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, args...) \

    47 if (slirp_debug & DBG_CALL) { fprintf(dfd, fmt, ## args); fflush(dfd); }

    48 #else

    49 #define dprintf(fmt, args...)

    50 #endif

    51 

    52 static BOOTPClient *get_new_addr(struct in_addr *paddr)

    53 {

    54     BOOTPClient *bc;

    55     int i;

    56 

    57     for(i = 0; i < NB_ADDR; i++) {

    58         if (!bootp_clients[i].allocated)

    59             goto found;

    60     }

    61     return NULL;

    62  found:

    63     bc = &bootp_clients[i];

    64     bc->allocated = 1;

    65     paddr->s_addr = htonl(ntohl(special_addr.s_addr) | (i + START_ADDR));

    66     return bc;

    67 }

    68 

    69 static BOOTPClient *find_addr(struct in_addr *paddr, const uint8_t *macaddr)

    70 {

    71     BOOTPClient *bc;

    72     int i;

    73 

    74     for(i = 0; i < NB_ADDR; i++) {

    75         if (!memcmp(macaddr, bootp_clients[i].macaddr, 6))

    76             goto found;

    77     }

    78     return NULL;

    79  found:

    80     bc = &bootp_clients[i];

    81     bc->allocated = 1;

    82     paddr->s_addr = htonl(ntohl(special_addr.s_addr) | (i + START_ADDR));

    83     return bc;

    84 }

    85 

    86 static void dhcp_decode(const uint8_t *buf, int size,

    87                         int *pmsg_type)

    88 {

    89     const uint8_t *p, *p_end;

    90     int len, tag;

    91 

    92     *pmsg_type = 0;

    93 

    94     p = buf;

    95     p_end = buf + size;

    96     if (size < 5)

    97         return;

    98     if (memcmp(p, rfc1533_cookie, 4) != 0)

    99         return;

   100     p += 4;

   101     while (p < p_end) {

   102         tag = p[0];

   103         if (tag == RFC1533_PAD) {

   104             p++;

   105         } else if (tag == RFC1533_END) {

   106             break;

   107         } else {

   108             p++;

   109             if (p >= p_end)

   110                 break;

   111             len = *p++;

   112             dprintf("dhcp: tag=0x%02x len=%d\n", tag, len);

   113 

   114             switch(tag) {

   115             case RFC2132_MSG_TYPE:

   116                 if (len >= 1)

   117                     *pmsg_type = p[0];

   118                 break;

   119             default:

   120                 break;

   121             }

   122             p += len;

   123         }

   124     }

   125 }

   126 

   127 static void bootp_reply(struct bootp_t *bp)

   128 {

   129     BOOTPClient *bc;

   130     struct mbuf *m;

   131     struct bootp_t *rbp;

   132     struct sockaddr_in saddr, daddr;

   133     struct in_addr dns_addr;

   134     int dhcp_msg_type, val;

   135     uint8_t *q;

   136 

   137     /* extract exact DHCP msg type */

   138     dhcp_decode(bp->bp_vend, DHCP_OPT_LEN, &dhcp_msg_type);

   139     dprintf("bootp packet op=%d msgtype=%d\n", bp->bp_op, dhcp_msg_type);

   140 

   141     if (dhcp_msg_type == 0)

   142         dhcp_msg_type = DHCPREQUEST; /* Force reply for old BOOTP clients */

   143 

   144     if (dhcp_msg_type != DHCPDISCOVER &&

   145         dhcp_msg_type != DHCPREQUEST)

   146         return;

   147     /* XXX: this is a hack to get the client mac address */

   148     memcpy(client_ethaddr, bp->bp_hwaddr, 6);

   149 

   150     if ((m = m_get()) == NULL)

   151         return;

   152     m->m_data += IF_MAXLINKHDR;

   153     rbp = (struct bootp_t *)m->m_data;

   154     m->m_data += sizeof(struct udpiphdr);

   155     memset(rbp, 0, sizeof(struct bootp_t));

   156 

   157     if (dhcp_msg_type == DHCPDISCOVER) {

   158     new_addr:

   159         bc = get_new_addr(&daddr.sin_addr);

