From 53873094ff9468428b900cdc7b0a714efabdcbc5 Mon Sep 17 00:00:00 2001
From: Shreyas Zare <shreyas@technitium.com>
Date: Sat, 17 Apr 2021 14:13:20 +0530
Subject: [PATCH] CacheZone: fixed bug in ContainsNameServerRecords() that
 caused returning true when the NS record contains special cache record. Code
 updated to use DnsResourceRecord.IsExpired() method to check if record is
 expired. Minor code refactoring done.

---
 DnsServerCore/Dns/Zones/CacheZone.cs | 30 ++++++++++------------------
 1 file changed, 11 insertions(+), 19 deletions(-)

diff --git a/DnsServerCore/Dns/Zones/CacheZone.cs b/DnsServerCore/Dns/Zones/CacheZone.cs
index 36140558..9d4a91f8 100644
--- a/DnsServerCore/Dns/Zones/CacheZone.cs
+++ b/DnsServerCore/Dns/Zones/CacheZone.cs
@@ -43,11 +43,8 @@ namespace DnsServerCore.Dns.Zones
             {
                 DnsResourceRecord record = records[0];
 
-                if (!serveStale && record.IsStale)
-                    return Array.Empty<DnsResourceRecord>(); //record is stale
-
-                if (record.TtlValue < 1u)
-                    return Array.Empty<DnsResourceRecord>(); //ttl expired
+                if (record.IsExpired(serveStale))
+                    return Array.Empty<DnsResourceRecord>(); //record expired
 
                 if (filterSpecialCacheRecords)
                 {
@@ -62,11 +59,8 @@ namespace DnsServerCore.Dns.Zones
 
             foreach (DnsResourceRecord record in records)
             {
-                if (!serveStale && record.IsStale)
-                    continue; //record is stale
-
-                if (record.TtlValue < 1u)
-                    continue; //ttl expired
+                if (record.IsExpired(serveStale))
+                    continue; //record expired
 
                 if (filterSpecialCacheRecords)
                 {
@@ -102,7 +96,7 @@ namespace DnsServerCore.Dns.Zones
                 //call trying to cache failure record
                 if (_entries.TryGetValue(type, out IReadOnlyList<DnsResourceRecord> existingRecords))
                 {
-                    if ((existingRecords.Count > 0) && !(existingRecords[0].RDATA is DnsCache.DnsFailureRecord) && (serveStale || !existingRecords[0].IsStale))
+                    if ((existingRecords.Count > 0) && !(existingRecords[0].RDATA is DnsCache.DnsFailureRecord) && !existingRecords[0].IsExpired(serveStale))
                         return; //skip to avoid overwriting a useful record with a failure record
                 }
             }
@@ -147,7 +141,7 @@ namespace DnsServerCore.Dns.Zones
 
                 foreach (DnsResourceRecord record in entry.Value)
                 {
-                    if ((record.TtlValue < 1u) || (!serveStale && record.IsStale))
+                    if (record.IsExpired(serveStale))
                     {
                         //record expired
                         isExpired = true;
@@ -161,7 +155,7 @@ namespace DnsServerCore.Dns.Zones
 
                     foreach (DnsResourceRecord record in entry.Value)
                     {
-                        if ((record.TtlValue < 1u) || (!serveStale && record.IsStale))
+                        if (record.IsExpired(serveStale))
                             continue; //record expired, skip it
 
                         if (newRecords == null)
@@ -202,9 +196,9 @@ namespace DnsServerCore.Dns.Zones
                 List<DnsResourceRecord> anyRecords = new List<DnsResourceRecord>();
 
                 foreach (KeyValuePair<DnsResourceRecordType, IReadOnlyList<DnsResourceRecord>> entry in _entries)
-                    anyRecords.AddRange(FilterExpiredRecords(type, entry.Value, serveStale, true));
+                    anyRecords.AddRange(entry.Value);
 
-                return anyRecords;
+                return FilterExpiredRecords(type, anyRecords, serveStale, true);
             }
 
             if (_entries.TryGetValue(type, out IReadOnlyList<DnsResourceRecord> existingRecords))
@@ -223,10 +217,8 @@ namespace DnsServerCore.Dns.Zones
                 if (record.IsStale)
                     continue;
 
-                if (record.TtlValue < 1u)
-                    continue;
-
-                return true;
+                if (record.RDATA is DnsNSRecord)
+                    return true;
             }
 
             return false;