text: #ifndef _IPXE_DHCP_H
  #define _IPXE_DHCP_H
  
  /** @file
   *
   * Dynamic Host Configuration Protocol
   *
   */
  
  FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
  
  #include <stdint.h>
  #include <stdarg.h>
  #include <ipxe/in.h>
  #include <ipxe/list.h>
  #include <ipxe/refcnt.h>
  #include <ipxe/tables.h>
  #include <ipxe/uuid.h>
  #include <ipxe/netdevice.h>
  #include <ipxe/uaccess.h>
  
  struct interface;
  struct dhcp_options;
  struct dhcp_packet;
  
  /** BOOTP/DHCP server port */
  #define BOOTPS_PORT 67
  
  /** BOOTP/DHCP client port */
  #define BOOTPC_PORT 68
  
  /** PXE server port */
  #define PXE_PORT 4011
  
  /** Construct a tag value for an encapsulated option
   *
   * This tag value can be passed to Etherboot functions when searching
   * for DHCP options in order to search for a tag within an
   * encapsulated options block.
   */
  #define DHCP_ENCAP_OPT( encapsulator, encapsulated ) \
  	( ( (encapsulator) << 8 ) | (encapsulated) )
  /** Extract encapsulating option block tag from encapsulated tag value */
  #define DHCP_ENCAPSULATOR( encap_opt ) ( (encap_opt) >> 8 )
  /** Extract encapsulated option tag from encapsulated tag value */
  #define DHCP_ENCAPSULATED( encap_opt ) ( (encap_opt) & 0xff )
  /** Option is encapsulated */
  #define DHCP_IS_ENCAP_OPT( opt ) DHCP_ENCAPSULATOR( opt )
  
  /**
   * @defgroup dhcpopts DHCP option tags
   * @{
   */
  
  /** Padding
   *
   * This tag does not have a length field; it is always only a single
   * byte in length.
   */
  #define DHCP_PAD 0
  
  /** Minimum normal DHCP option */
  #define DHCP_MIN_OPTION 1
  
  /** Subnet mask */
  #define DHCP_SUBNET_MASK 1
  
  /** Routers */
  #define DHCP_ROUTERS 3
  
  /** DNS servers */
  #define DHCP_DNS_SERVERS 6
  
  /** Syslog servers */
  #define DHCP_LOG_SERVERS 7
  
  /** Host name */
  #define DHCP_HOST_NAME 12
  
  /** Domain name */
  #define DHCP_DOMAIN_NAME 15
  
  /** Root path */
  #define DHCP_ROOT_PATH 17
  
  /** Maximum transmission unit */
  #define DHCP_MTU 26
  
  /** Vendor encapsulated options */
  #define DHCP_VENDOR_ENCAP 43
  
  /** PXE boot server discovery control */
  #define DHCP_PXE_DISCOVERY_CONTROL DHCP_ENCAP_OPT ( DHCP_VENDOR_ENCAP, 6 )
  
  /** PXE boot server discovery control bits */
  enum dhcp_pxe_discovery_control {
  	/** Inhibit broadcast discovery */
  	PXEBS_NO_BROADCAST = 1,
  	/** Inhibit multicast discovery */
  	PXEBS_NO_MULTICAST = 2,
  	/** Accept only servers in DHCP_PXE_BOOT_SERVERS list */
  	PXEBS_NO_UNKNOWN_SERVERS = 4,
  	/** Skip discovery if filename present */
  	PXEBS_SKIP = 8,
  };
  
  /** PXE boot server multicast address */
  #define DHCP_PXE_BOOT_SERVER_MCAST DHCP_ENCAP_OPT ( DHCP_VENDOR_ENCAP, 7 )
  
  /** PXE boot servers */
  #define DHCP_PXE_BOOT_SERVERS DHCP_ENCAP_OPT ( DHCP_VENDOR_ENCAP, 8 )
  
