fix(compose): Preserve the request port in the nginx Host header (#926)

Signed-off-by: Prasanth Baskar <prasanth@8gears.com>

Author: bupd

config/nginx/proxy.conf

@@ -5,7 +5,18 @@ client_max_body_size 0;
 proxy_buffering off;
 proxy_request_buffering off;
 
-proxy_set_header Host $host;
+# $http_host forwards the Host header verbatim, port included. $host drops a
+# non-default port, and core builds URLs back out of req.Host: the /v2/ token
+# challenge realm (src/server/middleware/v2auth/auth.go) and the cross-origin
+# check on /c/ both do. With $host, a deploy on PORT_HTTP=8080 hands docker a
+# realm of http://localhost/service/token and the push fails against port 80.
+# $http_host is empty for Host-less requests (HTTP/1.0, raw probes); fall
+# back to $host there so that traffic keeps the pre-existing behavior.
+set $forwarded_host $http_host;
+if ($http_host = '') {
+    set $forwarded_host $host;
+}
+proxy_set_header Host $forwarded_host;
 proxy_set_header X-Real-IP $remote_addr;
 proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
 proxy_set_header X-Forwarded-Proto $scheme;