/*
 * QEMU BOOTP/DHCP server
 *
 * Copyright (c) 2004 Fabrice Bellard
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
#include <slirp.h>
#include "helper.h"

/* XXX: only DHCP is supported */

#define NB_ADDR 16

#define START_ADDR 15

#define LEASE_TIME (24 * 3600)

typedef struct {
    uint8_t allocated;
    uint8_t macaddr[6];
} BOOTPClient;

static BOOTPClient bootp_clients[NB_ADDR];

const char *bootp_filename;

static const uint8_t rfc1533_cookie[] = { RFC1533_COOKIE };

#ifdef DEBUG
#define dprintf(fmt, ...) \
if (slirp_debug & DBG_CALL) { fprintf(dfd, fmt, ##  __VA_ARGS__); fflush(dfd); }
#else
#define dprintf(fmt, ...)
#endif

static BOOTPClient *get_new_addr(SockAddress*  paddr,
                                 const uint8_t *macaddr)
{
    BOOTPClient *bc;
    int i;

    for(i = 0; i < NB_ADDR; i++) {
        bc = &bootp_clients[i];
        if (!bc->allocated || !memcmp(macaddr, bc->macaddr, 6))
            goto found;
    }
    return NULL;
 found:
    bc = &bootp_clients[i];
    bc->allocated = 1;
    sock_address_init_inet( paddr,
                            special_addr_ip | (i+START_ADDR),
                            BOOTP_CLIENT );
    return bc;
}

static BOOTPClient *request_addr(const ipaddr_t *paddr,
                                 const uint8_t *macaddr)
{
    uint32_t req_addr  = ip_geth(*paddr);
    uint32_t spec_addr = special_addr_ip;
    BOOTPClient *bc;

    if (req_addr >= (spec_addr | START_ADDR) &&
        req_addr < (spec_addr | (NB_ADDR + START_ADDR))) {
        bc = &bootp_clients[(req_addr & 0xff) - START_ADDR];
        if (!bc->allocated || !memcmp(macaddr, bc->macaddr, 6)) {
            bc->allocated = 1;
            return bc;
        }
    }
    return NULL;
}

static BOOTPClient *find_addr(SockAddress *paddr, const uint8_t *macaddr)
{
    BOOTPClient *bc;
    int i;

    for(i = 0; i < NB_ADDR; i++) {
        if (!memcmp(macaddr, bootp_clients[i].macaddr, 6))
            goto found;
    }
    return NULL;
 found:
    bc = &bootp_clients[i];
    bc->allocated = 1;
    sock_address_init_inet( paddr,
                            special_addr_ip | (i + START_ADDR),
                            BOOTP_CLIENT );
    return bc;
}

static void dhcp_decode(const struct bootp_t *bp, int *pmsg_type,
                        const ipaddr_t **preq_addr)
{
    const uint8_t *p, *p_end;
    int len, tag;

    *pmsg_type = 0;
    *preq_addr = NULL;

    p = bp->bp_vend;
    p_end = p + DHCP_OPT_LEN;
    if (memcmp(p, rfc1533_cookie, 4) != 0)
        return;
    p += 4;
    while (p < p_end) {
        tag = p[0];
        if (tag == RFC1533_PAD) {
            p++;
        } else if (tag == RFC1533_END) {
            break;
        } else {
            p++;
            if (p >= p_end)
                break;
            len = *p++;
            dprintf("dhcp: tag=%d len=%d\n", tag, len);

            switch(tag) {
            case RFC2132_MSG_TYPE:
                if (len >= 1)
                    *pmsg_type = p[0];
                break;
            case RFC2132_REQ_ADDR:
                if (len >= 4)
                    *preq_addr = (const ipaddr_t *)p;
                break;
            default:
                break;
            }
            p += len;
        }
    }
    if (*pmsg_type == DHCPREQUEST && !*preq_addr && bp->bp_ciaddr) {
        *preq_addr = (const ipaddr_t*)&bp->bp_ciaddr;
    }
}

static void bootp_reply(const struct bootp_t *bp)
{
    BOOTPClient *bc = NULL;
    struct mbuf *m;
    struct bootp_t *rbp;
    SockAddress  saddr, daddr;
    uint32_t     dns_addr;
    const ipaddr_t *preq_addr;
    int dhcp_msg_type, val;
    uint8_t *q;

    /* extract exact DHCP msg type */
    dhcp_decode(bp, &dhcp_msg_type, &preq_addr);
    dprintf("bootp packet op=%d msgtype=%d", bp->bp_op, dhcp_msg_type);
    if (preq_addr) {
        dprintf(" req_addr=%08x\n", ntohl(*(uint32_t*)preq_addr));
    } else {
        dprintf("\n");
    }
    if (dhcp_msg_type == 0)
        dhcp_msg_type = DHCPREQUEST; /* Force reply for old BOOTP clients */

    if (dhcp_msg_type != DHCPDISCOVER &&
        dhcp_msg_type != DHCPREQUEST)
        return;
    /* XXX: this is a hack to get the client mac address */
    memcpy(client_ethaddr, bp->bp_hwaddr, 6);

