Add limits for prepare requests

src/XrdXrootd/XrdXrootdConfig.cc

@@ -481,6 +481,7 @@ int XrdXrootdProtocol::Config(const char *ConfigFN)
              else if TS_Xeq("redirect",      xred);
              else if TS_Xeq("seclib",        xsecl);
              else if TS_Xeq("trace",         xtrace);
+             else if TS_Xeq("limit",         xlimit);
              else {eDest.Say("Config warning: ignoring unknown directive '",var,"'.");
                    Config.Echo();
                    continue;
@@ -1547,3 +1548,42 @@ int XrdXrootdProtocol::xtrace(XrdOucStream &Config)
     XrdXrootdTrace->What = trval;
     return 0;
 }
+
+/******************************************************************************/
+/*                                x l i m i t                                 */
+/******************************************************************************/
+
+/* Function: xlimit
+
+   Purpose:  To parse the directive: limit [prepare <count>] [noerror]
+
+             prepare <count> The maximum number of prepares that are allowed
+                             during the course of a single connection
+
+             noerror         When possible, do not issue an error when a limit
+                             is hit.
+
+   Output: 0 upon success or 1 upon failure.
+*/
+int XrdXrootdProtocol::xlimit(XrdOucStream &Config)
+{
+   int plimit = -1;
+   const char *word;
+
+// Look for various limits set
+//
+   while ( (word = Config.GetWord()) ) {
+      if (!strcmp(word, "prepare")) {
+          if (!(word = Config.GetWord()))
+          {
+             eDest.Emsg("Config", "'limit prepare' value not specified");
+             return 1;
+          }
+          if (XrdOuca2x::a2i(eDest, "limit prepare", word, &plimit, 0)) { return 1; }
+      } else if (!strcmp(word, "noerror")) {
+          LimitError = false;
+      }
+   }
+   if (plimit >= 0) {PrepareLimit = plimit;}
+   return 0;
+}

src/XrdXrootd/XrdXrootdProtocol.cc

@@ -118,6 +118,9 @@ int                   XrdXrootdProtocol::myPID = static_cast<int>(getpid());
 int                   XrdXrootdProtocol::myRole = 0;
 int                   XrdXrootdProtocol::myRolf = 0;
 
+int                   XrdXrootdProtocol::PrepareLimit = -1;
+bool                  XrdXrootdProtocol::LimitError = true;
+
 struct XrdXrootdProtocol::RD_Table XrdXrootdProtocol::Route[RD_Num];
 
 /******************************************************************************/
@@ -846,4 +849,5 @@ void XrdXrootdProtocol::Reset()
    rdType             = 0;
    memset(&Entity, 0, sizeof(Entity));
    memset(Stream,  0, sizeof(Stream));
+   PrepareCount       = 0;
 }

src/XrdXrootd/XrdXrootdProtocol.hh

@@ -222,6 +222,7 @@ static void  xred_set(RD_func func, char *rHost[2], int rPort[2]);
 static bool  xred_xok(int     func, char *rHost[2], int rPort[2]);
 static int   xsecl(XrdOucStream &Config);
 static int   xtrace(XrdOucStream &Config);
+static int   xlimit(XrdOucStream &Config);
 
 static XrdObjectQ<XrdXrootdProtocol> ProtStack;
 XrdObject<XrdXrootdProtocol>         ProtLink;
@@ -389,6 +390,13 @@ char                       doWrite;
 char                       doWriteC;
 char                       rvSeq;
 
+// Track usage limts.
+//
+static bool                LimitError;  // Indicates that hitting a limit should result in an error response.
+                                        // If false, when possible, silently ignore errors.
+int                        PrepareCount;
+static int                 PrepareLimit;
+
 // Buffers to handle client requests
 //
 XrdXrootdReqID             ReqID;

src/XrdXrootd/XrdXrootdXeq.cc

@@ -1416,6 +1416,16 @@ int XrdXrootdProtocol::do_Prepare()
    XrdXrootdPrepArgs pargs(0, 0);
    XrdSfsPrep fsprep;
 
+// Apply prepare limits, as necessary.
+   if ((PrepareLimit >= 0) && (++PrepareCount > PrepareLimit)) {
+      if (LimitError) {
+         return Response.Send(kXR_noserver,
+                              "Surpassed this connection's prepare limit.");
+      } else {
+         return Response.Send();
+      }
+   }
+
 // Grab the options
 //
    opts = Request.prepare.options;