github.com/stackdocker/rkt@v0.10.1-0.20151109095037-1aa827478248/stage1/enter_kvm/enter_kvm.go (about)

     1  // Copyright 2015 The rkt 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 main
    16  
    17  import (
    18  	"flag"
    19  	"fmt"
    20  	"os"
    21  	"os/exec"
    22  	"path/filepath"
    23  	"syscall"
    24  
    25  	"github.com/coreos/rkt/networking/netinfo"
    26  	"github.com/coreos/rkt/pkg/lock"
    27  )
    28  
    29  const (
    30  	kvmSettingsDir        = "kvm"
    31  	kvmPrivateKeyFilename = "ssh_kvm_key"
    32  	// TODO: overwrite below default by environment value + generate .socket unit just before pod start
    33  	kvmSSHPort = "122" // hardcoded value in .socket file
    34  )
    35  
    36  var (
    37  	podPid  string
    38  	appName string
    39  )
    40  
    41  func init() {
    42  	flag.StringVar(&podPid, "pid", "", "podPID")
    43  	flag.StringVar(&appName, "appname", "", "application to use")
    44  }
    45  
    46  func getPodDefaultIP(workDir string) (string, error) {
    47  	// get pod lock
    48  	l, err := lock.NewLock(workDir, lock.Dir)
    49  	if err != nil {
    50  		return "", err
    51  	}
    52  
    53  	// get file descriptor for lock
    54  	fd, err := l.Fd()
    55  	if err != nil {
    56  		return "", err
    57  	}
    58  
    59  	// use this descriptor as method of reading pod network configuration
    60  	nets, err := netinfo.LoadAt(fd)
    61  	if err != nil {
    62  		return "", err
    63  	}
    64  	// kvm flavored container must have at first position default vm<->host network
    65  	if len(nets) == 0 {
    66  		return "", fmt.Errorf("Pod has no configured networks")
    67  	}
    68  	return nets[0].IP.String(), nil
    69  }
    70  
    71  func getAppexecArgs() []string {
    72  	// Documentation/devel/stage1-implementors-guide.md#arguments-1
    73  	// also from ../enter/enter.c
    74  	args := []string{
    75  		"/appexec",
    76  		fmt.Sprintf("/opt/stage2/%s/rootfs", appName),
    77  		"/", // as in ../enter/enter.c - this should be app.WorkingDirectory
    78  		fmt.Sprintf("/rkt/env/%s", appName),
    79  		"0", // uid
    80  		"0", // gid
    81  	}
    82  	return append(args, flag.Args()...)
    83  }
    84  
    85  func execSSH() error {
    86  	workDir, err := os.Getwd()
    87  	if err != nil {
    88  		return fmt.Errorf("Cannot get working directory: %v", err)
    89  	}
    90  
    91  	podDefaultIP, err := getPodDefaultIP(workDir)
    92  	if err != nil {
    93  		return fmt.Errorf("Cannot load networking configuration: %v", err)
    94  	}
    95  
    96  	// escape from running pod directory into base directory
    97  	if err = os.Chdir("../../.."); err != nil {
    98  		return fmt.Errorf("Cannot change directory to rkt work directory: %v", err)
    99  	}
   100  
   101  	// find path to ssh binary
   102  	sshPath, err := exec.LookPath("ssh")
   103  	if err != nil {
   104  		return fmt.Errorf("Cannot find 'ssh' binary in PATH: %v", err)
   105  	}
   106  
   107  	// prepare args for ssh invocation
   108  	keyFile := filepath.Join(kvmSettingsDir, kvmPrivateKeyFilename)
   109  	args := []string{
   110  		"ssh",
   111  		"-t",          // use tty
   112  		"-i", keyFile, // use keyfile
   113  		"-l", "root", // login as user
   114  		"-p", kvmSSHPort, // port to connect
   115  		"-o", "StrictHostKeyChecking=no", // do not check changing host keys
   116  		"-o", "UserKnownHostsFile=/dev/null", // do not add host key to default knownhosts file
   117  		"-o", "LogLevel=quiet", // do not log minor informations
   118  		podDefaultIP,
   119  	}
   120  	args = append(args, getAppexecArgs()...)
   121  
   122  	// this should not return in case of success
   123  	err = syscall.Exec(sshPath, args, os.Environ())
   124  	return fmt.Errorf("Cannot exec to ssh: %v", err)
   125  }
   126  
   127  func main() {
   128  	flag.Parse()
   129  	if appName == "" {
   130  		fmt.Fprintf(os.Stderr, "--appname not set to correct value\n")
   131  		os.Exit(1)
   132  	}
   133  
   134  	// execSSH should returns only with error
   135  	fmt.Fprintf(os.Stderr, "%v\n", execSSH())
   136  	os.Exit(2)
   137  }