/*
 *  OpenVPN -- An application to securely tunnel IP networks
 *             over a single TCP/UDP port, with support for SSL/TLS-based
 *             session authentication and key exchange,
 *             packet encryption, packet authentication, and
 *             packet compression.
 *
 *  Copyright (C) 2002-2018 OpenVPN Inc <sales@openvpn.net>
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License version 2
 *  as published by the Free Software Foundation.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, write to the Free Software Foundation, Inc.,
 *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

#ifdef HAVE_CONFIG_H
#include "config.h"
#elif defined(_MSC_VER)
#include "config-msvc.h"
#endif

#include "syshead.h"

#include "pool.h"
#include "buffer.h"
#include "error.h"
#include "socket.h"
#include "otime.h"

#include "memdbg.h"

#if P2MP

static void
ifconfig_pool_entry_free(struct ifconfig_pool_entry *ipe, bool hard)
{
    ipe->in_use = false;
    if (hard && ipe->common_name)
    {
        free(ipe->common_name);
        ipe->common_name = NULL;
    }
    if (hard)
    {
        ipe->last_release = 0;
    }
    else
    {
        ipe->last_release = now;
    }
}

static int
ifconfig_pool_find(struct ifconfig_pool *pool, const char *common_name)
{
    int i;
    time_t earliest_release = 0;
    int previous_usage = -1;
    int new_usage = -1;

    for (i = 0; i < pool->size; ++i)
    {
        struct ifconfig_pool_entry *ipe = &pool->list[i];
        if (!ipe->in_use)
        {
            /*
             * If duplicate_cn mode, take first available IP address
             */
            if (pool->duplicate_cn)
            {
                new_usage = i;
                break;
            }

            /*
             * Keep track of the unused IP address entry which
             * was released earliest.
             */
            if ((new_usage == -1 || ipe->last_release < earliest_release) && !ipe->fixed)
            {
                earliest_release = ipe->last_release;
                new_usage = i;
            }

            /*
             * Keep track of a possible allocation to us
             * from an earlier session.
             */
            if (previous_usage < 0
                && common_name
                && ipe->common_name
                && !strcmp(common_name, ipe->common_name))
            {
                previous_usage = i;
            }

        }
    }

    if (previous_usage >= 0)
    {
        return previous_usage;
    }

    if (new_usage >= 0)
    {
        return new_usage;
    }

    return -1;
}

/*
 * Verify start/end range
 */
bool
ifconfig_pool_verify_range(const int msglevel, const in_addr_t start, const in_addr_t end)
{
    struct gc_arena gc = gc_new();
    bool ret = true;

    if (start > end)
    {
        msg(msglevel, "--ifconfig-pool start IP [%s] is greater than end IP [%s]",
            print_in_addr_t(start, 0, &gc),
            print_in_addr_t(end, 0, &gc));
        ret = false;
    }
    if (end - start >= IFCONFIG_POOL_MAX)
    {
        msg(msglevel, "--ifconfig-pool address range is too large [%s -> %s].  Current maximum is %d addresses, as defined by IFCONFIG_POOL_MAX variable.",
            print_in_addr_t(start, 0, &gc),
            print_in_addr_t(end, 0, &gc),
            IFCONFIG_POOL_MAX);
        ret = false;
    }
    gc_free(&gc);
    return ret;
}

struct ifconfig_pool *
ifconfig_pool_init(int type, in_addr_t start, in_addr_t end,
                   const bool duplicate_cn,
                   const bool ipv6_pool, const struct in6_addr ipv6_base,
                   const int ipv6_netbits )
{
    struct gc_arena gc = gc_new();
    struct ifconfig_pool *pool = NULL;

