+/**
+ * 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.