Unable to decode LinkType 20

[HaibaraAi119]

i use tcpdump to get a tcp package,and then save a cap file,
but i use gopacket parsing this cap file,following error occurs:
"Packet decoding error: Unable to decode LinkType 20"

my code:
handle, err = pcap.OpenOffline(capFile)

packetSource := gopacket.NewPacketSource(handle, handle.LinkType())
//go print_counter()
for packet := range packetSource.Packets() {
fmt.Println(packet) //Packet decoding error: Unable to decode LinkType 20
printPacketInfo(packet)
}

... ...

tcpLayer := packet.Layer(layers.LayerTypeTCP) //Causes an error here ,is null

[scila1996]

Please switch to this. The newer link type with the latest device has been updated, and it is working for me

https://pkg.go.dev/github.com/gopacket/gopacket

[8ugr4]

I fixed it like this once, it was causing because of linux sll2 packet and afaik this lib doesn't include it. so smth like

const sll2HeaderSize       = 20
// remove the first 20 bytes that only has sll2 information, unrelated to the packet info.
packetBytes := packet.Data()[sll2HeaderSize:] 
// create new packet 
packet = gopacket.NewPacket(packetBytes, layers.LayerTypeIPv4, gopacket.Default)

[HaibaraAi119]

Please switch to this. The newer link type with the latest device has been updated, and it is working for me

https://pkg.go.dev/github.com/gopacket/gopacket

gopacket

i'd like to how about its compatibility with old gopacket

[8ugr4]

It's the same, just a maintained fork afaik.

[HaibaraAi119]

It's the same, just a maintained fork afaik.

i had tested it today,it's working great !!!
Thank you again.