Fix Complement not using HSPortBindingIP (127.0.0.1) for the homeserver BaseURL

[MadLittleMods]

Fix Complement not using config.HSPortBindingIP (127.0.0.1) for the homeserver BaseURL.

Regressed in #776 which started using the Docker default HostIP (0.0.0.0) because we removed the specific HSPortBindingIP port bindings for 8008 and 8448 (see "Root cause" section below).

Problem

This caused downstream issues in some of our out-of-repo Complement tests (Element internal) which stress some SSO/OIDC login flows with Synapse.

Before #776, SsoRedirectServlet received a request like this http://127.0.0.1:8008/_matrix/client/v3/login/sso/redirect/oidc-test_idp?redirectUrl=http%3A%2F%2Fapp.my-fake-client.io%2Fclient-callback. But now it's seeing http://0.0.0.0:8008/_matrix/client/v3/login/sso/redirect/oidc-test_idp?redirectUrl=http%3A%2F%2Fapp.my-fake-client.io%2Fclient-callback and tries to redirect to the canonical http://127.0.0.1:8008/ address which would then go to the step we expect in the tests (authorization endpoint).

Basically, the host header in the request used to be set to 127.0.0.1:8008 but now it's 0.0.0.0:8008. Synapse wants to use the canonical URL so the cookies are available so it redirects you to the canonical public_baseurl version first. Relevant Synapse code that cares about using the canonical URL to get cookies back -> SsoRedirectServlet

We could alternatively, update our out-of-repo tests to account for this extra redirect but it seems more appropriate to update Complement to use the the configured HSPortBindingIP as expected.

Root cause

The host name used in the requests during the Complement tests is from the client.BaseURL which is sourced from the Docker container port mapping/bindings in Complement.

In #776, we removed the explicit port bindings for 8008 with HSPortBindingIP (127.0.0.1) so now it uses Docker's default 0.0.0.0.

diff --git a/internal/docker/deployer.go b/internal/docker/deployer.go
index cdcf51a5..a186b30d 100644
--- a/internal/docker/deployer.go
+++ b/internal/docker/deployer.go
@@ -382,20 +380,8 @@ func deployImage(
 	}, &container.HostConfig{
 		CapAdd:          []string{"NET_ADMIN"}, // TODO : this should be some sort of option
 		PublishAllPorts: true,
-		PortBindings: nat.PortMap{
-			nat.Port("8008/tcp"): []nat.PortBinding{
-				{
-					HostIP: cfg.HSPortBindingIP,
-				},
-			},
-			nat.Port("8448/tcp"): []nat.PortBinding{
-				{
-					HostIP: cfg.HSPortBindingIP,
-				},
-			},
-		},

Dev notes

Locally link Complement package into your tests

See https://thewebivore.com/using-replace-in-go-mod-to-point-to-your-local-module/

So you can edit the Complement source code and use it in the tests.

1. Add the following to complement/go.mod

   // TODO: Remove as this is only for local development
   replace github.com/matrix-org/complement => /home/eric/Documents/github/element/complement
   

2. cd complement && go mod tidy && cd ..
3. Run Complement how you normally would

Pull Request Checklist

• Pull request includes a sign off

[MadLittleMods]

To clean things up, I've refactored waitForPorts(...) to only do the waiting part as described. We now assemble BaseURL and FedBaseUrl via getHostAccessibleHomeserverUrls(...)

[richvdh]

A few nitpicks and questions.

[richvdh]

LGTM otherwise

[MadLittleMods]

Thanks for the review @richvdh 🦘