1 files changed, 271 insertions, 0 deletions
diff --git a/networking/udhcp/clientpacket.c b/networking/udhcp/clientpacket.c
new file mode 100644
index 0000000..3f9522f
--- /dev/null
+++ b/networking/udhcp/clientpacket.c
@@ -0,0 +1,271 @@
+/* vi: set sw=4 ts=4: */
+/* clientpacket.c
+ *
+ * Packet generation and dispatching functions for the DHCP client.
+ *
+ * Russ Dill <Russ.Dill@asu.edu> July 2001
+ *
+ * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
+ */
+
+#include <features.h>
+#if (defined(__GLIBC__) && __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 "common.h"
+#include "dhcpd.h"
+#include "dhcpc.h"
+#include "options.h"
+
+
+/* Create a random xid */
+uint32_t FAST_FUNC random_xid(void)
+{
+	static smallint initialized;
+
+	if (!initialized) {
+		srand(monotonic_us());
+		initialized = 1;
+	}
+	return rand();
+}
+
+
+/* initialize a packet with the proper defaults */
+static void init_packet(struct dhcpMessage *packet, char type)
+{
+	udhcp_init_header(packet, type);
+	memcpy(packet->chaddr, client_config.arp, 6);
+	if (client_config.clientid)
+		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);
+	if ((type != DHCPDECLINE) && (type != DHCPRELEASE))
+		add_option_string(packet->options, client_config.vendorclass);
+}
+
+
+/* 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_param_req_option(struct dhcpMessage *packet)
+{
+	uint8_t c;
+	int end = end_option(packet->options);
+	int i, len = 0;
+
+	for (i = 0; (c = dhcp_options[i].code) != 0; i++) {
+		if (((dhcp_options[i].flags & OPTION_REQ)
+		     && !client_config.no_default_options)
+		 || (client_config.opt_mask[c >> 3] & (1 << (c & 7)))
+		) {
+			packet->options[end + OPT_DATA + len] = c;
+			len++;
+		}
+	}
+	if (len) {
+		packet->options[end + OPT_CODE] = DHCP_PARAM_REQ;
+		packet->options[end + OPT_LEN] = len;
+		packet->options[end + OPT_DATA + len] = DHCP_END;
+	}
+}
+
+/* RFC 2131
+ * 4.4.4 Use of broadcast and unicast
+ *
+ * The DHCP client broadcasts DHCPDISCOVER, DHCPREQUEST and DHCPINFORM
+ * messages, unless the client knows the address of a DHCP server.
+ * The client unicasts DHCPRELEASE messages to the server. Because
+ * the client is declining the use of the IP address supplied by the server,
+ * the client broadcasts DHCPDECLINE messages.
+ *
+ * When the DHCP client knows the address of a DHCP server, in either
+ * INIT or REBOOTING state, the client may use that address
+ * in the DHCPDISCOVER or DHCPREQUEST rather than the IP broadcast address.
+ * The client may also use unicast to send DHCPINFORM messages
+ * to a known DHCP server. If the client receives no response to DHCP
+ * messages sent to the IP address of a known DHCP server, the DHCP
+ * client reverts to using the IP broadcast address.
+ */
+
+static int raw_bcast_from_client_config_ifindex(struct dhcpMessage *packet)
+{
+	return udhcp_send_raw_packet(packet,
+		/*src*/ INADDR_ANY, CLIENT_PORT,
+		/*dst*/ INADDR_BROADCAST, SERVER_PORT, MAC_BCAST_ADDR,
+		client_config.ifindex);
+}
+
+
+#if ENABLE_FEATURE_UDHCPC_ARPING
+/* Broadcast a DHCP decline message */
+int FAST_FUNC send_decline(uint32_t xid, uint32_t server, uint32_t requested)
+{
+	struct dhcpMessage packet;
+
+	init_packet(&packet, DHCPDECLINE);
+	packet.xid = xid;
+	add_simple_option(packet.options, DHCP_REQUESTED_IP, requested);
+	add_simple_option(packet.options, DHCP_SERVER_ID, server);
+
+	bb_info_msg("Sending decline...");
+
+	return raw_bcast_from_client_config_ifindex(&packet);
+}
+#endif
+
+/* Broadcast a DHCP discover packet to the network, with an optionally requested IP */
+int FAST_FUNC send_discover(uint32_t xid, uint32_t requested)
+{
+	struct dhcpMessage packet;
+
+	init_packet(&packet, DHCPDISCOVER);
+	packet.xid = xid;
+	if (requested)
+		add_simple_option(packet.options, DHCP_REQUESTED_IP, requested);
+
+	/* Explicitly saying that we want RFC-compliant packets helps
+	 * some buggy DHCP servers to NOT send bigger packets */
+	add_simple_option(packet.options, DHCP_MAX_SIZE, htons(576));
+
+	add_param_req_option(&packet);
+
+	bb_info_msg("Sending discover...");
+	return raw_bcast_from_client_config_ifindex(&packet);
+}
+
+
+/* Broadcasts a DHCP request message */
+/* RFC 2131 3.1 paragraph 3:
+ * "The client _broadcasts_ a DHCPREQUEST message..."
