internal/ip/ip_darwin.go

// Copyright (c) 2016 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

package ip

import (
	"net"

	"github.com/uber/arachne/defines"

	"github.com/google/gopacket"
	"github.com/google/gopacket/layers"
)

func bindToDevice(s int, ifname string) error {
	return nil
}

// GetIPLayerOptions is used to get the gopacket serialization options.
func GetIPLayerOptions() gopacket.SerializeOptions {
	return gopacket.SerializeOptions{
		ComputeChecksums: true,
		// Gopacket does not yet support making lengths host-byte order for BSD-based Kernels
		FixLengths: false,
	}
}

func getIPHeaderLayerV4(tos DSCPValue, tcpLen uint16, srcIP net.IP, dstIP net.IP) *layers.IPv4 {
	header := &layers.IPv4{
		Version:    4, // IP Version 4
		TOS:        uint8(tos),
		IHL:        5,           // IHL: 20 bytes
		Length:     tcpLen + 20, // Total IP packet length
		FragOffset: 0,           // No fragmentation
		Flags:      0,           // Flags for fragmentation
		TTL:        defines.IPTTL,
		Protocol:   layers.IPProtocolTCP,
		Checksum:   0, // Computed at serialization time
		SrcIP:      srcIP,
		DstIP:      dstIP,
	}

	// Manually convert Length and FragOffset to host-byte order for Darwin
	header.Length = (header.Length << 8) | (header.Length >> 8)
	nf := layers.IPv4Flag(header.FragOffset & 0xE0)
	header.FragOffset = (header.FragOffset & 0x1F << 8) | (header.FragOffset>>8 | uint16(header.Flags))
	header.Flags = nf

	return header
}