/get the RX CCID, since v2.6.30-rc1). */
+#define DCCP_SOCKOPT_RX_CCID 15
+#endif
+
+#ifndef SOL_DCCP
+#define SOL_DCCP 269 /**< Linux socket level. */
+#endif
+
+#ifndef DCCP_SOCKOPT_GET_CUR_MPS
+#define DCCP_SOCKOPT_GET_CUR_MPS 5 /**< Max packet size, RFC 4340, 14. */
+#endif
+
+#ifndef DCCP_SOCKOPT_AVAILABLE_CCIDS
+#define DCCP_SOCKOPT_AVAILABLE_CCIDS 12 /**< List of supported CCIDs. */
+#endif
+
+#ifndef DCCP_SOCKOPT_CCID
+#define DCCP_SOCKOPT_CCID 13 /**< Sets both TX/RX CCID. */
+#endif
+
+#ifndef DCCP_SOCKOPT_TX_CCID
+#define DCCP_SOCKOPT_TX_CCID 14 /**< Set/get the TX CCID. */
+#endif
+
+/**
+ * Flowopts: Transport-layer independent encapsulation of socket options
+ * that need to be registered prior to setting up a connection.
+ */
+struct flowopts;
+
+extern struct flowopts *flowopt_new(void);
+extern void flowopt_add(struct flowopts *fo, int level, int opt,
+ const char *name, const void *val, int len);
+void flowopt_cleanup(struct flowopts *fo);
+/** Flowopt shortcut macros */
+#define OPT_ADD(fo, lev, opt, val, len) flowopt_add(fo, lev, opt, #opt, val, len)
+
+/**
+ * Functions to parse and validate (parts of) URLs.
+ */
+extern char *parse_cidr(const char *cidr,
+ char *addr, ssize_t addrlen, int32_t *netmask);
+extern char *parse_url(const char *url,
+ char *host, ssize_t hostlen, int32_t *port);
+extern const char *stringify_port(int port, const char *transport);
+/**
+ * Ensure that string conforms to the IPv4 address format.