header_rewrite: Allow Txn reenable to be deferred.

plugins/header_rewrite/header_rewrite.cc

@@ -299,6 +299,7 @@ cont_rewrite_headers(TSCont contp, TSEvent event, void *edata)
     break;
   }
 
+  bool reenable{true};
   if (hook != TS_HTTP_LAST_HOOK) {
     const RuleSet *rule = conf->rule(hook);
     Resources      res(txnp, contp);
@@ -311,6 +312,10 @@ cont_rewrite_headers(TSCont contp, TSEvent event, void *edata)
       if (rule->eval(res)) {
         OperModifiers rt = rule->exec(res);
 
+        if (rt & OPER_NO_REENABLE) {
+          reenable = false;
+        }
+
         if (rule->last() || (rt & OPER_LAST)) {
           break; // Conditional break, force a break with [L]
         }
@@ -319,7 +324,9 @@ cont_rewrite_headers(TSCont contp, TSEvent event, void *edata)
     }
   }
 
-  TSHttpTxnReenable(txnp, TS_EVENT_HTTP_CONTINUE);
+  if (reenable) {
+    TSHttpTxnReenable(txnp, TS_EVENT_HTTP_CONTINUE);
+  }
   return 0;
 }
 
@@ -523,6 +530,8 @@ TSRemapDoRemap(void *ih, TSHttpTxn rh, TSRemapRequestInfo *rri)
     if (rule->eval(res)) {
       OperModifiers rt = rule->exec(res);
 
+      ink_assert((rt & OPER_NO_REENABLE) == 0);
+
       if (res.changed_url == true) {
         rval = TSREMAP_DID_REMAP;
       }

plugins/header_rewrite/operator.h

@@ -31,11 +31,12 @@
 
 // Operator modifiers
 enum OperModifiers {
-  OPER_NONE = 0,
-  OPER_LAST = 1,
-  OPER_NEXT = 2,
-  OPER_QSA  = 4,
-  OPER_INV  = 8,
+  OPER_NONE        = 0,
+  OPER_LAST        = 1,
+  OPER_NEXT        = 2,
+  OPER_QSA         = 4,
+  OPER_INV         = 8,
+  OPER_NO_REENABLE = 16,
 };
 
 ///////////////////////////////////////////////////////////////////////////////
@@ -55,17 +56,24 @@ class Operator : public Statement
   OperModifiers get_oper_modifiers() const;
   void          initialize(Parser &p) override;
 
-  void
+  // Returns number of executed operators that need to defer call to TSHttpTxnReenable().  It is a fatal error if this
+  // returns more than 1.  If multiple operators need to defer reenable on the same hook, issue 11549 should be
+  // revisited.  In this case, one possible approach would be to add a per-transaction user parameter, pointing to
+  // a count of operators that are deferred the reeanable for a particular hook.
+  unsigned
   do_exec(const Resources &res) const
   {
-    exec(res);
+    unsigned no_reenable{exec(res) ? 0U : 1U};
     if (nullptr != _next) {
-      static_cast<Operator *>(_next)->do_exec(res);
+      no_reenable += static_cast<Operator *>(_next)->do_exec(res);
     }
+    return no_reenable;
   }
 
 protected:
-  virtual void exec(const Resources &res) const = 0;
+  // Return false to disable call of TSHttpTxnReenable().  Operators executed in the remap pseudo-hook MUST return true,
+  // as reenable is implicit in remap execution.
+  virtual bool exec(const Resources &res) const = 0;
 
 private:
   OperModifiers _mods = OPER_NONE;