diff --git a/cbindgen.toml b/ffi/cbindgen.toml
similarity index 100%
rename from cbindgen.toml
rename to ffi/cbindgen.toml
diff --git a/ffi/onetun.h b/ffi/onetun.h
new file mode 100644
index 0000000..b44f536
--- /dev/null
+++ b/ffi/onetun.h
@@ -0,0 +1,90 @@
+#include <stdarg.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+
+/**
+ * The capacity of the channel for received IP packets.
+ */
+#define DISPATCH_CAPACITY 1000
+
+typedef struct Bus Bus;
+
+typedef struct Config Config;
+
+typedef struct PortForwardConfig PortForwardConfig;
+
+/**
+ * Creates a new bus struct
+ * # Arguments
+ * *none*
+ * # Returns
+ * A pointer to a bus struct
+ */
+struct Bus *onetun_new_bus(void);
+
+/**
+ * Creates a new config struct for starting a tunnel
+ * # Arguments
+ * * `port_forwards` - A pointer to an array of pointers to port forwards, generated with `onetun_new_port_forward`
+ * * `port_forwards_len` - The length of the array of pointers to port forwards
+ * * `remote_forwards` - A pointer to an array of pointers to port forwards, generated with `onetun_new_port_forward`
+ * * `remote_forwards_len` - The length of the array of pointers to port forwards
+ * * `private_key` - A pointer to an array of chars containing the private key
+ * * `public_key` - A pointer to an array of chars containing the public key
+ * * `endpoint_addr` - A pointer to an array of chars containing the endpoint address
+ * * `endpoint_bind_addr` - A pointer to an array of chars containing the endpoint bind address
+ * * `source_peer_ip` - A pointer to an array of chars containing the source peer IP address
+ * * `keepalive_seconds` - A number representing the keepalive interval, or -1 for None
+ * * `max_transmission_unit` - A number representing the maximum transmission unit
+ * * `log` - A pointer to an array of chars containing the log level (e.g. "INFO", "DEBUG", "TRACE")
+ * * `pcap_file` - A pointer to an array of chars containing the pcap file path, or NULL for none
+ * # Returns
+ * A pointer to a config struct, or NULL on failure
+ * # Safety
+ * All pointers must be valid and not null, unless specified and expected to be NULL.
+ */
+struct Config *onetun_new_config(struct PortForwardConfig *const *port_forwards,
+                                 unsigned int port_forwards_len,
+                                 struct PortForwardConfig *const *remote_forwards,
+                                 unsigned int remote_forwards_len,
+                                 const char *private_key,
+                                 const char *public_key,
+                                 const char *endpoint_addr,
+                                 const char *endpoint_bind_addr,
+                                 const char *source_peer_ip,
+                                 int keepalive_seconds,
+                                 int max_transmission_unit,
+                                 const char *log,
+                                 const char *pcap_file);
+
+/**
+ * Creates a new port forward configuration
+ * # Arguments
+ * * `source` - A list of chars representing a socket address
+ * * `destination` - A list of chars representing a socket address
+ * * `protocol` - Either `tcp` or `udp`
+ * * `port` - Whether this forward is remote: 1 for true, 0 for false
+ * # Returns
+ * A pointer to a port forward config struct, or NULL on failure
+ * # Safety
+ * All pointers must be valid. Strings may be freed after this function returns.
+ */
+struct PortForwardConfig *onetun_new_port_forward(const char *source,
+                                                  const char *destination,
+                                                  const char *protocol,
+                                                  unsigned int remote);
+
+/**
+ * Starts a new onetun tunnel
+ * # Arguments
+ * * `config` - The configuration for the tunnel, generated with `onetun_new_config`
+ * * `bus` - The bus to publish events on, generated with `onetun_new_bus`
+ * # Returns
+ * 0 on success, non-zero on failure
+ * # Safety
+ * All pointers must be valid and not null.
+ */
+int32_t onetun_start_tunnels(struct Config *config, struct Bus *bus);