From fe92030438be83e94c36b3be1de253c183100104 Mon Sep 17 00:00:00 2001
From: Ruakij <ruakij@ruekov.eu>
Date: Tue, 22 Apr 2025 11:50:01 +0200
Subject: [PATCH] Default route handling for IPv6 conversion

---
 README.md       |  2 ++
 cmd/app/main.go | 11 ++++++++++-
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index db5e614..a35a6ab 100644
--- a/README.md
+++ b/README.md
@@ -24,6 +24,8 @@ The program will convert IPv4-only wireguard-interfaces to IPv6. It converts and
 
 IPv6-Adresses are generated based on the IPv4-Adress.
 
+If not filtered out, then default routes (0.0.0.0/0) are handled specially and are converted to the IPv6 default route (::/0).
+
 Beware: This program needs `NET_ADMIN` privileges for setting Adresses and to access the wireguard-daemon.
 
 <br>
diff --git a/cmd/app/main.go b/cmd/app/main.go
index 4baccd2..4d540d7 100644
--- a/cmd/app/main.go
+++ b/cmd/app/main.go
@@ -17,6 +17,7 @@ import (
 var envRequired = []string{
 	"INTERFACE",
 }
+
 var envDefaults = map[string]string{
 	"IPV6_FORMAT":      "fc12::%02x%02x:%02x%02x/%d",
 	"FILTER_PREFIX":    "100.100",
@@ -111,7 +112,7 @@ func main() {
 
 		for _, peer := range wgDevice.Peers {
 			// Create slice for 1 expected addition
-			var addAllowedIPs = make([]net.IPNet, 0, 1)
+			addAllowedIPs := make([]net.IPNet, 0, 1)
 
 			// Loop through the allowed-ips and add the ones starting with 100.100
 			for _, allowedIP := range peer.AllowedIPs {
@@ -162,6 +163,14 @@ func main() {
 }
 
 func convertIPv4ToIPv6(ipv6Format *string, ipv4 *net.IPNet) *string {
+	// Check if this is a default route (0.0.0.0/0)
+	if ipv4.IP.Equal(net.IPv4zero) {
+		if ones, _ := ipv4.Mask.Size(); ones == 0 {
+			defaultRoute := "::/0"
+			return &defaultRoute
+		}
+	}
+
 	CIDR, _ := ipv4.Mask.Size()
 	// Run format
 	ipv6Str := fmt.Sprintf(*ipv6Format, (*ipv4).IP[0], (*ipv4).IP[1], (*ipv4).IP[2], (*ipv4).IP[3], net.IPv6len*8-(net.IPv4len*8-CIDR))