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Annotation of qemu/slirp/bootp.c, revision 1.1

1.1     ! root        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: BOOTPClient bootp_clients[NB_ADDR];
        !            40: 
        !            41: static const uint8_t rfc1533_cookie[] = { RFC1533_COOKIE };
        !            42: 
        !            43: #ifdef DEBUG
        !            44: #define dprintf(fmt, args...) \
        !            45: if (slirp_debug & DBG_CALL) { fprintf(dfd, fmt, ## args); fflush(dfd); }
        !            46: #else
        !            47: #define dprintf(fmt, args...)
        !            48: #endif
        !            49: 
        !            50: static BOOTPClient *get_new_addr(struct in_addr *paddr)
        !            51: {
        !            52:     BOOTPClient *bc;
        !            53:     int i;
        !            54: 
        !            55:     for(i = 0; i < NB_ADDR; i++) {
        !            56:         if (!bootp_clients[i].allocated)
        !            57:             goto found;
        !            58:     }
        !            59:     return NULL;
        !            60:  found:
        !            61:     bc = &bootp_clients[i];
        !            62:     bc->allocated = 1;
        !            63:     paddr->s_addr = htonl(ntohl(special_addr.s_addr) | (i + START_ADDR));
        !            64:     return bc;
        !            65: }
        !            66: 
        !            67: static BOOTPClient *find_addr(struct in_addr *paddr, const uint8_t *macaddr)
        !            68: {
        !            69:     BOOTPClient *bc;
        !            70:     int i;
        !            71: 
        !            72:     for(i = 0; i < NB_ADDR; i++) {
        !            73:         if (!memcmp(macaddr, bootp_clients[i].macaddr, 6))
        !            74:             goto found;
        !            75:     }
        !            76:     return NULL;
        !            77:  found:
        !            78:     bc = &bootp_clients[i];
        !            79:     bc->allocated = 1;
        !            80:     paddr->s_addr = htonl(ntohl(special_addr.s_addr) | (i + START_ADDR));
        !            81:     return bc;
        !            82: }
        !            83: 
        !            84: static void dhcp_decode(const uint8_t *buf, int size,
        !            85:                         int *pmsg_type)
        !            86: {
        !            87:     const uint8_t *p, *p_end;
        !            88:     int len, tag;
        !            89: 
        !            90:     *pmsg_type = 0;    
        !            91: 
        !            92:     p = buf;
        !            93:     p_end = buf + size;
        !            94:     if (size < 5)
        !            95:         return;
        !            96:     if (memcmp(p, rfc1533_cookie, 4) != 0)
        !            97:         return;
        !            98:     p += 4;
        !            99:     while (p < p_end) {
        !           100:         tag = p[0];
        !           101:         if (tag == RFC1533_PAD) {
        !           102:             p++; 
        !           103:         } else if (tag == RFC1533_END) {
        !           104:             break;
        !           105:         } else {
        !           106:             p++;
        !           107:             if (p >= p_end)
        !           108:                 break;
        !           109:             len = *p++;
        !           110:             dprintf("dhcp: tag=0x%02x len=%d\n", tag, len);
        !           111: 
        !           112:             switch(tag) {
        !           113:             case RFC2132_MSG_TYPE:
        !           114:                 if (len >= 1)
        !           115:                     *pmsg_type = p[0];
        !           116:                 break;
        !           117:             default:
        !           118:                 break;
        !           119:             }
        !           120:             p += len;
        !           121:         }
        !           122:     }
        !           123: }
        !           124: 
        !           125: static void bootp_reply(struct bootp_t *bp)
        !           126: {
        !           127:     BOOTPClient *bc;
        !           128:     struct mbuf *m;
        !           129:     struct bootp_t *rbp;
        !           130:     struct sockaddr_in saddr, daddr;
        !           131:     struct in_addr dns_addr;
        !           132:     int dhcp_msg_type, val;
        !           133:     uint8_t *q;
        !           134: 
        !           135:     /* extract exact DHCP msg type */
        !           136:     dhcp_decode(bp->bp_vend, DHCP_OPT_LEN, &dhcp_msg_type);
        !           137:     dprintf("bootp packet op=%d msgtype=%d\n", bp->bp_op, dhcp_msg_type);
        !           138:     
        !           139:     if (dhcp_msg_type == 0)
        !           140:         dhcp_msg_type = DHCPREQUEST; /* Force reply for old BOOTP clients */
        !           141:         
        !           142:     if (dhcp_msg_type != DHCPDISCOVER && 
        !           143:         dhcp_msg_type != DHCPREQUEST)
        !           144:         return;
