Quietly log error on UDP_NETRESET ioctl on Windows. (#1453)

* Quietly log error on UDP_NETRESET ioctl on Windows.

* dampen unexpected error warnings

udp/udp_generic.go

@@ -10,9 +10,11 @@ package udp
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"net"
 	"net/netip"
+	"time"
 
 	"github.com/sirupsen/logrus"
 	"github.com/slackhq/nebula/config"
@@ -80,12 +82,22 @@ func (u *GenericConn) ListenOut(r EncReader, lhf LightHouseHandlerFunc, cache *f
 	fwPacket := &firewall.Packet{}
 	nb := make([]byte, 12, 12)
 
+	var lastRecvErr time.Time
+
 	for {
 		// Just read one packet at a time
 		n, rua, err := u.ReadFromUDPAddrPort(buffer)
 		if err != nil {
-			u.l.WithError(err).Debug("udp socket is closed, exiting read loop")
-			return
+			if errors.Is(err, net.ErrClosed) {
+				u.l.WithError(err).Debug("udp socket is closed, exiting read loop")
+				return
+			}
+			// Dampen unexpected message warns to once per minute
+			if lastRecvErr.IsZero() || time.Since(lastRecvErr) > time.Minute {
+				lastRecvErr = time.Now()
+				u.l.WithError(err).Warn("unexpected udp socket receive error")
+			}
+			continue
 		}
 
 		r(