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package nonbypassable
import (
"bufio"
"context"
"encoding/json"
"errors"
"fmt"
"io"
"net"
"os"
"os/exec"
"os/signal"
"strconv"
"sync"
"github.com/rootless-containers/bypass4netns/pkg/bypass4netns/nsagent/types"
"github.com/rootless-containers/bypass4netns/pkg/util"
"github.com/sirupsen/logrus"
"golang.org/x/sys/unix"
)
func New(staticList []net.IPNet) *NonBypassable {
x := &NonBypassable{
staticList: staticList,
}
return x
}
// NonBypassable maintains the list of the non-bypassable CIDRs,
// such as 127.0.0.0/8 and CNI bridge CIDRs in the slirp's network namespace.
type NonBypassable struct {
staticList []net.IPNet
dynamicList []net.IPNet
mu sync.RWMutex
}
func (x *NonBypassable) Contains(ip net.IP) bool {
x.mu.RLock()
defer x.mu.RUnlock()
for _, subnet := range append(x.staticList, x.dynamicList...) {
if subnet.Contains(ip) {
return true
}
}
return false
}
//func (x *NonBypassable) IsInterfaceIPAddress(ip net.IP) bool {
// x.mu.RLock()
// defer x.mu.RUnlock()
// for _, intf := range x.interfaces {
// for _, intfIP := range intf.Addresses {
// if intfIP.IP.Equal(ip) {
// return true
// }
// }
// }
//
// return false
//}
//
//func (x *NonBypassable) GetInterfaces() []com.Interface {
// x.mu.RLock()
// defer x.mu.RUnlock()
// ips := append([]com.Interface{}, x.interfaces...)
// return ips
//}
//
//func (x *NonBypassable) GetLastUpdateUnix() int64 {
// x.mu.RLock()
// defer x.mu.RUnlock()
// return x.lastUpdateUnix
//}
// WatchNS watches the NS associated with the PID and updates the internal dynamic list on receiving SIGHUP.
func (x *NonBypassable) WatchNS(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, "--nsagent")
cmd := exec.CommandContext(ctx, nsenter, nsenterFlags...)
cmd.SysProcAttr = &unix.SysProcAttr{
Pdeathsig: unix.SIGTERM,
}
cmd.Stderr = os.Stderr
r, w := io.Pipe()
cmd.Stdout = w
if err := cmd.Start(); err != nil {
return fmt.Errorf("failed to start %v: %w", cmd.Args, err)
}
cmdPid := cmd.Process.Pid
logrus.Infof("Dynamic non-bypassable list: started NSAgent (PID=%d, target PID=%d)", cmdPid, pid)
go x.watchNS(r)
// > It is allowed to call Notify multiple times with different channels and the same signals:
// > each channel receives copies of incoming signals independently.
// https://pkg.go.dev/os/signal#Notify
sigCh := make(chan os.Signal, 1)
signal.Notify(sigCh, unix.SIGHUP)
for sig := range sigCh {
if uSig, ok := sig.(unix.Signal); ok {
_ = unix.Kill(cmdPid, uSig)
}
}
return nil
}
func (x *NonBypassable) watchNS(r io.Reader) {
scanner := bufio.NewScanner(r)
for scanner.Scan() {
line := scanner.Text()
var msg types.Message
if err := json.Unmarshal([]byte(line), &msg); err != nil {
logrus.WithError(err).Warnf("Dynamic non-bypassable list: Failed to parse nsagent message %q", line)
continue
}
var newList []net.IPNet
for _, intf := range msg.Interfaces {
for _, cidr := range intf.CIDRs {
_, ipNet, err := net.ParseCIDR(cidr)
if err != nil {
logrus.WithError(err).Warnf("Dynamic non-bypassable list: Failed to parse nsagent message %q: %q: bad CIDR %q", line, intf.Name, cidr)
continue
}
if ipNet != nil {
newList = append(newList, *ipNet)
}
}
}
x.mu.Lock()
logrus.Infof("Dynamic non-bypassable list: old dynamic=%v, new dynamic=%v, static=%v", x.dynamicList, newList, x.staticList)
x.dynamicList = newList
x.mu.Unlock()
}
if err := scanner.Err(); err != nil {
if !errors.Is(err, io.EOF) {
logrus.WithError(err).Warn("Dynamic non-bypassable list: Error while parsing nsagent messages")
}
}
}
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