tailscale/ssh/tailssh/context.go

// Copyright (c) 2022 Tailscale Inc & AUTHORS All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package tailssh

import (
	"context"
	"sync"
	"time"
)

// sshContext is the context.Context implementation we use for SSH
// that adds a CloseWithError method. Otherwise it's just a normalish
// Context.
type sshContext struct {
	underlying context.Context
	cancel     context.CancelFunc // cancels underlying
	mu         sync.Mutex
	closed     bool
	err        error
}

func newSSHContext(ctx context.Context) *sshContext {
	ctx, cancel := context.WithCancel(ctx)
	return &sshContext{underlying: ctx, cancel: cancel}
}

func (ctx *sshContext) CloseWithError(err error) {
	ctx.mu.Lock()
	defer ctx.mu.Unlock()
	if ctx.closed {
		return
	}
	ctx.closed = true
	ctx.err = err
	ctx.cancel()
}

func (ctx *sshContext) Err() error {
	ctx.mu.Lock()
	defer ctx.mu.Unlock()
	return ctx.err
}

func (ctx *sshContext) Done() <-chan struct{}                   { return ctx.underlying.Done() }
func (ctx *sshContext) Deadline() (deadline time.Time, ok bool) { return }
func (ctx *sshContext) Value(k any) any                         { return ctx.underlying.Value(k) }

// userVisibleError is a wrapper around an error that implements
// SSHTerminationError, so msg is written to their session.
type userVisibleError struct {
	msg string
	error
}

func (ue userVisibleError) SSHTerminationMessage() string { return ue.msg }

// SSHTerminationError is implemented by errors that terminate an SSH
// session and should be written to user's sessions.
type SSHTerminationError interface {
	error
	SSHTerminationMessage() string
}