   160         if (!bc) {

   161             dprintf("no address left\n");

   162             return;

   163         }

   164         memcpy(bc->macaddr, client_ethaddr, 6);

   165     } else {

   166         bc = find_addr(&daddr.sin_addr, bp->bp_hwaddr);

   167         if (!bc) {

   168             /* if never assigned, behaves as if it was already

   169                assigned (windows fix because it remembers its address) */

   170             goto new_addr;

   171         }

   172     }

   173 

   174     if (bootp_filename)

   175         snprintf((char *)rbp->bp_file, sizeof(rbp->bp_file), "%s",

   176                  bootp_filename);

   177 

   178     dprintf("offered addr=%08x\n", ntohl(daddr.sin_addr.s_addr));

   179 

   180     saddr.sin_addr.s_addr = htonl(ntohl(special_addr.s_addr) | CTL_ALIAS);

   181     saddr.sin_port = htons(BOOTP_SERVER);

   182 

   183     daddr.sin_port = htons(BOOTP_CLIENT);

   184 

   185     rbp->bp_op = BOOTP_REPLY;

   186     rbp->bp_xid = bp->bp_xid;

   187     rbp->bp_htype = 1;

   188     rbp->bp_hlen = 6;

   189     memcpy(rbp->bp_hwaddr, bp->bp_hwaddr, 6);

   190 

   191     rbp->bp_yiaddr = daddr.sin_addr; /* Client IP address */

   192     rbp->bp_siaddr = saddr.sin_addr; /* Server IP address */

   193 

   194     q = rbp->bp_vend;

   195     memcpy(q, rfc1533_cookie, 4);

   196     q += 4;

   197 

   198     if (dhcp_msg_type == DHCPDISCOVER) {

   199         *q++ = RFC2132_MSG_TYPE;

   200         *q++ = 1;

   201         *q++ = DHCPOFFER;

   202     } else if (dhcp_msg_type == DHCPREQUEST) {

   203         *q++ = RFC2132_MSG_TYPE;

   204         *q++ = 1;

   205         *q++ = DHCPACK;

   206     }

   207 

   208     if (dhcp_msg_type == DHCPDISCOVER ||

   209         dhcp_msg_type == DHCPREQUEST) {

   210         *q++ = RFC2132_SRV_ID;

   211         *q++ = 4;

   212         memcpy(q, &saddr.sin_addr, 4);

   213         q += 4;

   214 

   215         *q++ = RFC1533_NETMASK;

   216         *q++ = 4;

   217         *q++ = 0xff;

   218         *q++ = 0xff;

   219         *q++ = 0xff;

   220         *q++ = 0x00;

   221 

   222         *q++ = RFC1533_GATEWAY;

   223         *q++ = 4;

   224         memcpy(q, &saddr.sin_addr, 4);

   225         q += 4;

   226 

   227         *q++ = RFC1533_DNS;

   228         *q++ = 4;

   229         dns_addr.s_addr = htonl(ntohl(special_addr.s_addr) | CTL_DNS);

   230         memcpy(q, &dns_addr, 4);

   231         q += 4;

   232 

   233         *q++ = RFC2132_LEASE_TIME;

   234         *q++ = 4;

   235         val = htonl(LEASE_TIME);

   236         memcpy(q, &val, 4);

   237         q += 4;

   238 

   239         if (*slirp_hostname) {

   240             val = strlen(slirp_hostname);

   241             *q++ = RFC1533_HOSTNAME;

   242             *q++ = val;

   243             memcpy(q, slirp_hostname, val);

   244             q += val;

   245         }

   246     }

   247     *q++ = RFC1533_END;

   248 

   249     m->m_len = sizeof(struct bootp_t) -

   250         sizeof(struct ip) - sizeof(struct udphdr);

   251     udp_output2(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);

   252 }

   253 

   254 void bootp_input(struct mbuf *m)

   255 {

   256     struct bootp_t *bp = mtod(m, struct bootp_t *);

   257 

   258     if (bp->bp_op == BOOTP_REQUEST) {

   259         bootp_reply(bp);

   260     }

   261 }