    ASSERT(start <= end && end - start < IFCONFIG_POOL_MAX);
    ALLOC_OBJ_CLEAR(pool, struct ifconfig_pool);

    pool->type = type;
    pool->duplicate_cn = duplicate_cn;

    switch (type)
    {
        case IFCONFIG_POOL_30NET:
            pool->base = start & ~3;
            pool->size = (((end | 3) + 1) - pool->base) >> 2;
            break;

        case IFCONFIG_POOL_INDIV:
            pool->base = start;
            pool->size = end - start + 1;
            break;

        default:
            ASSERT(0);
    }

    /* IPv6 pools are always "INDIV" type */
    pool->ipv6 = ipv6_pool;

    if (pool->ipv6)
    {
        pool->base_ipv6 = ipv6_base;
        pool->size_ipv6 = ipv6_netbits>96 ? ( 1<<(128-ipv6_netbits) )
                          : IFCONFIG_POOL_MAX;

        msg( D_IFCONFIG_POOL, "IFCONFIG POOL IPv6: (IPv4) size=%d, size_ipv6=%d, netbits=%d, base_ipv6=%s",
             pool->size, pool->size_ipv6, ipv6_netbits,
             print_in6_addr( pool->base_ipv6, 0, &gc ));

        /* the current code is very simple and assumes that the IPv6
         * pool is at least as big as the IPv4 pool, and we don't need
         * to do separate math etc. for IPv6
         */
        ASSERT( pool->size < pool->size_ipv6 );
    }

    ALLOC_ARRAY_CLEAR(pool->list, struct ifconfig_pool_entry, pool->size);

    msg(D_IFCONFIG_POOL, "IFCONFIG POOL: base=%s size=%d, ipv6=%d",
        print_in_addr_t(pool->base, 0, &gc),
        pool->size, pool->ipv6 );

    gc_free(&gc);
    return pool;
}

void
ifconfig_pool_free(struct ifconfig_pool *pool)
{
    if (pool)
    {
        int i;
        for (i = 0; i < pool->size; ++i)
        {
            ifconfig_pool_entry_free(&pool->list[i], true);
        }
        free(pool->list);
        free(pool);
    }
}

ifconfig_pool_handle
ifconfig_pool_acquire(struct ifconfig_pool *pool, in_addr_t *local, in_addr_t *remote, struct in6_addr *remote_ipv6, const char *common_name)
{
    int i;

    i = ifconfig_pool_find(pool, common_name);
    if (i >= 0)
    {
        struct ifconfig_pool_entry *ipe = &pool->list[i];
        ASSERT(!ipe->in_use);
        ifconfig_pool_entry_free(ipe, true);
        ipe->in_use = true;
        if (common_name)
        {
            ipe->common_name = string_alloc(common_name, NULL);
        }

        switch (pool->type)
        {
            case IFCONFIG_POOL_30NET:
            {
                in_addr_t b = pool->base + (i << 2);
                *local = b + 1;
                *remote = b + 2;
                break;
            }

            case IFCONFIG_POOL_INDIV:
            {
                in_addr_t b = pool->base + i;
                *local = 0;
                *remote = b;
                break;
            }

            default:
                ASSERT(0);
        }

        /* IPv6 pools are always INDIV (--linear) */
        if (pool->ipv6 && remote_ipv6)
        {
            *remote_ipv6 = add_in6_addr( pool->base_ipv6, i );
        }
    }
    return i;
}

bool
ifconfig_pool_release(struct ifconfig_pool *pool, ifconfig_pool_handle hand, const bool hard)
{
    bool ret = false;
    if (pool && hand >= 0 && hand < pool->size)
    {
        ifconfig_pool_entry_free(&pool->list[hand], hard);
        ret = true;
    }
    return ret;
}

/*
 * private access functions
 */

static ifconfig_pool_handle
ifconfig_pool_ip_base_to_handle(const struct ifconfig_pool *pool, const in_addr_t addr)
{
    ifconfig_pool_handle ret = -1;

    switch (pool->type)
    {
        case IFCONFIG_POOL_30NET:
        {
            ret = (addr - pool->base) >> 2;
            break;
        }

        case IFCONFIG_POOL_INDIV:
        {
            ret = (addr - pool->base);
            break;
        }

        default:
            ASSERT(0);
    }

    if (ret < 0 || ret >= pool->size)
    {
        ret = -1;
    }

    return ret;
}

static in_addr_t
ifconfig_pool_handle_to_ip_base(const struct ifconfig_pool *pool, ifconfig_pool_handle hand)
{
    in_addr_t ret = 0;

    if (hand >= 0 && hand < pool->size)
    {
        switch (pool->type)
        {
            case IFCONFIG_POOL_30NET:
            {
                ret = pool->base + (hand << 2);
                break;
            }

            case IFCONFIG_POOL_INDIV:
            {
                ret = pool->base + hand;
                break;
            }

            default:
                ASSERT(0);
        }
    }

    return ret;
}

static struct in6_addr
ifconfig_pool_handle_to_ipv6_base(const struct ifconfig_pool *pool, ifconfig_pool_handle hand)
{
    struct in6_addr ret = in6addr_any;