  /** PXE boot server */
  struct dhcp_pxe_boot_server {
  	/** "Type" */
  	uint16_t type;
  	/** Number of IPv4 addresses */
  	uint8_t num_ip;
  	/** IPv4 addresses */
  	struct in_addr ip[0];
  } __attribute__ (( packed ));
  
  /** PXE boot menu */
  #define DHCP_PXE_BOOT_MENU DHCP_ENCAP_OPT ( DHCP_VENDOR_ENCAP, 9 )
  
  /** PXE boot menu */
  struct dhcp_pxe_boot_menu {
  	/** "Type" */
  	uint16_t type;
  	/** Description length */
  	uint8_t desc_len;
  	/** Description */
  	char desc[0];
  } __attribute__ (( packed ));
  
  /** PXE boot menu prompt */
  #define DHCP_PXE_BOOT_MENU_PROMPT DHCP_ENCAP_OPT ( DHCP_VENDOR_ENCAP, 10 )
  
  /** PXE boot menu prompt */
  struct dhcp_pxe_boot_menu_prompt {
  	/** Timeout
  	 *
  	 * A value of 0 means "time out immediately and select first
  	 * boot item, without displaying the prompt".  A value of 255
  	 * means "display menu immediately with no timeout".  Any
  	 * other value means "display prompt, wait this many seconds
  	 * for keypress, if key is F8, display menu, otherwise select
  	 * first boot item".
  	 */
  	uint8_t timeout;
  	/** Prompt to press F8 */
  	char prompt[0];
  } __attribute__ (( packed ));
  
  /** PXE boot menu item */
  #define DHCP_PXE_BOOT_MENU_ITEM DHCP_ENCAP_OPT ( DHCP_VENDOR_ENCAP, 71 )
  
  /** PXE boot menu item */
  struct dhcp_pxe_boot_menu_item {
  	/** "Type"
  	 *
  	 * This field actually identifies the specific boot server (or
  	 * cluster of boot servers offering identical boot files).
  	 */
  	uint16_t type;
  	/** "Layer"
  	 *
  	 * Just don't ask.
  	 */
  	uint16_t layer;
  } __attribute__ (( packed ));
  
  /** Requested IP address */
  #define DHCP_REQUESTED_ADDRESS 50
  
  /** Lease time */
  #define DHCP_LEASE_TIME 51
  
  /** Option overloading
   *
   * The value of this option is the bitwise-OR of zero or more
   * DHCP_OPTION_OVERLOAD_XXX constants.
   */
  #define DHCP_OPTION_OVERLOAD 52
  
  /** The "file" field is overloaded to contain extra DHCP options */
  #define DHCP_OPTION_OVERLOAD_FILE 1
  
  /** The "sname" field is overloaded to contain extra DHCP options */
  #define DHCP_OPTION_OVERLOAD_SNAME 2
  
  /** DHCP message type */
  #define DHCP_MESSAGE_TYPE 53
  #define DHCPNONE 0
  #define DHCPDISCOVER 1
  #define DHCPOFFER 2
  #define DHCPREQUEST 3
  #define DHCPDECLINE 4
  #define DHCPACK 5
  #define DHCPNAK 6
  #define DHCPRELEASE 7
  #define DHCPINFORM 8
  
  /** DHCP server identifier */
  #define DHCP_SERVER_IDENTIFIER 54
  
  /** Parameter request list */
  #define DHCP_PARAMETER_REQUEST_LIST 55
  
  /** Maximum DHCP message size */
  #define DHCP_MAX_MESSAGE_SIZE 57
  
  /** Vendor class identifier */
  #define DHCP_VENDOR_CLASS_ID 60
  
  /** Vendor class identifier for PXE clients */
  #define DHCP_VENDOR_PXECLIENT( arch, ndi )				\
  	'P', 'X', 'E', 'C', 'l', 'i', 'e', 'n', 't', ':',		\
  	'A', 'r', 'c', 'h', ':', DHCP_VENDOR_PXECLIENT_ARCH ( arch ),	\
  	':', 'U', 'N', 'D', 'I', ':', DHCP_VENDOR_PXECLIENT_UNDI ( ndi )
  
