X-Git-Url: https://git.grml.org/?a=blobdiff_plain;f=udhcp%2Fclientpacket.c;fp=udhcp%2Fclientpacket.c;h=c5e1c210b0377c2369886b1a78680d2d4d9d5722;hb=d0c93c365e33f6970a0417dff7009a4a4fe2a3b1;hp=0000000000000000000000000000000000000000;hpb=184a9d3153e3fae4fa1ea20a186c12e9c0a83db2;p=grml-terminalserver.git diff --git a/udhcp/clientpacket.c b/udhcp/clientpacket.c new file mode 100644 index 0000000..c5e1c21 --- /dev/null +++ b/udhcp/clientpacket.c @@ -0,0 +1,249 @@ +/* clientpacket.c + * + * Packet generation and dispatching functions for the DHCP client. + * + * Russ Dill July 2001 + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. + */ + +#include +#include +#include +#if __GLIBC__ >=2 && __GLIBC_MINOR >= 1 +#include +#include +#else +#include +#include +#include +#endif +#include +#include +#include +#include +#include +#include + + +#include "dhcpd.h" +#include "clientpacket.h" +#include "options.h" +#include "dhcpc.h" +#include "common.h" + + +/* Create a random xid */ +unsigned long random_xid(void) +{ + static int initialized; + if (!initialized) { + int fd; + unsigned long seed; + + fd = open("/dev/urandom", 0); + if (fd < 0 || read(fd, &seed, sizeof(seed)) < 0) { + LOG(LOG_WARNING, "Could not load seed from /dev/urandom: %m"); + seed = time(0); + } + if (fd >= 0) close(fd); + srand(seed); + initialized++; + } + return rand(); +} + + +/* initialize a packet with the proper defaults */ +static void init_packet(struct dhcpMessage *packet, char type) +{ + struct vendor { + char vendor, length; + char str[sizeof("udhcp "VERSION)]; + } vendor_id = { DHCP_VENDOR, sizeof("udhcp "VERSION) - 1, "udhcp "VERSION}; + + init_header(packet, type); + memcpy(packet->chaddr, client_config.arp, 6); + add_option_string(packet->options, client_config.clientid); + if (client_config.hostname) add_option_string(packet->options, client_config.hostname); + if (client_config.fqdn) add_option_string(packet->options, client_config.fqdn); + add_option_string(packet->options, (uint8_t *) &vendor_id); +} + + +/* Add a parameter request list for stubborn DHCP servers. Pull the data + * from the struct in options.c. Don't do bounds checking here because it + * goes towards the head of the packet. */ +static void add_requests(struct dhcpMessage *packet) +{ + int end = end_option(packet->options); + int i, len = 0; + + packet->options[end + OPT_CODE] = DHCP_PARAM_REQ; + for (i = 0; dhcp_options[i].code; i++) + if (dhcp_options[i].flags & OPTION_REQ) + packet->options[end + OPT_DATA + len++] = dhcp_options[i].code; + packet->options[end + OPT_LEN] = len; + packet->options[end + OPT_DATA + len] = DHCP_END; + +} + + +/* Broadcast a DHCP discover packet to the network, with an optionally requested IP */ +int send_discover(unsigned long xid, unsigned long requested) +{ + struct dhcpMessage packet; + + init_packet(&packet, DHCPDISCOVER); + packet.xid = xid; + if (requested) + add_simple_option(packet.options, DHCP_REQUESTED_IP, requested); + + add_requests(&packet); + LOG(LOG_DEBUG, "Sending discover..."); + return raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST, + SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex); +} + + +/* Broadcasts a DHCP request message */ +int send_selecting(unsigned long xid, unsigned long server, unsigned long requested) +{ + struct dhcpMessage packet; + struct in_addr addr; + + init_packet(&packet, DHCPREQUEST); + packet.xid = xid; + + add_simple_option(packet.options, DHCP_REQUESTED_IP, requested); + add_simple_option(packet.options, DHCP_SERVER_ID, server); + + add_requests(&packet); + addr.s_addr = requested; + LOG(LOG_DEBUG, "Sending select for %s...", inet_ntoa(addr)); + return raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST, + SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex); +} + + +/* Unicasts or broadcasts a DHCP renew message */ +int send_renew(unsigned long xid, unsigned long server, unsigned long ciaddr) +{ + struct dhcpMessage packet; + int ret = 0; + + init_packet(&packet, DHCPREQUEST); + packet.xid = xid; + packet.ciaddr = ciaddr; + + add_requests(&packet); + LOG(LOG_DEBUG, "Sending renew..."); + if (server) + ret = kernel_packet(&packet, ciaddr, CLIENT_PORT, server, SERVER_PORT); + else ret = raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST, + SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex); + return ret; +} + + +/* Unicasts a DHCP release message */ +int send_release(unsigned long server, unsigned long ciaddr) +{ + struct dhcpMessage packet; + + init_packet(&packet, DHCPRELEASE); + packet.xid = random_xid(); + packet.ciaddr = ciaddr; + + add_simple_option(packet.options, DHCP_REQUESTED_IP, ciaddr); + add_simple_option(packet.options, DHCP_SERVER_ID, server); + + LOG(LOG_DEBUG, "Sending release..."); + return kernel_packet(&packet, ciaddr, CLIENT_PORT, server, SERVER_PORT); +} + + +/* return -1 on errors that are fatal for the socket, -2 for those that aren't */ +int get_raw_packet(struct dhcpMessage *payload, int fd) +{ + int bytes; + struct udp_dhcp_packet packet; + uint32_t source, dest; + uint16_t check; + + memset(&packet, 0, sizeof(struct udp_dhcp_packet)); + bytes = read(fd, &packet, sizeof(struct udp_dhcp_packet)); + if (bytes < 0) { + DEBUG(LOG_INFO, "couldn't read on raw listening socket -- ignoring"); + usleep(500000); /* possible down interface, looping condition */ + return -1; + } + + if (bytes < (int) (sizeof(struct iphdr) + sizeof(struct udphdr))) { + DEBUG(LOG_INFO, "message too short, ignoring"); + return -2; + } + + if (bytes < ntohs(packet.ip.tot_len)) { + DEBUG(LOG_INFO, "Truncated packet"); + return -2; + } + + /* ignore any extra garbage bytes */ + bytes = ntohs(packet.ip.tot_len); + + /* Make sure its the right packet for us, and that it passes sanity checks */ + if (packet.ip.protocol != IPPROTO_UDP || packet.ip.version != IPVERSION || + packet.ip.ihl != sizeof(packet.ip) >> 2 || packet.udp.dest != htons(CLIENT_PORT) || + bytes > (int) sizeof(struct udp_dhcp_packet) || + ntohs(packet.udp.len) != (uint16_t) (bytes - sizeof(packet.ip))) { + DEBUG(LOG_INFO, "unrelated/bogus packet"); + return -2; + } + + /* check IP checksum */ + check = packet.ip.check; + packet.ip.check = 0; + if (check != checksum(&(packet.ip), sizeof(packet.ip))) { + DEBUG(LOG_INFO, "bad IP header checksum, ignoring"); + return -1; + } + + /* verify the UDP checksum by replacing the header with a psuedo header */ + source = packet.ip.saddr; + dest = packet.ip.daddr; + check = packet.udp.check; + packet.udp.check = 0; + memset(&packet.ip, 0, sizeof(packet.ip)); + + packet.ip.protocol = IPPROTO_UDP; + packet.ip.saddr = source; + packet.ip.daddr = dest; + packet.ip.tot_len = packet.udp.len; /* cheat on the psuedo-header */ + if (check && check != checksum(&packet, bytes)) { + DEBUG(LOG_ERR, "packet with bad UDP checksum received, ignoring"); + return -2; + } + + memcpy(payload, &(packet.data), bytes - (sizeof(packet.ip) + sizeof(packet.udp))); + + if (ntohl(payload->cookie) != DHCP_MAGIC) { + LOG(LOG_ERR, "received bogus message (bad magic) -- ignoring"); + return -2; + } + DEBUG(LOG_INFO, "oooooh!!! got some!"); + return bytes - (sizeof(packet.ip) + sizeof(packet.udp)); + +}