golang.org/x/net@v0.25.1-0.20240516223405-c87a5b62e243/ipv6/bpf_test.go (about)

     1  // Copyright 2016 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package ipv6_test
     6  
     7  import (
     8  	"net"
     9  	"runtime"
    10  	"testing"
    11  	"time"
    12  
    13  	"golang.org/x/net/bpf"
    14  	"golang.org/x/net/ipv6"
    15  	"golang.org/x/net/nettest"
    16  )
    17  
    18  func TestBPF(t *testing.T) {
    19  	if runtime.GOOS != "linux" {
    20  		t.Skipf("not supported on %s", runtime.GOOS)
    21  	}
    22  	if _, err := nettest.RoutedInterface("ip6", net.FlagUp|net.FlagLoopback); err != nil {
    23  		t.Skip("ipv6 is not enabled for loopback interface")
    24  	}
    25  
    26  	l, err := net.ListenPacket("udp6", "[::1]:0")
    27  	if err != nil {
    28  		t.Fatal(err)
    29  	}
    30  	defer l.Close()
    31  
    32  	p := ipv6.NewPacketConn(l)
    33  
    34  	// This filter accepts UDP packets whose first payload byte is
    35  	// even.
    36  	prog, err := bpf.Assemble([]bpf.Instruction{
    37  		// Load the first byte of the payload (skipping UDP header).
    38  		bpf.LoadAbsolute{Off: 8, Size: 1},
    39  		// Select LSB of the byte.
    40  		bpf.ALUOpConstant{Op: bpf.ALUOpAnd, Val: 1},
    41  		// Byte is even?
    42  		bpf.JumpIf{Cond: bpf.JumpEqual, Val: 0, SkipFalse: 1},
    43  		// Accept.
    44  		bpf.RetConstant{Val: 4096},
    45  		// Ignore.
    46  		bpf.RetConstant{Val: 0},
    47  	})
    48  	if err != nil {
    49  		t.Fatalf("compiling BPF: %s", err)
    50  	}
    51  
    52  	if err = p.SetBPF(prog); err != nil {
    53  		t.Fatalf("attaching filter to Conn: %s", err)
    54  	}
    55  
    56  	s, err := net.Dial("udp6", l.LocalAddr().String())
    57  	if err != nil {
    58  		t.Fatal(err)
    59  	}
    60  	defer s.Close()
    61  	go func() {
    62  		for i := byte(0); i < 10; i++ {
    63  			s.Write([]byte{i})
    64  		}
    65  	}()
    66  
    67  	l.SetDeadline(time.Now().Add(2 * time.Second))
    68  	seen := make([]bool, 5)
    69  	for {
    70  		var b [512]byte
    71  		n, _, err := l.ReadFrom(b[:])
    72  		if err != nil {
    73  			t.Fatalf("reading from listener: %s", err)
    74  		}
    75  		if n != 1 {
    76  			t.Fatalf("unexpected packet length, want 1, got %d", n)
    77  		}
    78  		if b[0] >= 10 {
    79  			t.Fatalf("unexpected byte, want 0-9, got %d", b[0])
    80  		}
    81  		if b[0]%2 != 0 {
    82  			t.Fatalf("got odd byte %d, wanted only even bytes", b[0])
    83  		}
    84  		seen[b[0]/2] = true
    85  
    86  		seenAll := true
    87  		for _, v := range seen {
    88  			if !v {
    89  				seenAll = false
    90  				break
    91  			}
    92  		}
    93  		if seenAll {
    94  			break
    95  		}
    96  	}
    97  }