text: /* vi: set sw=4 ts=4: */
  /*
   * Packet ops
   *
   * Rewrite by Russ Dill <Russ.Dill@asu.edu> July 2001
   *
   * Licensed under GPLv2, see file LICENSE in this source tree.
   */
  #include "common.h"
  #include "dhcpd.h"
  #include <netinet/in.h>
  #include <netinet/if_ether.h>
  #include <netpacket/packet.h>
  
  void FAST_FUNC udhcp_init_header(struct dhcp_packet *packet, char type)
  {
  	memset(packet, 0, sizeof(*packet));
  	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 = 1; /* ethernet */
  	packet->hlen = 6;
  	packet->cookie = htonl(DHCP_MAGIC);
  	if (DHCP_END != 0)
  		packet->options[0] = DHCP_END;
  	udhcp_add_simple_option(packet, DHCP_MESSAGE_TYPE, type);
  }
  
  #if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 2
  void FAST_FUNC udhcp_dump_packet(struct dhcp_packet *packet)
  {
  	char buf[sizeof(packet->chaddr)*2 + 1];
  
  	if (dhcp_verbose < 2)
  		return;
  
  	bb_info_msg(
  		//" op %x"
  		//" htype %x"
  		" hlen %x"
  		//" hops %x"
  		" xid %x"
  		//" secs %x"
  		//" flags %x"
  		" ciaddr %x"
  		" yiaddr %x"
  		" siaddr %x"
  		" giaddr %x"
  		//" chaddr %s"
  		//" sname %s"
  		//" file %s"
  		//" cookie %x"
  		//" options %s"
  		//, packet->op
  		//, packet->htype
  		, packet->hlen
  		//, packet->hops
  		, packet->xid
  		//, packet->secs
  		//, packet->flags
  		, packet->ciaddr
  		, packet->yiaddr
  		, packet->siaddr_nip
  		, packet->gateway_nip
  		//, packet->chaddr[16]
  		//, packet->sname[64]
  		//, packet->file[128]
  		//, packet->cookie
  		//, packet->options[]
  	);
  	*bin2hex(buf, (void *) packet->chaddr, sizeof(packet->chaddr)) = '\0';
  	bb_info_msg(" chaddr %s", buf);
  }
  #endif
  
  /* Read a packet from socket fd, return -1 on read error, -2 on packet error */
  int FAST_FUNC udhcp_recv_kernel_packet(struct dhcp_packet *packet, int fd)
  {
  	int bytes;
  	unsigned char *vendor;
  
  	memset(packet, 0, sizeof(*packet));
  	bytes = safe_read(fd, packet, sizeof(*packet));
  	if (bytes < 0) {
  		log1("Packet read error, ignoring");
  		return bytes; /* returns -1 */
  	}
  
  	if (packet->cookie != htonl(DHCP_MAGIC)) {
  		bb_info_msg("Packet with bad magic, ignoring");
  		return -2;
  	}
  	log1("Received a packet");
  	udhcp_dump_packet(packet);
  
  	if (packet->op == BOOTREQUEST) {
  		vendor = udhcp_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 - OPT_DATA] == (uint8_t)strlen(broken_vendors[i])
  				 && strncmp((char*)vendor, broken_vendors[i], vendor[OPT_LEN - OPT_DATA]) == 0
  				) {
  					log1("Broken client (%s), forcing broadcast replies",
  						broken_vendors[i]);
  					packet->flags |= htons(BROADCAST_FLAG);
  				}
  			}
  #else
  			if (vendor[OPT_LEN - OPT_DATA] == (uint8_t)(sizeof("MSFT 98")-1)
  			 && memcmp(vendor, "MSFT 98", sizeof("MSFT 98")-1) == 0
  			) {
  				log1("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 dhcp_packet *dhcp_pkt,
  		uint32_t source_nip, int source_port,
  		uint32_t dest_nip, int dest_port, const uint8_t *dest_arp,
  		int ifindex)
  {
  	struct sockaddr_ll dest_sll;
  	struct ip_udp_dhcp_packet packet;
  	unsigned padding;
  	int fd;
  	int result = -1;
  	const char *msg;
  
  	fd = socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP));
  	if (fd < 0) {
  		msg = "socket(%s)";
  		goto ret_msg;
  	}
  
  	memset(&dest_sll, 0, sizeof(dest_sll));
  	memset(&packet, 0, offsetof(struct ip_udp_dhcp_packet, data));
  	packet.data = *dhcp_pkt; /* struct copy */
  
  	dest_sll.sll_family = AF_PACKET;
  	dest_sll.sll_protocol = htons(ETH_P_IP);
  	dest_sll.sll_ifindex = ifindex;
  	dest_sll.sll_halen = 6;
  	memcpy(dest_sll.sll_addr, dest_arp, 6);
  
  	if (bind(fd, (struct sockaddr *)&dest_sll, sizeof(dest_sll)) < 0) {
  		msg = "bind(%s)";
  		goto ret_close;
  	}
  
  	/* We were sending full-sized DHCP packets (zero padded),
  	 * but some badly configured servers were seen dropping them.
  	 * Apparently they drop all DHCP packets >576 *ethernet* octets big,
  	 * whereas they may only drop packets >576 *IP* octets big
  	 * (which for typical Ethernet II means 590 octets: 6+6+2 + 576).
  	 *
  	 * In order to work with those buggy servers,
  	 * we truncate packets after end option byte.
  	 */
  	padding = DHCP_OPTIONS_BUFSIZE - 1 - udhcp_end_option(packet.data.options);
  
  	packet.ip.protocol = IPPROTO_UDP;
  	packet.ip.saddr = source_nip;
  	packet.ip.daddr = dest_nip;
  	packet.udp.source = htons(source_port);
  	packet.udp.dest = htons(dest_port);
  	/* size, excluding IP header: */
  	packet.udp.len = htons(UDP_DHCP_SIZE - padding);
  	/* 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_UDP_DHCP_SIZE - padding);
  	/* but for sending, it is set to IP packet len */
  	packet.ip.tot_len = htons(IP_UDP_DHCP_SIZE - padding);
  	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));
  
  	udhcp_dump_packet(dhcp_pkt);
  	result = sendto(fd, &packet, IP_UDP_DHCP_SIZE - padding, /*flags:*/ 0,
  			(struct sockaddr *) &dest_sll, sizeof(dest_sll));
  	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 dhcp_packet *dhcp_pkt,
  		uint32_t source_nip, int source_port,
  		uint32_t dest_nip, int dest_port)
  {
  	struct sockaddr_in client;
  	unsigned padding;
  	int fd;
  	int result = -1;
  	const char *msg;
  
  	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_nip;
  	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_nip;
  	if (connect(fd, (struct sockaddr *)&client, sizeof(client)) == -1) {
  		msg = "connect";
  		goto ret_close;
  	}
  
  	udhcp_dump_packet(dhcp_pkt);
  
  	padding = DHCP_OPTIONS_BUFSIZE - 1 - udhcp_end_option(dhcp_pkt->options);
  	result = safe_write(fd, dhcp_pkt, DHCP_SIZE - padding);
  	msg = "write";
   ret_close:
  	close(fd);
  	if (result < 0) {
   ret_msg:
  		bb_perror_msg(msg, "UDP");
  	}
  	return result;
  }
  