126 lines
2.9 KiB
Go
126 lines
2.9 KiB
Go
//go:build linux
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/*
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* Copyright (C) 2020-2022, IrineSistiana
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*
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* This file is part of mosdns.
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*
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* mosdns is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* mosdns is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <https://www.gnu.org/licenses/>.
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*/
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package server
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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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"golang.org/x/net/ipv4"
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"golang.org/x/net/ipv6"
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"golang.org/x/sys/unix"
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)
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var (
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errCmNoDstAddr = errors.New("control msg does not have dst address")
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)
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func getOOBFromCM4(oob []byte) (net.IP, error) {
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var cm ipv4.ControlMessage
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if err := cm.Parse(oob); err != nil {
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return nil, err
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}
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if cm.Dst == nil {
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return nil, errCmNoDstAddr
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}
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return cm.Dst, nil
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}
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func getOOBFromCM6(oob []byte) (net.IP, error) {
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var cm ipv6.ControlMessage
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if err := cm.Parse(oob); err != nil {
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return nil, err
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}
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if cm.Dst == nil {
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return nil, errCmNoDstAddr
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}
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return cm.Dst, nil
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}
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func srcIP2Cm(ip net.IP) []byte {
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if ip4 := ip.To4(); ip4 != nil {
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return (&ipv4.ControlMessage{
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Src: ip,
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}).Marshal()
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}
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if ip6 := ip.To16(); ip6 != nil {
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return (&ipv6.ControlMessage{
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Src: ip,
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}).Marshal()
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}
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return nil
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}
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func initOobHandler(c *net.UDPConn) (getSrcAddrFromOOB, writeSrcAddrToOOB, error) {
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if !c.LocalAddr().(*net.UDPAddr).IP.IsUnspecified() {
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return nil, nil, nil
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}
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sc, err := c.SyscallConn()
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if err != nil {
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return nil, nil, err
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}
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var getter getSrcAddrFromOOB
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var setter writeSrcAddrToOOB
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var controlErr error
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if err := sc.Control(func(fd uintptr) {
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v, err := unix.GetsockoptInt(int(fd), unix.SOL_SOCKET, unix.SO_DOMAIN)
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if err != nil {
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controlErr = os.NewSyscallError("failed to get SO_PROTOCOL", err)
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return
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}
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switch v {
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case unix.AF_INET:
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c4 := ipv4.NewPacketConn(c)
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if err := c4.SetControlMessage(ipv4.FlagDst, true); err != nil {
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controlErr = fmt.Errorf("failed to set ipv4 cmsg flags, %w", err)
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}
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getter = getOOBFromCM4
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setter = srcIP2Cm
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return
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case unix.AF_INET6:
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c6 := ipv6.NewPacketConn(c)
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if err := c6.SetControlMessage(ipv6.FlagDst, true); err != nil {
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controlErr = fmt.Errorf("failed to set ipv6 cmsg flags, %w", err)
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}
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getter = getOOBFromCM6
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setter = srcIP2Cm
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return
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default:
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controlErr = fmt.Errorf("socket protocol %d is not supported", v)
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}
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}); err != nil {
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return nil, nil, fmt.Errorf("control fd err, %w", controlErr)
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}
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if controlErr != nil {
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return nil, nil, fmt.Errorf("failed to set up socket, %w", controlErr)
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}
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return getter, setter, nil
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}
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