[#722,!1] Addressed review comments

   revamped Dhpc6srv::sanityCheckDuid() per review comments on
   1.4.0 version.

ChangeLog

@@ -218,6 +218,9 @@ Kea 1.6.0-beta2 released on July 24, 2019
 1610.	[build]		fdupont
 	Removed the obsolete compatcheck top directory.
 	(Gitlab #667,!391, git 8cb113a52f0cf56fbdb5cb0e87464135234c2ac1)
+=======
+	(Gitlab #722,!1-p git TBD)
+>>>>>>> [#722,!1] Addressed review comments
 
 1609.	[bug]		fdupont
 	Fixed the implementation of authentication keys in DHCPv6

src/bin/dhcp6/dhcp6_srv.cc

@@ -1411,17 +1411,10 @@ void Dhcpv6Srv::sanityCheckDUID(const OptionPtr& opt, const std::string& opt_nam
     // The client-id or server-id has to have at least 3 bytes of useful data:
     // two for duid type and one more for actual duid value.
     uint16_t len = opt->len() - opt->getHeaderLen();
-    if (len < 3) {
-        isc_throw(RFCViolation, "Received empty or truncated " << opt_name << " option: "
-                  << len << " byte(s) only");
-    }
-
-    // We need to make sure we can construct one, if not we're toast later on.
-    try {
-        DuidPtr tmp(new DUID(opt->getData()));
-    } catch (const std::exception& ex) {
-        isc_throw(RFCViolation, "Received invalid content for "
-                  << opt_name << ", " << ex.what());
+    if (len < 3 || len > DUID::MAX_DUID_LEN || opt->getData().empty()) {
+        isc_throw(RFCViolation, "Received invalid DUID for " << opt_name << ", received "
+                  << len << " byte(s). It must be at least 3 and no more than "
+                  << DUID::MAX_DUID_LEN);
     }
 }