mirror of
https://github.com/tailscale/tailscale.git
synced 2024-12-02 22:45:37 +00:00
83 lines
2.6 KiB
Go
83 lines
2.6 KiB
Go
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// Copyright (c) Tailscale Inc & AUTHORS
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// SPDX-License-Identifier: BSD-3-Clause
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package tstun
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import (
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"errors"
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"net/netip"
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"runtime"
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"github.com/tailscale/wireguard-go/tun"
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"golang.org/x/sys/unix"
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"gvisor.dev/gvisor/pkg/tcpip"
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"gvisor.dev/gvisor/pkg/tcpip/checksum"
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"gvisor.dev/gvisor/pkg/tcpip/header"
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"tailscale.com/envknob"
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"tailscale.com/net/tsaddr"
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)
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// SetLinkFeaturesPostUp configures link features on t based on select TS_TUN_
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// environment variables and OS feature tests. Callers should ensure t is
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// up prior to calling, otherwise OS feature tests may be inconclusive.
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func (t *Wrapper) SetLinkFeaturesPostUp() {
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if t.isTAP || runtime.GOOS == "android" {
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return
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}
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if groDev, ok := t.tdev.(tun.GRODevice); ok {
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if envknob.Bool("TS_TUN_DISABLE_UDP_GRO") {
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groDev.DisableUDPGRO()
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}
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if envknob.Bool("TS_TUN_DISABLE_TCP_GRO") {
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groDev.DisableTCPGRO()
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}
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err := probeTCPGRO(groDev)
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if errors.Is(err, unix.EINVAL) {
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groDev.DisableTCPGRO()
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groDev.DisableUDPGRO()
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t.logf("disabled TUN TCP & UDP GRO due to GRO probe error: %v", err)
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}
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}
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}
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func probeTCPGRO(dev tun.GRODevice) error {
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ipPort := netip.MustParseAddrPort(tsaddr.TailscaleServiceIPString + ":0")
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fingerprint := []byte("tailscale-probe-tun-gro")
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segmentSize := len(fingerprint)
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iphLen := 20
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tcphLen := 20
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totalLen := iphLen + tcphLen + segmentSize
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ipAs4 := ipPort.Addr().As4()
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bufs := make([][]byte, 2)
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for i := range bufs {
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bufs[i] = make([]byte, PacketStartOffset+totalLen, PacketStartOffset+(totalLen*2))
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ipv4H := header.IPv4(bufs[i][PacketStartOffset:])
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ipv4H.Encode(&header.IPv4Fields{
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SrcAddr: tcpip.AddrFromSlice(ipAs4[:]),
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DstAddr: tcpip.AddrFromSlice(ipAs4[:]),
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Protocol: unix.IPPROTO_TCP,
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// Use a zero value TTL as best effort means to reduce chance of
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// probe packet leaking further than it needs to.
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TTL: 0,
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TotalLength: uint16(totalLen),
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})
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tcpH := header.TCP(bufs[i][PacketStartOffset+iphLen:])
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tcpH.Encode(&header.TCPFields{
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SrcPort: ipPort.Port(),
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DstPort: ipPort.Port(),
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SeqNum: 1 + uint32(i*segmentSize),
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AckNum: 1,
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DataOffset: 20,
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Flags: header.TCPFlagAck,
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WindowSize: 3000,
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})
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copy(bufs[i][PacketStartOffset+iphLen+tcphLen:], fingerprint)
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ipv4H.SetChecksum(^ipv4H.CalculateChecksum())
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pseudoCsum := header.PseudoHeaderChecksum(unix.IPPROTO_TCP, ipv4H.SourceAddress(), ipv4H.DestinationAddress(), uint16(tcphLen+segmentSize))
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pseudoCsum = checksum.Checksum(bufs[i][PacketStartOffset+iphLen+tcphLen:], pseudoCsum)
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tcpH.SetChecksum(^tcpH.CalculateChecksum(pseudoCsum))
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}
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_, err := dev.Write(bufs, PacketStartOffset)
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return err
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}
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