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// Copyright 2020 The gVisor Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package testbench
import (
"encoding/binary"
"fmt"
"net"
"testing"
"time"
"golang.org/x/sys/unix"
"gvisor.dev/gvisor/pkg/hostarch"
)
// Sniffer can sniff raw packets on the wire.
type Sniffer struct {
fd int
}
func htons(x uint16) uint16 {
buf := [2]byte{}
binary.BigEndian.PutUint16(buf[:], x)
return hostarch.ByteOrder.Uint16(buf[:])
}
// NewSniffer creates a Sniffer connected to *device.
func (n *DUTTestNet) NewSniffer(t *testing.T) (Sniffer, error) {
t.Helper()
ifInfo, err := net.InterfaceByName(n.LocalDevName)
if err != nil {
return Sniffer{}, err
}
var haddr [8]byte
copy(haddr[:], ifInfo.HardwareAddr)
sa := unix.SockaddrLinklayer{
Protocol: htons(unix.ETH_P_ALL),
Ifindex: ifInfo.Index,
}
snifferFd, err := unix.Socket(unix.AF_PACKET, unix.SOCK_RAW, int(htons(unix.ETH_P_ALL)))
if err != nil {
return Sniffer{}, err
}
if err := unix.Bind(snifferFd, &sa); err != nil {
return Sniffer{}, err
}
if err := unix.SetsockoptInt(snifferFd, unix.SOL_SOCKET, unix.SO_RCVBUF, 1e7); err != nil {
t.Fatalf("can't setsockopt SO_RCVBUF to 10M: %s", err)
}
return Sniffer{
fd: snifferFd,
}, nil
}
// maxReadSize should be large enough for the maximum frame size in bytes. If a
// packet too large for the buffer arrives, the test will get a fatal error.
const maxReadSize int = 65536
// Recv tries to read one frame until the timeout is up. If the timeout given
// is 0, then no read attempt will be made.
func (s *Sniffer) Recv(t *testing.T, timeout time.Duration) []byte {
t.Helper()
deadline := time.Now().Add(timeout)
for {
timeout = time.Until(deadline)
if timeout <= 0 {
return nil
}
usec := timeout.Microseconds()
if usec == 0 {
// Timeout is less than a microsecond; set usec to 1 to avoid
// blocking indefinitely.
usec = 1
}
const microsInOne = 1e6
tv := unix.Timeval{
Sec: usec / microsInOne,
Usec: usec % microsInOne,
}
if err := unix.SetsockoptTimeval(s.fd, unix.SOL_SOCKET, unix.SO_RCVTIMEO, &tv); err != nil {
t.Fatalf("can't setsockopt SO_RCVTIMEO: %s", err)
}
buf := make([]byte, maxReadSize)
nread, _, err := unix.Recvfrom(s.fd, buf, unix.MSG_TRUNC)
if err == unix.EINTR || err == unix.EAGAIN {
// There was a timeout.
continue
}
if err != nil {
t.Fatalf("can't read: %s", err)
}
if nread > maxReadSize {
t.Fatalf("received a truncated frame of %d bytes, want at most %d bytes", nread, maxReadSize)
}
return buf[:nread]
}
}
// Drain drains the Sniffer's socket receive buffer by receiving until there's
// nothing else to receive.
func (s *Sniffer) Drain(t *testing.T) {
t.Helper()
flags, err := unix.FcntlInt(uintptr(s.fd), unix.F_GETFL, 0)
if err != nil {
t.Fatalf("failed to get sniffer socket fd flags: %s", err)
}
nonBlockingFlags := flags | unix.O_NONBLOCK
if _, err := unix.FcntlInt(uintptr(s.fd), unix.F_SETFL, nonBlockingFlags); err != nil {
t.Fatalf("failed to make sniffer socket non-blocking with flags %b: %s", nonBlockingFlags, err)
}
for {
buf := make([]byte, maxReadSize)
_, _, err := unix.Recvfrom(s.fd, buf, unix.MSG_TRUNC)
if err == unix.EINTR || err == unix.EAGAIN || err == unix.EWOULDBLOCK {
break
}
}
if _, err := unix.FcntlInt(uintptr(s.fd), unix.F_SETFL, flags); err != nil {
t.Fatalf("failed to restore sniffer socket fd flags to %b: %s", flags, err)
}
}
// close the socket that Sniffer is using.
func (s *Sniffer) close() error {
if err := unix.Close(s.fd); err != nil {
return fmt.Errorf("can't close sniffer socket: %w", err)
}
s.fd = -1
return nil
}
// Injector can inject raw frames.
type Injector struct {
fd int
}
// NewInjector creates a new injector on *device.
func (n *DUTTestNet) NewInjector(t *testing.T) (Injector, error) {
t.Helper()
ifInfo, err := net.InterfaceByName(n.LocalDevName)
if err != nil {
return Injector{}, err
}
var haddr [8]byte
copy(haddr[:], ifInfo.HardwareAddr)
sa := unix.SockaddrLinklayer{
Protocol: htons(unix.ETH_P_IP),
Ifindex: ifInfo.Index,
Halen: uint8(len(ifInfo.HardwareAddr)),
Addr: haddr,
}
injectFd, err := unix.Socket(unix.AF_PACKET, unix.SOCK_RAW, int(htons(unix.ETH_P_ALL)))
if err != nil {
return Injector{}, err
}
if err := unix.Bind(injectFd, &sa); err != nil {
return Injector{}, err
}
return Injector{
fd: injectFd,
}, nil
}
// Send a raw frame.
func (i *Injector) Send(t *testing.T, b []byte) {
t.Helper()
n, err := unix.Write(i.fd, b)
if err != nil {
t.Fatalf("can't write bytes of len %d: %s", len(b), err)
}
if n != len(b) {
t.Fatalf("got %d bytes written, want %d", n, len(b))
}
}
// close the underlying socket.
func (i *Injector) close() error {
if err := unix.Close(i.fd); err != nil {
return fmt.Errorf("can't close sniffer socket: %w", err)
}
i.fd = -1
return nil
}
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