slirp/dhcpv6.c

   1 /*
   2  * SLIRP stateless DHCPv6
   3  *
   4  * We only support stateless DHCPv6, e.g. for network booting.
   5  * See RFC 3315, RFC 3736, RFC 3646 and RFC 5970 for details.
   6  *
   7  * Copyright 2016 Thomas Huth, Red Hat Inc.
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License as published by
  11  * the Free Software Foundation; either version 2 of the License,
  12  * or (at your option) any later version.
  13  *
  14  * This program is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17  * GNU General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU General Public License
  20  * along with this program; if not, see <http://www.gnu.org/licenses/>.
  21  */
  22
  23 #include "slirp.h"
  24 #include "dhcpv6.h"
  25
  26 /* DHCPv6 message types */
  27 #define MSGTYPE_REPLY        7
  28 #define MSGTYPE_INFO_REQUEST 11
  29
  30 /* DHCPv6 option types */
  31 #define OPTION_CLIENTID      1
  32 #define OPTION_IAADDR        5
  33 #define OPTION_ORO           6
  34 #define OPTION_DNS_SERVERS   23
  35 #define OPTION_BOOTFILE_URL  59
  36
  37 struct requested_infos {
  38     uint8_t *client_id;
  39     int client_id_len;
  40     bool want_dns;
  41     bool want_boot_url;
  42 };
  43
  44 /**
  45  * Analyze the info request message sent by the client to see what data it
  46  * provided and what it wants to have. The information is gathered in the
  47  * "requested_infos" struct. Note that client_id (if provided) points into
  48  * the odata region, thus the caller must keep odata valid as long as it
  49  * needs to access the requested_infos struct.
  50  */
  51 static int dhcpv6_parse_info_request(Slirp *slirp, uint8_t *odata, int olen,
  52                                      struct requested_infos *ri)
  53 {
  54     int i, req_opt;
  55
  56     while (olen > 4) {
  57         /* Parse one option */
  58         int option = odata[0] << 8 | odata[1];
  59         int len = odata[2] << 8 | odata[3];
  60
  61         if (len + 4 > olen) {
  62             slirp->cb->guest_error("Guest sent bad DHCPv6 packet!", slirp->opaque);
  63             return -E2BIG;
  64         }
  65
  66         switch (option) {
  67         case OPTION_IAADDR:
  68             /* According to RFC3315, we must discard requests with IA option */
  69             return -EINVAL;
  70         case OPTION_CLIENTID:
  71             if (len > 256) {
  72                 /* Avoid very long IDs which could cause problems later */
  73                 return -E2BIG;
  74             }
  75             ri->client_id = odata + 4;
  76             ri->client_id_len = len;
  77             break;
  78         case OPTION_ORO:        /* Option request option */
  79             if (len & 1) {
  80                 return -EINVAL;
  81             }
  82             /* Check which options the client wants to have */
  83             for (i = 0; i < len; i += 2) {
  84                 req_opt = odata[4 + i] << 8 | odata[4 + i + 1];
  85                 switch (req_opt) {
  86                 case OPTION_DNS_SERVERS:
  87                     ri->want_dns = true;
  88                     break;
  89                 case OPTION_BOOTFILE_URL:
  90                     ri->want_boot_url = true;
  91                     break;
  92                 default:
  93                     DEBUG_MISC("dhcpv6: Unsupported option request %d",
  94                                req_opt);
  95                 }
  96             }
  97             break;
  98         default:
  99             DEBUG_MISC("dhcpv6 info req: Unsupported option %d, len=%d",
 100                        option, len);
 101         }
 102
 103         odata += len + 4;
 104         olen -= len + 4;
 105     }
 106
 107     return 0;
 108 }
 109
 110
 111 /**
 112  * Handle information request messages
