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      1 /*
      2  * QEMU BOOTP/DHCP server
      3  *
      4  * Copyright (c) 2004 Fabrice Bellard
      5  *
      6  * Permission is hereby granted, free of charge, to any person obtaining a copy
      7  * of this software and associated documentation files (the "Software"), to deal
      8  * in the Software without restriction, including without limitation the rights
      9  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
     10  * copies of the Software, and to permit persons to whom the Software is
     11  * furnished to do so, subject to the following conditions:
     12  *
     13  * The above copyright notice and this permission notice shall be included in
     14  * all copies or substantial portions of the Software.
     15  *
     16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
     17  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
     18  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
     19  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
     20  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
     21  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
     22  * THE SOFTWARE.
     23  */
     24 #include <slirp.h>
     25 
     26 /* XXX: only DHCP is supported */
     27 
     28 #define NB_ADDR 16
     29 
     30 #define START_ADDR 15
     31 
     32 #define LEASE_TIME (24 * 3600)
     33 
     34 typedef struct {
     35     uint8_t allocated;
     36     uint8_t macaddr[6];
     37 } BOOTPClient;
     38 
     39 static BOOTPClient bootp_clients[NB_ADDR];
     40 
     41 const char *bootp_filename;
     42 
     43 static const uint8_t rfc1533_cookie[] = { RFC1533_COOKIE };
     44 
     45 #ifdef DEBUG
     46 #define dprintf(fmt, ...) \
     47 if (slirp_debug & DBG_CALL) { fprintf(dfd, fmt, ##  __VA_ARGS__); fflush(dfd); }
     48 #else
     49 #define dprintf(fmt, ...)
     50 #endif
     51 
     52 static BOOTPClient *get_new_addr(struct in_addr *paddr,
     53                                  const uint8_t *macaddr)
     54 {
     55     BOOTPClient *bc;
     56     int i;
     57 
     58     for(i = 0; i < NB_ADDR; i++) {
     59         bc = &bootp_clients[i];
     60         if (!bc->allocated || !memcmp(macaddr, bc->macaddr, 6))
     61             goto found;
     62     }
     63     return NULL;
     64  found:
     65     bc = &bootp_clients[i];
     66     bc->allocated = 1;
     67     paddr->s_addr = htonl(ntohl(special_addr.s_addr) | (i + START_ADDR));
     68     return bc;
     69 }
     70 
     71 static BOOTPClient *request_addr(const struct in_addr *paddr,
     72                                  const uint8_t *macaddr)
     73 {
     74     uint32_t req_addr = ntohl(paddr->s_addr);
     75     uint32_t spec_addr = ntohl(special_addr.s_addr);
     76     BOOTPClient *bc;
     77 
     78     if (req_addr >= (spec_addr | START_ADDR) &&
     79         req_addr < (spec_addr | (NB_ADDR + START_ADDR))) {
     80         bc = &bootp_clients[(req_addr & 0xff) - START_ADDR];
     81         if (!bc->allocated || !memcmp(macaddr, bc->macaddr, 6)) {
     82             bc->allocated = 1;
     83             return bc;
     84         }
     85     }
     86     return NULL;
     87 }
     88 
     89 static BOOTPClient *find_addr(struct in_addr *paddr, const uint8_t *macaddr)
     90 {
     91     BOOTPClient *bc;
     92     int i;
     93 
     94     for(i = 0; i < NB_ADDR; i++) {
     95         if (!memcmp(macaddr, bootp_clients[i].macaddr, 6))
     96             goto found;
     97     }
     98     return NULL;
     99  found:
    100     bc = &bootp_clients[i];
    101     bc->allocated = 1;
    102     paddr->s_addr = htonl(ntohl(special_addr.s_addr) | (i + START_ADDR));
    103     return bc;
    104 }
    105 
    106 static void dhcp_decode(const struct bootp_t *bp, int *pmsg_type,
