Exit proc_lib gracefully on proxy header mismatch

If the proxy header was not to match (like, the header not being sent),
cowboy libraries were expecting really strict matching and then crashing
the proc_lib with a badmatch, that generates a hard error report. I
believe this error should be expected and termination should be graceful.

src/cowboy_clear.erl

@@ -33,12 +33,9 @@ start_link(Ref, Transport, Opts) ->
 
 -spec connection_process(pid(), ranch:ref(), module(), cowboy:opts()) -> ok.
 connection_process(Parent, Ref, Transport, Opts) ->
-	ProxyInfo = case maps:get(proxy_header, Opts, false) of
+	ProxyInfo = case maybe_proxy_info(Ref, Opts) of
-		true ->
+            {ok, ProxyInfo0} -> ProxyInfo0;
-			{ok, ProxyInfo0} = ranch:recv_proxy_header(Ref, 1000),
+            Error -> exit({shutdown, Error})
-			ProxyInfo0;
-		false ->
-			undefined
 	end,
 	{ok, Socket} = ranch:handshake(Ref),
 	%% Use cowboy_http2 directly only when 'http' is missing.
@@ -58,3 +55,11 @@ init(Parent, Ref, Socket, Transport, ProxyInfo, Opts, Protocol) ->
 		supervisor -> process_flag(trap_exit, true)
 	end,
 	Protocol:init(Parent, Ref, Socket, Transport, ProxyInfo, Opts).
+
+maybe_proxy_info(Ref, Opts) ->
+	case maps:get(proxy_header, Opts, false) of
+		true ->
+			ranch:recv_proxy_header(Ref, 1000);
+		false ->
+			undefined
+	end.

src/cowboy_tls.erl

@@ -33,12 +33,9 @@ start_link(Ref, Transport, Opts) ->
 
 -spec connection_process(pid(), ranch:ref(), module(), cowboy:opts()) -> ok.
 connection_process(Parent, Ref, Transport, Opts) ->
-	ProxyInfo = case maps:get(proxy_header, Opts, false) of
+	ProxyInfo = case maybe_proxy_info(Ref, Opts) of
-		true ->
+            {ok, ProxyInfo0} -> ProxyInfo0;
-			{ok, ProxyInfo0} = ranch:recv_proxy_header(Ref, 1000),
+            Error -> exit({shutdown, Error})
-			ProxyInfo0;
-		false ->
-			undefined
 	end,
 	{ok, Socket} = ranch:handshake(Ref),
 	case ssl:negotiated_protocol(Socket) of
@@ -54,3 +51,11 @@ init(Parent, Ref, Socket, Transport, ProxyInfo, Opts, Protocol) ->
 		supervisor -> process_flag(trap_exit, true)
 	end,
 	Protocol:init(Parent, Ref, Socket, Transport, ProxyInfo, Opts).
+
+maybe_proxy_info(Ref, Opts) ->
+	case maps:get(proxy_header, Opts, false) of
+		true ->
+			ranch:recv_proxy_header(Ref, 1000);
+		false ->
+			undefined
+	end.