From b8e798802b0f5140cb6f5876b3477008e1f04813 Mon Sep 17 00:00:00 2001
From: Brian Bockelman <bbockelm@cse.unl.edu>
Date: Fri, 11 Sep 2015 09:43:29 -0500
Subject: [PATCH] Do not forward the 'tried=' CGI within the proxy interface.

This may cause the proxy to respond with 'file not found', causing
upstream redirectors to believe the file is not present behind
the proxy at all - even if it's just 'not found' because the only
source was excluded.
---
 src/XrdPss/XrdPss.cc | 23 ++++++++++++++++++++---
 1 file changed, 20 insertions(+), 3 deletions(-)

diff --git a/src/XrdPss/XrdPss.cc b/src/XrdPss/XrdPss.cc
index a747f90b6ee..05403820cb0 100644
--- a/src/XrdPss/XrdPss.cc
+++ b/src/XrdPss/XrdPss.cc
@@ -973,9 +973,26 @@ const char *XrdPssSys::P2CGI(int &cgilen, char *cbuff, int cblen,
    if (!Cgi1) {cgilen = strlen(Cgi2); return Cgi2;}
    if (!Cgi2) return Cgi1;
 
-// Compose the two cgi elements together
-//
-   cgilen = snprintf(cbuff, cblen, "%s&%s", Cgi1, Cgi2);
+// Strip out any 'tried='
+// Then, Compose the two cgi elements together
+   const char * tried_loc = strstr(Cgi1, "tried=");
+   if (tried_loc != NULL) {
+      const char *next_amp = strchr(tried_loc, '&');
+      size_t bytes_to_copy = tried_loc-Cgi1;
+      if (bytes_to_copy >= static_cast<size_t>(cblen)) {return NULL;}
+      memcpy(cbuff, Cgi1, bytes_to_copy);
+      cgilen = bytes_to_copy;
+      if (next_amp)
+      {
+          cgilen += snprintf(cbuff+bytes_to_copy, cblen-bytes_to_copy, "%s&%s", next_amp, Cgi2);
+      }
+      else
+      {
+          cgilen += snprintf(cbuff+bytes_to_copy, cblen-bytes_to_copy, "&%s", Cgi2);
+      }
+   } else {
+      cgilen = snprintf(cbuff, cblen, "%s&%s", Cgi1, Cgi2);
+   }
    return (cgilen >= cblen ? 0 : cbuff);
 }