+ */
+int FAST_FUNC send_select(uint32_t xid, uint32_t server, uint32_t 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_param_req_option(&packet);
+
+	addr.s_addr = requested;
+	bb_info_msg("Sending select for %s...", inet_ntoa(addr));
+	return raw_bcast_from_client_config_ifindex(&packet);
+}
+
+
+/* Unicasts or broadcasts a DHCP renew message */
+int FAST_FUNC send_renew(uint32_t xid, uint32_t server, uint32_t ciaddr)
+{
+	struct dhcpMessage packet;
+
+	init_packet(&packet, DHCPREQUEST);
+	packet.xid = xid;
+	packet.ciaddr = ciaddr;
+
+	add_param_req_option(&packet);
+	bb_info_msg("Sending renew...");
+	if (server)
+		return udhcp_send_kernel_packet(&packet,
+			ciaddr, CLIENT_PORT,
+			server, SERVER_PORT);
+
+	return raw_bcast_from_client_config_ifindex(&packet);
+}
+
+
+/* Unicasts a DHCP release message */
+int FAST_FUNC send_release(uint32_t server, uint32_t ciaddr)
+{
+	struct dhcpMessage packet;
+
+	init_packet(&packet, DHCPRELEASE);
+	packet.xid = random_xid();
+	packet.ciaddr = ciaddr;
+
+	add_simple_option(packet.options, DHCP_SERVER_ID, server);
+
+	bb_info_msg("Sending release...");
+	return udhcp_send_kernel_packet(&packet, ciaddr, CLIENT_PORT, server, SERVER_PORT);
+}
+
+
+/* Returns -1 on errors that are fatal for the socket, -2 for those that aren't */
+int FAST_FUNC udhcp_recv_raw_packet(struct dhcpMessage *payload, int fd)
+{
+	int bytes;
+	struct udp_dhcp_packet packet;
+	uint16_t check;
+
+	memset(&packet, 0, sizeof(packet));
+	bytes = safe_read(fd, &packet, sizeof(packet));
+	if (bytes < 0) {
+		DEBUG("Cannot read on raw listening socket - ignoring");
+		/* NB: possible down interface, etc. Caller should pause. */
+		return bytes; /* returns -1 */
+	}
+
+	if (bytes < (int) (sizeof(packet.ip) + sizeof(packet.udp))) {
+		DEBUG("Packet is too short, ignoring");
+		return -2;
+	}
+
+	if (bytes < ntohs(packet.ip.tot_len)) {
+		/* packet is bigger than sizeof(packet), we did partial read */
+		DEBUG("Oversized packet, ignoring");
+		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(packet) - can't happen */
+	 || ntohs(packet.udp.len) != (uint16_t)(bytes - sizeof(packet.ip))
+	) {
+		DEBUG("Unrelated/bogus packet");
+		return -2;
+	}
+
+	/* verify IP checksum */
+	check = packet.ip.check;
+	packet.ip.check = 0;
+	if (check != udhcp_checksum(&packet.ip, sizeof(packet.ip))) {
+		DEBUG("Bad IP header checksum, ignoring");
+		return -2;
+	}
+
+	/* verify UDP checksum. IP header has to be modified for this */
+	memset(&packet.ip, 0, offsetof(struct iphdr, protocol));
+	/* ip.xx fields which are not memset: protocol, check, saddr, daddr */
+	packet.ip.tot_len = packet.udp.len; /* yes, this is needed */
+	check = packet.udp.check;
+	packet.udp.check = 0;
+	if (check && check != udhcp_checksum(&packet, bytes)) {
+		bb_error_msg("packet with bad UDP checksum received, ignoring");
+		return -2;
+	}
+
+	memcpy(payload, &packet.data, bytes - (sizeof(packet.ip) + sizeof(packet.udp)));
+
+	if (payload->cookie != htonl(DHCP_MAGIC)) {
+		bb_error_msg("received bogus message (bad magic), ignoring");
+		return -2;
+	}
+	DEBUG("Got valid DHCP packet");
+	return bytes - (sizeof(packet.ip) + sizeof(packet.udp));
+}