Fix health checks not working behind load balancers

The change in
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/24199 caused
requests coming from a load balancer to arrive as 127.0.0.1 instead of
the actual IP.

`Rack::Request#ip` behaves slightly differently different than
`ActionDispatch::Request#remote_ip`: the former will return the first
X-Forwarded-For IP if all of the IPs are trusted proxies, while the
second one filters out all proxies and falls back to REMOTE_ADDR, which
is 127.0.0.1.

For now, we can revert back to using `Rack::Request` because these
middlewares don't manipulate parameters. The actual fix problem involves
fixing Rails: https://github.com/rails/rails/issues/28436.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/58573

1 files changed, 26 insertions, 1 deletions

diff --git a/spec/lib/gitlab/request_context_spec.rb b/spec/lib/gitlab/request_context_spec.rb
index fd443cc1f71..3ed57c2c916 100644
--- a/spec/lib/gitlab/request_context_spec.rb
+++ b/spec/lib/gitlab/request_context_spec.rb
@@ -6,6 +6,31 @@ describe Gitlab::RequestContext do
     let(:app) { -> (env) {} }
     let(:env) { Hash.new }
 
+    context 'with X-Forwarded-For headers', :request_store do
+      let(:load_balancer_ip) { '1.2.3.4' }
+      let(:headers) do
+        {
+          'HTTP_X_FORWARDED_FOR' => "#{load_balancer_ip}, 127.0.0.1",
+          'REMOTE_ADDR' => '127.0.0.1'
+        }
+      end
+
+      let(:env) { Rack::MockRequest.env_for("/").merge(headers) }
+
+      it 'returns the load balancer IP' do
+        client_ip = nil
+
+        endpoint = proc do
+          client_ip = Gitlab::SafeRequestStore[:client_ip]
+          [200, {}, ["Hello"]]
+        end
+
+        Rails.application.middleware.build(endpoint).call(env)
+
+        expect(client_ip).to eq(load_balancer_ip)
+      end
+    end
+
     context 'when RequestStore::Middleware is used' do
       around do |example|
         RequestStore::Middleware.new(-> (env) { example.run }).call({})
@@ -15,7 +40,7 @@ describe Gitlab::RequestContext do
         let(:ip) { '192.168.1.11' }
 
         before do
-          allow_any_instance_of(ActionDispatch::Request).to receive(:ip).and_return(ip)
+          allow_any_instance_of(Rack::Request).to receive(:ip).and_return(ip)
           described_class.new(app).call(env)
         end