mirror of https://github.com/tailscale/tailscale/
net/packet, wgengine, tstun: add inter-node TSMP protocol for connect errors
This adds a new IP Protocol type, TSMP on protocol number 99 for sending inter-tailscale messages over WireGuard, currently just for why a peer rejects TCP SYNs (ACL rejection, shields up, and in the future: nothing listening, something listening on that port but wrong interface, etc) Updates #1094 Updates tailscale/corp#1185 Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>pull/1135/head
Brad Fitzpatrick
4 years ago
committed by
Brad Fitzpatrick
parent
01e8b7fb7e
commit
b560386c1a
@ -0,0 +1,140 @@
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// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// TSMP is our ICMP-like "Tailscale Message Protocol" for signaling
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// Tailscale-specific messages between nodes. It uses IP protocol 99
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// (reserved for "any private encryption scheme") within
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// Wireguard's normal encryption between peers and never hits the host
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// network stack.
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package packet
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import (
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"encoding/binary"
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"errors"
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"fmt"
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"inet.af/netaddr"
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"tailscale.com/net/flowtrack"
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)
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// TailscaleRejectedHeader is a TSMP message that says that one
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// Tailscale node has rejected the connection from another. Unlike a
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// TCP RST, this includes a reason.
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//
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// On the wire, after the IP header, it's currently 7 bytes:
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// * '!'
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// * IPProto byte (IANA protocol number: TCP or UDP)
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// * 'A' or 'S' (RejectedDueToACLs, RejectedDueToShieldsUp)
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// * srcPort big endian uint16
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// * dstPort big endian uint16
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//
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// In the future it might also accept 16 byte IP flow src/dst IPs
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// after the header, if they're different than the IP-level ones.
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type TailscaleRejectedHeader struct {
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IPSrc netaddr.IP // IPv4 or IPv6 header's src IP
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IPDst netaddr.IP // IPv4 or IPv6 header's dst IP
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Src netaddr.IPPort // rejected flow's src
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Dst netaddr.IPPort // rejected flow's dst
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Proto IPProto // proto that was rejected (TCP or UDP)
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Reason TailscaleRejectReason // why the connection was rejected
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}
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func (rh TailscaleRejectedHeader) Flow() flowtrack.Tuple {
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return flowtrack.Tuple{Src: rh.Src, Dst: rh.Dst}
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}
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func (rh TailscaleRejectedHeader) String() string {
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return fmt.Sprintf("TSMP-reject-flow{%s %s > %s}: %s", rh.Proto, rh.Src, rh.Dst, rh.Reason)
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}
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type TSMPType uint8
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const (
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TSMPTypeRejectedConn TSMPType = '!'
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)
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type TailscaleRejectReason byte
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const (
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RejectedDueToACLs TailscaleRejectReason = 'A'
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RejectedDueToShieldsUp TailscaleRejectReason = 'S'
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)
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func (r TailscaleRejectReason) String() string {
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switch r {
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case RejectedDueToACLs:
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return "acl"
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case RejectedDueToShieldsUp:
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return "shields"
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}
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return fmt.Sprintf("0x%02x", byte(r))
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}
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func (h TailscaleRejectedHeader) Len() int {
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var ipHeaderLen int
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if h.IPSrc.Is4() {
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ipHeaderLen = ip4HeaderLength
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} else if h.IPSrc.Is6() {
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ipHeaderLen = ip6HeaderLength
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}
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return ipHeaderLen +
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1 + // TSMPType byte
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1 + // IPProto byte
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1 + // TailscaleRejectReason byte
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2*2 // 2 uint16 ports
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}
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func (h TailscaleRejectedHeader) Marshal(buf []byte) error {
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if len(buf) < h.Len() {
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return errSmallBuffer
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}
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if len(buf) > maxPacketLength {
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return errLargePacket
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}
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if h.Src.IP.Is4() {
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iph := IP4Header{
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IPProto: TSMP,
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Src: h.IPSrc,
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Dst: h.IPDst,
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}
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iph.Marshal(buf)
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buf = buf[ip4HeaderLength:]
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} else if h.Src.IP.Is6() {
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iph := IP6Header{
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IPProto: TSMP,
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Src: h.IPSrc,
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Dst: h.IPDst,
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}
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iph.Marshal(buf)
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buf = buf[ip6HeaderLength:]
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} else {
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return errors.New("bogus src IP")
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}
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buf[0] = byte(TSMPTypeRejectedConn)
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buf[1] = byte(h.Proto)
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buf[2] = byte(h.Reason)
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binary.BigEndian.PutUint16(buf[3:5], h.Src.Port)
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binary.BigEndian.PutUint16(buf[5:7], h.Dst.Port)
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return nil
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}
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// AsTailscaleRejectedHeader parses pp as an incoming rejection
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// connection TSMP message.
