From 9722e2bd6a800b0953480bc3e2e4da043b5a49dc Mon Sep 17 00:00:00 2001
From: Kevin Pollet <pollet.kevin@gmail.com>
Date: Thu, 13 Nov 2025 10:34:09 +0100
Subject: [PATCH] Revert "Avoid allocations in readLoop by using sync.Pool"

---
 .golangci.yml   |  6 ++----
 pkg/udp/conn.go | 36 ++++++++----------------------------
 2 files changed, 10 insertions(+), 32 deletions(-)

diff --git a/.golangci.yml b/.golangci.yml
index 949f689dc..50afac812 100644
--- a/.golangci.yml
+++ b/.golangci.yml
@@ -239,6 +239,8 @@ linters:
         text: ' always receives '
         linters:
           - unparam
+      - path: pkg/server/service/bufferpool.go
+        text: 'SA6002: argument should be pointer-like to avoid allocations'
       - path: pkg/server/middleware/middlewares.go
         text: Function 'buildConstructor' has too many statements
         linters:
@@ -314,12 +316,8 @@ linters:
         text: 'the methods of "wasmMiddlewareBuilder" use pointer receiver and non-pointer receiver.'
         linters:
           - recvcheck
-      - path: pkg/server/service/bufferpool.go
-        text: 'SA6002: argument should be pointer-like to avoid allocations'
       - path: pkg/proxy/httputil/bufferpool.go
         text: 'SA6002: argument should be pointer-like to avoid allocations'
-      - path: pkg/udp/conn.go
-        text: 'SA6002: argument should be pointer-like to avoid allocations'
       - path: integration/integration_test.go
         text: 'var (gatewayAPIConformanceRunTest|traefikVersion) is unused'
       - path: pkg/server/router/router.go
diff --git a/pkg/udp/conn.go b/pkg/udp/conn.go
index 2a53b0a6b..36778f648 100644
--- a/pkg/udp/conn.go
+++ b/pkg/udp/conn.go
@@ -32,9 +32,6 @@ type Listener struct {
 	// timeout defines how long to wait on an idle session,
 	// before releasing its related resources.
 	timeout time.Duration
-
-	// readBufferPool is a pool of byte slices for UDP packet reading.
-	readBufferPool sync.Pool
 }
 
 // ListenPacketConn creates a new listener from PacketConn.
@@ -54,11 +51,6 @@ func ListenPacketConn(packetConn net.PacketConn, timeout time.Duration) (*Listen
 		conns:     make(map[string]*Conn),
 		accepting: true,
 		timeout:   timeout,
-		readBufferPool: sync.Pool{
-			New: func() interface{} {
-				return make([]byte, maxDatagramSize)
-			},
-		},
 	}
 
 	go l.readLoop()
@@ -160,26 +152,21 @@ func (l *Listener) readLoop() {
 	for {
 		// Allocating a new buffer for every read avoids
 		// overwriting data in c.msgs in case the next packet is received
-		// before c.msgs is emptied via Read().
-		// Reuses buffers via the readBufferPool sync.Pool.
-		buf := l.readBufferPool.Get().([]byte)
+		// before c.msgs is emptied via Read()
+		buf := make([]byte, maxDatagramSize)
 
 		n, raddr, err := l.pConn.ReadFrom(buf)
 		if err != nil {
-			l.readBufferPool.Put(buf)
 			return
 		}
 		conn, err := l.getConn(raddr)
 		if err != nil {
-			l.readBufferPool.Put(buf)
 			continue
 		}
 
 		select {
-		// Receiver must call releaseReadBuffer() when done reading the data.
 		case conn.receiveCh <- buf[:n]:
 		case <-conn.doneCh:
-			l.readBufferPool.Put(buf)
 			continue
 		}
 	}
@@ -224,15 +211,15 @@ type Conn struct {
 	listener *Listener
 	rAddr    net.Addr
 
-	receiveCh chan []byte // to receive the data from the listener's readLoop.
-	readCh    chan []byte // to receive the buffer into which we should Read.
-	sizeCh    chan int    // to synchronize with the end of a Read.
-	msgs      [][]byte    // to store data from listener, to be consumed by Reads.
+	receiveCh chan []byte // to receive the data from the listener's readLoop
+	readCh    chan []byte // to receive the buffer into which we should Read
+	sizeCh    chan int    // to synchronize with the end of a Read
+	msgs      [][]byte    // to store data from listener, to be consumed by Reads
 
 	muActivity   sync.RWMutex
-	lastActivity time.Time // the last time the session saw either read or write activity.
+	lastActivity time.Time // the last time the session saw either read or write activity
 
-	timeout  time.Duration // for timeouts.
+	timeout  time.Duration // for timeouts
 	doneOnce sync.Once
 	doneCh   chan struct{}
 }
@@ -267,8 +254,6 @@ func (c *Conn) readLoop() {
 			msg := c.msgs[0]
 			c.msgs = c.msgs[1:]
 			n := copy(cBuf, msg)
-			// Return buffer to sync.Pool once done reading from it.
-			c.listener.readBufferPool.Put(msg)
 			c.sizeCh <- n
 		case msg := <-c.receiveCh:
 			c.msgs = append(c.msgs, msg)
@@ -314,11 +299,6 @@ func (c *Conn) Write(p []byte) (n int, err error) {
 
 func (c *Conn) close() {
 	c.doneOnce.Do(func() {
-		// Release any buffered data before closing.
-		for _, msg := range c.msgs {
-			c.listener.readBufferPool.Put(msg)
-		}
-		c.msgs = nil
 		close(c.doneCh)
 	})
 }