MSC2923: Connect Matrix room to another Matrix room #2923

MadLittleMods · 2020-12-22T23:26:33Z

Connect Matrix room to another Matrix room to effectively create a native Matrix to Matrix bridge.

As discussed with @oprypin:matrix.org at https://matrix.to/#/!ViClwbclMrgQwyPuvH:matrix.org/$gxUxuw3BIbLwaHZ4OkwyEhEBLkd6bGxtQfB9-4Afk2U?via=half-shot.uk&via=matrix.org&via=vector.modular.im
- There is also another Matrix to Matrix bridge discussion that I am unable to find via search
Matrix to Matrix bridge (room) turt2live/matrix-wishlist#56
Room Translation Bridge turt2live/matrix-wishlist#167

Todo

Needs more technical discussion around actual ideas to accomplish
Needs MSC number assigned

ara4n · 2020-12-22T23:36:06Z

proposals/connect-matrix-to-matrix.md

@@ -0,0 +1,62 @@
+# MSC0000: Matrix to Matrix connections


I would be well up for figuring out a way (like this) to figure out how to replace plumbed bridged rooms with a generic "reversibly link this room to another matrix room" mechanism.

Currrently all bridges which support plumbing have to implement it separately, and hook up their own admin APIs for managing it, whereas in the end, the problem of saying "i have a community in #foo:matrix.org and a community in #foo_bar:gitter.im - please can i just sync their content, assuming the admins of both rooms are happy to do so" feels like it's a generic useful mechanism.

I haven't dug through the proposal in this MSC yet tho'.

(@MadLittleMods: MSC numbers aren't allocated, other than via GH - this one is 2923)

proposals/2923-connect-matrix-to-matrix.md

Half-Shot · 2020-12-23T11:56:31Z

proposals/2923-connect-matrix-to-matrix.md

@@ -0,0 +1,62 @@
+# MSC2923: Matrix to Matrix connections


This may go some way to solving decentralised bridges too. If each bridge maintains its own portal room, it can then be up to the bridges to negotiate on who bridges who.

Half-Shot · 2020-12-23T12:06:59Z

proposals/2923-connect-matrix-to-matrix.md

+
+## Proposal
+
+Add a mechanism to homeservers to be able connect and ferry messages back and forth from another Matrix room.


(I'm going to put out thoughts here in different threads).

I'd like to avoid mixing messages between rooms at the DAG level, and this connection be a layer on top supported by the homeserver. Rooms would continue to be separate at that level, but the client would still see a room with messages mixed in from both rooms.

This however presents a problem in that it's difficult to splice together two different rooms as the DAG is used for ordering. You'd need some way to interject messages in a way that works. And then you can have things like replies/relationships which would be cross room, and would cause all sorts of headaches.

This however presents a problem in that it's difficult to splice together two different rooms as the DAG is used for ordering. You'd need some way to interject messages in a way that works

Relates to #2716 and incrementally importing existing message history but we haven't come up with anything concrete there yet.

When someone sends a message to a room, we can also put a pointer reference event to the message in the connected room. This way we can follow the pointer to the single source of truth which may have edits, etc. This also makes it ordered in the DAG as expected for both rooms.

I added your potential solution (@Half-Shot) and the one I just mentioned to the MSC 👍

Message pointer reference events

Connection layer on top of the DAG

Half-Shot · 2020-12-23T12:07:47Z

proposals/2923-connect-matrix-to-matrix.md

+## Proposal
+
+Add a mechanism to homeservers to be able connect and ferry messages back and forth from another Matrix room.
+


If Alice joins room A, they would not see history until they join room B too? Would we need some kind of auto-join / auto-invite > join mechanism to avoid split brain views of the room?

Federated peeking 🤷

Re: #2923 (comment), if there are pointer reference events in the connected room, we can show a placeholder that you need to join the other room to see the message

Half-Shot · 2020-12-23T12:09:05Z

proposals/2923-connect-matrix-to-matrix.md

+## Proposal
+
+Add a mechanism to homeservers to be able connect and ferry messages back and forth from another Matrix room.
+


How would power levels work in this instance? Presumably if a bridge has admin in it's portal room, it would not automatically get authority in the other room. This presents a problem in so far that if a IRC OP kicks/bans a Matrix user from the chat, how would the bridge handle that?

Would users be expected to op the bridge in the plumbed room, which would feel somewhat awkward and unexpected?

If someone gets banned in a Matrix room, messages coming from the connected Matrix room would also be blocked. But I don't think the ban would necessarily carry through to the connected room by default.

Maybe we could add an option to "ban in connected rooms" as well which would only work if you were also authorized there.

This relates to the PL(power-level/permission) syncing across rooms in a space from MSC1772 (see "room admin bot"), https://github.com/matrix-org/matrix-doc/pull/1772/files. We could probably re-use the same mechanism for syncing bans.

