feat(dvc): add DvcChannelListener for multi-instance DVC support

[uchouT (uchouT)]

Resolves #1135

• implement the client-side without breaking the current API signatures by introducing OnceListener wrapper for pre-registered DVCs.
• implement server side with a new method create_channel for DrdynvcServer.

---

older discussion

I try to implement the client-side without breaking the current API signatures by introducing OnceListener wrapper for pre-registered DVCs. But get_dvc_by_type_id's behavior has changed, it returns None until CreateRequest arrives.

This is unavoidable — the old 1:1 name→channel mapping cannot support multiple channels with the same name. The ChannelId is assigned by the server at CreateRequest time, so the DVC cannot exist before that point. And this behavior follows the RDPEDYC's expectation.

Marc-Andre Lureau (@elmarco) Benoît Cortier (@CBenoit) Does this approach acceptable and make sense?

[Marc-Andre Lureau (elmarco)]

uchouT (@uchouT) lgtm, perhaps squash or reorganize some of your changes (PERF, ..)

[uchouT (uchouT)]

uchouT (uchouT (@uchouT)) lgtm, perhaps squash or reorganize some of your changes (PERF, ..)

Squashed, thanks for reminding.

I found that ironrdp-session would be affected by this, but I didn't go further.

IronRDP/crates/ironrdp-session/src/x224/mod.rs

Lines 98 to 100 in db2f40b

	pub fn get_dvc<T: DvcProcessor + 'static>(&self) -> Option<&DynamicVirtualChannel> {
	self.get_svc_processor::<DrdynvcClient>()?.get_dvc_by_type_id::<T>()
	}

If this is acceptable, I will try the server-side implementation.

[Greg Lamberson (glamberson)]

If this is acceptable, I will try the server-side implementation.

This is good work. The listener/factory pattern is exactly the right approach for multi-instance DVCs. The OnceListener wrapper preserving backward compatibility for single-instance channels is a nice touch.

We're using IronRDP on the server side (lamco-rdp-server) and this direction aligns well with what we'll need for URBDRC support down the road. The encode_dvc_messages() and DvcProcessor trait being untouched means our current code should be unaffected by the client-side refactor.

Looking forward to the server-side implementation with take_new_channels(). Happy to help test once that lands.

Regards,
Greg Lamberson
Lamco Development

[uchouT (uchouT)]

Looking forward to the server-side implementation with take_new_channels(). Happy to help test once that lands.

Thanks for the review, the positive feedback, and your willingness to help test, Greg Lamberson (@glamberson)!

Regarding the take_new_channels() approach, I still have some hesitations about the implementation details. I left my thoughts here #1135 (comment) , would love to hear your input.

[Copilot]

Pull request overview

This PR implements multi-instance DVC (Dynamic Virtual Channel) support by introducing a DvcChannelListener factory trait that produces a new DvcClientProcessor instance per DYNVC_CREATE_REQ. It preserves the existing single-instance API by internally wrapping pre-registered DvcProcessor instances in an OnceListener. On the server side, a new create_channel method is added to DrdynvcServer to allow opening new DVC channels mid-session.

Changes:

• Introduces DvcChannelListener trait and OnceListener adapter, refactors DynamicChannelSet (moved from lib.rs to client.rs) to key active channels by DynamicChannelId rather than by name
• Adds DrdynvcServer::create_channel() for mid-session server-side DVC channel creation
• Removes the now-obsolete DynamicChannelSet struct from lib.rs, replacing DynamicVirtualChannel::new with from_boxed

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 5 comments.

File	Description
crates/ironrdp-dvc/src/client.rs	Adds DvcChannelListener trait + OnceListener, refactors DynamicChannelSet to support multi-instance channels, updates process() to use new listener-based creation flow
crates/ironrdp-dvc/src/lib.rs	Removes DynamicChannelSet, changes DynamicVirtualChannel constructor to from_boxed
crates/ironrdp-dvc/src/server.rs	Adds create_channel() for mid-session DVC channel creation; removes stale FIXME comment

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

You can also share your feedback on Copilot code review. Take the survey.

[uchouT (uchouT)]

Addressed Copilot's review. Benoît Cortier (@CBenoit)