def parse_dhcp_resp(self, response):
"""
Parse DHCP response:
Returns endpoint server or None on error.
"""
self.logger.log('Parsing Dhcp response')
bytes_recv = len(response)
endpoint = None
gateway = None
routes = None
# Walk all the returned options, parsing out what we need, ignoring the
# others. We need the custom option 245 to find the the endpoint we talk to
# options 3 for default gateway and 249 for routes; 255 is end.
i = 0xF0 # offset to first option
while i < bytes_recv:
option = dhcpUtils.str_to_ord(response[i])
length = 0
if (i + 1) < bytes_recv:
length = dhcpUtils.str_to_ord(response[i + 1])
self.logger.log(
"DHCP option {0} at offset:{1} with length:{2}".format(
hex(option), hex(i), hex(length)))
if option == 255:
self.logger.log("DHCP packet ended at offset:{0}".format(
hex(i)))
break
elif option == 249:
routes = self.parse_route(response, option, i, length,
bytes_recv)
elif option == 3:
gateway = self.parse_ip_addr(response, option, i, length,
bytes_recv)
self.logger.log("Default gateway:{0}, at {1}".format(
gateway, hex(i)))
elif option == 245:
endpoint = self.parse_ip_addr(response, option, i, length,
bytes_recv)
self.logger.log(
"Azure scheduled events endpoint IP:{0}, at {1}".format(
endpoint, hex(i)))
else:
self.logger.log(
"Skipping DHCP option:{0} at {1} with length {2}".format(
hex(option), hex(i), hex(length)))
i += length + 2
return endpoint, gateway, routes
def parse_dhcp_resp(self, response):
"""
Parse DHCP response:
Returns endpoint server or None on error.
"""
self.logger.log('Parsing Dhcp response')
bytes_recv = len(response)
endpoint = None
gateway = None
routes = None
# Walk all the returned options, parsing out what we need, ignoring the
# others. We need the custom option 245 to find the the endpoint we talk to
# options 3 for default gateway and 249 for routes; 255 is end.
i = 0xF0 # offset to first option
while i < bytes_recv:
option = dhcpUtils.str_to_ord(response[i])
length = 0
if (i + 1) < bytes_recv:
length = dhcpUtils.str_to_ord(response[i + 1])
self.logger.log("DHCP option {0} at offset:{1} with length:{2}".format(hex(option), hex(i), hex(length)))
if option == 255:
self.logger.log("DHCP packet ended at offset:{0}".format(hex(i)))
break
elif option == 249:
routes = self.parse_route(response, option, i, length, bytes_recv)
elif option == 3:
gateway = self.parse_ip_addr(response, option, i, length, bytes_recv)
self.logger.log("Default gateway:{0}, at {1}".format(gateway, hex(i)))
elif option == 245:
endpoint = self.parse_ip_addr(response, option, i, length, bytes_recv)
self.logger.log("Azure scheduled events endpoint IP:{0}, at {1}".format(endpoint, hex(i)))
else:
self.logger.log("Skipping DHCP option:{0} at {1} with length {2}".format(hex(option), hex(i), hex(length)))
i += length + 2
return endpoint, gateway, routes
def parse_route(self, response, option, i, length, bytes_recv):
# http://msdn.microsoft.com/en-us/library/cc227282%28PROT.10%29.aspx
self.logger.log("Routes at offset: {0} with length:{1}".format(hex(i), hex(length)))
routes = []
if length < 5:
self.logger.log("Data too small for option:{0}" + str(option))
j = i + 2
while j < (i + length + 2):
mask_len_bits = dhcpUtils.str_to_ord(response[j])
mask_len_bytes = (((mask_len_bits + 7) & ~7) >> 3)
mask = 0xFFFFFFFF & (0xFFFFFFFF << (32 - mask_len_bits))
j += 1
net = dhcpUtils.unpack_big_endian(response, j, mask_len_bytes)
net <<= (32 - mask_len_bytes * 8)
net &= mask
j += mask_len_bytes
gateway = dhcpUtils.unpack_big_endian(response, j, 4)
j += 4
routes.append((net, mask, gateway))
if j != (i + length + 2):
self.logger.log("Unable to parse routes")
return routes
def parse_route(self, response, option, i, length, bytes_recv):
# http://msdn.microsoft.com/en-us/library/cc227282%28PROT.10%29.aspx
self.logger.log("Routes at offset: {0} with length:{1}".format(
hex(i), hex(length)))
routes = []
if length < 5:
self.logger.log("Data too small for option:{0}" + str(option))
j = i + 2
while j < (i + length + 2):
mask_len_bits = dhcpUtils.str_to_ord(response[j])
mask_len_bytes = (((mask_len_bits + 7) & ~7) >> 3)
mask = 0xFFFFFFFF & (0xFFFFFFFF << (32 - mask_len_bits))
j += 1
net = dhcpUtils.unpack_big_endian(response, j, mask_len_bytes)
net <<= (32 - mask_len_bytes * 8)
net &= mask
j += mask_len_bytes
gateway = dhcpUtils.unpack_big_endian(response, j, 4)
j += 4
routes.append((net, mask, gateway))
if j != (i + length + 2):
self.logger.log("Unable to parse routes")
return routes
def build_dhcp_request(self, 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 = self.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] = dhcpUtils.str_to_ord(trans_id[a])
self.logger.log("BuildDhcpRequest: transactionId:{0},{1:04x}".format(
dhcpUtils.hex_dump2(trans_id),
dhcpUtils.unpack_big_endian(request, 4, 4)))
if request_broadcast:
# set broadcast flag to true to request the dhcp sever
# 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] = dhcpUtils.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(self, 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 = self.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] = dhcpUtils.str_to_ord(trans_id[a])
self.logger.log("BuildDhcpRequest: transactionId:{0},{1:04x}".format(dhcpUtils.hex_dump2(trans_id), dhcpUtils.unpack_big_endian(request, 4, 4)))
if request_broadcast:
# set broadcast flag to true to request the dhcp sever
# 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] = dhcpUtils.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)