Allow a comma separated upgrade header

The upgrade header might be comma separated and FlashMQ shouldn't
refuse to upgrade in such a case. This splits and trims the upgrade
header first.

In our case the header is actually send by accident. It used to be:
Upgrade: websocket\r\n
Upgrade: websocket\r\n

But newer nginx proxies transform that into:
Upgrade: websocket, websocket\r\n

And hence a websocket connection could no longer be established.

Author: jhofstee

utils.cpp

@@ -315,9 +315,18 @@ bool parseHttpHeader(CirBuf &buf, std::string &websocket_key, int &websocket_ver
         trim(value);
         std::string value_lower = str_tolower(value);
 
-        if (name == "upgrade" && value_lower == "websocket")
-            upgradeHeaderSeen = true;
-        else if (name == "connection" && strContains(value_lower, "upgrade"))
+        if (name == "upgrade") {
+            std::vector<std::string> protocols = splitToVector(value_lower, ',');
+            for(std::string &prot : protocols)
+            {
+                trim(prot);
+
+                if (prot == "websocket")
+                {
+                    upgradeHeaderSeen = true;
+                }
+            }
+        } else if (name == "connection" && strContains(value_lower, "upgrade"))
             connectionHeaderSeen = true;
         else if (name == "sec-websocket-key")
             websocket_key = value;