Generating GOOSE Messages
This is a continuation of a previous post. It that previous post, an implementation of the GOOSE ASN.1 encoder. I have since update that repository to include an example showing how to created a GOOSE message using that ASN.1 definition and the scapy library. The example is explained below.
First, the IECGoosePDU ASN.1 type is created.
from pyasn1.type import tag
from goose_pdu import IECGoosePDU
g = IECGoosePDU().subtype(
implicitTag=tag.Tag(
tag.tagClassApplication,
tag.tagFormatConstructed,
1
)
)
Next, the static portion of the GOOSE message is created by setting each of the fields to an appropriate value. gocbRef, datSet, and goID are set to strings. timeAllowedtoLive, stNum, sqNum, confRev, and numDatSetEntries are set to integers. t is set to a valid timestamp. test and ndsCom are boolean values.
g.setComponentByName('gocbRef', 'PDC-2+11+700G_G1CFG/LLNO$GO$GooseDset_BF')
g.setComponentByName('timeAllowedtoLive', 2000)
g.setComponentByName('datSet', 'PDC02_11_700G_G1CFG/LLN0$Dset_BF')
g.setComponentByName('goID, '11_700G_G1_Dset_BF')
g.setComponentByName('t', b'\x55\x15\x1b\x9b\x69\x37\x40\x92')
g.setComponentByName('stNum', 5)
g.setComponentByName('sqNum', 1757)
g.setComponentByName('test', False)
g.setComponentByName('confRev', 3)
g.setComponentByName('ndsCom', False)
g.setComponentByName('numDatSetEntries', 6)
The dynamic data is then added. In this example, 2 boolean values are added to the message, including their associated quality and timestamp. Each of the 6 data items are created and added to the 'allData' field. The 'allData' field is then added to the GOOSE message.
from goose_pdu import AllData
from goose_pdu import Data()
d = AllData().subtype(
implicitTag=tag.Tag(
tag.tagClassContext,
tag.tagFormatConstructed,
11
)
)
d1 = Data()
d1.setComponentByName('boolean', False)
d2 = Data()
d2.setComponentByName('bit-string', "'0000000000000'B")
d3 = Data()
d3.setComponentByName'utc-time', b'\x55\x15\x14\xc0\xc8\xf5\xc0\x92')
d4 = Data()
d4.setComponentByName('boolean', False)
d5 = Data()
d5.setComponentByName('bit-string', "'0000000000000'B")
d6 = Data()
d6.setComponentByName'utc-time', b'\x55\x15\x14\xaa\x3a\x9f\x80\x92')
d.setComponentByPosition(0, d1)
d.setComponentByPosition(1, d2)
d.setComponentByPosition(2, d3)
d.setComponentByPosition(3, d4)
d.setComponentByPosition(4, d5)
d.setComponentByPosition(5, d6)
g.setComponentByName('addData', d)
The last step is to create the scapy packet. The Ethernet frame is created with the GOOSE multicast destination address. VLAN information is added to the packet placing the message in VLAN 10 with priority 6, and GOOSE as the type. The GOOSE static data fields are then added followed by the dynamic ASN.1 encoded fields.
from pyasn1.codec.ber import encoder
from scapy.layers.l2 import Ether
from scapy.layers.l2 import Dot1Q
from scapy.utils import hexdump
from goose import GOOSE
hexdump(
Ether(dst='01:0c:cd:01:00:14') /
Dot1Q(vlan=10, type=0x88b8, prio=6) /
GOOSE(appid=int(0x00b1)) /
encoder.encode(g)
)
Next Steps
The next step in this experiment will be to use this GOOSE message in a network packet created with scapy and transmit it on a network interface using the scapy.sendp() function.