    107                         const struct in_addr **preq_addr)
    108 {
    109     const uint8_t *p, *p_end;
    110     int len, tag;
    111 
    112     *pmsg_type = 0;
    113     *preq_addr = NULL;
    114 
    115     p = bp->bp_vend;
    116     p_end = p + DHCP_OPT_LEN;
    117     if (memcmp(p, rfc1533_cookie, 4) != 0)
    118         return;
    119     p += 4;
    120     while (p < p_end) {
    121         tag = p[0];
    122         if (tag == RFC1533_PAD) {
    123             p++;
    124         } else if (tag == RFC1533_END) {
    125             break;
    126         } else {
    127             p++;
    128             if (p >= p_end)
    129                 break;
    130             len = *p++;
    131             dprintf("dhcp: tag=%d len=%d\n", tag, len);
    132 
    133             switch(tag) {
    134             case RFC2132_MSG_TYPE:
    135                 if (len >= 1)
    136                     *pmsg_type = p[0];
    137                 break;
    138             case RFC2132_REQ_ADDR:
    139                 if (len >= 4)
    140                     *preq_addr = (struct in_addr *)p;
    141                 break;
    142             default:
    143                 break;
    144             }
    145             p += len;
    146         }
    147     }
    148     if (*pmsg_type == DHCPREQUEST && !*preq_addr && bp->bp_ciaddr.s_addr) {
    149         *preq_addr = &bp->bp_ciaddr;
    150     }
    151 }
    152 
    153 static void bootp_reply(const struct bootp_t *bp)
    154 {
    155     BOOTPClient *bc = NULL;
    156     struct mbuf *m;
    157     struct bootp_t *rbp;
    158     struct sockaddr_in saddr, daddr;
    159     struct in_addr dns_addr;
    160     const struct in_addr *preq_addr;
    161     int dhcp_msg_type, val;
    162     uint8_t *q;
    163 
    164     /* extract exact DHCP msg type */
    165     dhcp_decode(bp, &dhcp_msg_type, &preq_addr);
    166     dprintf("bootp packet op=%d msgtype=%d", bp->bp_op, dhcp_msg_type);
    167     if (preq_addr)
    168         dprintf(" req_addr=%08x\n", ntohl(preq_addr->s_addr));
    169     else
    170         dprintf("\n");
    171 
    172     if (dhcp_msg_type == 0)
    173         dhcp_msg_type = DHCPREQUEST; /* Force reply for old BOOTP clients */
    174 
    175     if (dhcp_msg_type != DHCPDISCOVER &&
    176         dhcp_msg_type != DHCPREQUEST)
    177         return;
    178     /* XXX: this is a hack to get the client mac address */
    179     memcpy(client_ethaddr, bp->bp_hwaddr, 6);
    180 
    181     if ((m = m_get()) == NULL)
    182         return;
    183     m->m_data += IF_MAXLINKHDR;
    184     rbp = (struct bootp_t *)m->m_data;
    185     m->m_data += sizeof(struct udpiphdr);
    186     memset(rbp, 0, sizeof(struct bootp_t));
    187 
    188     if (dhcp_msg_type == DHCPDISCOVER) {
    189         if (preq_addr) {
    190             bc = request_addr(preq_addr, client_ethaddr);
    191             if (bc) {
    192                 daddr.sin_addr = *preq_addr;
    193             }
    194         }
    195         if (!bc) {
    196          new_addr:
    197             bc = get_new_addr(&daddr.sin_addr, client_ethaddr);
    198             if (!bc) {
    199                 dprintf("no address left\n");
    200                 return;
    201             }
    202         }
    203         memcpy(bc->macaddr, client_ethaddr, 6);
    204     } else if (preq_addr) {
    205         bc = request_addr(preq_addr, client_ethaddr);
    206         if (bc) {
    207             daddr.sin_addr = *preq_addr;
    208             memcpy(bc->macaddr, client_ethaddr, 6);
    209         } else {
    210             daddr.sin_addr.s_addr = 0;
    211         }
    212     } else {
    213         bc = find_addr(&daddr.sin_addr, bp->bp_hwaddr);
    214         if (!bc) {
