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// +build linux
package nsinit
import (
"fmt"
"github.com/dotcloud/docker/pkg/label"
"github.com/dotcloud/docker/pkg/libcontainer"
"github.com/dotcloud/docker/pkg/system"
"os"
"path/filepath"
"strconv"
"syscall"
)
// ExecIn uses an existing pid and joins the pid's namespaces with the new command.
func (ns *linuxNs) ExecIn(container *libcontainer.Container, nspid int, args []string) (int, error) {
for _, nsv := range container.Namespaces {
// skip the PID namespace on unshare because it it not supported
if nsv.Key != "NEWPID" {
if err := system.Unshare(nsv.Value); err != nil {
return -1, err
}
}
}
fds, err := ns.getNsFds(nspid, container)
closeFds := func() {
for _, f := range fds {
system.Closefd(f)
}
}
if err != nil {
closeFds()
return -1, err
}
processLabel, err := label.GetPidCon(nspid)
if err != nil {
closeFds()
return -1, err
}
// foreach namespace fd, use setns to join an existing container's namespaces
for _, fd := range fds {
if fd > 0 {
ns.logger.Printf("setns on %d\n", fd)
if err := system.Setns(fd, 0); err != nil {
closeFds()
return -1, fmt.Errorf("setns %s", err)
}
}
system.Closefd(fd)
}
// if the container has a new pid and mount namespace we need to
// remount proc and sys to pick up the changes
if container.Namespaces.Contains("NEWNS") && container.Namespaces.Contains("NEWPID") {
ns.logger.Println("forking to remount /proc and /sys")
pid, err := system.Fork()
if err != nil {
return -1, err
}
if pid == 0 {
// TODO: make all raw syscalls to be fork safe
if err := system.Unshare(syscall.CLONE_NEWNS); err != nil {
return -1, err
}
if err := remountProc(); err != nil {
return -1, fmt.Errorf("remount proc %s", err)
}
if err := remountSys(); err != nil {
return -1, fmt.Errorf("remount sys %s", err)
}
goto dropAndExec
}
proc, err := os.FindProcess(pid)
if err != nil {
return -1, err
}
state, err := proc.Wait()
if err != nil {
return -1, err
}
os.Exit(state.Sys().(syscall.WaitStatus).ExitStatus())
}
dropAndExec:
if err := finalizeNamespace(container); err != nil {
return -1, err
}
err = label.SetProcessLabel(processLabel)
if err != nil {
return -1, err
}
if err := system.Execv(args[0], args[0:], container.Env); err != nil {
return -1, err
}
panic("unreachable")
}
func (ns *linuxNs) getNsFds(pid int, container *libcontainer.Container) ([]uintptr, error) {
fds := make([]uintptr, len(container.Namespaces))
for i, ns := range container.Namespaces {
f, err := os.OpenFile(filepath.Join("/proc/", strconv.Itoa(pid), "ns", ns.File), os.O_RDONLY, 0)
if err != nil {
return fds, err
}
fds[i] = f.Fd()
}
return fds, nil
}
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