From cee9da0da53ba9d04fbb989e2b35108266b2e787 Mon Sep 17 00:00:00 2001 From: Quentin Gliech Date: Tue, 26 Nov 2024 19:43:26 +0100 Subject: [PATCH] MSC4108: Add a Content-Type header on the PUT response (#17253) This is a workaround for some proxy setup, where the ETag header gets stripped from the response headers unless there is a Content-Type header set. In particular, we saw this bug when putting Cloudflare in front of Synapse. I'm pretty sure this is a Cloudflare bug, as this behaviour isn't documented anywhere, and doesn't make sense whatsoever. --------- Co-authored-by: Andrew Morgan <1342360+anoadragon453@users.noreply.github.com> --- changelog.d/17253.misc | 1 + rust/src/rendezvous/mod.rs | 7 +++++++ 2 files changed, 8 insertions(+) create mode 100644 changelog.d/17253.misc diff --git a/changelog.d/17253.misc b/changelog.d/17253.misc new file mode 100644 index 000000000..868691624 --- /dev/null +++ b/changelog.d/17253.misc @@ -0,0 +1 @@ +[MSC4108](https://github.com/matrix-org/matrix-spec-proposals/pull/4108): Add a `Content-Type` header on the `PUT` response to work around a faulty behavior in some caching reverse proxies. diff --git a/rust/src/rendezvous/mod.rs b/rust/src/rendezvous/mod.rs index f69f45490..55df0203f 100644 --- a/rust/src/rendezvous/mod.rs +++ b/rust/src/rendezvous/mod.rs @@ -288,6 +288,13 @@ impl RendezvousHandler { let mut response = Response::new(Bytes::new()); *response.status_mut() = StatusCode::ACCEPTED; prepare_headers(response.headers_mut(), session); + + // Even though this isn't mandated by the MSC, we set a Content-Type on the response. It + // doesn't do any harm as the body is empty, but this helps escape a bug in some reverse + // proxy/cache setup which strips the ETag header if there is no Content-Type set. + // Specifically, we noticed this behaviour when placing Synapse behind Cloudflare. + response.headers_mut().typed_insert(ContentType::text()); + http_response_to_twisted(twisted_request, response)?; Ok(())