  /** Vendor class identifier architecture for PXE clients */
  #define DHCP_VENDOR_PXECLIENT_ARCH( arch )				\
  	( '0' + ( ( (arch) / 10000 ) % 10 ) ),				\
  	( '0' + ( ( (arch) /  1000 ) % 10 ) ),				\
  	( '0' + ( ( (arch) /   100 ) % 10 ) ),				\
  	( '0' + ( ( (arch) /    10 ) % 10 ) ),				\
  	( '0' + ( ( (arch) /     1 ) % 10 ) )
  
  /** Vendor class identifier UNDI version for PXE clients */
  #define DHCP_VENDOR_PXECLIENT_UNDI( type, major, minor )		\
  	DHCP_VENDOR_PXECLIENT_UNDI_VERSION ( major ),			\
  	DHCP_VENDOR_PXECLIENT_UNDI_VERSION ( minor )
  #define DHCP_VENDOR_PXECLIENT_UNDI_VERSION( version )			\
  	( '0' + ( ( (version) /   100 ) % 10 ) ),			\
  	( '0' + ( ( (version) /    10 ) % 10 ) ),			\
  	( '0' + ( ( (version) /     1 ) % 10 ) )
  
  /** Client identifier */
  #define DHCP_CLIENT_ID 61
  
  /** Client identifier */
  struct dhcp_client_id {
  	/** Link-layer protocol */
  	uint8_t ll_proto;
  	/** Link-layer address */
  	uint8_t ll_addr[MAX_LL_ADDR_LEN];
  } __attribute__ (( packed ));
  
  /** TFTP server name
   *
   * This option replaces the fixed "sname" field, when that field is
   * used to contain overloaded options.
   */
  #define DHCP_TFTP_SERVER_NAME 66
  
  /** Bootfile name
   *
   * This option replaces the fixed "file" field, when that field is
   * used to contain overloaded options.
   */
  #define DHCP_BOOTFILE_NAME 67
  
  /** User class identifier */
  #define DHCP_USER_CLASS_ID 77
  
  /** Client system architecture */
  #define DHCP_CLIENT_ARCHITECTURE 93
  
  /** DHCP client architecture */
  struct dhcp_client_architecture {
  	uint16_t arch;
  } __attribute__ (( packed ));
  
  /** DHCP client architecture values
   *
   * These are defined by the PXE specification and redefined by
   * RFC4578.
   */
  enum dhcp_client_architecture_values {
  	/** Intel x86 PC */
  	DHCP_CLIENT_ARCHITECTURE_X86 = 0x0000,
  	/** NEC/PC98 */
  	DHCP_CLIENT_ARCHITECTURE_PC98 = 0x0001,
  	/** EFI Itanium */
  	DHCP_CLIENT_ARCHITECTURE_IA64 = 0x0002,
  	/** DEC Alpha */
  	DHCP_CLIENT_ARCHITECTURE_ALPHA = 0x0003,
  	/** Arc x86 */
  	DHCP_CLIENT_ARCHITECTURE_ARCX86 = 0x0004,
  	/** Intel Lean Client */
  	DHCP_CLIENT_ARCHITECTURE_LC = 0x0005,
  	/** EFI IA32 */
  	DHCP_CLIENT_ARCHITECTURE_IA32 = 0x0006,
  	/** EFI x86-64 */
  	DHCP_CLIENT_ARCHITECTURE_X86_64 = 0x0007,
  	/** EFI Xscale */
  	DHCP_CLIENT_ARCHITECTURE_XSCALE = 0x0008,
  	/** EFI BC */
  	DHCP_CLIENT_ARCHITECTURE_EFI = 0x0009,
  	/** EFI 32-bit ARM */
  	DHCP_CLIENT_ARCHITECTURE_ARM32 = 0x000a,
  	/** EFI 64-bit ARM */
  	DHCP_CLIENT_ARCHITECTURE_ARM64 = 0x000b,
  };
  
