Fix recv_error receipt limit allowance for v1.9.x (#1459)

* Fix recv_error receipt limit allowance

* backport #1463 recv_error behavior changes

---------

Co-authored-by: JackDoan <me@jackdoan.com>

Author: nbrownus

hostmap.go

@@ -22,7 +22,6 @@ const defaultPromoteEvery = 1000       // Count of packets sent before we try mo
 const defaultReQueryEvery = 5000       // Count of packets sent before re-querying a hostinfo to the lighthouse
 const defaultReQueryWait = time.Minute // Minimum amount of seconds to wait before re-querying a hostinfo the lighthouse. Evaluated every ReQueryEvery
 const MaxRemotes = 10
-const maxRecvError = 4
 
 // MaxHostInfosPerVpnIp is the max number of hostinfos we will track for a given vpn ip
 // 5 allows for an initial handshake and each host pair re-handshaking twice
@@ -220,7 +219,6 @@ type HostInfo struct {
 	remoteIndexId   uint32
 	localIndexId    uint32
 	vpnIp           netip.Addr
-	recvError       atomic.Uint32
 	remoteCidr      *bart.Table[struct{}]
 	relayState      RelayState
 
@@ -705,13 +703,6 @@ func (i *HostInfo) SetRemoteIfPreferred(hm *HostMap, newRemote netip.AddrPort) b
 	return false
 }
 
-func (i *HostInfo) RecvErrorExceeded() bool {
-	if i.recvError.Add(1) >= maxRecvError {
-		return true
-	}
-	return true
-}
-
 func (i *HostInfo) CreateRemoteCIDR(c *cert.NebulaCertificate) {
 	if len(c.Details.Ips) == 1 && len(c.Details.Subnets) == 0 {
 		// Simple case, no CIDRTree needed

outside.go

@@ -286,16 +286,18 @@ func (f *Interface) handleHostRoaming(hostinfo *HostInfo, ip netip.AddrPort) {
 
 }
 
+// handleEncrypted returns true if a packet should be processed, false otherwise
 func (f *Interface) handleEncrypted(ci *ConnectionState, addr netip.AddrPort, h *header.H) bool {
-	// If connectionstate exists and the replay protector allows, process packet
-	// Else, send recv errors for 300 seconds after a restart to allow fast reconnection.
-	if ci == nil || !ci.window.Check(f.l, h.MessageCounter) {
+	// If connectionstate does not exist, send a recv error, if possible, to encourage a fast reconnect
+	if ci == nil {
 		if addr.IsValid() {
 			f.maybeSendRecvError(addr, h.RemoteIndex)
-			return false
-		} else {
-			return false
 		}
+		return false
+	}
+	// If the window check fails, refuse to process the packet, but don't send a recv error
+	if !ci.window.Check(f.l, h.MessageCounter) {
+		return false
 	}
 
 	return true
@@ -458,10 +460,6 @@ func (f *Interface) handleRecvError(addr netip.AddrPort, h *header.H) {
 		return
 	}
 
-	if !hostinfo.RecvErrorExceeded() {
-		return
-	}
-
 	if hostinfo.remote.IsValid() && hostinfo.remote != addr {
 		f.l.Infoln("Someone spoofing recv_errors? ", addr, hostinfo.remote)
 		return