Padding and Fcs

[xiaofei-1024]

Question

EthLayer.cpp

How to detect padding and FCS in the Ethernet Layer, not identify padding and fcs may cause parsing issues.

Operating systems

No response

[seladb]

@xiaofei-1024 can you provide a pcap file that contains padding and FCS that we can look at?

[xiaofei-1024]

ff ff ff ff ff ff 02 00 00 00 00 01 08 00 45 00
00 24 bd 8f 40 00 40 11 68 28 0a 00 0b 12 ff ff
ff ff 9c 40 34 58 00 10 17 26 02 fd 00 01 00 00
00 00 00 00 00 00 00 00 00 00 00 00

[seladb]

@xiaofei-1024 can you attach a pcap file to this issue?

[xiaofei-1024]

Frame 1: 60 bytes on wire (480 bits), 60 bytes captured (480 bits)
Encapsulation type: Ethernet (1)
Arrival Time: Jul 4, 2025 11:54:04.514484000 中国标准时间
UTC Arrival Time: Jul 4, 2025 03:54:04.514484000 UTC
Epoch Arrival Time: 1751601244.514484000
[Time shift for this packet: 0.000000000 seconds]
[Time delta from previous captured frame: 0.000000000 seconds]
[Time delta from previous displayed frame: 0.000000000 seconds]
[Time since reference or first frame: 0.000000000 seconds]
Frame Number: 1
Frame Length: 60 bytes (480 bits)
Capture Length: 60 bytes (480 bits)
[Frame is marked: False]
[Frame is ignored: False]
[Protocols in frame: eth:ethertype:ip:udp:doip]
[Coloring Rule Name: UDP]
[Coloring Rule String: udp]
Ethernet II, Src: 02:00:00:00:00:01 (02:00:00:00:00:01), Dst: Broadcast (ff:ff:ff:ff:ff:ff)
Destination: Broadcast (ff:ff:ff:ff:ff:ff)
Source: 02:00:00:00:00:01 (02:00:00:00:00:01)
Type: IPv4 (0x0800)
[Stream index: 0]
Padding: 00000000000000000000
Internet Protocol Version 4, Src: 10.0.11.18, Dst: 255.255.255.255
0100 .... = Version: 4
.... 0101 = Header Length: 20 bytes (5)
Differentiated Services Field: 0x00 (DSCP: CS0, ECN: Not-ECT)
0000 00.. = Differentiated Services Codepoint: Default (0)
.... ..00 = Explicit Congestion Notification: Not ECN-Capable Transport (0)
Total Length: 36
Identification: 0xbd8f (48527)
010. .... = Flags: 0x2, Don't fragment
0... .... = Reserved bit: Not set
.1.. .... = Don't fragment: Set
..0. .... = More fragments: Not set
...0 0000 0000 0000 = Fragment Offset: 0
Time to Live: 64
Protocol: UDP (17)
Header Checksum: 0x6828 [validation disabled]
[Header checksum status: Unverified]
Source Address: 10.0.11.18
Destination Address: 255.255.255.255
[Stream index: 0]
User Datagram Protocol, Src Port: 40000, Dst Port: 13400
Source Port: 40000
Destination Port: 13400
Length: 16
Checksum: 0x1726 [unverified]
[Checksum Status: Unverified]
[Stream index: 0]
[Stream Packet Number: 1]
[Timestamps]
UDP payload (8 bytes)
DoIP (ISO13400) Protocol
Header
Version: DoIP ISO 13400-2:2012 (0x02)
Inverse version: 0xfd
Type: Vehicle identification request (0x0001)
Length: 0
this is from wireshark
modify output.txt to output.pcap

output.txt