  /** Client network device interface */
  #define DHCP_CLIENT_NDI 94
  
  /** UUID client identifier */
  #define DHCP_CLIENT_UUID 97
  
  /** UUID client identifier */
  struct dhcp_client_uuid {
  	/** Identifier type */
  	uint8_t type;
  	/** UUID */
  	union uuid uuid;
  } __attribute__ (( packed ));
  
  #define DHCP_CLIENT_UUID_TYPE 0
  
  /** DNS domain search list */
  #define DHCP_DOMAIN_SEARCH 119
  
  /** Etherboot-specific encapsulated options
   *
   * This encapsulated options field is used to contain all options
   * specific to Etherboot (i.e. not assigned by IANA or other standards
   * bodies).
   */
  #define DHCP_EB_ENCAP 175
  
  /** Priority of this options block
   *
   * This is a signed 8-bit integer field indicating the priority of
   * this block of options.  It can be used to specify the relative
   * priority of multiple option blocks (e.g. options from non-volatile
   * storage versus options from a DHCP server).
   */
  #define DHCP_EB_PRIORITY DHCP_ENCAP_OPT ( DHCP_EB_ENCAP, 0x01 )
  
  /** "Your" IP address
   *
   * This option is used internally to contain the value of the "yiaddr"
   * field, in order to provide a consistent approach to storing and
   * processing options.  It should never be present in a DHCP packet.
   */
  #define DHCP_EB_YIADDR DHCP_ENCAP_OPT ( DHCP_EB_ENCAP, 0x02 )
  
  /** "Server" IP address
   *
   * This option is used internally to contain the value of the "siaddr"
   * field, in order to provide a consistent approach to storing and
   * processing options.  It should never be present in a DHCP packet.
   */
  #define DHCP_EB_SIADDR DHCP_ENCAP_OPT ( DHCP_EB_ENCAP, 0x03 )
  
  /** Keep SAN drive registered
   *
   * If set to a non-zero value, iPXE will not detach any SAN drive
   * after failing to boot from it.  (This option is required in order
   * to perform an installation direct to an iSCSI target.)
   */
  #define DHCP_EB_KEEP_SAN DHCP_ENCAP_OPT ( DHCP_EB_ENCAP, 0x08 )
  
  /** Skip booting from SAN drive
   *
   * If set to a non-zero value, iPXE will skip booting from any SAN
   * drive.  (This option is sometimes required in conjunction with @c
   * DHCP_EB_KEEP_SAN in order to perform an installation direct to an
   * iSCSI target.)
   */
  #define DHCP_EB_SKIP_SAN_BOOT DHCP_ENCAP_OPT ( DHCP_EB_ENCAP, 0x09 )
  
  /*
   * Tags in the range 0x10-0x4f are reserved for feature markers
   *
   */
  
  /** Scriptlet
   *
   * If a scriptlet exists, it will be executed in place of the usual
   * call to autoboot()
   */
  #define DHCP_EB_SCRIPTLET DHCP_ENCAP_OPT ( DHCP_EB_ENCAP, 0x51 )
  
  /** Encrypted syslog server */
  #define DHCP_EB_SYSLOGS_SERVER DHCP_ENCAP_OPT ( DHCP_EB_ENCAP, 0x55 )
  
  /** Trusted root certficate fingerprints */
  #define DHCP_EB_TRUST DHCP_ENCAP_OPT ( DHCP_EB_ENCAP, 0x5a )
  
  /** Client certficate */
  #define DHCP_EB_CERT DHCP_ENCAP_OPT ( DHCP_EB_ENCAP, 0x5b )
  
  /** Client private key */
  #define DHCP_EB_KEY DHCP_ENCAP_OPT ( DHCP_EB_ENCAP, 0x5c )
  
