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Force Attach() to send a SIGWINCH and redraw

Browse source 
Basically, we want to force the application in the container to
(iff the container was made with a terminal) redraw said terminal
immediately after an attach completes, so the fresh Attach
session will be able to see what's going on (e.g. will have a
shell prompt). Our current attach functions are unfortunately
geared more towards `podman run` than `podman attach` and will
start forwarding resize events *immediately* instead of waiting
until the attach session is alive (much safer for short-lived
`podman run` sessions, but broken for the `podman attach` case).
To avoid a major rewrite, let's just manually send a SIGWINCH
after attach succeeds to force a redraw.

Fixes #6253

Signed-off-by: Matthew Heon <matthew.heon@pm.me>
This commit is contained in:
Matthew Heon 2020-09-10 17:28:22 -04:00
parent 1184cdf03d
commit 4c155d36cb
3 changed files with 23 additions and 4 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

20
libpod/container_api.go
View file

@ -9,6 +9,7 @@ import (
"github.com/containers/podman/v2/libpod/define"
"github.com/containers/podman/v2/libpod/events"
"github.com/containers/podman/v2/pkg/signal"
"github.com/opentracing/opentracing-go"
"github.com/pkg/errors"
"github.com/sirupsen/logrus"
@ -129,7 +130,7 @@ func (c *Container) StartAndAttach(ctx context.Context, streams *define.AttachSt
// Attach to the container before starting it
go func() {
if err := c.attach(streams, keys, resize, true, startedChan); err != nil {
if err := c.attach(streams, keys, resize, true, startedChan, nil); err != nil {
attachChan <- err
}
close(attachChan)
@ -243,8 +244,23 @@ func (c *Container) Attach(streams *define.AttachStreams, keys string, resize <-
return errors.Wrapf(define.ErrCtrStateInvalid, "can only attach to created or running containers")
}
// HACK: This is really gross, but there isn't a better way without
// splitting attach into separate versions for StartAndAttach and normal
// attaching, and I really do not want to do that right now.
// Send a SIGWINCH after attach succeeds so that most programs will
// redraw the screen for the new attach session.
attachRdy := make(chan bool)
if c.config.Spec.Process != nil && c.config.Spec.Process.Terminal {
go func() {
<-attachRdy
if err := c.ociRuntime.KillContainer(c, uint(signal.SIGWINCH), false); err != nil {
logrus.Warnf("Unable to send SIGWINCH to container %s after attach: %v", c.ID(), err)
}
}()
}
c.newContainerEvent(events.Attach)
return c.attach(streams, keys, resize, false, nil)
return c.attach(streams, keys, resize, false, nil, attachRdy)
}
// HTTPAttach forwards an attach session over a hijacked HTTP session.

5
libpod/oci_attach_linux.go
View file

@ -31,7 +31,7 @@ const (
// Attach to the given container
// Does not check if state is appropriate
// started is only required if startContainer is true
func (c *Container) attach(streams *define.AttachStreams, keys string, resize <-chan remotecommand.TerminalSize, startContainer bool, started chan bool) error {
func (c *Container) attach(streams *define.AttachStreams, keys string, resize <-chan remotecommand.TerminalSize, startContainer bool, started chan bool, attachRdy chan<- bool) error {
if !streams.AttachOutput && !streams.AttachError && !streams.AttachInput {
return errors.Wrapf(define.ErrInvalidArg, "must provide at least one stream to attach to")
}
@ -74,6 +74,9 @@ func (c *Container) attach(streams *define.AttachStreams, keys string, resize <-
}
receiveStdoutError, stdinDone := setupStdioChannels(streams, conn, detachKeys)
if attachRdy != nil {
attachRdy <- true
}
return readStdio(streams, receiveStdoutError, stdinDone)
}

2
libpod/oci_attach_unsupported.go
View file

@ -9,7 +9,7 @@ import (
"k8s.io/client-go/tools/remotecommand"
)
func (c *Container) attach(streams *define.AttachStreams, keys string, resize <-chan remotecommand.TerminalSize, startContainer bool, started chan bool) error {
func (c *Container) attach(streams *define.AttachStreams, keys string, resize <-chan remotecommand.TerminalSize, startContainer bool, started chan bool, attachRdy chan<- bool) error {
return define.ErrNotImplemented
}