def build_dhcp_request(mac_addr, request_broadcast):
"""
Build DHCP request string.
"""
#
# typedef struct _DHCP {
# UINT8 Opcode; /* op: BOOTREQUEST or BOOTREPLY */
# UINT8 HardwareAddressType; /* htype: ethernet */
# UINT8 HardwareAddressLength; /* hlen: 6 (48 bit mac address) */
# UINT8 Hops; /* hops: 0 */
# UINT8 TransactionID[4]; /* xid: random */
# UINT8 Seconds[2]; /* secs: 0 */
# UINT8 Flags[2]; /* flags: 0 or 0x8000 for broadcast*/
# UINT8 ClientIpAddress[4]; /* ciaddr: 0 */
# UINT8 YourIpAddress[4]; /* yiaddr: 0 */
# UINT8 ServerIpAddress[4]; /* siaddr: 0 */
# UINT8 RelayAgentIpAddress[4]; /* giaddr: 0 */
# UINT8 ClientHardwareAddress[16]; /* chaddr: 6 byte eth MAC address */
# UINT8 ServerName[64]; /* sname: 0 */
# UINT8 BootFileName[128]; /* file: 0 */
# UINT8 MagicCookie[4]; /* 99 130 83 99 */
# /* 0x63 0x82 0x53 0x63 */
# /* options -- hard code ours */
#
# UINT8 MessageTypeCode; /* 53 */
# UINT8 MessageTypeLength; /* 1 */
# UINT8 MessageType; /* 1 for DISCOVER */
# UINT8 End; /* 255 */
# } DHCP;
#
# tuple of 244 zeros
# (struct.pack_into would be good here, but requires Python 2.5)
request = [0] * 244
trans_id = gen_trans_id()
# Opcode = 1
# HardwareAddressType = 1 (ethernet/MAC)
# HardwareAddressLength = 6 (ethernet/MAC/48 bits)
for a in range(0, 3):
request[a] = [1, 1, 6][a]
# fill in transaction id (random number to ensure response matches request)
for a in range(0, 4):
request[4 + a] = str_to_ord(trans_id[a])
logger.verbose("BuildDhcpRequest: transactionId:%s,%04X" %
(hex_dump2(trans_id), unpack_big_endian(request, 4, 4)))
if request_broadcast:
# set broadcast flag to true to request the dhcp server
# to respond to a boradcast address,
# this is useful when user dhclient fails.
request[0x0A] = 0x80
# fill in ClientHardwareAddress
for a in range(0, 6):
request[0x1C + a] = str_to_ord(mac_addr[a])
# DHCP Magic Cookie: 99, 130, 83, 99
# MessageTypeCode = 53 DHCP Message Type
# MessageTypeLength = 1
# MessageType = DHCPDISCOVER
# End = 255 DHCP_END
for a in range(0, 8):
request[0xEC + a] = [99, 130, 83, 99, 53, 1, 1, 255][a]
return array.array("B", request)
def build_dhcp_request(mac_addr, request_broadcast):
"""
Build DHCP request string.
"""
#
# typedef struct _DHCP {
# UINT8 Opcode; /* op: BOOTREQUEST or BOOTREPLY */
# UINT8 HardwareAddressType; /* htype: ethernet */
# UINT8 HardwareAddressLength; /* hlen: 6 (48 bit mac address) */
# UINT8 Hops; /* hops: 0 */
# UINT8 TransactionID[4]; /* xid: random */
# UINT8 Seconds[2]; /* secs: 0 */
# UINT8 Flags[2]; /* flags: 0 or 0x8000 for broadcast*/
# UINT8 ClientIpAddress[4]; /* ciaddr: 0 */
# UINT8 YourIpAddress[4]; /* yiaddr: 0 */
# UINT8 ServerIpAddress[4]; /* siaddr: 0 */
# UINT8 RelayAgentIpAddress[4]; /* giaddr: 0 */
# UINT8 ClientHardwareAddress[16]; /* chaddr: 6 byte eth MAC address */
# UINT8 ServerName[64]; /* sname: 0 */
# UINT8 BootFileName[128]; /* file: 0 */
# UINT8 MagicCookie[4]; /* 99 130 83 99 */
# /* 0x63 0x82 0x53 0x63 */
# /* options -- hard code ours */
#
# UINT8 MessageTypeCode; /* 53 */
# UINT8 MessageTypeLength; /* 1 */
# UINT8 MessageType; /* 1 for DISCOVER */
# UINT8 End; /* 255 */
# } DHCP;
#
# tuple of 244 zeros
# (struct.pack_into would be good here, but requires Python 2.5)
request = [0] * 244
trans_id = gen_trans_id()
# Opcode = 1
# HardwareAddressType = 1 (ethernet/MAC)
# HardwareAddressLength = 6 (ethernet/MAC/48 bits)
for a in range(0, 3):
request[a] = [1, 1, 6][a]
# fill in transaction id (random number to ensure response matches request)
for a in range(0, 4):
request[4 + a] = str_to_ord(trans_id[a])
logger.verbose("BuildDhcpRequest: transactionId:%s,%04X" % (
hex_dump2(trans_id),
unpack_big_endian(request, 4, 4)))
if request_broadcast:
# set broadcast flag to true to request the dhcp server
# to respond to a boradcast address,
# this is useful when user dhclient fails.
request[0x0A] = 0x80;
# fill in ClientHardwareAddress
for a in range(0, 6):
request[0x1C + a] = str_to_ord(mac_addr[a])
# DHCP Magic Cookie: 99, 130, 83, 99
# MessageTypeCode = 53 DHCP Message Type
# MessageTypeLength = 1
# MessageType = DHCPDISCOVER
# End = 255 DHCP_END
for a in range(0, 8):
request[0xEC + a] = [99, 130, 83, 99, 53, 1, 1, 255][a]
return array.array("B", request)
