Cleanup iptables bug TODOs

There are many references to unimplemented iptables features that link to #170,
but that bug is about Istio support specifically. Istio is supported, so the
references should change.

Some TODOs are addressed, some removed because they are not features requested
by users, and some are left as implementation notes.

Fixes #170.

PiperOrigin-RevId: 379328488

10 files changed, 40 insertions, 59 deletions

diff --git a/pkg/sentry/socket/netfilter/BUILD b/pkg/sentry/socket/netfilter/BUILD
index 61b2c9755..608474fa1 100644
--- a/pkg/sentry/socket/netfilter/BUILD
+++ b/pkg/sentry/socket/netfilter/BUILD
@@ -25,6 +25,7 @@ go_library(
         "//pkg/log",
         "//pkg/marshal",
         "//pkg/sentry/kernel",
+        "//pkg/sentry/kernel/auth",
         "//pkg/syserr",
         "//pkg/tcpip",
         "//pkg/tcpip/header",
diff --git a/pkg/sentry/socket/netfilter/extensions.go b/pkg/sentry/socket/netfilter/extensions.go
index 6fc7781ad..3f1b4a17b 100644
--- a/pkg/sentry/socket/netfilter/extensions.go
+++ b/pkg/sentry/socket/netfilter/extensions.go
@@ -19,20 +19,12 @@ import (
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/bits"
+	"gvisor.dev/gvisor/pkg/sentry/kernel"
 	"gvisor.dev/gvisor/pkg/syserr"
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/stack"
 )
 
-// TODO(gvisor.dev/issue/170): The following per-matcher params should be
-// supported:
-// - Table name
-// - Match size
-// - User size
-// - Hooks
-// - Proto
-// - Family
-
 // matchMaker knows how to (un)marshal the matcher named name().
 type matchMaker interface {
 	// name is the matcher name as stored in the xt_entry_match struct.
@@ -43,7 +35,7 @@ type matchMaker interface {
 
 	// unmarshal converts from the ABI matcher struct to an
 	// stack.Matcher.
-	unmarshal(buf []byte, filter stack.IPHeaderFilter) (stack.Matcher, error)
+	unmarshal(task *kernel.Task, buf []byte, filter stack.IPHeaderFilter) (stack.Matcher, error)
 }
 
 type matcher interface {
@@ -94,12 +86,12 @@ func marshalEntryMatch(name string, data []byte) []byte {
 	return buf
 }
 
-func unmarshalMatcher(match linux.XTEntryMatch, filter stack.IPHeaderFilter, buf []byte) (stack.Matcher, error) {
+func unmarshalMatcher(task *kernel.Task, match linux.XTEntryMatch, filter stack.IPHeaderFilter, buf []byte) (stack.Matcher, error) {
 	matchMaker, ok := matchMakers[match.Name.String()]
 	if !ok {
 		return nil, fmt.Errorf("unsupported matcher with name %q", match.Name.String())
 	}
-	return matchMaker.unmarshal(buf, filter)
+	return matchMaker.unmarshal(task, buf, filter)
 }
 
 // targetMaker knows how to (un)marshal a target. Once registered,
diff --git a/pkg/sentry/socket/netfilter/ipv4.go b/pkg/sentry/socket/netfilter/ipv4.go
index cb78ef60b..d8bd86292 100644
--- a/pkg/sentry/socket/netfilter/ipv4.go
+++ b/pkg/sentry/socket/netfilter/ipv4.go
@@ -18,6 +18,7 @@ import (
 	"fmt"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/sentry/kernel"
 	"gvisor.dev/gvisor/pkg/syserr"
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
@@ -123,7 +124,7 @@ func getEntries4(table stack.Table, tablename linux.TableName) (linux.KernelIPTG
 	return entries, info
 }
 
-func modifyEntries4(stk *stack.Stack, optVal []byte, replace *linux.IPTReplace, table *stack.Table) (map[uint32]int, *syserr.Error) {
+func modifyEntries4(task *kernel.Task, stk *stack.Stack, optVal []byte, replace *linux.IPTReplace, table *stack.Table) (map[uint32]int, *syserr.Error) {
 	nflog("set entries: setting entries in table %q", replace.Name.String())
 
 	// Convert input into a list of rules and their offsets.
@@ -148,23 +149,19 @@ func modifyEntries4(stk *stack.Stack, optVal []byte, replace *linux.IPTReplace,
 			return nil, syserr.ErrInvalidArgument
 		}
 
-		// TODO(gvisor.dev/issue/170): We should support more IPTIP
-		// filtering fields.
 		filter, err := filterFromIPTIP(entry.IP)
 		if err != nil {
 			nflog("bad iptip: %v", err)
 			return nil, syserr.ErrInvalidArgument
 		}
 
-		// TODO(gvisor.dev/issue/170): Matchers and targets can specify
-		// that they only work for certain protocols, hooks, tables.
 		// Get matchers.
 		matchersSize := entry.TargetOffset - linux.SizeOfIPTEntry
 		if len(optVal) < int(matchersSize) {
 			nflog("entry doesn't have enough room for its matchers (only %d bytes remain)", len(optVal))
 			return nil, syserr.ErrInvalidArgument
 		}
-		matchers, err := parseMatchers(filter, optVal[:matchersSize])
+		matchers, err := parseMatchers(task, filter, optVal[:matchersSize])
 		if err != nil {
 			nflog("failed to parse matchers: %v", err)
 			return nil, syserr.ErrInvalidArgument
diff --git a/pkg/sentry/socket/netfilter/ipv6.go b/pkg/sentry/socket/netfilter/ipv6.go
index 5cb7fe4aa..c68230847 100644
--- a/pkg/sentry/socket/netfilter/ipv6.go
+++ b/pkg/sentry/socket/netfilter/ipv6.go
@@ -18,6 +18,7 @@ import (
 	"fmt"
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/sentry/kernel"
 	"gvisor.dev/gvisor/pkg/syserr"
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
@@ -126,7 +127,7 @@ func getEntries6(table stack.Table, tablename linux.TableName) (linux.KernelIP6T
 	return entries, info
 }
 
