100 lines
2.7 KiB
Go
100 lines
2.7 KiB
Go
// 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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"os"
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"strconv"
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"testing"
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)
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// Test the default MTU in the presence of various envknobs.
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func TestDefaultTunMTU(t *testing.T) {
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// Save and restore the envknobs we will be changing.
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// TS_DEBUG_MTU sets the MTU to a specific value.
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defer os.Setenv("TS_DEBUG_MTU", os.Getenv("TS_DEBUG_MTU"))
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os.Setenv("TS_DEBUG_MTU", "")
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// TS_DEBUG_ENABLE_PMTUD enables path MTU discovery.
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defer os.Setenv("TS_DEBUG_ENABLE_PMTUD", os.Getenv("TS_DEBUG_ENABLE_PMTUD"))
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os.Setenv("TS_DEBUG_ENABLE_PMTUD", "")
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// With no MTU envknobs set, we should get the conservative MTU.
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if DefaultTUNMTU() != safeTUNMTU {
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t.Errorf("default TUN MTU = %d, want %d", DefaultTUNMTU(), safeTUNMTU)
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}
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// If set, TS_DEBUG_MTU should set the MTU.
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mtu := maxTUNMTU - 1
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os.Setenv("TS_DEBUG_MTU", strconv.Itoa(int(mtu)))
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if DefaultTUNMTU() != mtu {
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t.Errorf("default TUN MTU = %d, want %d, TS_DEBUG_MTU ignored", DefaultTUNMTU(), mtu)
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}
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// MTU should be clamped to maxTunMTU.
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mtu = maxTUNMTU + 1
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os.Setenv("TS_DEBUG_MTU", strconv.Itoa(int(mtu)))
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if DefaultTUNMTU() != maxTUNMTU {
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t.Errorf("default TUN MTU = %d, want %d, clamping failed", DefaultTUNMTU(), maxTUNMTU)
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}
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// If PMTUD is enabled, the MTU should default to the safe MTU, but only
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// if the user hasn't requested a specific MTU.
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//
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// TODO: When PMTUD is generating PTB responses, this will become the
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// largest MTU we probe.
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os.Setenv("TS_DEBUG_MTU", "")
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os.Setenv("TS_DEBUG_ENABLE_PMTUD", "true")
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if DefaultTUNMTU() != safeTUNMTU {
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t.Errorf("default TUN MTU = %d, want %d", DefaultTUNMTU(), safeTUNMTU)
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}
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// TS_DEBUG_MTU should take precedence over TS_DEBUG_ENABLE_PMTUD.
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mtu = WireToTUNMTU(MaxPacketSize - 1)
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os.Setenv("TS_DEBUG_MTU", strconv.Itoa(int(mtu)))
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if DefaultTUNMTU() != mtu {
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t.Errorf("default TUN MTU = %d, want %d", DefaultTUNMTU(), mtu)
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}
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}
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// Test the conversion of wire MTU to/from Tailscale TUN MTU corner cases.
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func TestMTUConversion(t *testing.T) {
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tests := []struct {
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w WireMTU
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t TUNMTU
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}{
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{w: 0, t: 0},
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{w: wgHeaderLen - 1, t: 0},
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{w: wgHeaderLen, t: 0},
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{w: wgHeaderLen + 1, t: 1},
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{w: 1360, t: 1280},
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{w: 1500, t: 1420},
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{w: 9000, t: 8920},
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}
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for _, tt := range tests {
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m := WireToTUNMTU(tt.w)
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if m != tt.t {
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t.Errorf("conversion of wire MTU %v to TUN MTU = %v, want %v", tt.w, m, tt.t)
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}
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}
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tests2 := []struct {
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t TUNMTU
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w WireMTU
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}{
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{t: 0, w: wgHeaderLen},
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{t: 1, w: wgHeaderLen + 1},
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{t: 1280, w: 1360},
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{t: 1420, w: 1500},
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{t: 8920, w: 9000},
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}
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for _, tt := range tests2 {
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m := TUNToWireMTU(tt.t)
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if m != tt.w {
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t.Errorf("conversion of TUN MTU %v to wire MTU = %v, want %v", tt.t, m, tt.w)
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}
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}
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}
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