    /* IPv6 pools are always INDIV (--linear) */
    if (hand >= 0 && hand < pool->size_ipv6)
    {
        ret = add_in6_addr( pool->base_ipv6, hand );
    }
    return ret;
}

static void
ifconfig_pool_set(struct ifconfig_pool *pool, const char *cn, const in_addr_t addr, const bool fixed)
{
    ifconfig_pool_handle h = ifconfig_pool_ip_base_to_handle(pool, addr);
    if (h >= 0)
    {
        struct ifconfig_pool_entry *e = &pool->list[h];
        ifconfig_pool_entry_free(e, true);
        e->in_use = false;
        e->common_name = string_alloc(cn, NULL);
        e->last_release = now;
        e->fixed = fixed;
    }
}

static void
ifconfig_pool_list(const struct ifconfig_pool *pool, struct status_output *out)
{
    if (pool && out)
    {
        struct gc_arena gc = gc_new();
        int i;

        for (i = 0; i < pool->size; ++i)
        {
            const struct ifconfig_pool_entry *e = &pool->list[i];
            if (e->common_name)
            {
                const in_addr_t ip = ifconfig_pool_handle_to_ip_base(pool, i);
                if (pool->ipv6)
                {
                    struct in6_addr ip6 = ifconfig_pool_handle_to_ipv6_base(pool, i);
                    status_printf(out, "%s,%s,%s",
                                  e->common_name,
                                  print_in_addr_t(ip, 0, &gc),
                                  print_in6_addr(ip6, 0, &gc));
                }
                else
                {
                    status_printf(out, "%s,%s",
                                  e->common_name,
                                  print_in_addr_t(ip, 0, &gc));
                }
            }
        }
        gc_free(&gc);
    }
}

static void
ifconfig_pool_msg(const struct ifconfig_pool *pool, int msglevel)
{
    struct status_output *so = status_open(NULL, 0, msglevel, NULL, 0);
    ASSERT(so);
    status_printf(so, "IFCONFIG POOL LIST");
    ifconfig_pool_list(pool, so);
    status_close(so);
}

/*
 * Deal with reading/writing the ifconfig pool database to a file
 */

struct ifconfig_pool_persist *
ifconfig_pool_persist_init(const char *filename, int refresh_freq)
{
    struct ifconfig_pool_persist *ret;

    ASSERT(filename);

    ALLOC_OBJ_CLEAR(ret, struct ifconfig_pool_persist);
    if (refresh_freq > 0)
    {
        ret->fixed = false;
        ret->file = status_open(filename, refresh_freq, -1, NULL, STATUS_OUTPUT_READ|STATUS_OUTPUT_WRITE);
    }
    else
    {
        ret->fixed = true;
        ret->file = status_open(filename, 0, -1, NULL, STATUS_OUTPUT_READ);
    }
    return ret;
}

void
ifconfig_pool_persist_close(struct ifconfig_pool_persist *persist)
{
    if (persist)
    {
        if (persist->file)
        {
            status_close(persist->file);
        }
        free(persist);
    }
}

bool
ifconfig_pool_write_trigger(struct ifconfig_pool_persist *persist)
{
    if (persist->file)
    {
        return status_trigger(persist->file);
    }
    else
    {
        return false;
    }
}

void
ifconfig_pool_read(struct ifconfig_pool_persist *persist, struct ifconfig_pool *pool)
{
    const int buf_size = 128;

    update_time();
    if (persist && persist->file && pool)
    {
        struct gc_arena gc = gc_new();
        struct buffer in = alloc_buf_gc(256, &gc);
        char *cn_buf;
        char *ip_buf;
        int line = 0;

