userapps/opensource/udhcp/clientpacket.c

   1 /* clientpacket.c
   2  *
   3  * Packet generation and dispatching functions for the DHCP client.
   4  *
   5  * Russ Dill <Russ.Dill@asu.edu> July 2001
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  20  */
  21
  22 #include <string.h>
  23 #include <sys/socket.h>
  24 #include <features.h>
  25 #if __GLIBC__ >=2 && __GLIBC_MINOR >= 1
  26 #include <netpacket/packet.h>
  27 #include <net/ethernet.h>
  28 #else
  29 #include <asm/types.h>
  30 #include <linux/if_packet.h>
  31 #include <linux/if_ether.h>
  32 #endif
  33 #include <stdlib.h>
  34 #include <time.h>
  35 #include <unistd.h>
  36 #include <netinet/in.h>
  37 #include <arpa/inet.h>
  38
  39
  40 #include "dhcpd.h"
  41 #include "packet.h"
  42 #include "options.h"
  43 #include "dhcpc.h"
  44 #include "debug.h"
  45
  46
  47 /* Create a random xid */
  48 unsigned long random_xid(void)
  49 {
  50         static int initialized;
  51         if (!initialized) {
  52                 srand(time(0));
  53                 initialized++;
  54         }
  55         return rand();
  56 }
  57
  58
  59 /* initialize a packet with the proper defaults */
  60 static void init_packet(struct dhcpMessage *packet, char type)
  61 {
  62         //brcm
  63         char VIinfo[VENDOR_IDENTIFYING_INFO_LEN];
  64
  65         struct vendor  {
  66                 char vendor, length;
  67                 char str[sizeof("uDHCP "VERSION)];
  68         } vendor_id = { DHCP_VENDOR,  sizeof("uDHCP "VERSION) - 1, "uDHCP "VERSION};
  69
  70         memset(packet, 0, sizeof(struct dhcpMessage));
  71
  72         packet->op = BOOTREQUEST;
  73         packet->htype = ETH_10MB;
  74         packet->hlen = ETH_10MB_LEN;
  75         packet->cookie = htonl(DHCP_MAGIC);
  76         packet->options[0] = DHCP_END;
  77         memcpy(packet->chaddr, client_config.arp, 6);
  78         add_simple_option(packet->options, DHCP_MESSAGE_TYPE, type);
  79         if (client_config.clientid) add_option_string(packet->options, client_config.clientid);
  80         if (client_config.hostname) add_option_string(packet->options, client_config.hostname);
  81         // brcm
  82         if (strlen(vendor_class_id)) {
  83             vendor_id.length = strlen(vendor_class_id);
  84             sprintf(vendor_id.str, "%s", vendor_class_id);
  85         }
  86         add_option_string(packet->options, (char *) &vendor_id);
  87         if (createVIoption(VENDOR_IDENTIFYING_FOR_DEVICE,VIinfo) != -1)
  88             add_option_string(packet->options,VIinfo);
  89 }
  90
  91
  92 /* Add a paramater request list for stubborn DHCP servers */
  93 static void add_requests(struct dhcpMessage *packet)
  94 {
  95         char request_list[] = {DHCP_PARAM_REQ, 0, PARM_REQUESTS};
  96
  97         request_list[OPT_LEN] = sizeof(request_list) - 2;
  98         add_option_string(packet->options, request_list);
  99 }
 100
 101
 102 /* Broadcast a DHCP discover packet to the network, with an optionally requested IP */
 103 int send_discover(unsigned long xid, unsigned long requested)
 104 {
 105         struct dhcpMessage packet;
 106
 107         init_packet(&packet, DHCPDISCOVER);
 108         packet.xid = xid;
 109         if (requested)
 110                 add_simple_option(packet.options, DHCP_REQUESTED_IP, ntohl(requested));
 111
 112         add_requests(&packet);
 113         // brcm
 114         // LOG(LOG_DEBUG, "Sending discover...");
 115         return raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
 116                                 SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex);
 117 }
 118
 119
 120 /* Broadcasts a DHCP request message */
 121 int send_selecting(unsigned long xid, unsigned long server, unsigned long requested)
 122 {
 123         struct dhcpMessage packet;
 124         struct in_addr addr;
 125
 126         init_packet(&packet, DHCPREQUEST);
 127         packet.xid = xid;
 128
 129         /* expects host order */
 130         add_simple_option(packet.options, DHCP_REQUESTED_IP, ntohl(requested));
 131
 132         /* expects host order */
 133         add_simple_option(packet.options, DHCP_SERVER_ID, ntohl(server));
 134
 135         add_requests(&packet);
 136         addr.s_addr = requested;
 137         // brcm
 138         //LOG(LOG_DEBUG, "Sending select for %s...", inet_ntoa(addr));
