Using this option with an argument being set to one of
none/policy/always instructs libcurl how to deal with GSS
credentials. Or rather how it tells the server that delegation is fine
or not.

---
  src/main.c |   28 +++++++++++++++++++++++++---
  1 files changed, 25 insertions(+), 3 deletions(-)
diff --git a/src/main.c b/src/main.c
index eae45de..588e971 100644
--- a/src/main.c
+++ b/src/main.c
@@ -655,6 +655,7 @@ struct Configurable {
                               basically each given URL to transfer */
    struct OutStruct *outs;
    bool xattr; /* store metadata in extended attributes */
+  long gssapi_delegation;
  };
  #define WARN_PREFIX "Warning: "
@@ -812,6 +813,7 @@ static void help(void)
      "     --data-ascii DATA  HTTP POST ASCII data (H)",
      "     --data-binary DATA  HTTP POST binary data (H)",
      "     --data-urlencode DATA  HTTP POST data url encoded (H)",
+    "     --delegation STRING GSS-API delegation permission",
      "     --digest        Use HTTP Digest Authentication (H)",
      "     --disable-eprt  Inhibit using EPRT or LPRT (F)",
      "     --disable-epsv  Inhibit using EPSV (F)",
@@ -1818,6 +1820,18 @@ static int sockoptcallback(void *clientp, curl_socket_t curlfd,
    return 0;
  }
+static long delegation(struct Configurable *config,
+                       char *str)
+{
+  if(curlx_raw_equal("none", str))
+    return CURLGSSAPI_DELEGATION_NONE;
+  if(curlx_raw_equal("policy", str))
+    return CURLGSSAPI_DELEGATION_POLICY_FLAG;
+  if(curlx_raw_equal("always", str))
+    return CURLGSSAPI_DELEGATION_FLAG;
+  warnf(config, "unrecognized delegation method '%s', using none\n", str);
+  return CURLGSSAPI_DELEGATION_NONE;
+}
  static ParameterError getparameter(char *flag, /* f or -long-flag */
                                     char *nextarg, /* NULL if unset */
@@ -1938,6 +1952,7 @@ static ParameterError getparameter(char *flag, /* f or -long-flag */
      {"$D", "proto",      TRUE},
      {"$E", "proto-redir", TRUE},
      {"$F", "resolve",    TRUE},
+    {"$G", "delegation", TRUE},
      {"0", "http1.0",     FALSE},
      {"1", "tlsv1",       FALSE},
      {"2", "sslv2",       FALSE},
@@ -2523,6 +2538,9 @@ static ParameterError getparameter(char *flag, /* f or -long-flag */
          if(err)
            return err;
          break;
+      case 'G': /* --delegation LEVEL */
+        config->gssapi_delegation = delegation(config, nextarg);
+        break;
        }
        break;
      case '#': /* --progress-bar */
@@ -5597,9 +5615,13 @@ operate(struct Configurable *config, int argc, argv_item_t argv[])
            /* new in 7.21.3 */
            my_setopt(curl, CURLOPT_RESOLVE, config->resolve);
-        /* TODO: new in ### */
-        curl_easy_setopt(curl, CURLOPT_TLSAUTH_USERNAME, config->tls_username);
-        curl_easy_setopt(curl, CURLOPT_TLSAUTH_PASSWORD, config->tls_password);
+        /* new in 7.21.4 */
+        my_setopt_str(curl, CURLOPT_TLSAUTH_USERNAME, config->tls_username);
+        my_setopt_str(curl, CURLOPT_TLSAUTH_PASSWORD, config->tls_password);
+
+        if(config->gssapi_delegation)
+          my_setopt_str(curl, CURLOPT_GSSAPI_DELEGATION,
+                        config->gssapi_delegation);
          retry_numretries = config->req_retry;
-- 
1.7.5.4
-- 
  / daniel.haxx.se
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