readLoop 和 tx 优化 (#313)

* chores: use modern platform optimize

* refactor: readloop, tx

* chores: drop older linux compatibility

Go 1.24+ requires linux kernel 3.2

readloop.go

@@ -31,24 +31,33 @@ import (
 // defaultReadLoop is the standard procedure for reading from a connection
 func (s *UDPSession) defaultReadLoop() {
 	buf := make([]byte, mtuLimit)
+
 	var src string
 	for {
-		if n, addr, err := s.conn.ReadFrom(buf); err == nil {
-			if s.isClosed() {
-				return
-			}
-			// make sure the packet is from the same source
-			if src == "" { // set source address
-				src = addr.String()
-			} else if addr.String() != src {
-				atomic.AddUint64(&DefaultSnmp.InErrs, 1)
-				continue
-			}
-			s.packetInput(buf[:n])
-		} else {
+		n, addr, err := s.conn.ReadFrom(buf)
+		if err != nil {
 			s.notifyReadError(errors.WithStack(err))
 			return
 		}
+
+		if s.isClosed() {
+			return
+		}
+
+		// make sure the packet is from the same source
+		switch src {
+		case "":
+			// set source address if not set
+			src = addr.String()
+		case addr.String():
+			// source valid
+		default:
+			// source invalid
+			atomic.AddUint64(&DefaultSnmp.InErrs, 1)
+			continue
+		}
+
+		s.packetInput(buf[:n])
 	}
 }
 
@@ -56,11 +65,12 @@ func (s *UDPSession) defaultReadLoop() {
 func (l *Listener) defaultMonitor() {
 	buf := make([]byte, mtuLimit)
 	for {
-		if n, from, err := l.conn.ReadFrom(buf); err == nil {
-			l.packetInput(buf[:n], from)
-		} else {
+		n, from, err := l.conn.ReadFrom(buf)
+		if err != nil {
 			l.notifyReadError(errors.WithStack(err))
 			return
 		}
+
+		l.packetInput(buf[:n], from)
 	}
 }