From c9cd856c8c70c66ae82724df2be0daf944f48fff Mon Sep 17 00:00:00 2001
From: Lz <imlangzi@qq.com>
Date: Sun, 11 Jan 2026 21:42:19 +0800
Subject: [PATCH] fix: distinguish NXDOMAIN from network errors in RDNS lookup

- Use *net.DNSError.IsNotFound to detect NXDOMAIN (no PTR record)
- NXDOMAIN now returns StatusFailed instead of StatusPending
- Network errors (timeout, connection issues) still return StatusPending for retry
---
 bot.go | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/bot.go b/bot.go
index 81d6a34..0e1f708 100644
--- a/bot.go
+++ b/bot.go
@@ -216,7 +216,13 @@ func (b *Bot) VerifyRDNS(ipStr string) ResultStatus {
 	// Perform RDNS lookup
 	names, err := net.LookupAddr(ipStr)
 	if err != nil {
-		// Network error - allow retry, do not add to fail cache
+		// Distinguish network errors from NXDOMAIN (no PTR record)
+		if dnsErr, ok := err.(*net.DNSError); ok && dnsErr.IsNotFound {
+			// NXDOMAIN: PTR record does not exist - verification failed
+			b.fail.Add(ipStr)
+			return StatusFailed
+		}
+		// Network error (timeout, connection issue, etc.) - allow retry
 		return StatusPending
 	}
 	if len(names) == 0 {