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 "qemu/osdep.h"
  24 #include "qemu/log.h"
  25 #include "slirp.h"
  26 #include "dhcpv6.h"
  27
  28 /* DHCPv6 message types */
  29 #define MSGTYPE_REPLY        7
  30 #define MSGTYPE_INFO_REQUEST 11
  31
  32 /* DHCPv6 option types */
  33 #define OPTION_CLIENTID      1
  34 #define OPTION_IAADDR        5
  35 #define OPTION_ORO           6
  36 #define OPTION_DNS_SERVERS   23
  37 #define OPTION_BOOTFILE_URL  59
  38
  39 struct requested_infos {
  40     uint8_t *client_id;
  41     int client_id_len;
  42     bool want_dns;
  43     bool want_boot_url;
  44 };
  45
  46 /**
  47  * Analyze the info request message sent by the client to see what data it
  48  * provided and what it wants to have. The information is gathered in the
  49  * "requested_infos" struct. Note that client_id (if provided) points into
  50  * the odata region, thus the caller must keep odata valid as long as it
  51  * needs to access the requested_infos struct.
  52  */
  53 static int dhcpv6_parse_info_request(uint8_t *odata, int olen,
  54                                      struct requested_infos *ri)
  55 {
  56     int i, req_opt;
  57
  58     while (olen > 4) {
  59         /* Parse one option */
  60         int option = odata[0] << 8 | odata[1];
  61         int len = odata[2] << 8 | odata[3];
  62
  63         if (len + 4 > olen) {
  64             qemu_log_mask(LOG_GUEST_ERROR, "Guest sent bad DHCPv6 packet!\n");
  65             return -E2BIG;
  66         }
  67
  68         switch (option) {
  69         case OPTION_IAADDR:
  70             /* According to RFC3315, we must discard requests with IA option */
  71             return -EINVAL;
  72         case OPTION_CLIENTID:
  73             if (len > 256) {
  74                 /* Avoid very long IDs which could cause problems later */
  75                 return -E2BIG;
  76             }
  77             ri->client_id = odata + 4;
  78             ri->client_id_len = len;
  79             break;
  80         case OPTION_ORO:        /* Option request option */
  81             if (len & 1) {
  82                 return -EINVAL;
  83             }
  84             /* Check which options the client wants to have */
  85             for (i = 0; i < len; i += 2) {
  86                 req_opt = odata[4 + i] << 8 | odata[4 + i + 1];
  87                 switch (req_opt) {
  88                 case OPTION_DNS_SERVERS:
  89                     ri->want_dns = true;
  90                     break;
  91                 case OPTION_BOOTFILE_URL:
  92                     ri->want_boot_url = true;
  93                     break;
  94                 default:
  95                     DEBUG_MISC((dfd, "dhcpv6: Unsupported option request %d\n",
  96                                 req_opt));
  97                 }
  98             }
  99             break;
 100         default:
 101             DEBUG_MISC((dfd, "dhcpv6 info req: Unsupported option %d, len=%d\n",
 102                         option, len));
 103         }
 104
 105         odata += len + 4;
 106         olen -= len + 4;
 107     }
 108
 109     return 0;
 110 }
 111
 112
 113 /**
 114  * Handle information request messages
 115  */
 116 static void dhcpv6_info_request(Slirp *slirp, struct sockaddr_in6 *srcsas,
 117                                 uint32_t xid, uint8_t *odata, int olen)
 118 {
 119     struct requested_infos ri = { NULL };
 120     struct sockaddr_in6 sa6, da6;
 121     struct mbuf *m;
 122     uint8_t *resp;
 123
