From 5b43f3a47d811952634e7d4314b3ea9f3a56989e Mon Sep 17 00:00:00 2001
From: yvvw <15168529+yvvw@users.noreply.github.com>
Date: Mon, 5 Feb 2024 03:47:46 +0800
Subject: [PATCH] Fix Compress UDP DNS response instead of truncate

---
 outbound/dns.go | 22 +++-------------------
 1 file changed, 3 insertions(+), 19 deletions(-)

diff --git a/outbound/dns.go b/outbound/dns.go
index 0f003377..44654867 100644
--- a/outbound/dns.go
+++ b/outbound/dns.go
@@ -241,9 +241,11 @@ func (d *DNS) newPacketConnection(ctx context.Context, conn N.PacketConn, readWa
 					return err
 				}
 				timeout.Update()
-				response = truncateDNSMessage(response, 512) // TODO: add an option to custom UDP buffer size
 				responseBuffer := buf.NewSize(dns.FixedPacketSize)
 				responseBuffer.Resize(1024, 0)
+				if response.Len() > 512 {
+					response.Compress = true // TODO: add an option to compress UDP
+				}
 				n, err := response.PackBuffer(responseBuffer.FreeBytes())
 				if err != nil {
 					cancel(err)
@@ -264,21 +266,3 @@ func (d *DNS) newPacketConnection(ctx context.Context, conn N.PacketConn, readWa
 	})
 	return group.Run(fastClose)
 }
-
-func truncateDNSMessage(response *mDNS.Msg, maxLen int) *mDNS.Msg {
-	responseLen := response.Len()
-	if responseLen <= maxLen {
-		return response
-	}
-	response = response.Copy()
-	for len(response.Answer) > 0 && responseLen > maxLen {
-		response.Answer = response.Answer[:len(response.Answer)-1]
-		response.Truncated = true
-		responseLen = response.Len()
-	}
-	if responseLen > maxLen {
-		response.Ns = nil
-		response.Extra = nil
-	}
-	return response
-}