How to Craft and Send Raw TCP Packets in Go using gopacket?

Crafting and Sending Raw TCP Packets with Golang (gopacket)

To create custom raw TCP packets and transmit them over raw sockets using gopacket, follow these steps:

1. Crafting the Raw TCP Packet

• Import gopacket and net.
• Set the source and destination IP addresses (e.g., srcIP := net.ParseIP("127.0.0.1")).
• Create an IPv4 packet layer with the specified IP addresses and protocol.
• Create a TCP packet layer with the desired source and destination ports and flags (e.g., SYN: true).
• Set the network layer for the TCP layer checksum calculation.
• Serialize the packet layers using gopacket.SerializeLayers() to create a raw packet buffer.

2. Sending the Raw Packet

• Create a raw socket using net.ListenPacket("ip4:tcp", "0.0.0.0").
• Obtain the destination IP address information using net.IPAddr{}.
• Write the raw packet buffer to the raw socket using WriteTo().

Troubleshooting:

• Ensure that the specified source IP address is valid and not restricted (e.g., 127.0.0.1).
• Verify that IP headers can be included in the outgoing packets by setting the IP_HDRINCL socket option. This may require a third-party package or OS-specific configuration.
• Check if the packet is properly serialized and contains all the necessary information, including checksums and correct IP addresses.

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