Failures when receiving events/PDUs without the `origin` field

[matrixbot]

This issue was originally created by @gnieto at matrix-org/dendrite#2736.

Background information

• Dendrite version or git SHA:
• Monolith or Polylith?: Both
• SQLite3 or Postgres?: Both
• Running in Docker?: Yes
• go version:
• Client used (if applicable):

Description

• What is the problem:

After removing origin fields from events in sytest (see matrix-org/sytest#1293), Dendrite builds failed. According to the v1.3 spec release, origin fields in PDUs are not required (matrix-org/matrix-spec#998).

Dendrite and gomatrixserverlib checks this field in several places and leads to failing tests in sytest (after removign the origin field; see the failed GHA runs on sytest's linked PR). For example, CheckFields validation from gometrixserverlib will fail if this field is not present: https://github.com/matrix-org/gomatrixserverlib/blob/2217f6c65ce3ab829b5d103d70be4891e68dc518/event.go#L751-L780

Dendrite is also doing some additional checks. For example, SendJoin is doing some additional checks here : https://github.com/matrix-org/dendrite/blob/3e87096a21729fcc7e074d09ee12da56394dd15d/federationapi/routing/join.go#L207-L212

Steps to reproduce

• Remove origin in any federation endpoint receiving an event (for example, SendJoin)

[matrixbot]

This comment was originally posted by @gnieto at matrix-org/dendrite#2736 (comment).

This issue has been fixed in: matrix-org/dendrite#2737