 124     if (dhcpv6_parse_info_request(odata, olen, &ri) < 0) {
 125         return;
 126     }
 127
 128     m = m_get(slirp);
 129     if (!m) {
 130         return;
 131     }
 132     memset(m->m_data, 0, m->m_size);
 133     m->m_data += IF_MAXLINKHDR;
 134     resp = (uint8_t *)m->m_data + sizeof(struct ip6) + sizeof(struct udphdr);
 135
 136     /* Fill in response */
 137     *resp++ = MSGTYPE_REPLY;
 138     *resp++ = (uint8_t)(xid >> 16);
 139     *resp++ = (uint8_t)(xid >> 8);
 140     *resp++ = (uint8_t)xid;
 141
 142     if (ri.client_id) {
 143         *resp++ = OPTION_CLIENTID >> 8;         /* option-code high byte */
 144         *resp++ = OPTION_CLIENTID;              /* option-code low byte */
 145         *resp++ = ri.client_id_len >> 8;        /* option-len high byte */
 146         *resp++ = ri.client_id_len;             /* option-len low byte */
 147         memcpy(resp, ri.client_id, ri.client_id_len);
 148         resp += ri.client_id_len;
 149     }
 150     if (ri.want_dns) {
 151         *resp++ = OPTION_DNS_SERVERS >> 8;      /* option-code high byte */
 152         *resp++ = OPTION_DNS_SERVERS;           /* option-code low byte */
 153         *resp++ = 0;                            /* option-len high byte */
 154         *resp++ = 16;                           /* option-len low byte */
 155         memcpy(resp, &slirp->vnameserver_addr6, 16);
 156         resp += 16;
 157     }
 158     if (ri.want_boot_url) {
 159         uint8_t *sa = slirp->vhost_addr6.s6_addr;
 160         int slen, smaxlen;
 161
 162         *resp++ = OPTION_BOOTFILE_URL >> 8;     /* option-code high byte */
 163         *resp++ = OPTION_BOOTFILE_URL;          /* option-code low byte */
 164         smaxlen = (uint8_t *)m->m_data + IF_MTU - (resp + 2);
 165         slen = snprintf((char *)resp + 2, smaxlen,
 166                         "tftp://[%02x%02x:%02x%02x:%02x%02x:%02x%02x:"
 167                                 "%02x%02x:%02x%02x:%02x%02x:%02x%02x]/%s",
 168                         sa[0], sa[1], sa[2], sa[3], sa[4], sa[5], sa[6], sa[7],
 169                         sa[8], sa[9], sa[10], sa[11], sa[12], sa[13], sa[14],
 170                         sa[15], slirp->bootp_filename);
 171         slen = min(slen, smaxlen);
 172         *resp++ = slen >> 8;                    /* option-len high byte */
 173         *resp++ = slen;                         /* option-len low byte */
 174         resp += slen;
 175     }
 176
 177     sa6.sin6_addr = slirp->vhost_addr6;
 178     sa6.sin6_port = DHCPV6_SERVER_PORT;
 179     da6.sin6_addr = srcsas->sin6_addr;
 180     da6.sin6_port = srcsas->sin6_port;
 181     m->m_data += sizeof(struct ip6) + sizeof(struct udphdr);
 182     m->m_len = resp - (uint8_t *)m->m_data;
 183     udp6_output(NULL, m, &sa6, &da6);
 184 }
 185
 186 /**
 187  * Handle DHCPv6 messages sent by the client
 188  */
 189 void dhcpv6_input(struct sockaddr_in6 *srcsas, struct mbuf *m)
 190 {
 191     uint8_t *data = (uint8_t *)m->m_data + sizeof(struct udphdr);
 192     int data_len = m->m_len - sizeof(struct udphdr);
 193     uint32_t xid;
 194
 195     if (data_len < 4) {
 196         return;
 197     }
 198
 199     xid = ntohl(*(uint32_t *)data) & 0xffffff;
 200
 201     switch (data[0]) {
 202     case MSGTYPE_INFO_REQUEST:
 203         dhcpv6_info_request(m->slirp, srcsas, xid, &data[4], data_len - 4);
 204         break;
 205     default:
 206         DEBUG_MISC((dfd, "dhcpv6_input: Unsupported message type 0x%x\n",
 207                     data[0]));
 208     }
 209 }