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*: console rewrite

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This implements {createTTY, detach} and all of the combinations and
negations of the two that were previously implemented. There are some
valid questions about out-of-OCI-scope topics like !createTTY and how
things should be handled (why do we dup the current stdio to the
process, and how is that not a security issue). However, these will be
dealt with in a separate patchset.

In order to allow for late console setup, split setupRootfs into the
"preparation" section where all of the mounts are created and the
"finalize" section where we pivot_root and set things as ro. In between
the two we can set up all of the console mountpoints and symlinks we
need.

We use two-stage synchronisation to ensures that when the syscalls are
reordered in a suboptimal way, an out-of-place read() on the parentPipe
will not gobble the ancilliary information.

This patch is part of the console rewrite patchset.

Signed-off-by: Aleksa Sarai <asarai@suse.de>
This commit is contained in:
Aleksa Sarai
2016-06-04 01:29:34 +10:00
parent 4776b4326a
commit 244c9fc426
23 changed files with 325 additions and 220 deletions
Download Patch File Download Diff File Expand all files Collapse all files
libcontainer/console_linux.go
+5 -15
View File
@@ -3,16 +3,15 @@ package libcontainer
import (
"fmt"
"os"
"path/filepath"
"syscall"
"unsafe"
"github.com/opencontainers/runc/libcontainer/label"
)
// NewConsole returns an initialized console that can be used within a container by copying bytes
// newConsole returns an initialized console that can be used within a container by copying bytes
// from the master side to the slave that is attached as the tty for the container's init process.
func NewConsole(uid, gid int) (Console, error) {
func newConsole(uid, gid int) (Console, error) {
master, err := os.OpenFile("/dev/ptmx", syscall.O_RDWR|syscall.O_NOCTTY|syscall.O_CLOEXEC, 0)
if err != nil {
return nil, err
@@ -39,14 +38,6 @@ func NewConsole(uid, gid int) (Console, error) {
}, nil
}
// newConsoleFromPath is an internal function returning an initialized console for use inside
// a container's MNT namespace.
func newConsoleFromPath(slavePath string) *linuxConsole {
return &linuxConsole{
slavePath: slavePath,
}
}
// linuxConsole is a linux pseudo TTY for use within a container.
type linuxConsole struct {
master *os.File
@@ -78,21 +69,20 @@ func (c *linuxConsole) Close() error {
// mount initializes the console inside the rootfs mounting with the specified mount label
// and applying the correct ownership of the console.
func (c *linuxConsole) mount(rootfs, mountLabel string) error {
func (c *linuxConsole) mount(mountLabel string) error {
oldMask := syscall.Umask(0000)
defer syscall.Umask(oldMask)
if err := label.SetFileLabel(c.slavePath, mountLabel); err != nil {
return err
}
dest := filepath.Join(rootfs, "/dev/console")
f, err := os.Create(dest)
f, err := os.Create("/dev/console")
if err != nil && !os.IsExist(err) {
return err
}
if f != nil {
f.Close()
}
return syscall.Mount(c.slavePath, dest, "bind", syscall.MS_BIND, "")
return syscall.Mount(c.slavePath, "/dev/console", "bind", syscall.MS_BIND, "")
}
// dupStdio opens the slavePath for the console and dups the fds to the current