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|
package tracer
import (
"context"
"encoding/json"
"fmt"
"io"
"os"
"os/exec"
"strconv"
"sync"
"github.com/rootless-containers/bypass4netns/pkg/util"
"golang.org/x/sys/unix"
)
type Tracer struct {
logPath string
tracerCmd *exec.Cmd
reader io.Reader
writer io.Writer
lock sync.Mutex
}
func NewTracer(logPath string) *Tracer {
return &Tracer{
logPath: logPath,
lock: sync.Mutex{},
}
}
// StartTracer starts tracer in NS associated with the PID.
func (x *Tracer) StartTracer(ctx context.Context, pid int) error {
selfExe, err := os.Executable()
if err != nil {
return err
}
nsenter, err := exec.LookPath("nsenter")
if err != nil {
return err
}
nsenterFlags := []string{
"-t", strconv.Itoa(pid),
"-F",
"-n",
}
selfPid := os.Getpid()
ok, err := util.SameUserNS(pid, selfPid)
if err != nil {
return fmt.Errorf("failed to check sameUserNS(%d, %d)", pid, selfPid)
}
if !ok {
nsenterFlags = append(nsenterFlags, "-U", "--preserve-credentials")
}
nsenterFlags = append(nsenterFlags, "--", selfExe, "--tracer-agent", "--log-file", x.logPath)
x.tracerCmd = exec.CommandContext(ctx, nsenter, nsenterFlags...)
x.tracerCmd.SysProcAttr = &unix.SysProcAttr{
Pdeathsig: unix.SIGTERM,
}
x.tracerCmd.Stderr = os.Stderr
x.reader, x.tracerCmd.Stdout = io.Pipe()
x.tracerCmd.Stdin, x.writer = io.Pipe()
if err := x.tracerCmd.Start(); err != nil {
return fmt.Errorf("failed to start %v: %w", x.tracerCmd.Args, err)
}
return nil
}
func (x *Tracer) RegisterForwardPorts(ports []int) error {
cmd := TracerCommand{
Cmd: RegisterForwardPorts,
ForwardingPorts: ports,
}
m, err := json.Marshal(cmd)
if err != nil {
return err
}
writeSize, err := x.writer.Write(m)
if err != nil {
return err
}
if writeSize != len(m) {
return fmt.Errorf("unexpected written size expected=%d actual=%d", len(m), writeSize)
}
dec := json.NewDecoder(x.reader)
var resp TracerCommand
err = dec.Decode(&resp)
if err != nil {
return fmt.Errorf("invalid response: %q", err)
}
if resp.Cmd != Ok {
return fmt.Errorf("unexpected response: %d", resp.Cmd)
}
return nil
}
func (x *Tracer) ConnectToAddress(addrs []string) ([]string, error) {
x.lock.Lock()
defer x.lock.Unlock()
cmd := TracerCommand{
Cmd: ConnectToAddress,
DestinationAddress: addrs,
}
m, err := json.Marshal(cmd)
if err != nil {
return nil, err
}
writeSize, err := x.writer.Write(m)
if err != nil {
return nil, err
}
if writeSize != len(m) {
return nil, fmt.Errorf("unexpected written size expected=%d actual=%d", len(m), writeSize)
}
dec := json.NewDecoder(x.reader)
var resp TracerCommand
err = dec.Decode(&resp)
if err != nil {
return nil, fmt.Errorf("invalid response: %q", err)
}
if resp.Cmd != Ok {
return nil, fmt.Errorf("unexpected response: %d", resp.Cmd)
}
return resp.DestinationAddress, nil
}
|
