From ed7a9363aa29ef4ffe053cdf3f9dc60da200bd7f Mon Sep 17 00:00:00 2001
From: Viktor Liu <17948409+lixmal@users.noreply.github.com>
Date: Tue, 9 Jun 2026 20:26:43 +0900
Subject: [PATCH] [management] Emit IPv6 default permit firewall rule for exit
 node routes (#6368)

---
 .../server/types/networkmap_components.go     |  8 +++-
 .../networkmap_components_correctness_test.go | 43 +++++++++++++++++++
 2 files changed, 49 insertions(+), 2 deletions(-)

diff --git a/management/server/types/networkmap_components.go b/management/server/types/networkmap_components.go
index 3a7e20ec5..b5514e19b 100644
--- a/management/server/types/networkmap_components.go
+++ b/management/server/types/networkmap_components.go
@@ -557,7 +557,6 @@ func (c *NetworkMapComponents) getRoutingPeerRoutes(peerID string) (enabledRoute
 	return enabledRoutes, disabledRoutes
 }
 
-
 func (c *NetworkMapComponents) filterRoutesByGroups(routes []*route.Route, groupListMap LookupMap) []*route.Route {
 	var filteredRoutes []*route.Route
 	for _, r := range routes {
@@ -628,9 +627,14 @@ func (c *NetworkMapComponents) getDefaultPermit(r *route.Route, includeIPv6 bool
 
 	rules := []*RouteFirewallRule{&rule}
 
-	if includeIPv6 && r.IsDynamic() {
+	isDefaultV4 := r.Network.Addr().Is4() && r.Network.Bits() == 0
+	if includeIPv6 && (r.IsDynamic() || isDefaultV4) {
 		ruleV6 := rule
 		ruleV6.SourceRanges = []string{"::/0"}
+		if isDefaultV4 {
+			ruleV6.Destination = "::/0"
+			ruleV6.RouteID = r.ID + "-v6-default"
+		}
 		rules = append(rules, &ruleV6)
 	}
 
diff --git a/management/server/types/networkmap_components_correctness_test.go b/management/server/types/networkmap_components_correctness_test.go
index bcfb6fdf9..3785a7399 100644
--- a/management/server/types/networkmap_components_correctness_test.go
+++ b/management/server/types/networkmap_components_correctness_test.go
@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"net"
 	"net/netip"
+	"slices"
 	"testing"
 	"time"
 
@@ -1029,6 +1030,48 @@ func TestComponents_RouteDefaultPermit(t *testing.T) {
 	assert.True(t, hasDefaultPermit, "route without ACG should have default permit rule with 0.0.0.0/0 source")
 }
 
+// TestComponents_ExitNodeDefaultPermitIPv6 verifies that a default exit node route
+// (0.0.0.0/0) without AccessControlGroups also emits an IPv6 default permit rule
+// (::/0 source and destination) for peers that support IPv6, mirroring the route
+// the client installs. Without it, IPv6 traffic is routed to the exit node but
+// dropped at the forward chain.
+func TestComponents_ExitNodeDefaultPermitIPv6(t *testing.T) {
+	account, validatedPeers := scalableTestAccount(20, 2)
+
+	routingPeerID := "peer-5"
+	routingPeer := account.Peers[routingPeerID]
+	routingPeer.IPv6 = netip.MustParseAddr("fd00::5")
+	routingPeer.Meta.Capabilities = append(routingPeer.Meta.Capabilities, nbpeer.PeerCapabilityIPv6Overlay)
+
+	account.Routes["route-exit"] = &route.Route{
+		ID: "route-exit", Network: netip.MustParsePrefix("0.0.0.0/0"),
+		PeerID: routingPeerID, Peer: routingPeer.Key,
+		Enabled: true, Groups: []string{"group-all"}, PeerGroups: []string{"group-0"},
+		AccessControlGroups: []string{},
+		AccountID:           "test-account",
+	}
+
+	nm := componentsNetworkMap(account, routingPeerID, validatedPeers)
+	require.NotNil(t, nm)
+
+	hasV4 := false
+	hasV6 := false
+	for _, rfr := range nm.RoutesFirewallRules {
+		switch rfr.Destination {
+		case "0.0.0.0/0":
+			if slices.Contains(rfr.SourceRanges, "0.0.0.0/0") {
+				hasV4 = true
+			}
+		case "::/0":
+			if slices.Contains(rfr.SourceRanges, "::/0") {
+				hasV6 = true
+			}
+		}
+	}
+	assert.True(t, hasV4, "exit node route should have an IPv4 default permit rule (0.0.0.0/0)")
+	assert.True(t, hasV6, "exit node route should have an IPv6 default permit rule (::/0)")
+}
+
 // ──────────────────────────────────────────────────────────────────────────────
 // 15. MULTIPLE ROUTERS PER NETWORK
 // ──────────────────────────────────────────────────────────────────────────────