goscapy — Go Network Packet Crafting Library

Features

Everything you need for packet engineering — from crafting to sniffing with a clean, idiomatic Go API.

🔨 Builder API

Fluent method chaining for type-safe, explicit packet construction with compile-time guarantees.

⚡ Shortcut Functions

One-liners for common protocol stacks with sensible defaults. Build packets in a single function call.

🔬 Packet Dissect

Parse raw bytes into structured packets with automatic protocol detection and layer extraction.

📡 Send & Receive

Send and receive packets via raw sockets at both L2 (Ethernet) and L3 (IP) levels.

👃 Sniffing

Capture live traffic with callback or channel-based APIs, plus BPF filter support.

✅ Auto Checksums

IP, TCP, UDP, and ICMP checksums are computed automatically during serialization.

🔗 Layer Binding

Automatic field inference between adjacent layers — IP over Ethernet sets EtherType automatically.

💻 Cross-Platform

Works on macOS (Darwin) and Linux with platform-specific raw socket implementations.

Supported Protocols

Comprehensive coverage across the network stack layers.

Layer	Protocols
Link	Ethernet (CSMA/CD), ARP
Network	IPv4
Transport	TCP, UDP, ICMP
Payload	Raw bytes

Get Started in Seconds

Add goscapy to your project with a single command.

bash

# Install the latest version
go get github.com/smallnest/goscapy

Build a Packet in One Line

🔨 Builder API

            go
            
          

// Ethernet + IP + ICMP Echo Request
pkt, err := goscapy.NewEthernet().
    SrcMAC("aa:bb:cc:dd:ee:ff").
    DstMAC("ff:ff:ff:ff:ff:ff").
    Over(goscapy.NewIP().
        SrcIP("192.168.1.1").
        DstIP("8.8.8.8")).
    Over(goscapy.NewICMP().
        Type(8).Code(0)).
    Build()
          

⚡ Shortcut

            go
            
          

// Same packet, in one line
pkt, err := goscapy.EtherIPICMP(
    "ff:ff:ff:ff:ff:ff",
    "8.8.8.8",
    8, 0,
)
          

🔬 Dissect Raw Bytes

            go
            
// Parse raw bytes into structured packet
raw := []byte{0xff, 0xff, 0xff, 0xff, 0xff, 0xff, ...}
pkt, err := packet.Dissect(raw, packet.DissectEthernet)
fmt.Println(pkt.String()) // "Ethernet / IP / ICMP"