Add an API for Attach over HTTP API

The new APIv2 branch provides an HTTP-based remote API to Podman.
The requirements of this are, unfortunately, incompatible with
the existing Attach API. For non-terminal attach, we need append
a header to what was copied from the container, to multiplex
STDOUT and STDERR; to do this with the old API, we'd need to copy
into an intermediate buffer first, to handle the headers.

To avoid this, provide a new API to handle all aspects of
terminal and non-terminal attach, including closing the hijacked
HTTP connection. This might be a bit too specific, but for now,
it seems to be the simplest approach.

At the same time, add a Resize endpoint. This needs to be a
separate endpoint, so our existing channel approach does not work
here.

I wanted to rework the rest of attach at the same time (some
parts of it, particularly how we start the Attach session and how
we do resizing, are (in my opinion) handled much better here.
That may still be on the table, but I wanted to avoid breaking
existing APIs in this already massive change.

Signed-off-by: Matthew Heon <matthew.heon@pm.me>

1 files changed, 159 insertions, 0 deletions

diff --git a/pkg/api/handlers/containers_attach.go b/pkg/api/handlers/containers_attach.go
new file mode 100644
index 000000000..eb306348b
--- /dev/null
+++ b/pkg/api/handlers/containers_attach.go
@@ -0,0 +1,159 @@
+package handlers
+
+import (
+	"net/http"
+
+	"github.com/containers/libpod/libpod"
+	"github.com/containers/libpod/libpod/define"
+	"github.com/containers/libpod/pkg/api/handlers/utils"
+	"github.com/gorilla/mux"
+	"github.com/gorilla/schema"
+	"github.com/pkg/errors"
+	"github.com/sirupsen/logrus"
+	"k8s.io/client-go/tools/remotecommand"
+)
+
+func AttachContainer(w http.ResponseWriter, r *http.Request) {
+	runtime := r.Context().Value("runtime").(*libpod.Runtime)
+	decoder := r.Context().Value("decoder").(*schema.Decoder)
+
+	query := struct {
+		DetachKeys string `schema:"detachKeys"`
+		Logs       bool   `schema:"logs"`
+		Stream     bool   `schema:"stream"`
+		Stdin      bool   `schema:"stdin"`
+		Stdout     bool   `schema:"stdout"`
+		Stderr     bool   `schema:"stderr"`
+	}{}
+	if err := decoder.Decode(&query, r.URL.Query()); err != nil {
+		utils.Error(w, "Error parsing parameters", http.StatusBadRequest, err)
+		return
+	}
+
+	muxVars := mux.Vars(r)
+
+	// Detach keys: explicitly set to "" is very different from unset
+	// TODO: Our format for parsing these may be different from Docker.
+	var detachKeys *string
+	if _, found := muxVars["detachKeys"]; found {
+		detachKeys = &query.DetachKeys
+	}
+
+	streams := new(libpod.HTTPAttachStreams)
+	streams.Stdout = true
+	streams.Stderr = true
+	streams.Stdin = true
+	useStreams := false
+	if _, found := muxVars["stdin"]; found {
+		streams.Stdin = query.Stdin
+		useStreams = true
+	}
+	if _, found := muxVars["stdout"]; found {
+		streams.Stdout = query.Stdout
+		useStreams = true
+	}
+	if _, found := muxVars["stderr"]; found {
+		streams.Stderr = query.Stderr
+		useStreams = true
+	}
+	if !useStreams {
+		streams = nil
+	}
+	if useStreams && !streams.Stdout && !streams.Stderr && !streams.Stdin {
+		utils.Error(w, "Parameter conflict", http.StatusBadRequest, errors.Errorf("at least one of stdin, stdout, stderr must be true"))
+		return
+	}
+
+	// TODO: Investigate supporting these.
+	// Logs replays container logs over the attach socket.
+	// Stream seems to break things up somehow? Not 100% clear.
+	if query.Logs {
+		utils.Error(w, "Unsupported parameter", http.StatusBadRequest, errors.Errorf("the logs parameter to attach is not presently supported"))
+		return
+	}
+	// We only support stream=true or unset
+	if _, found := muxVars["stream"]; found && query.Stream {
+		utils.Error(w, "Unsupported parameter", http.StatusBadRequest, errors.Errorf("the stream parameter to attach is not presently supported"))
+		return
+	}
+
+	name := getName(r)
+	ctr, err := runtime.LookupContainer(name)
+	if err != nil {
+		utils.ContainerNotFound(w, name, err)
+		return
+	}
+
+	state, err := ctr.State()
+	if err != nil {
+		utils.InternalServerError(w, err)
+		return
+	}
+	if !(state == define.ContainerStateCreated || state == define.ContainerStateRunning) {
+		utils.InternalServerError(w, errors.Wrapf(define.ErrCtrStateInvalid, "can only attach to created or running containers"))
+		return
+	}
+
+	// Hijack the connection
+	hijacker, ok := w.(http.Hijacker)
+	if !ok {
+		utils.InternalServerError(w, errors.Errorf("unable to hijack connection"))
+		return
+	}
+
+	w.WriteHeader(http.StatusSwitchingProtocols)
+
+	connection, buffer, err := hijacker.Hijack()
+	if err != nil {
+		utils.InternalServerError(w, errors.Wrapf(err, "error hijacking connection"))
+		return
+	}
+
+	logrus.Debugf("Hijack for attach of container %s successful", ctr.ID())
+
+	// Perform HTTP attach.
+	// HTTPAttach will handle everything about the connection from here on
+	// (including closing it and writing errors to it).
+	if err := ctr.HTTPAttach(connection, buffer, streams, detachKeys, nil); err != nil {
+		// We can't really do anything about errors anymore. HTTPAttach
+		// should be writing them to the connection.
+		logrus.Errorf("Error attaching to container %s: %v", ctr.ID(), err)
+	}
+
+	logrus.Debugf("Attach for container %s completed successfully", ctr.ID())
+}
+
+func ResizeContainer(w http.ResponseWriter, r *http.Request) {
+	runtime := r.Context().Value("runtime").(*libpod.Runtime)
+	decoder := r.Context().Value("decoder").(*schema.Decoder)
+
+	query := struct {
+		Height uint16 `schema:"h"`
+		Width  uint16 `schema:"w"`
+	}{}
+	if err := decoder.Decode(&query, r.URL.Query()); err != nil {
+		// This is not a 400, despite the fact that is should be, for
+		// compatibility reasons.
+		utils.InternalServerError(w, errors.Wrapf(err, "error parsing query options"))
+		return
+	}
+
+	name := getName(r)
+	ctr, err := runtime.LookupContainer(name)
+	if err != nil {
+		utils.ContainerNotFound(w, name, err)
+		return
+	}
+
+	newSize := remotecommand.TerminalSize{
+		Width:  query.Width,
+		Height: query.Height,
+	}
+	if err := ctr.AttachResize(newSize); err != nil {
+		utils.InternalServerError(w, err)
+		return
+	}
+	// This is not a 204, even though we write nothing, for compatibility
+	// reasons.
+	utils.WriteResponse(w, http.StatusOK, "")
+}