    215             /* if never assigned, behaves as if it was already
    216                assigned (windows fix because it remembers its address) */
    217             goto new_addr;
    218         }
    219     }
    220 
    221     saddr.sin_addr.s_addr = htonl(ntohl(special_addr.s_addr) | CTL_ALIAS);
    222     saddr.sin_port = htons(BOOTP_SERVER);
    223 
    224     daddr.sin_port = htons(BOOTP_CLIENT);
    225 
    226     rbp->bp_op = BOOTP_REPLY;
    227     rbp->bp_xid = bp->bp_xid;
    228     rbp->bp_htype = 1;
    229     rbp->bp_hlen = 6;
    230     memcpy(rbp->bp_hwaddr, bp->bp_hwaddr, 6);
    231 
    232     rbp->bp_yiaddr = daddr.sin_addr; /* Client IP address */
    233     rbp->bp_siaddr = saddr.sin_addr; /* Server IP address */
    234 
    235     q = rbp->bp_vend;
    236     memcpy(q, rfc1533_cookie, 4);
    237     q += 4;
    238 
    239     if (bc) {
    240         dprintf("%s addr=%08x\n",
    241                 (dhcp_msg_type == DHCPDISCOVER) ? "offered" : "ack'ed",
    242                 ntohl(daddr.sin_addr.s_addr));
    243 
    244         if (dhcp_msg_type == DHCPDISCOVER) {
    245             *q++ = RFC2132_MSG_TYPE;
    246             *q++ = 1;
    247             *q++ = DHCPOFFER;
    248         } else /* DHCPREQUEST */ {
    249             *q++ = RFC2132_MSG_TYPE;
    250             *q++ = 1;
    251             *q++ = DHCPACK;
    252         }
    253 
    254         if (bootp_filename)
    255             snprintf((char *)rbp->bp_file, sizeof(rbp->bp_file), "%s",
    256                      bootp_filename);
    257 
    258         *q++ = RFC2132_SRV_ID;
    259         *q++ = 4;
    260         memcpy(q, &saddr.sin_addr, 4);
    261         q += 4;
    262 
    263         *q++ = RFC1533_NETMASK;
    264         *q++ = 4;
    265         *q++ = 0xff;
    266         *q++ = 0xff;
    267         *q++ = 0xff;
    268         *q++ = 0x00;
    269 
    270         if (!slirp_restrict) {
    271             *q++ = RFC1533_GATEWAY;
    272             *q++ = 4;
    273             memcpy(q, &saddr.sin_addr, 4);
    274             q += 4;
    275 
    276             *q++ = RFC1533_DNS;
    277             *q++ = 4;
    278             dns_addr.s_addr = htonl(ntohl(special_addr.s_addr) | CTL_DNS);
    279             memcpy(q, &dns_addr, 4);
    280             q += 4;
    281         }
    282 
    283         *q++ = RFC2132_LEASE_TIME;
    284         *q++ = 4;
    285         val = htonl(LEASE_TIME);
    286         memcpy(q, &val, 4);
    287         q += 4;
    288 
    289         if (*slirp_hostname) {
    290             val = strlen(slirp_hostname);
    291             *q++ = RFC1533_HOSTNAME;
    292             *q++ = val;
    293             memcpy(q, slirp_hostname, val);
    294             q += val;
    295         }
    296     } else {
    297         static const char nak_msg[] = "requested address not available";
    298 
    299         dprintf("nak'ed addr=%08x\n", ntohl(preq_addr->s_addr));
    300 
    301         *q++ = RFC2132_MSG_TYPE;
    302         *q++ = 1;
    303         *q++ = DHCPNAK;
    304 
    305         *q++ = RFC2132_MESSAGE;
    306         *q++ = sizeof(nak_msg) - 1;
    307         memcpy(q, nak_msg, sizeof(nak_msg) - 1);
    308         q += sizeof(nak_msg) - 1;
    309     }
    310     *q++ = RFC1533_END;
    311 
    312     daddr.sin_addr.s_addr = 0xffffffffu;
    313 
    314     m->m_len = sizeof(struct bootp_t) -
    315         sizeof(struct ip) - sizeof(struct udphdr);
    316     udp_output2(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);
    317 }
    318 
    319 void bootp_input(struct mbuf *m)
    320 {
    321     struct bootp_t *bp = mtod(m, struct bootp_t *);
    322 
    323     if (bp->bp_op == BOOTP_REQUEST) {
    324         bootp_reply(bp);
    325     }
    326 }
    327