[#1529] Avoid duplicating qualifying suffix

src/lib/dhcpsrv/d2_client_mgr.*
    D2ClientMgr::qualifyName() - modified to only add the qualifying
    suffix if the input name does not already end with it.

src/lib/dhcpsrv/tests/d2_client_unittest.cc
    TEST_F(D2ClientMgrParamsTest, qualifyNameWithoutDuplicatingSuffix) -
    new test

3 files changed, 77 insertions, 5 deletions

diff --git a/src/lib/dhcpsrv/d2_client_mgr.cc b/src/lib/dhcpsrv/d2_client_mgr.cc
index 6671471309..3ba12d172c 100644
--- a/src/lib/dhcpsrv/d2_client_mgr.cc
+++ b/src/lib/dhcpsrv/d2_client_mgr.cc
@@ -1,4 +1,4 @@
-// Copyright (C) 2014-2020 Internet Systems Consortium, Inc. ("ISC")
+// Copyright (C) 2014-2021 Internet Systems Consortium, Inc. ("ISC")
 //
 // This Source Code Form is subject to the terms of the Mozilla Public
 // License, v. 2.0. If a copy of the MPL was not distributed with this
@@ -186,14 +186,47 @@ D2ClientMgr::qualifyName(const std::string& partial_name,
 
     gen_name << partial_name;
     std::string suffix = ddns_params.getQualifyingSuffix();
+    bool suffix_present = true;
     if (!suffix.empty()) {
         std::string str = gen_name.str();
-        size_t len = str.length();
-        if ((len > 0) && (str[len - 1] != '.')) {
-            gen_name << ".";
+        auto suffix_rit = suffix.rbegin();
+        if (*suffix_rit == '.') {
+            ++suffix_rit;
+        }
+
+        auto gen_rit = str.rbegin();
+        if (*gen_rit == '.') {
+            ++gen_rit;
         }
 
-        gen_name << suffix;
+        while (suffix_rit != suffix.rend()) {
+            if ((gen_rit == str.rend()) ||
+                (*suffix_rit != *gen_rit)) {
+                // They don't match.
+                suffix_present = false;
+                break;
+            }
+
+            ++suffix_rit;
+            ++gen_rit;
+        }
+
+        // Catch the case where name has suffix embedded.
+        // input: foo.barexample.com   suffix: example.com
+        if ((suffix_present) && (suffix_rit == suffix.rend())) {
+            if (*gen_rit != '.') {
+                suffix_present = false;
+            }
+        }
+
+        if (!suffix_present) {
+            size_t len = str.length();
+            if ((len > 0) && (str[len - 1] != '.')) {
+                gen_name << ".";
+            }
+
+            gen_name << suffix;
+        }
     }
 
     std::string str = gen_name.str();
diff --git a/src/lib/dhcpsrv/d2_client_mgr.h b/src/lib/dhcpsrv/d2_client_mgr.h
index bfa611d8ad..33eb55a398 100644
--- a/src/lib/dhcpsrv/d2_client_mgr.h
+++ b/src/lib/dhcpsrv/d2_client_mgr.h
@@ -184,6 +184,9 @@ public:
     ///
     ///     <partial_name>.<qualifying-suffix>.
     ///
+    /// Note that the qualifying suffix will only be appended if the
+    /// input name does not already end with that suffix.
+    ///
     /// @param partial_name domain name to qualify
     /// @param ddns_params DDNS behavioral configuration parameters
     /// @param trailing_dot A boolean value which when true guarantees the
diff --git a/src/lib/dhcpsrv/tests/d2_client_unittest.cc b/src/lib/dhcpsrv/tests/d2_client_unittest.cc
index f246c152d8..6b900877b1 100644
--- a/src/lib/dhcpsrv/tests/d2_client_unittest.cc
+++ b/src/lib/dhcpsrv/tests/d2_client_unittest.cc
@@ -665,6 +665,42 @@ TEST_F(D2ClientMgrParamsTest, qualifyName) {
 
 }
 
+/// @brief Tests the qualifyName method's ability to avoid duplicating
+/// qualifying suffix.
+TEST_F(D2ClientMgrParamsTest, qualifyNameWithoutDuplicatingSuffix) {
+    D2ClientMgr mgr;
+    bool do_not_dot = false;
+    bool do_dot = true;
+
+    // Create enabled configuration
+    subnet_->setDdnsSendUpdates(true);
+    subnet_->setDdnsOverrideNoUpdate(false);
+    subnet_->setDdnsOverrideClientUpdate(false);
+    subnet_->setDdnsReplaceClientNameMode(D2ClientConfig::RCM_NEVER);
+    subnet_->setDdnsGeneratedPrefix("prefix");
+    subnet_->setDdnsQualifyingSuffix("suffix.com");
+    subnet_->setHostnameCharSet("");
+    subnet_->setHostnameCharReplacement("");
+
+    // Verify that the qualifying suffix does not get appended when the
+    // input name has the suffix but no trailing dot.
+    std::string partial_name = "somehost.suffix.com";
+    std::string qualified_name = mgr.qualifyName(partial_name, *ddns_params_, do_dot);
+    EXPECT_EQ("somehost.suffix.com.", qualified_name);
+
+    // Verify that the qualifying suffix does not get appended when the
+    // input name has the suffix and a trailing dot.
+    partial_name = "somehost.suffix.com.";
+    qualified_name = mgr.qualifyName(partial_name, *ddns_params_, do_dot);
+    EXPECT_EQ("somehost.suffix.com.", qualified_name);
+
+    // Verify that the qualifying suffix does get appended when the
+    // input name has the suffix embedded in it.
+    partial_name = "somehost.almostsuffix.com";
+    qualified_name = mgr.qualifyName(partial_name, *ddns_params_, do_dot);
+    EXPECT_EQ("somehost.almostsuffix.com.suffix.com.", qualified_name);
+}
+
 /// @brief Tests the generateFdqn method's ability to construct FQDNs
 TEST_F(D2ClientMgrParamsTest, generateFqdn) {
     D2ClientMgr mgr;