// SPDX-License-Identifier: ISC OR GPL-2.0-or-later
/*
 * Public definitions pertaining to the Forwarding Plane Manager component.
 *
 * Permission is granted to use, copy, modify and/or distribute this
 * software under either one of the licenses below.
 *
 * Note that if you use other files from the Quagga tree directly or
 * indirectly, then the licenses in those files still apply.
 *
 * Please retain both licenses below when modifying this code in the
 * Quagga tree.
 *
 * Copyright (C) 2012 by Open Source Routing.
 * Copyright (C) 2012 by Internet Systems Consortium, Inc. ("ISC")
 */

/*
 * License Option 1: GPL
 * License Option 2: ISC License
 */

#ifndef _FPM_H
#define _FPM_H

/*
 * The Forwarding Plane Manager (FPM) is an optional component that
 * may be used in scenarios where the router has a forwarding path
 * that is distinct from the kernel, commonly a hardware-based fast
 * path. It is responsible for programming forwarding information
 * (such as routes and nexthops) in the fast path.
 *
 * In Quagga, the Routing Information Base is maintained in the
 * 'zebra' infrastructure daemon. Routing protocols communicate their
 * best routes to zebra, and zebra computes the best route across
 * protocols for each prefix. This latter information comprises the
 * bulk of the Forwarding Information Base.
 *
 * This header file defines a point-to-point interface using which
 * zebra can update the FPM about changes in routes. The communication
 * takes place over a stream socket. The FPM listens on a well-known
 * TCP port, and zebra initiates the connection.
 *
 * All messages sent over the connection start with a short FPM
 * header, fpm_msg_hdr_t. In the case of route add/delete messages,
 * the header is followed by a netlink message. Zebra should send a
 * complete copy of the forwarding table(s) to the FPM, including
 * routes that it may have picked up from the kernel.
 *
 * The FPM interface uses replace semantics. That is, if a 'route add'
 * message for a prefix is followed by another 'route add' message, the
 * information in the second message is complete by itself, and replaces
 * the information sent in the first message.
 *
 * If the connection to the FPM goes down for some reason, the client
 * (zebra) should send the FPM a complete copy of the forwarding
 * table(s) when it reconnects.
 */

/*
 * Local host as a default server for fpm connection
 */
#define FPM_DEFAULT_IP              (htonl (INADDR_LOOPBACK))

/*
 * Largest message that can be sent to or received from the FPM.
 */
#define FPM_MAX_MSG_LEN 4096

#ifdef __SUNPRO_C
#pragma pack(1)
#endif

/*
 * Header that precedes each fpm message to/from the FPM.
 */
typedef struct fpm_msg_hdr_t_ {
	/*
	 * Protocol version.
	 */
	uint8_t version;

	/*
	 * Type of message, see below.
	 */
	uint8_t msg_type;

	/*
	 * Length of entire message, including the header, in network byte
	 * order.
	 */
	uint16_t msg_len;
} __attribute__((packed)) fpm_msg_hdr_t;

#ifdef __SUNPRO_C
#pragma pack()
#endif

/*
 * The current version of the FPM protocol is 1.
 */
#define FPM_PROTO_VERSION 1

typedef enum fpm_msg_type_e_ {
	FPM_MSG_TYPE_NONE = 0,

	/*
	 * Indicates that the payload is a completely formed netlink
	 * message.
	 *
	 * XXX Netlink cares about the alignment of messages. When any
	 * FPM_MSG_TYPE_NETLINK messages are sent over a channel, then all
	 * messages should be sized such that netlink alignment is
	 * maintained.
	 */
	FPM_MSG_TYPE_NETLINK = 1,
	FPM_MSG_TYPE_PROTOBUF = 2,
} fpm_msg_type_e;

/*
 * The FPM message header is aligned to the same boundary as netlink
 * messages (4). This means that a netlink message does not need
 * padding when encapsulated in an FPM message.
 */
#define FPM_MSG_ALIGNTO 4

/*
 * fpm_msg_align
 *
 * Round up the given length to the desired alignment.
 *
 * **NB**: Alignment is required only when netlink messages are used.
 */
static inline size_t fpm_msg_align(size_t len)
{
	return (len + FPM_MSG_ALIGNTO - 1) & ~(FPM_MSG_ALIGNTO - 1);
}

/*
 * The (rounded up) size of the FPM message header. This ensures that
 * the message payload always starts at an aligned address.
 */
#define FPM_MSG_HDR_LEN (sizeof(fpm_msg_hdr_t))

#ifndef COMPILE_ASSERT
#define COMPILE_ASSERT(x) extern int __dummy[2 * !!(x) - 1]
#endif

COMPILE_ASSERT(FPM_MSG_ALIGNTO == FPM_MSG_HDR_LEN);

/*
 * fpm_data_len_to_msg_len
 *
 * The length value that should be placed in the msg_len field of the
 * header for a *payload* of size 'data_len'.
 */
static inline size_t fpm_data_len_to_msg_len(size_t data_len)
{
	return data_len + FPM_MSG_HDR_LEN;
}

/*
 * fpm_msg_data
 *
 * Pointer to the payload of the given fpm header.
 */
static inline void *fpm_msg_data(fpm_msg_hdr_t *hdr)
{
	return ((char *)hdr) + FPM_MSG_HDR_LEN;
}

/*
 * fpm_msg_len
 */
static inline size_t fpm_msg_len(const fpm_msg_hdr_t *hdr)
{
	return ntohs(hdr->msg_len);
}

/*
 * fpm_msg_data_len
 */
static inline size_t fpm_msg_data_len(const fpm_msg_hdr_t *hdr)
{
	return (fpm_msg_len(hdr) - FPM_MSG_HDR_LEN);
}

/*
 * fpm_msg_next
 *
 * Move to the next message in a buffer.
 */
static inline fpm_msg_hdr_t *fpm_msg_next(fpm_msg_hdr_t *hdr, size_t *len)
{
	size_t msg_len;

	msg_len = fpm_msg_len(hdr);

	if (len) {
		if (*len < msg_len) {
			assert(0);
			return NULL;
		}
		*len -= msg_len;
	}

	return (fpm_msg_hdr_t *)(((char *)hdr) + msg_len);
}

/*
 * fpm_msg_hdr_ok
 *
 * Returns true if a message header looks well-formed.
 */
static inline int fpm_msg_hdr_ok(const fpm_msg_hdr_t *hdr)
{
	size_t msg_len;

	if (hdr->msg_type == FPM_MSG_TYPE_NONE)
		return 0;

	msg_len = fpm_msg_len(hdr);

	if (msg_len < FPM_MSG_HDR_LEN || msg_len > FPM_MAX_MSG_LEN)
		return 0;

	/*
	 * Netlink messages must be aligned properly.
	 */
	if (hdr->msg_type == FPM_MSG_TYPE_NETLINK
	    && fpm_msg_align(msg_len) != msg_len)
		return 0;

	return 1;
}

/*
 * fpm_msg_ok
 *
 * Returns true if a message looks well-formed.
 *
 * @param len The length in bytes from 'hdr' to the end of the buffer.
 */
static inline int fpm_msg_ok(const fpm_msg_hdr_t *hdr, size_t len)
{
	if (len < FPM_MSG_HDR_LEN)
		return 0;

	if (!fpm_msg_hdr_ok(hdr))
		return 0;

	if (fpm_msg_len(hdr) > len)
		return 0;

	return 1;
}

// tcp maximum range
#define TCP_MAX_PORT   65535

// tcp minimum range
#define TCP_MIN_PORT   1

#endif /* _FPM_H */