--- /dev/null
+/* clientpacket.c
+ *
+ * Packet generation and dispatching functions for the DHCP client.
+ *
+ * Russ Dill <Russ.Dill@asu.edu> 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 <string.h>
+#include <sys/socket.h>
+#include <features.h>
+#if __GLIBC__ >=2 && __GLIBC_MINOR >= 1
+#include <netpacket/packet.h>
+#include <net/ethernet.h>
+#else
+#include <asm/types.h>
+#include <linux/if_packet.h>
+#include <linux/if_ether.h>
+#endif
+#include <stdlib.h>
+#include <time.h>
+#include <unistd.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <fcntl.h>
+
+
+#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));
+
+}
projects / grml-terminalserver.git / blobdiff