70 lines
1.6 KiB
Go
70 lines
1.6 KiB
Go
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// +build linux
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package redir
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import (
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"encoding/binary"
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"errors"
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"net"
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"syscall"
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)
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const (
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IPV6_TRANSPARENT = 0x4b
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IPV6_RECVORIGDSTADDR = 0x4a
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)
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func setsockopt(c *net.UDPConn, addr string) error {
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isIPv6 := true
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host, _, err := net.SplitHostPort(addr)
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if err != nil {
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return err
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}
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ip := net.ParseIP(host)
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if ip != nil && ip.To4() != nil {
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isIPv6 = false
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}
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rc, err := c.SyscallConn()
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if err != nil {
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return err
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}
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rc.Control(func(fd uintptr) {
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err = syscall.SetsockoptInt(int(fd), syscall.SOL_IP, syscall.IP_TRANSPARENT, 1)
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if err == nil && isIPv6 {
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err = syscall.SetsockoptInt(int(fd), syscall.SOL_IPV6, IPV6_TRANSPARENT, 1)
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}
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if err == nil {
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err = syscall.SetsockoptInt(int(fd), syscall.SOL_IP, syscall.IP_RECVORIGDSTADDR, 1)
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}
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if err == nil && isIPv6 {
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err = syscall.SetsockoptInt(int(fd), syscall.SOL_IPV6, IPV6_RECVORIGDSTADDR, 1)
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}
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})
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return err
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}
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func getOrigDst(oob []byte, oobn int) (*net.UDPAddr, error) {
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msgs, err := syscall.ParseSocketControlMessage(oob[:oobn])
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if err != nil {
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return nil, err
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}
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for _, msg := range msgs {
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if msg.Header.Level == syscall.SOL_IP && msg.Header.Type == syscall.IP_RECVORIGDSTADDR {
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ip := net.IP(msg.Data[4:8])
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port := binary.BigEndian.Uint16(msg.Data[2:4])
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return &net.UDPAddr{IP: ip, Port: int(port)}, nil
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} else if msg.Header.Level == syscall.SOL_IPV6 && msg.Header.Type == IPV6_RECVORIGDSTADDR {
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ip := net.IP(msg.Data[8:24])
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port := binary.BigEndian.Uint16(msg.Data[2:4])
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return &net.UDPAddr{IP: ip, Port: int(port)}, nil
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}
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}
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return nil, errors.New("cannot find origDst")
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}
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