[client] Fix forwarder peers never excluded from lazy connections (#6674)

* [client] Extract peerRoutesAddr helper in toExcludedLazyPeers

Refactor: pull the AllowedIPs match into a named
peerRoutesAddr helper and document why forward-target peers are excluded
from lazy connections. No behavior change; the existing address match is
preserved as-is.

* [client] Add failing test for lazy-conn forward-target exclusion

toExcludedLazyPeers compares AllowedIPs (CIDR) against the unmasked
TranslatedAddress, so forward-target peers are never excluded. This test
asserts the peer is excluded and fails on the current behavior; the fix
follows.

* [client] Fix lazy-conn exclusion for ingress forward peers

peerRoutesAddr compared AllowedIPs (CIDR, e.g. a peer's overlay IP as /32)
against the unmasked TranslatedAddress string, so the match never fired and
forward-target peers were never excluded from lazy connections. Use prefix
containment so a routed address matches the peer's AllowedIP

* [client] Reuse parsed AllowedIPs from peerStore in lazy exclusion

Instead of re-parsing the network map AllowedIPs strings, look up the
already-parsed []netip.Prefix from peerStore.AllowedIPs (the same typed
value the lazy manager itself consumes). A down/lazy peer still has its
conn in the store, so exclusion is unaffected by connection state. Extract
a pure prefixesContain helper and unit-test it.

client/internal/engine.go

@@ -2605,13 +2605,14 @@ func (e *Engine) updateForwardRules(rules []*mgmProto.ForwardingRule) ([]firewal
 
 func (e *Engine) toExcludedLazyPeers(rules []firewallManager.ForwardRule, peers []*mgmProto.RemotePeerConfig) map[string]bool {
 	excludedPeers := make(map[string]bool)
+
+	// Ingress forward targets: inbound forwarded traffic is initiated remotely and
+	// cannot wake a lazy connection, so the peer routing the target must stay
+	// permanently connected. AllowedIPs are already parsed on the peer conn, so
+	// reuse those typed prefixes instead of re-parsing the network map strings.
 	for _, r := range rules {
-		ip := r.TranslatedAddress
 		for _, p := range peers {
-			for _, allowedIP := range p.GetAllowedIps() {
-				if allowedIP != ip.String() {
-					continue
-				}
+			if e.peerRoutesAddr(p, r.TranslatedAddress) {
 				log.Infof("exclude forwarder peer from lazy connection: %s", p.GetWgPubKey())
 				excludedPeers[p.GetWgPubKey()] = true
 			}
@@ -2621,6 +2622,27 @@ func (e *Engine) toExcludedLazyPeers(rules []firewallManager.ForwardRule, peers
 	return excludedPeers
 }
 
+// peerRoutesAddr reports whether the peer is a router for addr, matched against
+// the peer's already-parsed AllowedIPs from the store (the same typed value the
+// lazy manager consumes) rather than re-parsing the network map strings.
+func (e *Engine) peerRoutesAddr(p *mgmProto.RemotePeerConfig, addr netip.Addr) bool {
+	prefixes, ok := e.peerStore.AllowedIPs(p.GetWgPubKey())
+	if !ok {
+		return false
+	}
+	return prefixesContain(prefixes, addr)
+}
+
+// prefixesContain reports whether addr falls within any of the prefixes.
+func prefixesContain(prefixes []netip.Prefix, addr netip.Addr) bool {
+	for _, prefix := range prefixes {
+		if prefix.Contains(addr) {
+			return true
+		}
+	}
+	return false
+}
+
 // isChecksEqual checks if two slices of checks are equal.
 func isChecksEqual(checks1, checks2 []*mgmProto.Checks) bool {
 	normalize := func(checks []*mgmProto.Checks) []string {