    if ((m = m_get()) == NULL)
        return;
    m->m_data += IF_MAXLINKHDR;
    rbp = (struct bootp_t *)m->m_data;
    m->m_data += sizeof(struct udpiphdr);
    memset(rbp, 0, sizeof(struct bootp_t));

    if (dhcp_msg_type == DHCPDISCOVER) {
        if (preq_addr) {
            bc = request_addr(preq_addr, client_ethaddr);
            if (bc) {
				sock_address_init_inet(&daddr, ip_geth(*preq_addr), BOOTP_CLIENT);
            }
        }
        if (!bc) {
         new_addr:
	        bc = get_new_addr(&daddr, client_ethaddr);
            if (!bc) {
                dprintf("no address left\n");
                return;
            }
        }
        memcpy(bc->macaddr, client_ethaddr, 6);
    } else if (preq_addr) {
        bc = request_addr(preq_addr, client_ethaddr);
        if (bc) {
			sock_address_init_inet(&daddr, ip_geth(*preq_addr), BOOTP_CLIENT);
            memcpy(bc->macaddr, client_ethaddr, 6);
        } else {
            sock_address_init_inet(&daddr, 0, BOOTP_CLIENT);
        }
    } else {
        bc = find_addr(&daddr, bp->bp_hwaddr);
        if (!bc) {
            /* if never assigned, behaves as if it was already
               assigned (windows fix because it remembers its address) */
            goto new_addr;
        }
    }

    sock_address_init_inet( &saddr, special_addr_ip | CTL_ALIAS,
                            BOOTP_SERVER );

    rbp->bp_op = BOOTP_REPLY;
    rbp->bp_xid = bp->bp_xid;
    rbp->bp_htype = 1;
    rbp->bp_hlen = 6;
    memcpy(rbp->bp_hwaddr, bp->bp_hwaddr, 6);

    rbp->bp_yiaddr = htonl(sock_address_get_ip(&daddr)); /* Client IP address */
    rbp->bp_siaddr = htonl(sock_address_get_ip(&saddr)); /* Server IP address */

    q = rbp->bp_vend;
    memcpy(q, rfc1533_cookie, 4);
    q += 4;

    if (bc) {
        uint32_t  saddr_ip = htonl(sock_address_get_ip(&saddr));
        dprintf("%s addr=%08x\n",
                (dhcp_msg_type == DHCPDISCOVER) ? "offered" : "ack'ed",
                sock_address_get_ip(&daddr));

        if (dhcp_msg_type == DHCPDISCOVER) {
            *q++ = RFC2132_MSG_TYPE;
            *q++ = 1;
            *q++ = DHCPOFFER;
        } else /* DHCPREQUEST */ {
            *q++ = RFC2132_MSG_TYPE;
            *q++ = 1;
            *q++ = DHCPACK;
        }

        if (bootp_filename)
            snprintf((char *)rbp->bp_file, sizeof(rbp->bp_file), "%s",
                     bootp_filename);

        *q++ = RFC2132_SRV_ID;
        *q++ = 4;
        memcpy(q, &saddr_ip, 4);
        q += 4;

        *q++ = RFC1533_NETMASK;
        *q++ = 4;
        *q++ = 0xff;
        *q++ = 0xff;
        *q++ = 0xff;
        *q++ = 0x00;

        if (!slirp_restrict) {
            *q++ = RFC1533_GATEWAY;
            *q++ = 4;
            memcpy(q, &saddr_ip, 4);
            q += 4;

            *q++ = RFC1533_DNS;
            *q++ = 4;
            dns_addr = htonl(special_addr_ip | CTL_DNS);
            memcpy(q, &dns_addr, 4);
            q += 4;
        }

        *q++ = RFC2132_LEASE_TIME;
        *q++ = 4;
        val = htonl(LEASE_TIME);
        memcpy(q, &val, 4);
        q += 4;

        if (*slirp_hostname) {
            val = strlen(slirp_hostname);
            *q++ = RFC1533_HOSTNAME;
            *q++ = val;
            memcpy(q, slirp_hostname, val);
            q += val;
        }
    } else {
        static const char nak_msg[] = "requested address not available";

        dprintf("nak'ed addr=%08x\n", ip_geth(*preq_addr));

        *q++ = RFC2132_MSG_TYPE;
        *q++ = 1;
        *q++ = DHCPNAK;

        *q++ = RFC2132_MESSAGE;
        *q++ = sizeof(nak_msg) - 1;
        memcpy(q, nak_msg, sizeof(nak_msg) - 1);
        q += sizeof(nak_msg) - 1;
    }
    *q++ = RFC1533_END;

	sock_address_init_inet(&daddr, 0xffffffffu, BOOTP_CLIENT);

    m->m_len = sizeof(struct bootp_t) -
        sizeof(struct ip) - sizeof(struct udphdr);
    udp_output2_(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);
}

void bootp_input(struct mbuf *m)
{
    struct bootp_t *bp = mtod(m, struct bootp_t *);

    if (bp->bp_op == BOOTP_REQUEST) {
        bootp_reply(bp);
    }
}