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cf15d5bbc6
These are no longer needed as these are now part of a module. Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
83 lines
1.9 KiB
Go
83 lines
1.9 KiB
Go
package l2disco
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import (
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"context"
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"encoding/binary"
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"fmt"
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"net"
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"slices"
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"golang.org/x/sys/unix"
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)
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var (
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arpTemplate = []byte{
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0x00, 0x01, // Hardware type
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0x08, 0x00, // Protocol
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0x06, // Hardware address length
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0x04, // IPv4 address length
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0x00, 0x01, // ARP request
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0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // Sender MAC
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0x00, 0x00, 0x00, 0x00, // Sender IP
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0x00, 0x00, 0x00, 0x00, 0x00, 0x00, // Target MAC (always zeros)
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0x00, 0x00, 0x00, 0x00, // Target IP
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}
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bcastMAC = []byte{0xff, 0xff, 0xff, 0xff, 0xff, 0xff}
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)
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type UnsolARP struct {
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pkt []byte
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sd int
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sa *unix.SockaddrLinklayer
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}
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// NewUnsolARP returns a pointer to an object that can send unsolicited ARPs on
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// the interface with ifIndex, for ip and mac.
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func NewUnsolARP(_ context.Context, ip net.IP, mac net.HardwareAddr, ifIndex int) (*UnsolARP, error) {
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sd, err := unix.Socket(unix.AF_PACKET, unix.SOCK_DGRAM|unix.SOCK_CLOEXEC, 0)
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if err != nil {
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return nil, fmt.Errorf("create socket: %w", err)
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}
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pkt := slices.Clone(arpTemplate)
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copy(pkt[8:14], mac)
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copy(pkt[14:18], ip)
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copy(pkt[24:28], ip)
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sa := &unix.SockaddrLinklayer{
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Protocol: htons(unix.ETH_P_ARP),
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Ifindex: ifIndex,
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Hatype: unix.ARPHRD_ETHER,
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Halen: uint8(len(bcastMAC)),
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}
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copy(sa.Addr[:], bcastMAC)
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return &UnsolARP{
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pkt: pkt,
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sd: sd,
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sa: sa,
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}, nil
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}
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// Send sends an unsolicited ARP message.
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func (ua *UnsolARP) Send() error {
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return unix.Sendto(ua.sd, ua.pkt, 0, ua.sa)
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}
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// Close releases resources.
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func (ua *UnsolARP) Close() error {
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if ua.sd >= 0 {
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err := unix.Close(ua.sd)
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ua.sd = -1
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return err
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}
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return nil
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}
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// From https://github.com/mdlayher/packet/blob/f9999b41d9cfb0586e75467db1c81cfde4f965ba/packet_linux.go#L238-L248
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func htons(i uint16) uint16 {
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var bigEndian [2]byte
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binary.BigEndian.PutUint16(bigEndian[:], i)
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return binary.NativeEndian.Uint16(bigEndian[:])
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}
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