Pull request: aghnet: fix ipset init errors

Updates #4027.

Squashed commit of the following:

commit 9ac0cc27ca94e630cc321c90b60b271499af4d9b
Author: Ainar Garipov <A.Garipov@AdGuard.COM>
Date:   Mon Dec 27 20:26:22 2021 +0300

    aghnet: fix ipset init errors

CHANGELOG.md

@@ -29,6 +29,7 @@ and this project adheres to
 
 ### Fixed
 
+- `ipset` initialization bugs ([#4027]).
 - Legacy DNS rewrites from a wildcard pattern to a subdomain ([#4016]).
 - Service not being stopped before running the `uninstall` service action
   ([#3868]).
@@ -46,6 +47,7 @@ and this project adheres to
 [#3987]: https://github.com/AdguardTeam/AdGuardHome/issues/3987
 [#4008]: https://github.com/AdguardTeam/AdGuardHome/issues/4008
 [#4016]: https://github.com/AdguardTeam/AdGuardHome/issues/4016
+[#4027]: https://github.com/AdguardTeam/AdGuardHome/issues/4027
 
 
 

internal/aghnet/ipset.go

@@ -20,7 +20,12 @@ type IpsetManager interface {
 //
 //   DOMAIN[,DOMAIN].../IPSET_NAME[,IPSET_NAME]...
 //
-// The error is of type *aghos.UnsupportedError if the OS is not supported.
+// If ipsetConf is empty, msg and err are nil.  The error is of type
+// *aghos.UnsupportedError if the OS is not supported.
 func NewIpsetManager(ipsetConf []string) (mgr IpsetManager, err error) {
+	if len(ipsetConf) == 0 {
+		return nil, nil
+	}
+
 	return newIpsetMgr(ipsetConf)
 }

internal/aghnet/ipset_linux.go

@@ -14,6 +14,7 @@ import (
 	"github.com/digineo/go-ipset/v2"
 	"github.com/mdlayher/netlink"
 	"github.com/ti-mo/netfilter"
+	"golang.org/x/sys/unix"
 )
 
 // How to test on a real Linux machine:
@@ -42,11 +43,17 @@ import (
 
 // newIpsetMgr returns a new Linux ipset manager.
 func newIpsetMgr(ipsetConf []string) (set IpsetManager, err error) {
-	dial := func(pf netfilter.ProtoFamily, conf *netlink.Config) (conn ipsetConn, err error) {
-		return ipset.Dial(pf, conf)
+	return newIpsetMgrWithDialer(ipsetConf, defaultDial)
 }
 
-	return newIpsetMgrWithDialer(ipsetConf, dial)
+// defaultDial is the default netfilter dialing function.
+func defaultDial(pf netfilter.ProtoFamily, conf *netlink.Config) (conn ipsetConn, err error) {
+	conn, err = ipset.Dial(pf, conf)
+	if err != nil {
+		return nil, err
+	}
+
+	return conn, nil
 }
 
 // ipsetConn is the ipset conn interface.
@@ -103,8 +110,8 @@ func (m *ipsetMgr) dialNetfilter(conf *netlink.Config) (err error) {
 	// The kernel API does not actually require two sockets but package
 	// github.com/digineo/go-ipset does.
 	//
-	// TODO(a.garipov): Perhaps we can ditch package ipset altogether and
-	// just use packages netfilter and netlink.
+	// TODO(a.garipov): Perhaps we can ditch package ipset altogether and just
+	// use packages netfilter and netlink.
 	m.ipv4Conn, err = m.dial(netfilter.ProtoIPv4, conf)
 	if err != nil {
 		return fmt.Errorf("dialing v4: %w", err)
@@ -214,6 +221,14 @@ func newIpsetMgrWithDialer(ipsetConf []string, dial ipsetDialer) (mgr IpsetManag
 
 	err = m.dialNetfilter(&netlink.Config{})
 	if err != nil {
+		if errors.Is(err, unix.EPROTONOSUPPORT) {
+			// The implementation doesn't support this protocol version.  Just
+			// issue a warning.
+			log.Info("ipset: dialing netfilter: warning: %s", err)
+
+			return nil, nil
+		}
+
 		return nil, fmt.Errorf("dialing netfilter: %w", err)
 	}
 

internal/dnsforward/ipset.go

@@ -24,20 +24,19 @@ type ipsetCtx struct {
 func (c *ipsetCtx) init(ipsetConf []string) (err error) {
 	c.ipsetMgr, err = aghnet.NewIpsetManager(ipsetConf)
 	if errors.Is(err, os.ErrInvalid) || errors.Is(err, os.ErrPermission) {
-		// ipset cannot currently be initialized if the server was
-		// installed from Snap or when the user or the binary doesn't
-		// have the required permissions, or when the kernel doesn't
-		// support netfilter.
+		// ipset cannot currently be initialized if the server was installed
+		// from Snap or when the user or the binary doesn't have the required
+		// permissions, or when the kernel doesn't support netfilter.
 		//
 		// Log and go on.
 		//
-		// TODO(a.garipov): The Snap problem can probably be solved if
-		// we add the netlink-connector interface plug.
-		log.Info("warning: cannot initialize ipset: %s", err)
+		// TODO(a.garipov): The Snap problem can probably be solved if we add
+		// the netlink-connector interface plug.
+		log.Info("ipset: warning: cannot initialize: %s", err)
 
 		return nil
 	} else if unsupErr := (&aghos.UnsupportedError{}); errors.As(err, &unsupErr) {
-		log.Info("warning: %s", err)
+		log.Info("ipset: warning: %s", err)
 
 		return nil
 	} else if err != nil {