Cloudpods/backend/pkg/util/pod/remotecommand/reader.go

// Copyright 2019 Yunion
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package remotecommand

import (
	"io"
)

// readerWrapper delegates to an io.Reader so that only the io.Reader interface is implemented,
// to keep io.Copy from doing things we don't want when copying from the reader to the data stream.
//
// If the Stdin io.Reader provided to remotecommand implements a WriteTo function (like bytes.Buffer does[1]),
// io.Copy calls that method[2] to attempt to write the entire buffer to the stream in one call.
// That results in an oversized call to spdystream.Stream#Write [3],
// which results in a single oversized data frame[4] that is too large.
//
// [1] https://golang.org/pkg/bytes/#Buffer.WriteTo
// [2] https://golang.org/pkg/io/#Copy
// [3] https://github.com/kubernetes/kubernetes/blob/90295640ef87db9daa0144c5617afe889e7992b2/vendor/github.com/docker/spdystream/stream.go#L66-L73
// [4] https://github.com/kubernetes/kubernetes/blob/90295640ef87db9daa0144c5617afe889e7992b2/vendor/github.com/docker/spdystream/spdy/write.go#L302-L304
type readerWrapper struct {
	reader io.Reader
}

func (r readerWrapper) Read(p []byte) (int, error) {
	return r.reader.Read(p)
}