Send User-Agent as the monitor info

src/XrdHttp/XrdHttpProtocol.cc

@@ -582,9 +582,29 @@ int XrdHttpProtocol::Process(XrdLink *lp) // We ignore the argument here
 
     } else
       CurrentReq.reqstate++;
+  } else if (!DoneSetInfo && !CurrentReq.userAgent().empty()) { // DoingLogin is true, meaning the login finished.
+    std::string mon_info = "monitor info " + CurrentReq.userAgent();
+    DoneSetInfo = true;
+    if (mon_info.size() >= 1024) {
+      TRACEI(ALL, "User agent string too long");
+    } else if (!Bridge) {
+      TRACEI(ALL, "Internal logic error: Bridge is null after login");
+    } else {
+      TRACEI(DEBUG, "Setting " << mon_info);
+      memset(&CurrentReq.xrdreq, 0, sizeof (ClientRequest));
+      CurrentReq.xrdreq.set.requestid = htons(kXR_set);
+      CurrentReq.xrdreq.set.modifier = '\0';
+      memset(CurrentReq.xrdreq.set.reserved, '\0', sizeof(CurrentReq.xrdreq.set.reserved));
+      CurrentReq.xrdreq.set.dlen = htonl(mon_info.size());
+      if (!Bridge->Run((char *) &CurrentReq.xrdreq, (char *) mon_info.c_str(), mon_info.size())) {
+        SendSimpleResp(500, nullptr, nullptr, "Could not set user agent.", 0, false);
+        return -1;
+      }
+      return 0;
+    }
+  } else {
+    DoingLogin = false;
   }
-  DoingLogin = false;
-
 
   // Read the next request header, that is, read until a double CRLF is found
 
@@ -1856,6 +1876,7 @@ void XrdHttpProtocol::Reset() {
   myBuffStart = myBuffEnd = 0;
 
   DoingLogin = false;
+  DoneSetInfo = false;
 
   ResumeBytes = 0;
   Resume = 0;

src/XrdHttp/XrdHttpProtocol.hh

@@ -298,6 +298,9 @@ private:
 
   /// Tells that we are just logging in
   bool DoingLogin;
+
+  /// Indicates whether we've attempted to send app info.
+  bool DoneSetInfo;
 
   /// Tells that we are just waiting to have N bytes in the buffer
   long ResumeBytes;

src/XrdHttp/XrdHttpReq.cc

@@ -198,6 +198,9 @@ int XrdHttpReq::parseLine(char *line, int len) {
       if(prot->pmarkHandle != nullptr) {
         parseScitag(val);
       }
+    } else if (!strcasecmp(key, "User-Agent")) {
+      m_user_agent = val;
+      trim(m_user_agent);
     } else {
       // Some headers need to be translated into "local" cgi info.
       auto it = std::find_if(prot->hdr2cgimap.begin(), prot->hdr2cgimap.end(),[key](const auto & item) {
@@ -2755,6 +2758,7 @@ void XrdHttpReq::reset() {
   m_req_cksum = nullptr;
 
   m_resource_with_digest = "";
+  m_user_agent = "";
 
   headerok = false;
   keepalive = true;

src/XrdHttp/XrdHttpReq.hh

@@ -74,6 +74,9 @@ private:
   int httpStatusCode;
   std::string httpStatusText;
 
+  // The value of the user agent, if specified
+  std::string m_user_agent;
+
   // Whether transfer encoding was requested.
   bool m_transfer_encoding_chunked;
   long long m_current_chunk_offset;
@@ -191,6 +194,9 @@ public:
 
   void addCgi(const std::string & key, const std::string & value);
 
+  // Return the current user agent; if none has been specified, returns an empty string
+  const std::string &userAgent() const {return m_user_agent;}
+
   // ----------------
   // Description of the request. The header/body parsing
   // is supposed to populate these fields, for fast access while