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-rw-r--r--networking/udhcp/packet.c207
1 files changed, 207 insertions, 0 deletions
diff --git a/networking/udhcp/packet.c b/networking/udhcp/packet.c
new file mode 100644
index 0000000..ae06d53
--- /dev/null
+++ b/networking/udhcp/packet.c
@@ -0,0 +1,207 @@
+#include <unistd.h>
+#include <string.h>
+#include <netinet/in.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <features.h>
+#if (__GLIBC__ >= 2 && __GLIBC_MINOR >= 1) || defined _NEWLIB_VERSION
+#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 <errno.h>
+
+#include "common.h"
+#include "packet.h"
+#include "dhcpd.h"
+#include "options.h"
+
+
+void init_header(struct dhcpMessage *packet, char type)
+{
+ memset(packet, 0, sizeof(struct dhcpMessage));
+ switch (type) {
+ case DHCPDISCOVER:
+ case DHCPREQUEST:
+ case DHCPRELEASE:
+ case DHCPINFORM:
+ packet->op = BOOTREQUEST;
+ break;
+ case DHCPOFFER:
+ case DHCPACK:
+ case DHCPNAK:
+ packet->op = BOOTREPLY;
+ }
+ packet->htype = ETH_10MB;
+ packet->hlen = ETH_10MB_LEN;
+ packet->cookie = htonl(DHCP_MAGIC);
+ packet->options[0] = DHCP_END;
+ add_simple_option(packet->options, DHCP_MESSAGE_TYPE, type);
+}
+
+
+/* read a packet from socket fd, return -1 on read error, -2 on packet error */
+int get_packet(struct dhcpMessage *packet, int fd)
+{
+ static const char broken_vendors[][8] = {
+ "MSFT 98",
+ ""
+ };
+ int bytes;
+ int i;
+ char unsigned *vendor;
+
+ memset(packet, 0, sizeof(struct dhcpMessage));
+ bytes = read(fd, packet, sizeof(struct dhcpMessage));
+ if (bytes < 0) {
+ DEBUG(LOG_INFO, "couldn't read on listening socket, ignoring");
+ return -1;
+ }
+
+ if (ntohl(packet->cookie) != DHCP_MAGIC) {
+ LOG(LOG_ERR, "received bogus message, ignoring");
+ return -2;
+ }
+ DEBUG(LOG_INFO, "Received a packet");
+
+ if (packet->op == BOOTREQUEST && (vendor = get_option(packet, DHCP_VENDOR))) {
+ for (i = 0; broken_vendors[i][0]; i++) {
+ if (vendor[OPT_LEN - 2] == (uint8_t) strlen(broken_vendors[i]) &&
+ !strncmp((char*)vendor, broken_vendors[i], vendor[OPT_LEN - 2])) {
+ DEBUG(LOG_INFO, "broken client (%s), forcing broadcast",
+ broken_vendors[i]);
+ packet->flags |= htons(BROADCAST_FLAG);
+ }
+ }
+ }
+
+ return bytes;
+}
+
+
+uint16_t checksum(void *addr, int count)
+{
+ /* Compute Internet Checksum for "count" bytes
+ * beginning at location "addr".
+ */
+ register int32_t sum = 0;
+ uint16_t *source = (uint16_t *) addr;
+
+ while (count > 1) {
+ /* This is the inner loop */
+ sum += *source++;
+ count -= 2;
+ }
+
+ /* Add left-over byte, if any */
+ if (count > 0) {
+ /* Make sure that the left-over byte is added correctly both
+ * with little and big endian hosts */
+ uint16_t tmp = 0;
+ *(uint8_t *) (&tmp) = * (uint8_t *) source;
+ sum += tmp;
+ }
+ /* Fold 32-bit sum to 16 bits */
+ while (sum >> 16)
+ sum = (sum & 0xffff) + (sum >> 16);
+
+ return ~sum;
+}
+
+
+/* Construct a ip/udp header for a packet, and specify the source and dest hardware address */
+int raw_packet(struct dhcpMessage *payload, uint32_t source_ip, int source_port,
+ uint32_t dest_ip, int dest_port, uint8_t *dest_arp, int ifindex)
+{
+ int fd;
+ int result;
+ struct sockaddr_ll dest;
+ struct udp_dhcp_packet packet;
+
+ if ((fd = socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP))) < 0) {
+ DEBUG(LOG_ERR, "socket call failed: %m");
+ return -1;
+ }
+
+ memset(&dest, 0, sizeof(dest));
+ memset(&packet, 0, sizeof(packet));
+
+ dest.sll_family = AF_PACKET;
+ dest.sll_protocol = htons(ETH_P_IP);
+ dest.sll_ifindex = ifindex;
+ dest.sll_halen = 6;
+ memcpy(dest.sll_addr, dest_arp, 6);
+ if (bind(fd, (struct sockaddr *)&dest, sizeof(struct sockaddr_ll)) < 0) {
+ DEBUG(LOG_ERR, "bind call failed: %m");
+ close(fd);
+ return -1;
+ }
+
+ packet.ip.protocol = IPPROTO_UDP;
+ packet.ip.saddr = source_ip;
+ packet.ip.daddr = dest_ip;
+ packet.udp.source = htons(source_port);
+ packet.udp.dest = htons(dest_port);
+ packet.udp.len = htons(sizeof(packet.udp) + sizeof(struct dhcpMessage)); /* cheat on the psuedo-header */
+ packet.ip.tot_len = packet.udp.len;
+ memcpy(&(packet.data), payload, sizeof(struct dhcpMessage));
+ packet.udp.check = checksum(&packet, sizeof(struct udp_dhcp_packet));
+
+ packet.ip.tot_len = htons(sizeof(struct udp_dhcp_packet));
+ packet.ip.ihl = sizeof(packet.ip) >> 2;
+ packet.ip.version = IPVERSION;
+ packet.ip.ttl = IPDEFTTL;
+ packet.ip.check = checksum(&(packet.ip), sizeof(packet.ip));
+
+ result = sendto(fd, &packet, sizeof(struct udp_dhcp_packet), 0, (struct sockaddr *) &dest, sizeof(dest));
+ if (result <= 0) {
+ DEBUG(LOG_ERR, "write on socket failed: %m");
+ }
+ close(fd);
+ return result;
+}
+
+
+/* Let the kernel do all the work for packet generation */
+int kernel_packet(struct dhcpMessage *payload, uint32_t source_ip, int source_port,
+ uint32_t dest_ip, int dest_port)
+{
+ int n = 1;
+ int fd, result;
+ struct sockaddr_in client;
+
+ if ((fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0)
+ return -1;
+
+ if (setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, (char *) &n, sizeof(n)) == -1) {
+ close(fd);
+ return -1;
+ }
+
+ memset(&client, 0, sizeof(client));
+ client.sin_family = AF_INET;
+ client.sin_port = htons(source_port);
+ client.sin_addr.s_addr = source_ip;
+
+ if (bind(fd, (struct sockaddr *)&client, sizeof(struct sockaddr)) == -1) {
+ close(fd);
+ return -1;
+ }
+
+ memset(&client, 0, sizeof(client));
+ client.sin_family = AF_INET;
+ client.sin_port = htons(dest_port);
+ client.sin_addr.s_addr = dest_ip;
+
+ if (connect(fd, (struct sockaddr *)&client, sizeof(struct sockaddr)) == -1) {
+ close(fd);
+ return -1;
+ }
+
+ result = write(fd, payload, sizeof(struct dhcpMessage));
+ close(fd);
+ return result;
+}