gvisor.dev/gvisor@v0.0.0-20240520182842-f9d4d51c7e0f/tools/tracereplay/replay.go (about)

     1  // Copyright 2022 The gVisor Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package tracereplay
    16  
    17  import (
    18  	"encoding/json"
    19  	"errors"
    20  	"fmt"
    21  	"io"
    22  	"os"
    23  
    24  	"golang.org/x/sys/unix"
    25  	"google.golang.org/protobuf/proto"
    26  	"gvisor.dev/gvisor/pkg/log"
    27  	pb "gvisor.dev/gvisor/pkg/sentry/seccheck/points/points_go_proto"
    28  )
    29  
    30  // Replay implements the functionality required for the "replay" command.
    31  type Replay struct {
    32  	Endpoint string
    33  	In       string
    34  }
    35  
    36  // Execute connects to the remote endpoint and replays all messages stored in
    37  // the `In` file.
    38  func (r *Replay) Execute() error {
    39  	socket, err := connect(r.Endpoint)
    40  	if err != nil {
    41  		return err
    42  	}
    43  	defer socket.Close()
    44  
    45  	f, err := os.Open(r.In)
    46  	if err != nil {
    47  		return err
    48  	}
    49  	defer f.Close()
    50  
    51  	hdr := make([]byte, len(signature))
    52  	if err := readFull(f, hdr); err != nil {
    53  		return err
    54  	}
    55  	if string(hdr) != signature {
    56  		return fmt.Errorf("%q is not a replay file", r.In)
    57  	}
    58  
    59  	cfgJSON, err := readWithSize(f)
    60  	if err != nil {
    61  		return err
    62  	}
    63  	cfg := Config{}
    64  	if err := json.Unmarshal(cfgJSON, &cfg); err != nil {
    65  		return err
    66  	}
    67  	if err := handshake(socket, cfg.Version); err != nil {
    68  		return err
    69  	}
    70  	fmt.Printf("Handshake completed\n")
    71  
    72  	for count := 1; ; count++ {
    73  		bytes, err := readWithSize(f)
    74  		if err != nil {
    75  			if errors.Is(err, io.EOF) {
    76  				break
    77  			}
    78  			return err
    79  		}
    80  		fmt.Printf("\rReplaying message: %d", count)
    81  		if _, err := socket.Write(bytes); err != nil {
    82  			return err
    83  		}
    84  	}
    85  	fmt.Printf("\nDone\n")
    86  	return nil
    87  }
    88  
    89  func connect(endpoint string) (*os.File, error) {
    90  	log.Debugf("Connecting to %q", endpoint)
    91  	socket, err := unix.Socket(unix.AF_UNIX, unix.SOCK_SEQPACKET, 0)
    92  	if err != nil {
    93  		return nil, fmt.Errorf("socket(AF_UNIX, SOCK_SEQPACKET, 0): %w", err)
    94  	}
    95  	f := os.NewFile(uintptr(socket), endpoint)
    96  
    97  	addr := unix.SockaddrUnix{Name: endpoint}
    98  	if err := unix.Connect(int(f.Fd()), &addr); err != nil {
    99  		_ = f.Close()
   100  		return nil, fmt.Errorf("connect(%q): %w", endpoint, err)
   101  	}
   102  	return f, nil
   103  }
   104  
   105  // See common.proto for details about the handshake protocol.
   106  func handshake(socket *os.File, version uint32) error {
   107  	hsOut := pb.Handshake{Version: version}
   108  	out, err := proto.Marshal(&hsOut)
   109  	if err != nil {
   110  		return err
   111  	}
   112  	if _, err := socket.Write(out); err != nil {
   113  		return fmt.Errorf("sending handshake message: %w", err)
   114  	}
   115  
   116  	in := make([]byte, 10240)
   117  	read, err := socket.Read(in)
   118  	if err != nil && !errors.Is(err, io.EOF) {
   119  		return fmt.Errorf("reading handshake message: %w", err)
   120  	}
   121  	// Protect against the handshake becoming larger than the buffer.
   122  	if read == len(in) {
   123  		return fmt.Errorf("handshake message too big")
   124  	}
   125  	hsIn := pb.Handshake{}
   126  	if err := proto.Unmarshal(in[:read], &hsIn); err != nil {
   127  		return fmt.Errorf("unmarshalling handshake message: %w", err)
   128  	}
   129  
   130  	// Just validate that the message can unmarshall and accept any version from
   131  	// the server. Will try to replay and see what happens...
   132  	return nil
   133  }