  /** Cross-signed certificate source */
  #define DHCP_EB_CROSS_CERT DHCP_ENCAP_OPT ( DHCP_EB_ENCAP, 0x5d )
  
  /** Skip PXE DHCP protocol extensions such as ProxyDHCP
   *
   * If set to a non-zero value, iPXE will not wait for ProxyDHCP offers
   * and will ignore any PXE-specific DHCP options that it receives.
   */
  #define DHCP_EB_NO_PXEDHCP DHCP_ENCAP_OPT ( DHCP_EB_ENCAP, 0xb0 )
  
  /** Network device descriptor
   *
   * Byte 0 is the bus type ID; remaining bytes depend on the bus type.
   *
   * PCI devices:
   * Byte 0 : 1 (PCI)
   * Byte 1 : PCI vendor ID MSB
   * Byte 2 : PCI vendor ID LSB
   * Byte 3 : PCI device ID MSB
   * Byte 4 : PCI device ID LSB
   */
  #define DHCP_EB_BUS_ID DHCP_ENCAP_OPT ( DHCP_EB_ENCAP, 0xb1 )
  
  /** Network device descriptor */
  struct dhcp_netdev_desc {
  	/** Bus type ID */
  	uint8_t type;
  	/** Vendor ID */
  	uint16_t vendor;
  	/** Device ID */
  	uint16_t device;
  } __attribute__ (( packed ));
  
  /** Use cached network settings (obsolete; do not reuse this value) */
  #define DHCP_EB_USE_CACHED DHCP_ENCAP_OPT ( DHCP_EB_ENCAP, 0xb2 )
  
  /** SAN retry count
   *
   * This is the maximum number of times that SAN operations will be
   * retried.
   */
  #define DHCP_EB_SAN_RETRY DHCP_ENCAP_OPT ( DHCP_EB_ENCAP, 0xbb )
  
  /** SAN filename
   *
   * This is the path of the bootloader within the SAN device.
   */
  #define DHCP_EB_SAN_FILENAME DHCP_ENCAP_OPT ( DHCP_EB_ENCAP, 0xbc )
  
  /** SAN drive number
   *
   * This is the drive number for a SAN-hooked drive.  For BIOS, 0x80 is
   * the first hard disk, 0x81 is the second hard disk, etc.
   */
  #define DHCP_EB_SAN_DRIVE DHCP_ENCAP_OPT ( DHCP_EB_ENCAP, 0xbd )
  
  /** Username
   *
   * This will be used as the username for any required authentication.
   * It is expected that this option's value will be held in
   * non-volatile storage, rather than transmitted as part of a DHCP
   * packet.
   */
  #define DHCP_EB_USERNAME DHCP_ENCAP_OPT ( DHCP_EB_ENCAP, 0xbe )
  
  /** Password
   *
   * This will be used as the password for any required authentication.
   * It is expected that this option's value will be held in
   * non-volatile storage, rather than transmitted as part of a DHCP
   * packet.
   */
  #define DHCP_EB_PASSWORD DHCP_ENCAP_OPT ( DHCP_EB_ENCAP, 0xbf )
  
  /** Reverse username
   *
   * This will be used as the reverse username (i.e. the username
   * provided by the server) for any required authentication.  It is
   * expected that this option's value will be held in non-volatile
   * storage, rather than transmitted as part of a DHCP packet.
   */
  #define DHCP_EB_REVERSE_USERNAME DHCP_ENCAP_OPT ( DHCP_EB_ENCAP, 0xc0 )
  
  /** Reverse password
   *
   * This will be used as the reverse password (i.e. the password
   * provided by the server) for any required authentication.  It is
   * expected that this option's value will be held in non-volatile
   * storage, rather than transmitted as part of a DHCP packet.
   */
  #define DHCP_EB_REVERSE_PASSWORD DHCP_ENCAP_OPT ( DHCP_EB_ENCAP, 0xc1 )
  