 113  */
 114 static void dhcpv6_info_request(Slirp *slirp, struct sockaddr_in6 *srcsas,
 115                                 uint32_t xid, uint8_t *odata, int olen)
 116 {
 117     struct requested_infos ri = { NULL };
 118     struct sockaddr_in6 sa6, da6;
 119     struct mbuf *m;
 120     uint8_t *resp;
 121
 122     if (dhcpv6_parse_info_request(slirp, odata, olen, &ri) < 0) {
 123         return;
 124     }
 125
 126     m = m_get(slirp);
 127     if (!m) {
 128         return;
 129     }
 130     memset(m->m_data, 0, m->m_size);
 131     m->m_data += IF_MAXLINKHDR;
 132     resp = (uint8_t *)m->m_data + sizeof(struct ip6) + sizeof(struct udphdr);
 133
 134     /* Fill in response */
 135     *resp++ = MSGTYPE_REPLY;
 136     *resp++ = (uint8_t)(xid >> 16);
 137     *resp++ = (uint8_t)(xid >> 8);
 138     *resp++ = (uint8_t)xid;
 139
 140     if (ri.client_id) {
 141         *resp++ = OPTION_CLIENTID >> 8;         /* option-code high byte */
 142         *resp++ = OPTION_CLIENTID;              /* option-code low byte */
 143         *resp++ = ri.client_id_len >> 8;        /* option-len high byte */
 144         *resp++ = ri.client_id_len;             /* option-len low byte */
 145         memcpy(resp, ri.client_id, ri.client_id_len);
 146         resp += ri.client_id_len;
 147     }
 148     if (ri.want_dns) {
 149         *resp++ = OPTION_DNS_SERVERS >> 8;      /* option-code high byte */
 150         *resp++ = OPTION_DNS_SERVERS;           /* option-code low byte */
 151         *resp++ = 0;                            /* option-len high byte */
 152         *resp++ = 16;                           /* option-len low byte */
 153         memcpy(resp, &slirp->vnameserver_addr6, 16);
 154         resp += 16;
 155     }
 156     if (ri.want_boot_url) {
 157         uint8_t *sa = slirp->vhost_addr6.s6_addr;
 158         int slen, smaxlen;
 159
 160         *resp++ = OPTION_BOOTFILE_URL >> 8;     /* option-code high byte */
 161         *resp++ = OPTION_BOOTFILE_URL;          /* option-code low byte */
 162         smaxlen = (uint8_t *)m->m_data + IF_MTU - (resp + 2);
 163         slen = snprintf((char *)resp + 2, smaxlen,
 164                         "tftp://[%02x%02x:%02x%02x:%02x%02x:%02x%02x:"
 165                                 "%02x%02x:%02x%02x:%02x%02x:%02x%02x]/%s",
 166                         sa[0], sa[1], sa[2], sa[3], sa[4], sa[5], sa[6], sa[7],
 167                         sa[8], sa[9], sa[10], sa[11], sa[12], sa[13], sa[14],
 168                         sa[15], slirp->bootp_filename);
 169         slen = MIN(slen, smaxlen);
 170         *resp++ = slen >> 8;                    /* option-len high byte */
 171         *resp++ = slen;                         /* option-len low byte */
 172         resp += slen;
 173     }
 174
 175     sa6.sin6_addr = slirp->vhost_addr6;
 176     sa6.sin6_port = DHCPV6_SERVER_PORT;
 177     da6.sin6_addr = srcsas->sin6_addr;
 178     da6.sin6_port = srcsas->sin6_port;
 179     m->m_data += sizeof(struct ip6) + sizeof(struct udphdr);
 180     m->m_len = resp - (uint8_t *)m->m_data;
 181     udp6_output(NULL, m, &sa6, &da6);
 182 }
 183
 184 /**
 185  * Handle DHCPv6 messages sent by the client
 186  */
 187 void dhcpv6_input(struct sockaddr_in6 *srcsas, struct mbuf *m)
 188 {
 189     uint8_t *data = (uint8_t *)m->m_data + sizeof(struct udphdr);
 190     int data_len = m->m_len - sizeof(struct udphdr);
 191     uint32_t xid;
 192
 193     if (data_len < 4) {
 194         return;
 195     }
 196
 197     xid = ntohl(*(uint32_t *)data) & 0xffffff;
 198
 199     switch (data[0]) {
 200     case MSGTYPE_INFO_REQUEST:
 201         dhcpv6_info_request(m->slirp, srcsas, xid, &data[4], data_len - 4);
 202         break;
 203     default:
 204         DEBUG_MISC("dhcpv6_input: Unsupported message type 0x%x", data[0]);
 205     }
 206 }