From 186888ed39eb8a2e1cc531d180496d42eec04147 Mon Sep 17 00:00:00 2001
From: Andy Green <andy@warmcat.com>
Date: Sat, 26 Oct 2019 05:31:01 +0100
Subject: [PATCH] ws proxy: ensure upgrade request url starts with slash

In the case rpath is set to //, any urlargs will be added
right at the start.  Add a check to keep the initial / if so.

https://github.com/warmcat/libwebsockets/issues/1733
---
 lib/roles/http/server/server.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/lib/roles/http/server/server.c b/lib/roles/http/server/server.c
index 132e962fe..57af8fe1b 100644
--- a/lib/roles/http/server/server.c
+++ b/lib/roles/http/server/server.c
@@ -1106,7 +1106,12 @@ lws_http_proxy_start(struct lws *wsi, const struct lws_http_mount *hit,
 	lws_clean_url(rpath);
 	na = lws_hdr_total_length(wsi, WSI_TOKEN_HTTP_URI_ARGS);
 	if (na) {
-		char *p = rpath + n;
+		char *p;
+
+		if (!n) /* don't start with the ?... use the first / if so */
+			n++;
+
+		p = rpath + n;
 
 		if (na >= (int)sizeof(rpath) - n - 2) {
 			lwsl_info("%s: query string %d longer "