/*
 * util/proxy_protocol.c - event notification
 *
 * 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 functions.
 */
#include "util/proxy_protocol.h"

/**
 * Internal struct initialized with function pointers for writing uint16 and
 * uint32.
 */
struct proxy_protocol_data {
        void (*write_uint16)(void* buf, uint16_t data);
        void (*write_uint32)(void* buf, uint32_t data);
};
struct proxy_protocol_data pp_data;

/**
 * Internal lookup table; could be further generic like sldns_lookup_table
 * for all the future generic stuff.
 */
struct proxy_protocol_lookup_table {
        int id;
        const char *text;
};

/**
 * Internal parsing error text; could be exposed with pp_lookup_error.
 */
static struct proxy_protocol_lookup_table pp_parse_errors_data[] = {
        { PP_PARSE_NOERROR, "no parse error" },
        { PP_PARSE_SIZE, "not enough space for header" },
        { PP_PARSE_WRONG_HEADERv2, "could not match PROXYv2 header" },
        { PP_PARSE_UNKNOWN_CMD, "unknown command" },
        { PP_PARSE_UNKNOWN_FAM_PROT, "unknown family and protocol" },
};

void
pp_init(void (*write_uint16)(void* buf, uint16_t data),
        void (*write_uint32)(void* buf, uint32_t data)) {
        pp_data.write_uint16 = write_uint16;
        pp_data.write_uint32 = write_uint32;
}

const char*
pp_lookup_error(enum pp_parse_errors error) {
        return pp_parse_errors_data[error].text;
}

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)
{
        int af;
        size_t expected_size;
        if(!src) return 0;
        af = (int)((struct sockaddr_in*)src)->sin_family;
        expected_size = PP2_HEADER_SIZE + (af==AF_INET?12:36);
        if(buflen < expected_size) {
                return 0;
        }
        /* sig */
        memcpy(buf, PP2_SIG, PP2_SIG_LEN);
        buf += PP2_SIG_LEN;
        /* version and command */
        *buf = (PP2_VERSION << 4) | PP2_CMD_PROXY;
        buf++;
        switch(af) {
        case AF_INET:
                /* family and protocol */
                *buf = (PP2_AF_INET<<4) |
                        (stream?PP2_PROT_STREAM:PP2_PROT_DGRAM);
                buf++;
                /* length */
                (*pp_data.write_uint16)(buf, 12);
                buf += 2;
                /* src addr */
                memcpy(buf,
                        &((struct sockaddr_in*)src)->sin_addr.s_addr, 4);
                buf += 4;
                /* dst addr */
                (*pp_data.write_uint32)(buf, 0);
                buf += 4;
                /* src port */
                memcpy(buf,
                        &((struct sockaddr_in*)src)->sin_port, 2);
                buf += 2;
                /* dst addr */
                /* dst port */
                (*pp_data.write_uint16)(buf, 12);
                break;
#ifdef INET6
        case AF_INET6:
                /* family and protocol */
                *buf = (PP2_AF_INET6<<4) |
                        (stream?PP2_PROT_STREAM:PP2_PROT_DGRAM);
                buf++;
                /* length */
                (*pp_data.write_uint16)(buf, 36);
                buf += 2;
                /* src addr */
                memcpy(buf,
                        &((struct sockaddr_in6*)src)->sin6_addr, 16);
                buf += 16;
                /* dst addr */
                memset(buf, 0, 16);
                buf += 16;
                /* src port */
                memcpy(buf, &((struct sockaddr_in6*)src)->sin6_port, 2);
                buf += 2;
                /* dst port */
                (*pp_data.write_uint16)(buf, 0);
                break;
#endif /* INET6 */
        case AF_UNIX:
                /* fallthrough */
        default:
                return 0;
        }
        return expected_size;
}

int
pp2_read_header(uint8_t* buf, size_t buflen)
{
        size_t size;
        struct pp2_header* header = (struct pp2_header*)buf;
        /* Try to fail all the unsupported cases first. */
        if(buflen < PP2_HEADER_SIZE) {
                return PP_PARSE_SIZE;
        }
        /* Check for PROXYv2 header */
        if(memcmp(header, PP2_SIG, PP2_SIG_LEN) != 0 ||
                ((header->ver_cmd & 0xF0)>>4) != PP2_VERSION) {
                return PP_PARSE_WRONG_HEADERv2;
        }
        /* Check the length */
        size = PP2_HEADER_SIZE + ntohs(header->len);
        if(buflen < size) {
                return PP_PARSE_SIZE;
        }
        /* Check for supported commands */
        if((header->ver_cmd & 0xF) != PP2_CMD_LOCAL &&
                (header->ver_cmd & 0xF) != PP2_CMD_PROXY) {
                return PP_PARSE_UNKNOWN_CMD;
        }
        /* Check for supported family and protocol */
        if(header->fam_prot != PP2_UNSPEC_UNSPEC &&
                header->fam_prot != PP2_INET_STREAM &&
                header->fam_prot != PP2_INET_DGRAM &&
                header->fam_prot != PP2_INET6_STREAM &&
                header->fam_prot != PP2_INET6_DGRAM &&
                header->fam_prot != PP2_UNIX_STREAM &&
                header->fam_prot != PP2_UNIX_DGRAM) {
                return PP_PARSE_UNKNOWN_FAM_PROT;
        }
        /* We have a correct header */
        return PP_PARSE_NOERROR;
}