94 lines
1.9 KiB
Go
94 lines
1.9 KiB
Go
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// Copyright 2016 The Go 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 ipv4_test
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import (
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"net"
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"runtime"
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"testing"
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"time"
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"golang.org/x/net/bpf"
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"golang.org/x/net/ipv4"
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)
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func TestBPF(t *testing.T) {
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if runtime.GOOS != "linux" {
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t.Skipf("not supported on %s", runtime.GOOS)
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}
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l, err := net.ListenPacket("udp4", "127.0.0.1:0")
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if err != nil {
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t.Fatal(err)
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}
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defer l.Close()
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p := ipv4.NewPacketConn(l)
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// This filter accepts UDP packets whose first payload byte is
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// even.
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prog, err := bpf.Assemble([]bpf.Instruction{
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// Load the first byte of the payload (skipping UDP header).
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bpf.LoadAbsolute{Off: 8, Size: 1},
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// Select LSB of the byte.
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bpf.ALUOpConstant{Op: bpf.ALUOpAnd, Val: 1},
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// Byte is even?
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bpf.JumpIf{Cond: bpf.JumpEqual, Val: 0, SkipFalse: 1},
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// Accept.
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bpf.RetConstant{Val: 4096},
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// Ignore.
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bpf.RetConstant{Val: 0},
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})
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if err != nil {
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t.Fatalf("compiling BPF: %s", err)
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}
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if err = p.SetBPF(prog); err != nil {
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t.Fatalf("attaching filter to Conn: %s", err)
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}
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s, err := net.Dial("udp4", l.LocalAddr().String())
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if err != nil {
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t.Fatal(err)
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}
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defer s.Close()
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go func() {
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for i := byte(0); i < 10; i++ {
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s.Write([]byte{i})
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}
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}()
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l.SetDeadline(time.Now().Add(2 * time.Second))
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seen := make([]bool, 5)
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for {
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var b [512]byte
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n, _, err := l.ReadFrom(b[:])
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if err != nil {
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t.Fatalf("reading from listener: %s", err)
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}
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if n != 1 {
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t.Fatalf("unexpected packet length, want 1, got %d", n)
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}
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if b[0] >= 10 {
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t.Fatalf("unexpected byte, want 0-9, got %d", b[0])
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}
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if b[0]%2 != 0 {
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t.Fatalf("got odd byte %d, wanted only even bytes", b[0])
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}
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seen[b[0]/2] = true
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seenAll := true
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for _, v := range seen {
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if !v {
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seenAll = false
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break
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}
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}
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if seenAll {
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break
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}
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}
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}
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