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88 lines
1.9 KiB
88 lines
1.9 KiB
// +build darwin freebsd openbsd
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package arping
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import (
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"errors"
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"fmt"
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"net"
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"os"
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"syscall"
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"time"
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)
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var bpf *os.File
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var bpfFd int
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var buflen int
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var bpfArpFilter = []syscall.BpfInsn{
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// make sure this is an arp packet
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*syscall.BpfStmt(syscall.BPF_LD+syscall.BPF_H+syscall.BPF_ABS, 12),
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*syscall.BpfJump(syscall.BPF_JMP+syscall.BPF_JEQ+syscall.BPF_K, 0x0806, 0, 1),
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// if we passed all the tests, ask for the whole packet.
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*syscall.BpfStmt(syscall.BPF_RET+syscall.BPF_K, -1),
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// otherwise, drop it.
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*syscall.BpfStmt(syscall.BPF_RET+syscall.BPF_K, 0),
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}
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func initialize(iface net.Interface) (err error) {
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verboseLog.Println("search available /dev/bpfX")
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for i := 0; i <= 10; i++ {
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bpfPath := fmt.Sprintf("/dev/bpf%d", i)
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bpf, err = os.OpenFile(bpfPath, os.O_RDWR, 0666)
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if err != nil {
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verboseLog.Printf(" open failed: %s - %s\n", bpfPath, err.Error())
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} else {
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verboseLog.Printf(" open success: %s\n", bpfPath)
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break
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}
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}
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bpfFd = int(bpf.Fd())
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if bpfFd == -1 {
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return errors.New("unable to open /dev/bpfX")
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}
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if err := syscall.SetBpfInterface(bpfFd, iface.Name); err != nil {
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return err
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}
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if err := syscall.SetBpfImmediate(bpfFd, 1); err != nil {
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return err
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}
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buflen, err = syscall.BpfBuflen(bpfFd)
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if err != nil {
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return err
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}
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if err := syscall.SetBpf(bpfFd, bpfArpFilter); err != nil {
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return err
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}
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if err := syscall.FlushBpf(bpfFd); err != nil {
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return err
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}
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return nil
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}
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func send(request arpDatagram) (time.Time, error) {
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_, err := syscall.Write(bpfFd, request.MarshalWithEthernetHeader())
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return time.Now(), err
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}
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func receive() (arpDatagram, time.Time, error) {
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buffer := make([]byte, buflen)
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n, err := syscall.Read(bpfFd, buffer)
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if err != nil {
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return arpDatagram{}, time.Now(), err
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}
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// skip 26 bytes bpf header + 14 bytes ethernet header
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return parseArpDatagram(buffer[40:n]), time.Now(), nil
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}
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func deinitialize() error {
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return bpf.Close()
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}
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