1 files changed, 238 insertions, 0 deletions
diff --git a/networking/udhcp/packet.c b/networking/udhcp/packet.c
new file mode 100644
index 0000000..1a6f7e6
--- /dev/null
+++ b/networking/udhcp/packet.c
@@ -0,0 +1,238 @@
+/* vi: set sw=4 ts=4: */
+
+#include <netinet/in.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 "options.h"
+
+
+void FAST_FUNC udhcp_init_header(struct dhcpMessage *packet, char type)
+{
+	memset(packet, 0, sizeof(struct dhcpMessage));
+	packet->op = BOOTREQUEST; /* if client to a server */
+	switch (type) {
+	case DHCPOFFER:
+	case DHCPACK:
+	case DHCPNAK:
+		packet->op = BOOTREPLY; /* if server to client */
+	}
+	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 FAST_FUNC udhcp_recv_kernel_packet(struct dhcpMessage *packet, int fd)
+{
+	int bytes;
+	unsigned char *vendor;
+
+	memset(packet, 0, sizeof(*packet));
+	bytes = safe_read(fd, packet, sizeof(*packet));
+	if (bytes < 0) {
+		DEBUG("cannot read on listening socket, ignoring");
+		return bytes; /* returns -1 */
+	}
+
+	if (packet->cookie != htonl(DHCP_MAGIC)) {
+		bb_error_msg("received bogus message, ignoring");
+		return -2;
+	}
+	DEBUG("Received a packet");
+
+	if (packet->op == BOOTREQUEST) {
+		vendor = get_option(packet, DHCP_VENDOR);
+		if (vendor) {
+#if 0
+			static const char broken_vendors[][8] = {
+				"MSFT 98",
+				""
+			};
+			int i;
+			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("broken client (%s), forcing broadcast replies",
+						broken_vendors[i]);
+					packet->flags |= htons(BROADCAST_FLAG);
+				}
+			}
+#else
+			if (vendor[OPT_LEN - 2] == (uint8_t)(sizeof("MSFT 98")-1)
+			 && memcmp(vendor, "MSFT 98", sizeof("MSFT 98")-1) == 0
+			) {
+				DEBUG("broken client (%s), forcing broadcast replies", "MSFT 98");
+				packet->flags |= htons(BROADCAST_FLAG);
+			}
+#endif
+		}
+	}
+
+	return bytes;
+}
+
+
+uint16_t FAST_FUNC udhcp_checksum(void *addr, int count)
+{
+	/* Compute Internet Checksum for "count" bytes
+	 *         beginning at location "addr".
+	 */
+	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, send packet */
+int FAST_FUNC udhcp_send_raw_packet(struct dhcpMessage *payload,
+		uint32_t source_ip, int source_port,
+		uint32_t dest_ip, int dest_port, const uint8_t *dest_arp,
+		int ifindex)
+{
+	struct sockaddr_ll dest;
+	struct udp_dhcp_packet packet;
+	int fd;
+	int result = -1;
+	const char *msg;
+
+	enum {
+		IP_UPD_DHCP_SIZE = sizeof(struct udp_dhcp_packet) - CONFIG_UDHCPC_SLACK_FOR_BUGGY_SERVERS,
+		UPD_DHCP_SIZE    = IP_UPD_DHCP_SIZE - offsetof(struct udp_dhcp_packet, udp),
+	};
+
+	fd = socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP));
+	if (fd < 0) {
+		msg = "socket(%s)";
+		goto ret_msg;
+	}
+
+	memset(&dest, 0, sizeof(dest));
+	memset(&packet, 0, sizeof(packet));
+	packet.data = *payload; /* struct copy */
+
+	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(dest)) < 0) {
+		msg = "bind(%s)";
+		goto ret_close;
+	}
+
+	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);
+	/* size, excluding IP header: */
+	packet.udp.len = htons(UPD_DHCP_SIZE);
+	/* for UDP checksumming, ip.len is set to UDP packet len */
+	packet.ip.tot_len = packet.udp.len;
+	packet.udp.check = udhcp_checksum(&packet, IP_UPD_DHCP_SIZE);
+	/* but for sending, it is set to IP packet len */
+	packet.ip.tot_len = htons(IP_UPD_DHCP_SIZE);
+	packet.ip.ihl = sizeof(packet.ip) >> 2;
+	packet.ip.version = IPVERSION;
+	packet.ip.ttl = IPDEFTTL;
+	packet.ip.check = udhcp_checksum(&packet.ip, sizeof(packet.ip));
+
+	/* Currently we send full-sized DHCP packets (zero padded).
+	 * If you need to change this: last byte of the packet is
+	 * packet.data.options[end_option(packet.data.options)]
+	 */
+	result = sendto(fd, &packet, IP_UPD_DHCP_SIZE, 0,
+				(struct sockaddr *) &dest, sizeof(dest));
+	msg = "sendto";
+ ret_close:
+	close(fd);
+	if (result < 0) {
+ ret_msg:
+		bb_perror_msg(msg, "PACKET");
+	}
+	return result;
+}
+
+
+/* Let the kernel do all the work for packet generation */
+int FAST_FUNC udhcp_send_kernel_packet(struct dhcpMessage *payload,
+		uint32_t source_ip, int source_port,
+		uint32_t dest_ip, int dest_port)
+{
+	struct sockaddr_in client;
+	int fd;
+	int result = -1;
+	const char *msg;
+
+	enum {
+		DHCP_SIZE = sizeof(struct dhcpMessage) - CONFIG_UDHCPC_SLACK_FOR_BUGGY_SERVERS,
+	};
+
+	fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP);
+	if (fd < 0) {
+		msg = "socket(%s)";
+		goto ret_msg;
+	}
+	setsockopt_reuseaddr(fd);
+
+	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(client)) == -1) {
+		msg = "bind(%s)";
+		goto ret_close;
+	}
+
+	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(client)) == -1) {
+		msg = "connect";
+		goto ret_close;
+	}
+
+	/* Currently we send full-sized DHCP packets (see above) */
+	result = safe_write(fd, payload, DHCP_SIZE);
+	msg = "write";
+ ret_close:
+	close(fd);
+	if (result < 0) {
+ ret_msg:
+		bb_perror_msg(msg, "UDP");
+	}
+	return result;
+}