[2316] Passing option by reference as suggested in the review.

src/lib/dhcp/subnet.cc

@@ -97,7 +97,7 @@ Pool4Ptr Subnet4::getPool4(const isc::asiolink::IOAddress& hint /* = IOAddress("
 }
 
 void
-Subnet4::validateOption(OptionPtr option) const {
+Subnet4::validateOption(const OptionPtr& option) const {
     if (!option) {
         isc_throw(isc::BadValue, "option configured for subnet must not be NULL");
     } else if (option->getUniverse() != Option::V4) {
@@ -152,7 +152,7 @@ Pool6Ptr Subnet6::getPool6(const isc::asiolink::IOAddress& hint /* = IOAddress("
 }
 
 void
-Subnet6::validateOption(OptionPtr option) const {
+Subnet6::validateOption(const OptionPtr& option) const {
     if (!option) {
         isc_throw(isc::BadValue, "option configured for subnet must not be NULL");
     } else if (option->getUniverse() != Option::V6) {

src/lib/dhcp/subnet.h

@@ -255,7 +255,7 @@ protected:
     /// @brief Check if option is valid and can be added to a subnet.
     ///
     /// @param option option to be validated.
-    virtual void validateOption(OptionPtr option) const = 0;
+    virtual void validateOption(const OptionPtr& option) const = 0;
 
     /// @brief subnet-id
     ///
@@ -328,7 +328,7 @@ protected:
     /// @param option option to be validated.
     ///
     /// @throw isc::BadValue if provided option is invalid.
-    virtual void validateOption(OptionPtr option) const;
+    virtual void validateOption(const OptionPtr& option) const;
 
     /// @brief collection of pools in that list
     Pool4Collection pools_;
@@ -396,7 +396,7 @@ protected:
     /// @param option option to be validated.
     ///
     /// @throw isc::BadValue if provided option is invalid.
-    virtual void validateOption(OptionPtr option) const;
+    virtual void validateOption(const OptionPtr& option) const;
 
     /// @brief collection of pools in that list
     Pool6Collection pools_;