/*
* util/proxy_protocol.h - PROXY protocol
*
* Copyright (c) 2022, NLnet Labs. All rights reserved.
*
* This software is open source.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* Neither the name of the NLNET LABS nor the names of its contributors may
* be used to endorse or promote products derived from this software without
* specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
* HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
* TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

/**
* \file
*
* This file contains PROXY protocol structs and functions.
* Only v2 is supported. TLVs are not currently supported.
*/
#ifndef PROXY_PROTOCOL_H
#define PROXY_PROTOCOL_H

#include "config.h"

/** PROXYv2 minimum header size */
#define PP2_HEADER_SIZE 16

/** PROXYv2 header signature */
#define PP2_SIG "\x0D\x0A\x0D\x0A\x00\x0D\x0A\x51\x55\x49\x54\x0A"
#define PP2_SIG_LEN 12

/** PROXYv2 version (protocol value) */
#define PP2_VERSION 0x2

/**
* PROXYv2 command (protocol value).
*/
enum pp2_command {
       PP2_CMD_LOCAL = 0x0,
       PP2_CMD_PROXY = 0x1
};

/**
* PROXYv2 address family (protocol value).
*/
enum pp2_af {
       PP2_AF_UNSPEC = 0x0,
       PP2_AF_INET = 0x1,
       PP2_AF_INET6 = 0x2,
       PP2_AF_UNIX = 0x3
};

/**
* PROXYv2 protocol (protocol value).
*/
enum pp2_protocol {
       PP2_PROT_UNSPEC = 0x0,
       PP2_PROT_STREAM = 0x1,
       PP2_PROT_DGRAM = 0x2
};

/**
* Expected combinations of address family and protocol values used in checks.
*/
enum pp2_af_protocol_combination {
       PP2_UNSPEC_UNSPEC = (PP2_AF_UNSPEC<<4)|PP2_PROT_UNSPEC,
       PP2_INET_STREAM = (PP2_AF_INET<<4)|PP2_PROT_STREAM,
       PP2_INET_DGRAM = (PP2_AF_INET<<4)|PP2_PROT_DGRAM,
       PP2_INET6_STREAM = (PP2_AF_INET6<<4)|PP2_PROT_STREAM,
       PP2_INET6_DGRAM = (PP2_AF_INET6<<4)|PP2_PROT_DGRAM,
       PP2_UNIX_STREAM = (PP2_AF_UNIX<<4)|PP2_PROT_STREAM,
       PP2_UNIX_DGRAM = (PP2_AF_UNIX<<4)|PP2_PROT_DGRAM
};

/**
* PROXYv2 header.
*/
struct pp2_header {
       uint8_t sig[PP2_SIG_LEN];
       uint8_t ver_cmd;
       uint8_t fam_prot;
       uint16_t len;
       union {
               struct {  /* for TCP/UDP over IPv4, len = 12 */
                       uint32_t src_addr;
                       uint32_t dst_addr;
                       uint16_t src_port;
                       uint16_t dst_port;
               } addr4;
               struct {  /* for TCP/UDP over IPv6, len = 36 */
                       uint8_t  src_addr[16];
                       uint8_t  dst_addr[16];
                       uint16_t src_port;
                       uint16_t dst_port;
               } addr6;
               struct {  /* for AF_UNIX sockets, len = 216 */
                       uint8_t src_addr[108];
                       uint8_t dst_addr[108];
               } addru;
       } addr;
};

/**
* PROXY parse errors.
*/
enum pp_parse_errors {
       PP_PARSE_NOERROR = 0,
       PP_PARSE_SIZE,
       PP_PARSE_WRONG_HEADERv2,
       PP_PARSE_UNKNOWN_CMD,
       PP_PARSE_UNKNOWN_FAM_PROT,
};

/**
* Initialize the internal proxy structure.
* @param write_uint16: pointer to a function that can write uint16.
* @param write_uint32: pointer to a function that can write uint32.
*/
void pp_init(void (*write_uint16)(void* buf, uint16_t data),
       void (*write_uint32)(void* buf, uint32_t data));

/**
* Lookup the parsing error description.
* @param error: parsing error from pp2_read_header.
* @return the description.
*/
const char* pp_lookup_error(enum pp_parse_errors error);

/**
* Write a PROXYv2 header at the current position of the buffer.
* @param buf: pointer to the buffer to write data to.
* @param buflen: available size on the buffer.
* @param src: the source address.
* @param stream: if the protocol is stream or datagram.
* @return 1 on success, 0 on failure.
*/
size_t pp2_write_to_buf(uint8_t* buf, size_t buflen,
#ifdef INET6
       struct sockaddr_storage* src,
#else
       struct sockaddr_in* src,
#endif
       int stream);

/**
* Read a PROXYv2 header from the current position of the buffer.
* It does initial validation and returns a pointer to the buffer position on
* success.
* @param buf: pointer to the buffer data to read from.
* @param buflen: available size on the buffer.
* @return parsing error, 0 on success.
*/
int pp2_read_header(uint8_t* buf, size_t buflen);

#endif /* PROXY_PROTOCOL_H */