  /** User ID
   *
   * This will be used as the user id for AUTH_SYS based authentication in NFS.
   */
  #define DHCP_EB_UID DHCP_ENCAP_OPT ( DHCP_EB_ENCAP, 0xc2 )
  
  /** Group ID
   *
   * This will be used as the group id for AUTH_SYS based authentication in NFS.
   */
  #define DHCP_EB_GID DHCP_ENCAP_OPT ( DHCP_EB_ENCAP, 0xc3 )
  
  /** iPXE version number */
  #define DHCP_EB_VERSION DHCP_ENCAP_OPT ( DHCP_EB_ENCAP, 0xeb )
  
  /** iSCSI primary target IQN */
  #define DHCP_ISCSI_PRIMARY_TARGET_IQN 201
  
  /** iSCSI secondary target IQN */
  #define DHCP_ISCSI_SECONDARY_TARGET_IQN 202
  
  /** iSCSI initiator IQN */
  #define DHCP_ISCSI_INITIATOR_IQN 203
  
  /** Maximum normal DHCP option */
  #define DHCP_MAX_OPTION 254
  
  /** End of options
   *
   * This tag does not have a length field; it is always only a single
   * byte in length.
   */
  #define DHCP_END 255
  
  /** @} */
  
  /** Construct a DHCP option from a list of bytes */
  #define DHCP_OPTION( ... ) VA_ARG_COUNT ( __VA_ARGS__ ), __VA_ARGS__
  
  /** Construct a DHCP option from a list of characters */
  #define DHCP_STRING( ... ) DHCP_OPTION ( __VA_ARGS__ )
  
  /** Construct a byte-valued DHCP option */
  #define DHCP_BYTE( value ) DHCP_OPTION ( value )
  
  /** Construct a word-valued DHCP option */
  #define DHCP_WORD( value ) DHCP_OPTION ( ( ( (value) >> 8 ) & 0xff ),   \
  					 ( ( (value) >> 0 ) & 0xff ) )
  
  /** Construct a dword-valued DHCP option */
  #define DHCP_DWORD( value ) DHCP_OPTION ( ( ( (value) >> 24 ) & 0xff ), \
  					  ( ( (value) >> 16 ) & 0xff ), \
  					  ( ( (value) >> 8  ) & 0xff ), \
  					  ( ( (value) >> 0  ) & 0xff ) )
  
  /** Construct a DHCP encapsulated options field */
  #define DHCP_ENCAP( ... ) DHCP_OPTION ( __VA_ARGS__, DHCP_END )
  
  /**
   * A DHCP option
   *
   * DHCP options consist of a mandatory tag, a length field that is
   * mandatory for all options except @c DHCP_PAD and @c DHCP_END, and a
   * payload.  
   */
  struct dhcp_option {
  	/** Tag
  	 *
  	 * Must be a @c DHCP_XXX value.
  	 */
  	uint8_t tag;
  	/** Length
  	 *
  	 * This is the length of the data field (i.e. excluding the
  	 * tag and length fields).  For the two tags @c DHCP_PAD and
  	 * @c DHCP_END, the length field is implicitly zero and is
  	 * also missing, i.e. these DHCP options are only a single
  	 * byte in length.
  	 */
  	uint8_t len;
  	/** Option data */
  	uint8_t data[0];
  } __attribute__ (( packed ));
  
  /**
   * Length of a DHCP option header
   *
   * The header is the portion excluding the data, i.e. the tag and the
   * length.
   */
  #define DHCP_OPTION_HEADER_LEN ( offsetof ( struct dhcp_option, data ) )
  