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//
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// ok reports whether pp was a valid TSMP rejection packet.
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func (pp *Parsed) AsTailscaleRejectedHeader() (h TailscaleRejectedHeader, ok bool) {
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p := pp.Payload()
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if len(p) < 7 || p[0] != byte(TSMPTypeRejectedConn) {
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return
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}
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return TailscaleRejectedHeader{
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Proto: IPProto(p[1]),
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Reason: TailscaleRejectReason(p[2]),
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IPSrc: pp.Src.IP,
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IPDst: pp.Dst.IP,
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Src: netaddr.IPPort{IP: pp.Dst.IP, Port: binary.BigEndian.Uint16(p[3:5])},
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Dst: netaddr.IPPort{IP: pp.Src.IP, Port: binary.BigEndian.Uint16(p[5:7])},
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}, true
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}
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@ -0,0 +1,63 @@
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// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package packet
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import (
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"testing"
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"inet.af/netaddr"
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)
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func TestTailscaleRejectedHeader(t *testing.T) {
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tests := []struct {
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h TailscaleRejectedHeader
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wantStr string
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}{
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{
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h: TailscaleRejectedHeader{
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IPSrc: netaddr.MustParseIP("5.5.5.5"),
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IPDst: netaddr.MustParseIP("1.2.3.4"),
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Src: netaddr.MustParseIPPort("1.2.3.4:567"),
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Dst: netaddr.MustParseIPPort("5.5.5.5:443"),
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Proto: TCP,
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Reason: RejectedDueToACLs,
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},
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wantStr: "TSMP-reject-flow{TCP 1.2.3.4:567 > 5.5.5.5:443}: acl",
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},
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{
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h: TailscaleRejectedHeader{
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IPSrc: netaddr.MustParseIP("2::2"),
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IPDst: netaddr.MustParseIP("1::1"),
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Src: netaddr.MustParseIPPort("[1::1]:567"),
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Dst: netaddr.MustParseIPPort("[2::2]:443"),
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Proto: UDP,
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Reason: RejectedDueToShieldsUp,
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},
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wantStr: "TSMP-reject-flow{UDP [1::1]:567 > [2::2]:443}: shields",
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},
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}
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for i, tt := range tests {
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gotStr := tt.h.String()
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if gotStr != tt.wantStr {
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t.Errorf("%v. String = %q; want %q", i, gotStr, tt.wantStr)
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continue
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}
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pkt := make([]byte, tt.h.Len())
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tt.h.Marshal(pkt)
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var p Parsed
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p.Decode(pkt)
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t.Logf("Parsed: %+v", p)
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t.Logf("Parsed: %s", p.String())
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back, ok := p.AsTailscaleRejectedHeader()
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if !ok {
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t.Errorf("%v. %q (%02x) didn't parse back", i, gotStr, pkt)
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continue
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}
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if back != tt.h {
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t.Errorf("%v. %q parsed back as %q", i, tt.h, back)
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}
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}
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}
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