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;
+}