+/**
+ * Perform basic syntax checking on the host-part of an URL:
+ *
+ * - Since ':' is invalid in IPv4 addresses and DNS names, the
+ * presence of ':' causes interpretation as IPv6 address;
+ * - next the first-match-wins algorithm from RFC 3986 is applied;
+ * - else the string is considered as DNS name, to be resolved later.
+ *
+ * \param host The host string to check.
+ * \return True if \a host passes the syntax checks.
+ *
+ * \sa RFC 3986, 3.2.2; RFC 1123, 2.1; RFC 1034, 3.5
+ */
+static bool host_string_ok(const char *host)
+{
+ if (host == NULL || *host == '\0')
+ return false;
+ if (strchr(host, ':') != NULL)
+ return is_valid_ipv6_address(host);
+ if (is_v4_dot_quad(host))
+ return is_valid_ipv4_address(host);
+ return true;
+}
+
+/**
+ * Parse and validate URL string.
+ *
+ * The URL syntax is loosely based on RFC 3986, supporting one of
+ * - "["host"]"[:port] for native IPv6 addresses and
+ * - host[:port] for IPv4 hostnames and DNS names.
+ *
+ * Native IPv6 addresses must be enclosed in square brackets, since
+ * otherwise there is an ambiguity with the port separator `:'.
+ * The 'port' part is always considered to be a number; if absent,
+ * it is set to -1, to indicate that a default port is to be used.
+ *
+ * The following are valid examples:
+ * - 10.10.1.1
+ * - 10.10.1.2:8000
+ * - localhost
+ * - localhost:8001
+ * - [::1]:8000
+ * - [badc0de::1]
+ *
+ * \param url The URL string to take apart.
+ * \param host To return the copied host part of \a url.
+ * \param hostlen The maximum length of \a host.
+ * \param port To return the port number (if any) of \a url.
+ *
+ * \return Pointer to \a host, or NULL if failed.
+ * If NULL is returned, \a host and \a portnum are undefined. If no
+ * port number was present in \a url, \a portnum is set to -1.
+ *
+ * \sa RFC 3986, 3.2.2/3.2.3
+ */
+char *parse_url(const char *url,
+ char *host, ssize_t hostlen,
+ int32_t *port)
+{
+ const char *o = url;
+ char *c = host, *end = c + (hostlen - 1);
+
+ *port = -1;
+
+ if (o == NULL || hostlen < 1)
+ goto failed;
+
+ if (*o == '[') {
+ for (++o; (*c = *o == ']' ? '\0' : *o); c++, o++)
+ if (c == end)
+ goto failed;
+
+ if (*o++ != ']' || (*o != '\0' && *o != ':'))
+ goto failed;
+ } else {
+ for (; (*c = *o == ':'? '\0' : *o); c++, o++)
+ if (c == end)
+ goto failed;
+ }
+
+ if (*o == ':')
+ if (para_atoi32(++o, port) < 0 ||
+ *port < 0 || *port > 0xffff)
+ goto failed;
+
+ if (host_string_ok(host))
+ return host;
+failed:
+ *host = '\0';
+ return NULL;
+}
+
+/**
+ * Stringify port number, resolve into service name where defined.
+ * \param port 2-byte port number, in host-byte-order.
+ * \param transport Transport protocol name (e.g. "udp", "tcp"), or NULL.
+ * \return Pointer to static result buffer.
+ *
+ * \sa getservent(3), services(5), nsswitch.conf(5)
+ */
+const char *stringify_port(int port, const char *transport)
+{
+ static char service[NI_MAXSERV];
+
+ if (port < 0 || port > 0xFFFF) {
+ snprintf(service, sizeof(service), "undefined (%d)", port);
+ } else {
+ struct servent *se = getservbyport(htons(port), transport);
+
+ if (se == NULL)
+ snprintf(service, sizeof(service), "%u", port);
+ else
+ snprintf(service, sizeof(service), "%s", se->s_name);
+ }
+ return service;
+}
+
+/**
+ * Determine the socket type for a given layer-4 protocol.
+ *
+ * \param l4type The symbolic name of the transport-layer protocol.
+ *
+ * \sa ip(7), socket(2)
+ */
+static inline int sock_type(const unsigned l4type)
+{
+ switch (l4type) {
+ case IPPROTO_UDP: return SOCK_DGRAM;
+ case IPPROTO_TCP: return SOCK_STREAM;
+ case IPPROTO_DCCP: return SOCK_DCCP;
+ }
+ return -1; /* not supported here */
+}
+
+/**
+ * Pretty-print transport-layer name.
