Sometimes app crashes

[DeadNumbers]

Hi! I'm tested this code on Arch Linux, Gnome and Vino (https://wiki.gnome.org/Projects/Vino). Code from examples/client

package main

import (
	"context"
	"fmt"
	"net"
	"runtime"
	"time"

	vnc "github.com/amitbet/vnc2video"
	"github.com/amitbet/vnc2video/logger"
)

func main() {
	runtime.GOMAXPROCS(runtime.NumCPU())
	nc, err := net.DialTimeout("tcp", "127.0.0.1:5900", 60*time.Second)
	if err != nil {
		logger.Fatalf("Error connecting to VNC host. %v", err)
	}

	logger.Tracef("starting up the client, connecting to: %s", "127.0.0.1:5900")
	cchServer := make(chan vnc.ServerMessage)
	cchClient := make(chan vnc.ClientMessage)
	errorCh := make(chan error)

	ccfg := &vnc.ClientConfig{
		SecurityHandlers: []vnc.SecurityHandler{
			&vnc.ClientAuthVNC{Password: []byte("12345")},
			&vnc.ClientAuthNone{},
		},
		DrawCursor:      true,
		PixelFormat:     vnc.PixelFormat32bit,
		ClientMessageCh: cchClient,
		ServerMessageCh: cchServer,
		Messages:        vnc.DefaultServerMessages,
		Encodings: []vnc.Encoding{
			&vnc.RawEncoding{},
		},
		ErrorCh: errorCh,
	}

	cc, err := vnc.Connect(context.Background(), nc, ccfg)
	if err != nil {
		logger.Fatalf("Error negotiating connection to VNC host. %v", err)
	}
	fmt.Println(string(cc.DesktopName()))
}

Traceback

panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x30 pc=0x5129f6]

goroutine 8 [running]:
github.com/amitbet/vnc2video.(*VncCanvas).RemoveCursor(0x0, 0xc0000727e0, 0xc000044f07)
	github.com/amitbet/vnc2video/encoding_util.go:61 +0x26
github.com/amitbet/vnc2video.(*DefaultClientMessageHandler).Handle.func2(0xc00001c550, 0x5a4e80, 0xc000136500, 0xc0000126d0, 0xc000134000, 0xc0000727e0)
	github.com/amitbet/vnc2video/client.go:303 +0x28a
created by github.com/amitbet/vnc2video.(*DefaultClientMessageHandler).Handle
	github.com/amitbet/vnc2video/client.go:285 +0x2b8

Sometimes app print desktop name, but sometimes app crashed.

[DeadNumbers]

Any ideas?

[amitbet]

well, it looks like there is some nil pointer in there :) these situations really need a debugger attached.. remote advice according to an error won't do a lot of good. Would love to be of more help, if you have more info..

I never tested this on archlinux, and more importantly I don't know which vnc server this is working with. Sometimes they use some messages that I haven't programmed in, which makes the decoder derail (this is a binary stream after all), and sometimes there can be a message that sends a legit payload that I have not planned for. In VncProxy I think I have worked out most of these kinks, but this project was never in production. if you manage to debug it, it'll be glad to merge your code back in.

[amitbet]

I see Vino is a VNC-Server... I used tight to program this - so that would be a more compatible option if you don't have the time to debug.

[gyuchang]

@DeadNumbers

It seems that sometimes DefaultClientMessageHandler is called before the canvas is initialized. https://github.com/amitbet/vnc2video/blob/9d50b9dab1d92afd6c71ca5ccc5157135c121428/client.go#L37-L49

DefaultClientMessageHandler is set up and started in line 38 and canvas is set up in line 48.

See #14 for my proposed fix.