        ALLOC_ARRAY_CLEAR_GC(cn_buf, char, buf_size, &gc);
        ALLOC_ARRAY_CLEAR_GC(ip_buf, char, buf_size, &gc);

        while (true)
        {
            ASSERT(buf_init(&in, 0));
            if (!status_read(persist->file, &in))
            {
                break;
            }
            ++line;
            if (BLEN(&in))
            {
                int c = *BSTR(&in);
                if (c == '#' || c == ';')
                {
                    continue;
                }
                msg( M_INFO, "ifconfig_pool_read(), in='%s', TODO: IPv6",
                     BSTR(&in) );

                if (buf_parse(&in, ',', cn_buf, buf_size)
                    && buf_parse(&in, ',', ip_buf, buf_size))
                {
                    bool succeeded;
                    const in_addr_t addr = getaddr(GETADDR_HOST_ORDER, ip_buf, 0, &succeeded, NULL);
                    if (succeeded)
                    {
                        msg( M_INFO, "succeeded -> ifconfig_pool_set()");
                        ifconfig_pool_set(pool, cn_buf, addr, persist->fixed);
                    }
                }
            }
        }

        ifconfig_pool_msg(pool, D_IFCONFIG_POOL);

        gc_free(&gc);
    }
}

void
ifconfig_pool_write(struct ifconfig_pool_persist *persist, const struct ifconfig_pool *pool)
{
    if (persist && persist->file && (status_rw_flags(persist->file) & STATUS_OUTPUT_WRITE) && pool)
    {
        status_reset(persist->file);
        ifconfig_pool_list(pool, persist->file);
        status_flush(persist->file);
    }
}

/*
 * TESTING ONLY
 */

#ifdef IFCONFIG_POOL_TEST

#define DUP_CN

void
ifconfig_pool_test(in_addr_t start, in_addr_t end)
{
    struct gc_arena gc = gc_new();
    struct ifconfig_pool *p = ifconfig_pool_init(IFCONFIG_POOL_30NET, start, end);
    /*struct ifconfig_pool *p = ifconfig_pool_init (IFCONFIG_POOL_INDIV, start, end);*/
    ifconfig_pool_handle array[256];
    int i;

    CLEAR(array);

    msg(M_INFO | M_NOPREFIX, "************ 1");
    for (i = 0; i < (int) SIZE(array); ++i)
    {
        char *cn;
        ifconfig_pool_handle h;
        in_addr_t local, remote;
        char buf[256];
        openvpn_snprintf(buf, sizeof(buf), "common-name-%d", i);
#ifdef DUP_CN
        cn = NULL;
#else
        cn = buf;
#endif
        h = ifconfig_pool_acquire(p, &local, &remote, NULL, cn);
        if (h < 0)
        {
            break;
        }
        msg(M_INFO | M_NOPREFIX, "IFCONFIG_POOL TEST pass 1: l=%s r=%s cn=%s",
            print_in_addr_t(local, 0, &gc),
            print_in_addr_t(remote, 0, &gc),
            cn);
        array[i] = h;

    }

    msg(M_INFO | M_NOPREFIX, "************* 2");
    for (i = (int) SIZE(array) / 16; i < (int) SIZE(array) / 8; ++i)
    {
        msg(M_INFO, "Attempt to release %d cn=%s", array[i], p->list[i].common_name);
        if (!ifconfig_pool_release(p, array[i]))
        {
            break;
        }
        msg(M_INFO, "Succeeded");
    }

    CLEAR(array);

    msg(M_INFO | M_NOPREFIX, "**************** 3");
    for (i = 0; i < (int) SIZE(array); ++i)
    {
        char *cn;
        ifconfig_pool_handle h;
        in_addr_t local, remote;
        char buf[256];
        snprintf(buf, sizeof(buf), "common-name-%d", i+24);
#ifdef DUP_CN
        cn = NULL;
#else
        cn = buf;
#endif
        h = ifconfig_pool_acquire(p, &local, &remote, NULL, cn);
        if (h < 0)
        {
            break;
        }
        msg(M_INFO | M_NOPREFIX, "IFCONFIG_POOL TEST pass 3: l=%s r=%s cn=%s",
            print_in_addr_t(local, 0, &gc),
            print_in_addr_t(remote, 0, &gc),
            cn);
        array[i] = h;

    }

    ifconfig_pool_free(p);
    gc_free(&gc);
}

#endif /* ifdef IFCONFIG_POOL_TEST */

#endif /* if P2MP */