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/*
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 * QEMU BOOTP/DHCP server
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 *
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 * Copyright (c) 2004 Fabrice Bellard
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 *
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 * Permission is hereby granted, free of charge, to any person obtaining a copy
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 * of this software and associated documentation files (the "Software"), to deal
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 * in the Software without restriction, including without limitation the rights
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 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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 * copies of the Software, and to permit persons to whom the Software is
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 * furnished to do so, subject to the following conditions:
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 *
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 * The above copyright notice and this permission notice shall be included in
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 * all copies or substantial portions of the Software.
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 *
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 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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 * THE SOFTWARE.
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 */
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#include <slirp.h>
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/* XXX: only DHCP is supported */
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#define NB_ADDR 16
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#define START_ADDR 15
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#define LEASE_TIME (24 * 3600)
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typedef struct {
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    uint8_t allocated;
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    uint8_t macaddr[6];
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} BOOTPClient;
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BOOTPClient bootp_clients[NB_ADDR];
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const char *bootp_filename;
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static const uint8_t rfc1533_cookie[] = { RFC1533_COOKIE };
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#ifdef DEBUG
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#define dprintf(fmt, args...) \
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if (slirp_debug & DBG_CALL) { fprintf(dfd, fmt, ## args); fflush(dfd); }
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#else
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#define dprintf(fmt, args...)
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#endif
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static BOOTPClient *get_new_addr(struct in_addr *paddr)
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{
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    BOOTPClient *bc;
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    int i;
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    for(i = 0; i < NB_ADDR; i++) {
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        if (!bootp_clients[i].allocated)
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            goto found;
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    }
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    return NULL;
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 found:
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    bc = &bootp_clients[i];
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    bc->allocated = 1;
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    paddr->s_addr = htonl(ntohl(special_addr.s_addr) | (i + START_ADDR));
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    return bc;
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}
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static BOOTPClient *find_addr(struct in_addr *paddr, const uint8_t *macaddr)
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{
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    BOOTPClient *bc;
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    int i;
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    for(i = 0; i < NB_ADDR; i++) {
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        if (!memcmp(macaddr, bootp_clients[i].macaddr, 6))
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            goto found;
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    }
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    return NULL;
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 found:
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    bc = &bootp_clients[i];
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    bc->allocated = 1;
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    paddr->s_addr = htonl(ntohl(special_addr.s_addr) | (i + START_ADDR));
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    return bc;
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}
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static void dhcp_decode(const uint8_t *buf, int size,
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                        int *pmsg_type)
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{
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    const uint8_t *p, *p_end;
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    int len, tag;
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    *pmsg_type = 0;   
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    p = buf;
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    p_end = buf + size;
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    if (size < 5)
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        return;
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    if (memcmp(p, rfc1533_cookie, 4) != 0)
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        return;
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    p += 4;
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    while (p < p_end) {
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        tag = p[0];
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        if (tag == RFC1533_PAD) {
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            p++;
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        } else if (tag == RFC1533_END) {
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            break;
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        } else {
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            p++;
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            if (p >= p_end)
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                break;
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            len = *p++;
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            dprintf("dhcp: tag=0x%02x len=%d\n", tag, len);
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            switch(tag) {
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            case RFC2132_MSG_TYPE:
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                if (len >= 1)
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                    *pmsg_type = p[0];
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                break;
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            default:
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                break;
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            }
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            p += len;
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        }
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    }
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}
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static void bootp_reply(struct bootp_t *bp)
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{
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    BOOTPClient *bc;
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    struct mbuf *m;
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    struct bootp_t *rbp;
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    struct sockaddr_in saddr, daddr;
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    struct in_addr dns_addr;
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    int dhcp_msg_type, val;