  /** Maximum length for a single DHCP option */
  #define DHCP_MAX_LEN 0xff
  
  /**
   * A DHCP header
   *
   */
  struct dhcphdr {
  	/** Operation
  	 *
  	 * This must be either @c BOOTP_REQUEST or @c BOOTP_REPLY.
  	 */
  	uint8_t op;
  	/** Hardware address type
  	 *
  	 * This is an ARPHRD_XXX constant.  Note that ARPHRD_XXX
  	 * constants are nominally 16 bits wide; this could be
  	 * considered to be a bug in the BOOTP/DHCP specification.
  	 */
  	uint8_t htype;
  	/** Hardware address length */
  	uint8_t hlen;
  	/** Number of hops from server */
  	uint8_t hops;
  	/** Transaction ID */
  	uint32_t xid;
  	/** Seconds since start of acquisition */
  	uint16_t secs;
  	/** Flags */
  	uint16_t flags;
  	/** "Client" IP address
  	 *
  	 * This is filled in if the client already has an IP address
  	 * assigned and can respond to ARP requests.
  	 */
  	struct in_addr ciaddr;
  	/** "Your" IP address
  	 *
  	 * This is the IP address assigned by the server to the client.
  	 */
  	struct in_addr yiaddr;
  	/** "Server" IP address
  	 *
  	 * This is the IP address of the next server to be used in the
  	 * boot process.
  	 */
  	struct in_addr siaddr;
  	/** "Gateway" IP address
  	 *
  	 * This is the IP address of the DHCP relay agent, if any.
  	 */
  	struct in_addr giaddr;
  	/** Client hardware address */
  	uint8_t chaddr[16];
  	/** Server host name (null terminated)
  	 *
  	 * This field may be overridden and contain DHCP options
  	 */
  	char sname[64];
  	/** Boot file name (null terminated)
  	 *
  	 * This field may be overridden and contain DHCP options
  	 */
  	char file[128];
  	/** DHCP magic cookie
  	 *
  	 * Must have the value @c DHCP_MAGIC_COOKIE.
  	 */
  	uint32_t magic;
  	/** DHCP options
  	 *
  	 * Variable length; extends to the end of the packet.  Minimum
  	 * length (for the sake of sanity) is 1, to allow for a single
  	 * @c DHCP_END tag.
  	 */
  	uint8_t options[0];
  };
  
  /** Opcode for a request from client to server */
  #define BOOTP_REQUEST 1
  
  /** Opcode for a reply from server to client */
  #define BOOTP_REPLY 2
  
  /** BOOTP reply must be broadcast
   *
   * Clients that cannot accept unicast BOOTP replies must set this
   * flag.
   */
  #define BOOTP_FL_BROADCAST 0x8000
  
  /** DHCP magic cookie */
  #define DHCP_MAGIC_COOKIE 0x63825363UL
  
  /** DHCP minimum packet length
   *
   * This is the mandated minimum packet length that a DHCP participant
   * must be prepared to receive.
   */
  #define DHCP_MIN_LEN 552
  
  /** Settings block name used for DHCP responses */
  #define DHCP_SETTINGS_NAME "dhcp"
  
  /** Settings block name used for ProxyDHCP responses */
  #define PROXYDHCP_SETTINGS_NAME "proxydhcp"
  
  /** Setting block name used for BootServerDHCP responses */
  #define PXEBS_SETTINGS_NAME "pxebs"
  
  extern uint32_t dhcp_last_xid;
  extern int dhcp_create_packet ( struct dhcp_packet *dhcppkt,
  				struct net_device *netdev, uint8_t msgtype,
  				uint32_t xid, const void *options,
  				size_t options_len, void *data,
  				size_t max_len );
  extern int dhcp_create_request ( struct dhcp_packet *dhcppkt,
  				 struct net_device *netdev,
  				 unsigned int msgtype, uint32_t xid,
  				 struct in_addr ciaddr,
  				 void *data, size_t max_len );
  extern int start_dhcp ( struct interface *job, struct net_device *netdev );
  extern int start_pxebs ( struct interface *job, struct net_device *netdev,
  			 unsigned int pxe_type );
  
  #endif /* _IPXE_DHCP_H */
  