Annotation of qemu/slirp/bootp.c, revision 1.1.1.4

1.1       root        1: /*
                      2:  * QEMU BOOTP/DHCP server
1.1.1.3   root        3:  *
1.1       root        4:  * Copyright (c) 2004 Fabrice Bellard
1.1.1.3   root        5:  *
1.1       root        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: 
1.1.1.4 ! root       39: static BOOTPClient bootp_clients[NB_ADDR];
1.1       root       40: 
1.1.1.3   root       41: const char *bootp_filename;
                     42: 
1.1       root       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: 
1.1.1.3   root       92:     *pmsg_type = 0;
1.1       root       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) {
1.1.1.3   root      104:             p++;
1.1       root      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);
1.1.1.3   root      140: 
1.1       root      141:     if (dhcp_msg_type == 0)
                    142:         dhcp_msg_type = DHCPREQUEST; /* Force reply for old BOOTP clients */
1.1.1.3   root      143: 
                    144:     if (dhcp_msg_type != DHCPDISCOVER &&
1.1       root      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);
1.1.1.3   root      149: 
1.1       root      150:     if ((m = m_get()) == NULL)
                    151:         return;
1.1.1.3   root      152:     m->m_data += IF_MAXLINKHDR;
1.1       root      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:     }
1.1.1.3   root      173: 
                    174:     if (bootp_filename)
1.1.1.4 ! root      175:         snprintf((char *)rbp->bp_file, sizeof(rbp->bp_file), "%s",
        !           176:                  bootp_filename);
1.1.1.3   root      177: 
1.1       root      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: 
1.1.1.4 ! root      194:     daddr.sin_addr.s_addr = 0xffffffffu;
        !           195: 
1.1       root      196:     q = rbp->bp_vend;
                    197:     memcpy(q, rfc1533_cookie, 4);
                    198:     q += 4;
                    199: 
                    200:     if (dhcp_msg_type == DHCPDISCOVER) {
                    201:         *q++ = RFC2132_MSG_TYPE;
                    202:         *q++ = 1;
                    203:         *q++ = DHCPOFFER;
                    204:     } else if (dhcp_msg_type == DHCPREQUEST) {
                    205:         *q++ = RFC2132_MSG_TYPE;
                    206:         *q++ = 1;
                    207:         *q++ = DHCPACK;
                    208:     }
1.1.1.3   root      209: 
1.1       root      210:     if (dhcp_msg_type == DHCPDISCOVER ||
                    211:         dhcp_msg_type == DHCPREQUEST) {
                    212:         *q++ = RFC2132_SRV_ID;
                    213:         *q++ = 4;
                    214:         memcpy(q, &saddr.sin_addr, 4);
                    215:         q += 4;
                    216: 
                    217:         *q++ = RFC1533_NETMASK;
                    218:         *q++ = 4;
                    219:         *q++ = 0xff;
                    220:         *q++ = 0xff;
                    221:         *q++ = 0xff;
                    222:         *q++ = 0x00;
1.1.1.3   root      223: 
1.1.1.4 ! root      224:         if (!slirp_restrict) {
        !           225:             *q++ = RFC1533_GATEWAY;
        !           226:             *q++ = 4;
        !           227:             memcpy(q, &saddr.sin_addr, 4);
        !           228:             q += 4;
        !           229: 
        !           230:             *q++ = RFC1533_DNS;
        !           231:             *q++ = 4;
        !           232:             dns_addr.s_addr = htonl(ntohl(special_addr.s_addr) | CTL_DNS);
        !           233:             memcpy(q, &dns_addr, 4);
        !           234:             q += 4;
        !           235:         }
1.1       root      236: 
                    237:         *q++ = RFC2132_LEASE_TIME;
                    238:         *q++ = 4;
                    239:         val = htonl(LEASE_TIME);
                    240:         memcpy(q, &val, 4);
                    241:         q += 4;
1.1.1.2   root      242: 
                    243:         if (*slirp_hostname) {
                    244:             val = strlen(slirp_hostname);
                    245:             *q++ = RFC1533_HOSTNAME;
                    246:             *q++ = val;
                    247:             memcpy(q, slirp_hostname, val);
                    248:             q += val;
                    249:         }
1.1       root      250:     }
                    251:     *q++ = RFC1533_END;
1.1.1.3   root      252: 
                    253:     m->m_len = sizeof(struct bootp_t) -
1.1       root      254:         sizeof(struct ip) - sizeof(struct udphdr);
                    255:     udp_output2(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);
                    256: }
                    257: 
                    258: void bootp_input(struct mbuf *m)
                    259: {
                    260:     struct bootp_t *bp = mtod(m, struct bootp_t *);
                    261: 
                    262:     if (bp->bp_op == BOOTP_REQUEST) {
                    263:         bootp_reply(bp);
                    264:     }
                    265: }

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