        !           145:     /* XXX: this is a hack to get the client mac address */
        !           146:     memcpy(client_ethaddr, bp->bp_hwaddr, 6);
        !           147:     
        !           148:     if ((m = m_get()) == NULL)
        !           149:         return;
        !           150:     m->m_data += if_maxlinkhdr;
        !           151:     rbp = (struct bootp_t *)m->m_data;
        !           152:     m->m_data += sizeof(struct udpiphdr);
        !           153:     memset(rbp, 0, sizeof(struct bootp_t));
        !           154: 
        !           155:     if (dhcp_msg_type == DHCPDISCOVER) {
        !           156:     new_addr:
        !           157:         bc = get_new_addr(&daddr.sin_addr);
        !           158:         if (!bc) {
        !           159:             dprintf("no address left\n");
        !           160:             return;
        !           161:         }
        !           162:         memcpy(bc->macaddr, client_ethaddr, 6);
        !           163:     } else {
        !           164:         bc = find_addr(&daddr.sin_addr, bp->bp_hwaddr);
        !           165:         if (!bc) {
        !           166:             /* if never assigned, behaves as if it was already
        !           167:                assigned (windows fix because it remembers its address) */
        !           168:             goto new_addr;
        !           169:         }
        !           170:     }
        !           171:     dprintf("offered addr=%08x\n", ntohl(daddr.sin_addr.s_addr));
        !           172: 
        !           173:     saddr.sin_addr.s_addr = htonl(ntohl(special_addr.s_addr) | CTL_ALIAS);
        !           174:     saddr.sin_port = htons(BOOTP_SERVER);
        !           175: 
        !           176:     daddr.sin_port = htons(BOOTP_CLIENT);
        !           177: 
        !           178:     rbp->bp_op = BOOTP_REPLY;
        !           179:     rbp->bp_xid = bp->bp_xid;
        !           180:     rbp->bp_htype = 1;
        !           181:     rbp->bp_hlen = 6;
        !           182:     memcpy(rbp->bp_hwaddr, bp->bp_hwaddr, 6);
        !           183: 
        !           184:     rbp->bp_yiaddr = daddr.sin_addr; /* Client IP address */
        !           185:     rbp->bp_siaddr = saddr.sin_addr; /* Server IP address */
        !           186: 
        !           187:     q = rbp->bp_vend;
        !           188:     memcpy(q, rfc1533_cookie, 4);
        !           189:     q += 4;
        !           190: 
        !           191:     if (dhcp_msg_type == DHCPDISCOVER) {
        !           192:         *q++ = RFC2132_MSG_TYPE;
        !           193:         *q++ = 1;
        !           194:         *q++ = DHCPOFFER;
        !           195:     } else if (dhcp_msg_type == DHCPREQUEST) {
        !           196:         *q++ = RFC2132_MSG_TYPE;
        !           197:         *q++ = 1;
        !           198:         *q++ = DHCPACK;
        !           199:     }
        !           200:         
        !           201:     if (dhcp_msg_type == DHCPDISCOVER ||
        !           202:         dhcp_msg_type == DHCPREQUEST) {
        !           203:         *q++ = RFC2132_SRV_ID;
        !           204:         *q++ = 4;
        !           205:         memcpy(q, &saddr.sin_addr, 4);
        !           206:         q += 4;
        !           207: 
        !           208:         *q++ = RFC1533_NETMASK;
        !           209:         *q++ = 4;
        !           210:         *q++ = 0xff;
        !           211:         *q++ = 0xff;
        !           212:         *q++ = 0xff;
        !           213:         *q++ = 0x00;
        !           214:         
        !           215:         *q++ = RFC1533_GATEWAY;
        !           216:         *q++ = 4;
        !           217:         memcpy(q, &saddr.sin_addr, 4);
        !           218:         q += 4;
        !           219:         
        !           220:         *q++ = RFC1533_DNS;
        !           221:         *q++ = 4;
        !           222:         dns_addr.s_addr = htonl(ntohl(special_addr.s_addr) | CTL_DNS);
        !           223:         memcpy(q, &dns_addr, 4);
        !           224:         q += 4;
        !           225: 
        !           226:         *q++ = RFC2132_LEASE_TIME;
        !           227:         *q++ = 4;
        !           228:         val = htonl(LEASE_TIME);
        !           229:         memcpy(q, &val, 4);
        !           230:         q += 4;
        !           231:     }
        !           232:     *q++ = RFC1533_END;
        !           233:     
        !           234:     m->m_len = sizeof(struct bootp_t) - 
        !           235:         sizeof(struct ip) - sizeof(struct udphdr);
        !           236:     udp_output2(NULL, m, &saddr, &daddr, IPTOS_LOWDELAY);
        !           237: }
        !           238: 
        !           239: void bootp_input(struct mbuf *m)
        !           240: {
        !           241:     struct bootp_t *bp = mtod(m, struct bootp_t *);
        !           242: 
        !           243:     if (bp->bp_op == BOOTP_REQUEST) {
        !           244:         bootp_reply(bp);
        !           245:     }
        !           246: }

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