Possible ssh2Stream._channels[chan] leak (v0.8.9)

[Luluno01]

I am forwarding out TCP connections from remote system to local system. A few hundreds of connections were established and ended (the end event emitted). However, the ._channels also had hundreds of properties with numerical keys and true as their values. It looks something like

Client {
  ...
  _channels: {
    '0': [Function (anonymous)],
    '1': [Function (anonymous)],
    '2': true,
    '3': true,
    '4': true,
    '5': true,
    '6': true,
    '7': true,
    '8': true,
    '9': true,
    '10': true,
    ...
    '478': true
  },
  ...
}

After searching for all accesses to _channels in the code and some inspection, I found it could be a leak. Here are the related code snippets for your easy reference.

Assignment to _channels[*]:

https://github.com/mscdex/ssh2/blob/v0.8.x/lib/client.js#L1508

Deletion of _channels[*]:

https://github.com/mscdex/ssh2/blob/v0.8.x/lib/client.js#L1199

Call chain of deletion:

https://github.com/mscdex/ssh2/blob/v0.8.x/lib/client.js#L338

https://github.com/mscdex/ssh2/blob/v0.8.x/lib/client.js#L1156

It seems these properties will be removed only when the underlying SSH connection is closed:

https://github.com/mscdex/ssh2/blob/v0.8.x/lib/client.js#L313-L338

This will eventually exhaust the memory because in my case the port forwarding is intended to be persistent.

[mscdex]

The reserved channel numbers are deleted when the channels themselves are closed.

Judging by the (large number of) true _channels values you're seeing, it appears either accept() or reject() are not being called for those incoming forward requests.

[mscdex]

Actually, upon further review, I think I may see what's happening here.....

[mscdex]

Thanks for the report!

[Luluno01]

Thank you for your attention! So the fix is only available in the latest unreleased version? Is it recommended to update to the latest version and how to migrate to the latest version? If not, when can I safely delete those leaked channels (as a workaround at the moment)?

[mscdex]

It will be included in the upcoming v1.0.0 release. I will probably do that release in the next couple of days or so.

[mscdex]

Regarding changes between v0.8.x and what will be v1.0.0, you can find most of them here: #935

[Luluno01]

Sounds great! Thanks!