+ */
+static const char *layer4_name(const unsigned l4type)
+{
+ switch (l4type) {
+ case IPPROTO_UDP: return "UDP";
+ case IPPROTO_TCP: return "TCP";
+ case IPPROTO_DCCP: return "DCCP";
+ }
+ return "UNKNOWN PROTOCOL";
+}
+
+/**
+ * Flowopts: Transport-layer independent encapsulation of socket options.
+ *
+ * These collect individual socket options into a queue, which is disposed of
+ * directly after makesock(). The 'pre_conn_opt' structure is for internal use
+ * only and should not be visible elsewhere.
+ *
+ * \sa setsockopt(2), makesock()
+ */
+struct pre_conn_opt {
+ int sock_level; /**< Second argument to setsockopt() */
+ int sock_option; /**< Third argument to setsockopt() */
+ char *opt_name; /**< Stringified \a sock_option */
+ void *opt_val; /**< Fourth argument to setsockopt() */
+ socklen_t opt_len; /**< Fifth argument to setsockopt() */
+
+ struct list_head node; /**< FIFO, as sockopt order matters. */
+};
+
+/** FIFO list of pre-connection socket options to be set */
+struct flowopts {
+ struct list_head sockopts;
+};
+
+struct flowopts *flowopt_new(void)
+{
+ struct flowopts *new = para_malloc(sizeof(*new));
+
+ INIT_LIST_HEAD(&new->sockopts);
+ return new;
+}
+
+/**
+ * Append new socket option to flowopt queue.
+ *
+ * \param fo The flowopt queue to append to.
+ * \param lev Level at which \a opt resides.
+ * \param opt New option to add.
+ * \param name Stringified name of \a opt.
+ * \param val The value to set \a opt to.
+ * \param len Length of \a val.
+ *
+ * \sa setsockopt(2)
+ */
+void flowopt_add(struct flowopts *fo, int lev, int opt,
+ char *name, const void *val, int len)
+{
+ struct pre_conn_opt *new = para_malloc(sizeof(*new));
+
+ new->sock_option = opt;
+ new->sock_level = lev;
+ new->opt_name = para_strdup(name);
+
+ if (val == NULL) {
+ new->opt_val = NULL;
+ new->opt_len = 0;
+ } else {
+ new->opt_val = para_malloc(len);
+ new->opt_len = len;
+ memcpy(new->opt_val, val, len);
+ }
+
+ list_add_tail(&new->node, &fo->sockopts);
+}
+
+void flowopt_add_bool(struct flowopts *fo, int lev, int opt,
+ char *optname, bool on_or_off)
+{
+ int on = on_or_off; /* kernel takes 'int' */
+
+ flowopt_add(fo, lev, opt, optname, &on, sizeof(on));
+}
+
+/** Set the entire bunch of pre-connection options at once. */
+static void flowopt_setopts(int sockfd, struct flowopts *fo)
+{
+ struct pre_conn_opt *pc;
+
+ if (fo == NULL)
+ return;
+
+ list_for_each_entry(pc, &fo->sockopts, node)
+ if (setsockopt(sockfd, pc->sock_level, pc->sock_option,
+ pc->opt_val, pc->opt_len) < 0) {
+ PARA_EMERG_LOG("Can not set %s socket option: %s",
+ pc->opt_name, strerror(errno));
+ exit(EXIT_FAILURE);
+ }
+}
+
+static void flowopt_cleanup(struct flowopts *fo)
+{
+ struct pre_conn_opt *cur, *next;
+
+ if (fo == NULL)
+ return;
+
+ list_for_each_entry_safe(cur, next, &fo->sockopts, node) {
+ free(cur->opt_name);
+ free(cur->opt_val);
+ free(cur);
+ }
+ free(fo);
+}
+
+/**
+ * Resolve IPv4/IPv6 address and create a ready-to-use active or passive socket.
+ *
+ * \param l4type The layer-4 type (\p IPPROTO_xxx).
+ * \param passive Whether this is a passive (1) or active (0) socket.
+ * \param host Remote or local hostname or IPv/6 address string.
+ * \param port_number Decimal port number.
+ * \param fo Socket options to be set before making the connection.
+ *
+ * This creates a ready-made IPv4/v6 socket structure after looking up the
+ * necessary parameters. The interpretation of \a host depends on the value of
+ * \a passive:
+ * - on a passive socket host is interpreted as an interface IPv4/6 address
+ * (can be left NULL);
+ * - on an active socket, \a host is the peer DNS name or IPv4/6 address
+ * to connect to;
+ * - \a port_number is in either case the numeric port number (not service
+ * string).
+ *
+ * Furthermore, bind(2) is called on passive sockets, and connect(2) on active
+ * sockets. The algorithm tries all possible address combinations until it
+ * succeeds. If \a fo is supplied, options are set and cleanup is performed.
+ *
+ * \return This function returns 1 on success and \a -E_ADDRESS_LOOKUP when no
+ * matching connection could be set up (with details in the error log).