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moby--moby/daemon/execdriver/native/exec.go

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// +build linux
package native
import (
"fmt"
"os"
"os/exec"
"strings"
"syscall"
"github.com/docker/docker/daemon/execdriver"
"github.com/opencontainers/runc/libcontainer"
// Blank import 'nsenter' so that init in that package will call c
// function 'nsexec()' to do 'setns' before Go runtime take over,
// it's used for join to exist ns like 'docker exec' command.
_ "github.com/opencontainers/runc/libcontainer/nsenter"
"github.com/opencontainers/runc/libcontainer/utils"
)
// Exec implements the exec driver Driver interface,
// it calls libcontainer APIs to execute a container.
func (d *Driver) Exec(c *execdriver.Command, processConfig *execdriver.ProcessConfig, pipes *execdriver.Pipes, hooks execdriver.Hooks) (int, error) {
active := d.activeContainers[c.ID]
if active == nil {
return -1, fmt.Errorf("No active container exists with ID %s", c.ID)
}
user := processConfig.User
if c.RemappedRoot.UID != 0 && user == "" {
//if user namespaces are enabled, set user explicitly so uid/gid is set to 0
//otherwise we end up with the overflow id and no permissions (65534)
user = "0"
}
p := &libcontainer.Process{
Args: append([]string{processConfig.Entrypoint}, processConfig.Arguments...),
Env: c.ProcessConfig.Env,
Cwd: c.WorkingDir,
User: user,
}
if processConfig.Privileged {
p.Capabilities = execdriver.GetAllCapabilities()
}
// add CAP_ prefix to all caps for new libcontainer update to match
// the spec format.
for i, s := range p.Capabilities {
if !strings.HasPrefix(s, "CAP_") {
p.Capabilities[i] = fmt.Sprintf("CAP_%s", s)
}
}
config := active.Config()
if err := setupPipes(&config, processConfig, p, pipes); err != nil {
return -1, err
}
if err := active.Start(p); err != nil {
return -1, err
}
if hooks.Start != nil {
pid, err := p.Pid()
if err != nil {
p.Signal(os.Kill)
p.Wait()
return -1, err
}
// A closed channel for OOM is returned here as it will be
// non-blocking and return the correct result when read.
chOOM := make(chan struct{})
close(chOOM)
hooks.Start(&c.ProcessConfig, pid, chOOM)
}
ps, err := p.Wait()
if err != nil {
exitErr, ok := err.(*exec.ExitError)
if !ok {
return -1, err
}
ps = exitErr.ProcessState
}
return utils.ExitStatus(ps.Sys().(syscall.WaitStatus)), nil
}