Or maybe MSC2313: Moderation policies as rooms (ban lists)

Half-Shot · 2020-12-23T12:13:31Z

proposals/2923-connect-matrix-to-matrix.md

+## Security considerations
+
+People might not realize their message is being shared more broadly to another audience. Also relating to a private room being connected to a public room.
+


You'd need a two way negotiation system for this kind of linking, or the guys at #badroom:evilcorp.com could easily bind themselves to #matrix:matrix.org and cause hell.

Added to security consideration section 👍

Context: #2923 (comment)

@Half-Shot

Context: #2923 (comment) As described by @Half-Shot

MadLittleMods · 2021-01-07T18:20:21Z

proposals/2923-connect-matrix-to-matrix.md

+
+This solution is flexible to solve any scenario but this functionality could also be built into the homeserver.
+
+This also requires more burden on people having to host their own bridge.


As noted by @Half-Shot: Maintaining senders will be a problem if it's an AS bridge

MadLittleMods · 2021-01-07T18:21:06Z

proposals/2923-connect-matrix-to-matrix.md

+
+This solution is flexible to solve any scenario but this functionality could also be built into the homeserver.
+
+This also requires more burden on people having to host their own bridge.


Also how does setting up the link/connection between rooms work for someone who doesn't own the homeserver

MurzNN · 2021-01-17T07:01:41Z

Also as alternative may be merging two separate rooms to one using Room Upgrades mechanism?

MurzNN · 2021-01-17T07:04:48Z

And will be good to add "Rendered" link in MSC description to full description, like in most other MSC.

MurzNN · 2021-01-17T07:07:56Z

Also as alternative may be merging two separate rooms to one using Room Upgrades mechanism?

Ow, this already proposed in:

This requires a lot of manual poking on the bridges side to get setup and additional work if rooms are already created on each side like adding m.room.tombstone to point people to the new correct place.

But not yet available for users in Matrix clients. Will be good to have some command to merge two rooms into one, using m.room.tombstone event, manually in Matrix client interface, at least. This will can already solve some problems with bridged rooms, for example when bridge moves from one server to another, like this: mautrix/telegram#394

MadLittleMods · 2021-10-13T02:59:19Z

proposals/2923-connect-matrix-to-matrix.md

+
+#### Message pointer reference events
+
+When someone sends a message to a room, we also send a pointer reference event to the connected room which marks that messages place in the DAG.


Maybe forwarded events, MSC2723 or MSC2730

MadLittleMods added proposal A matrix spec change proposal kind:feature MSC for not-core and not-maintenance stuff labels Dec 22, 2020

ara4n reviewed Dec 22, 2020

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Half-Shot self-requested a review December 22, 2020 23:46

turt2live changed the title ~~MSC0000: Connect Matrix room to another Matrix room~~ MSC2923: Connect Matrix room to another Matrix room Dec 23, 2020

turt2live added the proposal-in-review label Dec 23, 2020

Add draft MSC for connecting Matrix rooms together

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MadLittleMods force-pushed the msc-connect-matrix-to-matrix branch from 68561fd to 60e8f5c Compare December 23, 2020 00:12

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turt2live marked this pull request as draft December 23, 2020 05:11

erdnaxeli reviewed Dec 23, 2020

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Half-Shot reviewed Dec 23, 2020

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MadLittleMods added 3 commits December 23, 2020 15:38

Add potential issue with how to handle e2e rooms

90164c6

Context: #2923 (comment)

Add note about needing approval from both admin sides

1943826

Context: #2923 (comment)

Add a couple potential solutions mentioned in discussion

150c59b

Context: #2923 (comment) As described by @Half-Shot

MadLittleMods commented Jan 7, 2021

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JuniorJPDJ mentioned this pull request Jan 18, 2021

Matrix to Matrix bridge (room) turt2live/matrix-wishlist#56

Open

MurzNN mentioned this pull request Jan 22, 2021

Automate migrating Telegram bridge user to other instance with keeping old rooms and history mautrix/telegram#394

Closed

MadLittleMods mentioned this pull request Feb 17, 2021

Discontinue bridge in favour of native gitter federation matrix-org/matrix-appservice-gitter#104

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turt2live added the needs-implementation This MSC does not have a qualifying implementation for the SCT to review. The MSC cannot enter FCP. label Jun 8, 2021

turt2live force-pushed the old_master branch from e895827 to dca99ee Compare August 30, 2021 22:34

MadLittleMods commented Oct 13, 2021

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MSC2923: Connect Matrix room to another Matrix room #2923

MSC2923: Connect Matrix room to another Matrix room #2923

MadLittleMods commented Dec 22, 2020 •

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		## Proposal

		Add a mechanism to homeservers to be able connect and ferry messages back and forth from another Matrix room.

		## Security considerations

		People might not realize their message is being shared more broadly to another audience. Also relating to a private room being connected to a public room.


		This solution is flexible to solve any scenario but this functionality could also be built into the homeserver.

		This also requires more burden on people having to host their own bridge.


		#### Message pointer reference events

		When someone sends a message to a room, we also send a pointer reference event to the connected room which marks that messages place in the DAG.

MSC2923: Connect Matrix room to another Matrix room #2923

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MSC2923: Connect Matrix room to another Matrix room #2923

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