From 1015423a8fbaca4934840982dfd20a5d34c6d029 Mon Sep 17 00:00:00 2001
From: Vladimir Avtsenov <vladimir.lsk.cool@gmail.com>
Date: Fri, 6 Sep 2024 15:48:15 +0300
Subject: [PATCH] catch interface up/down

---
 README.md                              |  2 +-
 kvas2.go                               | 50 ++++++++++++++++++++++++--
 netfilter-helper/interface-to-ipset.go | 50 ++++++++++++++++----------
 3 files changed, 80 insertions(+), 22 deletions(-)

diff --git a/README.md b/README.md
index 6e84ede..a5b68fe 100644
--- a/README.md
+++ b/README.md
@@ -10,7 +10,7 @@ Realized features:
 - [X] IPSet integration
 - [X] IP integration
 - [X] IPTables rules to IPSet
-- [ ] Catch interface up/down
+- [X] Catch interface up/down
 - [ ] Catch `netfilter.d` event
 - [ ] Rule composer (CRUD)
 - [ ] GORM integration
diff --git a/kvas2.go b/kvas2.go
index 7cd3b83..824c9d7 100644
--- a/kvas2.go
+++ b/kvas2.go
@@ -13,6 +13,7 @@ import (
 	"kvas2-go/netfilter-helper"
 
 	"github.com/rs/zerolog/log"
+	"github.com/vishvananda/netlink"
 )
 
 var (
@@ -98,11 +99,54 @@ func (a *App) Listen(ctx context.Context) []error {
 		}
 	}()
 
-	select {
-	case <-ctx.Done():
-	case <-isError:
+	link := make(chan netlink.LinkUpdate)
+	done := make(chan struct{})
+	netlink.LinkSubscribe(link, done)
+
+Loop:
+	for {
+		select {
+		case event := <-link:
+			switch event.Change {
+			case 0x00000001:
+				log.Debug().
+					Str("interface", event.Link.Attrs().Name).
+					Str("operstatestr", event.Attrs().OperState.String()).
+					Int("operstate", int(event.Attrs().OperState)).
+					Msg("interface change")
+				if event.Attrs().OperState != netlink.OperDown {
+					for _, group := range a.Groups {
+						if group.Interface == event.Link.Attrs().Name {
+							err = group.ifaceToIPSet.IfaceHandle()
+							if err != nil {
+								log.Error().Int("group", group.ID).Err(err).Msg("error while handling interface up")
+							}
+						}
+					}
+				}
+			case 0xFFFFFFFF:
+				switch event.Header.Type {
+				case 16:
+					log.Debug().
+						Str("interface", event.Link.Attrs().Name).
+						Int("type", int(event.Header.Type)).
+						Msg("interface add")
+				case 17:
+					log.Debug().
+						Str("interface", event.Link.Attrs().Name).
+						Int("type", int(event.Header.Type)).
+						Msg("interface del")
+				}
+			}
+		case <-ctx.Done():
+			break Loop
+		case <-isError:
+			break Loop
+		}
 	}
 
+	close(done)
+
 	errs2 := a.dnsOverrider.Disable()
 	if errs2 != nil {
 		handleErrors(errs2)
diff --git a/netfilter-helper/interface-to-ipset.go b/netfilter-helper/interface-to-ipset.go
index 2c3c6d1..03ba3cc 100644
--- a/netfilter-helper/interface-to-ipset.go
+++ b/netfilter-helper/interface-to-ipset.go
@@ -25,18 +25,41 @@ type IfaceToIPSet struct {
 	ipRoute *netlink.Route
 }
 
+func (r *IfaceToIPSet) IfaceHandle() error {
+	// Find interface
+	iface, err := netlink.LinkByName(r.IfaceName)
+	if err != nil {
+		log.Warn().Str("interface", r.IfaceName).Err(err).Msg("error while getting interface")
+	}
+
+	// Mapping iface with table
+	if iface != nil {
+		route := &netlink.Route{
+			LinkIndex: iface.Attrs().Index,
+			Table:     r.table,
+			Dst:       &net.IPNet{IP: []byte{0, 0, 0, 0}, Mask: []byte{0, 0, 0, 0}},
+		}
+		// Delete rule if exists
+		err = netlink.RouteDel(route)
+		if err != nil {
+			log.Warn().Str("interface", r.IfaceName).Err(err).Msg("error while deleting route")
+		}
+		err = netlink.RouteAdd(route)
+		if err != nil {
+			return fmt.Errorf("error while mapping iface with table: %w", err)
+		}
+		r.ipRoute = route
+	}
+
+	return nil
+}
+
 func (r *IfaceToIPSet) ForceEnable() error {
 	// Release used mark and table
 	r.Disable()
 	r.mark = 0
 	r.table = 0
 
-	// Find interface
-	iface, err := netlink.LinkByName(r.IfaceName)
-	if err != nil {
-		log.Warn().Str("interface", r.IfaceName).Msg("error while getting interface")
-	}
-
 	// Find unused mark and table
 	markMap := make(map[uint32]struct{})
 	tableMap := map[int]struct{}{0: {}, 253: {}, 254: {}, 255: {}}
@@ -152,18 +175,9 @@ func (r *IfaceToIPSet) ForceEnable() error {
 	}
 	r.ipRule = rule
 
-	// Mapping iface with table
-	if iface != nil {
-		route := &netlink.Route{
-			LinkIndex: iface.Attrs().Index,
-			Table:     rule.Table,
-			Dst:       &net.IPNet{IP: []byte{0, 0, 0, 0}, Mask: []byte{0, 0, 0, 0}},
-		}
-		err = netlink.RouteAdd(route)
-		if err != nil {
-			return fmt.Errorf("error while mapping iface with table: %w", err)
-		}
-		r.ipRoute = route
+	err = r.IfaceHandle()
+	if err != nil {
+		return nil
 	}
 
 	return nil