 139         return raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
 140                                 SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex);
 141 }
 142
 143
 144 /* Unicasts or broadcasts a DHCP renew message */
 145 int send_renew(unsigned long xid, unsigned long server, unsigned long ciaddr)
 146 {
 147         struct dhcpMessage packet;
 148         int ret = 0;
 149
 150         init_packet(&packet, DHCPREQUEST);
 151         packet.xid = xid;
 152         packet.ciaddr = ciaddr;
 153
 154         LOG(LOG_DEBUG, "Sending renew...");
 155         if (server)
 156                 ret = kernel_packet(&packet, ciaddr, CLIENT_PORT, server, SERVER_PORT);
 157         else ret = raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
 158                                 SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex);
 159         return ret;
 160 }
 161
 162
 163 /* Unicasts a DHCP release message */
 164 int send_release(unsigned long server, unsigned long ciaddr)
 165 {
 166         struct dhcpMessage packet;
 167
 168         init_packet(&packet, DHCPRELEASE);
 169         packet.xid = random_xid();
 170         packet.ciaddr = ciaddr;
 171
 172         /* expects host order */
 173         add_simple_option(packet.options, DHCP_REQUESTED_IP, ntohl(ciaddr));
 174         add_simple_option(packet.options, DHCP_SERVER_ID, ntohl(server));
 175
 176         LOG(LOG_DEBUG, "Sending release...");
 177         return kernel_packet(&packet, ciaddr, CLIENT_PORT, server, SERVER_PORT);
 178 }
 179
 180
 181 int get_raw_packet(struct dhcpMessage *payload, int fd)
 182 {
 183         int bytes;
 184         struct udp_dhcp_packet packet;
 185         u_int32_t source, dest;
 186         u_int16_t check;
 187
 188         memset(&packet, 0, sizeof(struct udp_dhcp_packet));
 189         bytes = read(fd, &packet, sizeof(struct udp_dhcp_packet));
 190         if (bytes < 0) {
 191                 DEBUG(LOG_INFO, "couldn't read on raw listening socket -- ignoring");
 192                 usleep(500000); /* possible down interface, looping condition */
 193                 return -1;
 194         }
 195
 196         if (bytes < (int) (sizeof(struct iphdr) + sizeof(struct udphdr))) {
 197                 DEBUG(LOG_INFO, "message too short, ignoring");
 198                 return -1;
 199         }
 200
 201         /* Make sure its the right packet for us, and that it passes sanity checks */
 202         if (packet.ip.protocol != IPPROTO_UDP || packet.ip.version != IPVERSION ||
 203             packet.ip.ihl != sizeof(packet.ip) >> 2 || packet.udp.dest != htons(CLIENT_PORT) ||
 204             ntohs(packet.ip.tot_len) != bytes || bytes > (int) sizeof(struct udp_dhcp_packet) ||
 205             ntohs(packet.udp.len) != (short) (bytes - sizeof(packet.ip))) {
 206                 DEBUG(LOG_INFO, "unrelated/bogus packet");
 207                 return -1;
 208         }
 209
 210         /* check IP checksum */
 211         check = packet.ip.check;
 212         packet.ip.check = 0;
 213         if (check != checksum(&(packet.ip), sizeof(packet.ip))) {
 214                 DEBUG(LOG_INFO, "bad IP header checksum, ignoring");
 215                 return -1;
 216         }
 217
 218         /* verify the UDP checksum by replacing the header with a psuedo header */
 219         source = packet.ip.saddr;
 220         dest = packet.ip.daddr;
 221         check = packet.udp.check;
 222         packet.udp.check = 0;
 223         memset(&packet.ip, 0, sizeof(packet.ip));
 224
 225         packet.ip.protocol = IPPROTO_UDP;
 226         packet.ip.saddr = source;
 227         packet.ip.daddr = dest;
 228         packet.ip.tot_len = packet.udp.len; /* cheat on the psuedo-header */
 229         // brcm
 230         /*
 231         if (check != checksum(&packet, bytes)) {
 232                 DEBUG(LOG_ERR, "packet with bad UDP checksum received, ignoring");
 233                 // cwu
 234                 //return -1;
 235         }
 236         */
 237
 238         memcpy(payload, &(packet.data), bytes - (sizeof(packet.ip) + sizeof(packet.udp)));
 239
 240         if (ntohl(payload->cookie) != DHCP_MAGIC) {
 241                 LOG(LOG_ERR, "received bogus message (bad magic) -- ignoring");
 242                 return -1;
 243         }
 244         DEBUG(LOG_INFO, "oooooh!!! got some!");
 245         return bytes - (sizeof(packet.ip) + sizeof(packet.udp));
 246 }