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    uint8_t *q;
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    /* extract exact DHCP msg type */
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    dhcp_decode(bp->bp_vend, DHCP_OPT_LEN, &dhcp_msg_type);
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    dprintf("bootp packet op=%d msgtype=%d\n", bp->bp_op, dhcp_msg_type);
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    if (dhcp_msg_type == 0)
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        dhcp_msg_type = DHCPREQUEST; /* Force reply for old BOOTP clients */
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    if (dhcp_msg_type != DHCPDISCOVER &&
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        dhcp_msg_type != DHCPREQUEST)
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        return;
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    /* XXX: this is a hack to get the client mac address */
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    memcpy(client_ethaddr, bp->bp_hwaddr, 6);
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    if ((m = m_get()) == NULL)
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        return;
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    m->m_data += if_maxlinkhdr;
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    rbp = (struct bootp_t *)m->m_data;
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    m->m_data += sizeof(struct udpiphdr);
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    memset(rbp, 0, sizeof(struct bootp_t));
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    if (dhcp_msg_type == DHCPDISCOVER) {
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    new_addr:
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        bc = get_new_addr(&daddr.sin_addr);
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        if (!bc) {
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            dprintf("no address left\n");
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            return;
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        }
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        memcpy(bc->macaddr, client_ethaddr, 6);
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    } else {
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        bc = find_addr(&daddr.sin_addr, bp->bp_hwaddr);
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        if (!bc) {
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            /* if never assigned, behaves as if it was already
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               assigned (windows fix because it remembers its address) */
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            goto new_addr;
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        }
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    }
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    if (bootp_filename)
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        snprintf(rbp->bp_file, sizeof(rbp->bp_file), "%s", bootp_filename);
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    dprintf("offered addr=%08x\n", ntohl(daddr.sin_addr.s_addr));
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    saddr.sin_addr.s_addr = htonl(ntohl(special_addr.s_addr) | CTL_ALIAS);
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    saddr.sin_port = htons(BOOTP_SERVER);
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    daddr.sin_port = htons(BOOTP_CLIENT);
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    rbp->bp_op = BOOTP_REPLY;
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    rbp->bp_xid = bp->bp_xid;
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    rbp->bp_htype = 1;
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    rbp->bp_hlen = 6;
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    memcpy(rbp->bp_hwaddr, bp->bp_hwaddr, 6);
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    rbp->bp_yiaddr = daddr.sin_addr; /* Client IP address */
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    rbp->bp_siaddr = saddr.sin_addr; /* Server IP address */
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    q = rbp->bp_vend;
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    memcpy(q, rfc1533_cookie, 4);
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    q += 4;
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    if (dhcp_msg_type == DHCPDISCOVER) {
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        *q++ = RFC2132_MSG_TYPE;
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        *q++ = 1;
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        *q++ = DHCPOFFER;
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    } else if (dhcp_msg_type == DHCPREQUEST) {
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        *q++ = RFC2132_MSG_TYPE;
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        *q++ = 1;
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        *q++ = DHCPACK;
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    }
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    if (dhcp_msg_type == DHCPDISCOVER ||
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        dhcp_msg_type == DHCPREQUEST) {
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        *q++ = RFC2132_SRV_ID;
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        *q++ = 4;
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        memcpy(q, &saddr.sin_addr, 4);
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        q += 4;
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        *q++ = RFC1533_NETMASK;
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        *q++ = 4;
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        *q++ = 0xff;
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        *q++ = 0xff;
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        *q++ = 0xff;
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        *q++ = 0x00;
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        *q++ = RFC1533_GATEWAY;
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        *q++ = 4;
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        memcpy(q, &saddr.sin_addr, 4);
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        q += 4;
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        *q++ = RFC1533_DNS;
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        *q++ = 4;
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        dns_addr.s_addr = htonl(ntohl(special_addr.s_addr) | CTL_DNS);
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        memcpy(q, &dns_addr, 4);
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        q += 4;
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        *q++ = RFC2132_LEASE_TIME;
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        *q++ = 4;
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        val = htonl(LEASE_TIME);
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        memcpy(q, &val, 4);
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        q += 4;
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        if (*slirp_hostname) {
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            val = strlen(slirp_hostname);
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            *q++ = RFC1533_HOSTNAME;
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            *q++ = val;
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            memcpy(q, slirp_hostname, val);
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            q += val;
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        }
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    }
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    *q++ = RFC1533_END;
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    m->m_len = sizeof(struct bootp_t) -
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        sizeof(struct ip) - sizeof(struct udphdr);
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    udp_output2(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);
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}
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void bootp_input(struct mbuf *m)
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{
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    struct bootp_t *bp = mtod(m, struct bootp_t *);
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    if (bp->bp_op == BOOTP_REQUEST) {
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        bootp_reply(bp);
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    }
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}