Reconcile AllowedIPs from the routes of the interface instead of replaying route events

cmd/app/convert.go

@@ -0,0 +1,103 @@
+package main
+
+import (
+	"net"
+	"net/netip"
+	"slices"
+
+	"git.ruekov.eu/ruakij/routingtabletowg/lib/reconcile"
+
+	"github.com/vishvananda/netlink"
+	"golang.org/x/sys/unix"
+	"golang.zx2c4.com/wireguard/wgctrl/wgtypes"
+)
+
+// routeDst returns the destination of a route, the default route has none.
+func routeDst(route netlink.Route) (netip.Prefix, bool) {
+	if route.Dst != nil {
+		return reconcile.PrefixFromIPNet(*route.Dst)
+	}
+
+	// The family comes from the route, as a default route may have no gateway to tell it
+	switch route.Family {
+	case unix.AF_INET:
+		return netip.PrefixFrom(netip.IPv4Unspecified(), 0), true
+	case unix.AF_INET6:
+		return netip.PrefixFrom(netip.IPv6Unspecified(), 0), true
+	}
+	return netip.Prefix{}, false
+}
+
+// toRoutes converts the routes that can be translated, which are the ones with a
+// gateway and a destination that can be written to WireGuard. The destinations of
+// the latter are returned as skipped.
+func toRoutes(list []netlink.Route) (routes []reconcile.Route, skipped []netip.Prefix) {
+	routes = make([]reconcile.Route, 0, len(list))
+	for _, route := range list {
+		gw, ok := reconcile.AddrFromIP(route.Gw)
+		if !ok {
+			continue
+		}
+		dst, ok := routeDst(route)
+		if !ok {
+			continue
+		}
+		if !writable(reconcile.ToIPNet(dst)) {
+			skipped = append(skipped, dst)
+			continue
+		}
+		routes = append(routes, reconcile.Route{
+			Dst:    dst,
+			Gw:     gw,
+			Metric: route.Priority,
+			Table:  route.Table,
+		})
+	}
+	return routes, skipped
+}
+
+func toPeers(device *wgtypes.Device) []reconcile.Peer {
+	peers := make([]reconcile.Peer, 0, len(device.Peers))
+	for _, peer := range device.Peers {
+		allowed := make([]netip.Prefix, 0, len(peer.AllowedIPs))
+		for _, ipNet := range peer.AllowedIPs {
+			if prefix, ok := reconcile.PrefixFromIPNet(ipNet); ok {
+				allowed = append(allowed, prefix)
+			}
+		}
+		peers = append(peers, reconcile.Peer{Key: peer.PublicKey, AllowedIPs: allowed})
+	}
+	return peers
+}
+
+func toIPNets(prefixes []netip.Prefix) []net.IPNet {
+	ipNets := make([]net.IPNet, len(prefixes))
+	for i, prefix := range prefixes {
+		ipNets[i] = reconcile.ToIPNet(prefix)
+	}
+	return ipNets
+}
+
+// withoutPrefixes returns the list without the entries equal to one of the prefixes.
+// The others are returned as they are, so nothing gets rewritten into another form.
+func withoutPrefixes(list []net.IPNet, drop []netip.Prefix) []net.IPNet {
+	return slices.DeleteFunc(slices.Clone(list), func(n net.IPNet) bool {
+		prefix, ok := reconcile.PrefixFromIPNet(n)
+		return ok && slices.Contains(drop, prefix)
+	})
+}
+
+// writable tells if wgctrl sends the entry to the kernel as it is. wgctrl takes
+// every IP with a 4 byte form for IPv4, so an IPv4-mapped IPv6 entry such as
+// ::ffff:10.0.0.0/104 goes out as IPv4 with a mask too long for it and is rejected.
+func writable(n net.IPNet) bool {
+	_, bits := n.Mask.Size()
+	return bits != 128 || n.IP.To4() == nil
+}
+
+func prefixString(n net.IPNet) string {
+	if prefix, ok := reconcile.PrefixFromIPNet(n); ok {
+		return prefix.String()
+	}
+	return n.String()
+}