Prevent fail counter of a proxy overflows (#5990)

Signed-off-by: vanceli <vanceli@tencent.com>
Signed-off-by: Vance Li <vncl@YingyingM1.local>
Co-authored-by: vanceli <vanceli@tencent.com>

plugin/pkg/proxy/proxy.go

@@ -93,6 +93,16 @@ func (p *Proxy) SetReadTimeout(duration time.Duration) {
 	p.readTimeout = duration
 }
 
+// incrementFails increments the number of fails safely.
+func (p *Proxy) incrementFails() {
+	curVal := atomic.LoadUint32(&p.fails)
+	if curVal > curVal+1 {
+		// overflow occurred, do not update the counter again
+		return
+	}
+	atomic.AddUint32(&p.fails, 1)
+}
+
 const (
 	maxTimeout = 2 * time.Second
 )