-func modifyEntries6(stk *stack.Stack, optVal []byte, replace *linux.IPTReplace, table *stack.Table) (map[uint32]int, *syserr.Error) {
+func modifyEntries6(task *kernel.Task, stk *stack.Stack, optVal []byte, replace *linux.IPTReplace, table *stack.Table) (map[uint32]int, *syserr.Error) {
 	nflog("set entries: setting entries in table %q", replace.Name.String())
 
 	// Convert input into a list of rules and their offsets.
@@ -151,23 +152,19 @@ func modifyEntries6(stk *stack.Stack, optVal []byte, replace *linux.IPTReplace,
 			return nil, syserr.ErrInvalidArgument
 		}
 
-		// TODO(gvisor.dev/issue/170): We should support more IPTIP
-		// filtering fields.
 		filter, err := filterFromIP6TIP(entry.IPv6)
 		if err != nil {
 			nflog("bad iptip: %v", err)
 			return nil, syserr.ErrInvalidArgument
 		}
 
-		// TODO(gvisor.dev/issue/170): Matchers and targets can specify
-		// that they only work for certain protocols, hooks, tables.
 		// Get matchers.
 		matchersSize := entry.TargetOffset - linux.SizeOfIP6TEntry
 		if len(optVal) < int(matchersSize) {
 			nflog("entry doesn't have enough room for its matchers (only %d bytes remain)", len(optVal))
 			return nil, syserr.ErrInvalidArgument
 		}
-		matchers, err := parseMatchers(filter, optVal[:matchersSize])
+		matchers, err := parseMatchers(task, filter, optVal[:matchersSize])
 		if err != nil {
 			nflog("failed to parse matchers: %v", err)
 			return nil, syserr.ErrInvalidArgument
diff --git a/pkg/sentry/socket/netfilter/netfilter.go b/pkg/sentry/socket/netfilter/netfilter.go
index e1c4b06fc..e3eade180 100644
--- a/pkg/sentry/socket/netfilter/netfilter.go
+++ b/pkg/sentry/socket/netfilter/netfilter.go
@@ -174,13 +174,12 @@ func setHooksAndUnderflow(info *linux.IPTGetinfo, table stack.Table, offset uint
 
 // SetEntries sets iptables rules for a single table. See
 // net/ipv4/netfilter/ip_tables.c:translate_table for reference.
-func SetEntries(stk *stack.Stack, optVal []byte, ipv6 bool) *syserr.Error {
+func SetEntries(task *kernel.Task, stk *stack.Stack, optVal []byte, ipv6 bool) *syserr.Error {
 	var replace linux.IPTReplace
 	replaceBuf := optVal[:linux.SizeOfIPTReplace]
 	optVal = optVal[linux.SizeOfIPTReplace:]
 	replace.UnmarshalBytes(replaceBuf)
 
-	// TODO(gvisor.dev/issue/170): Support other tables.
 	var table stack.Table
 	switch replace.Name.String() {
 	case filterTable:
@@ -188,16 +187,16 @@ func SetEntries(stk *stack.Stack, optVal []byte, ipv6 bool) *syserr.Error {
 	case natTable:
 		table = stack.EmptyNATTable()
 	default:
-		nflog("we don't yet support writing to the %q table (gvisor.dev/issue/170)", replace.Name.String())
+		nflog("unknown iptables table %q", replace.Name.String())
 		return syserr.ErrInvalidArgument
 	}
 
 	var err *syserr.Error
 	var offsets map[uint32]int
 	if ipv6 {
-		offsets, err = modifyEntries6(stk, optVal, &replace, &table)
+		offsets, err = modifyEntries6(task, stk, optVal, &replace, &table)
 	} else {
-		offsets, err = modifyEntries4(stk, optVal, &replace, &table)
+		offsets, err = modifyEntries4(task, stk, optVal, &replace, &table)
 	}
 	if err != nil {
 		return err
@@ -272,7 +271,6 @@ func SetEntries(stk *stack.Stack, optVal []byte, ipv6 bool) *syserr.Error {
 		table.Rules[ruleIdx] = rule
 	}
 
-	// TODO(gvisor.dev/issue/170): Support other chains.
 	// Since we don't support FORWARD, yet, make sure all other chains point to
 	// ACCEPT rules.
 	for hook, ruleIdx := range table.BuiltinChains {
@@ -287,7 +285,7 @@ func SetEntries(stk *stack.Stack, optVal []byte, ipv6 bool) *syserr.Error {
 		}
 	}
 
-	// TODO(gvisor.dev/issue/170): Check the following conditions:
+	// TODO(gvisor.dev/issue/6167): Check the following conditions:
 	// - There are no loops.
 	// - There are no chains without an unconditional final rule.
 	// - There are no chains without an unconditional underflow rule.
@@ -297,7 +295,7 @@ func SetEntries(stk *stack.Stack, optVal []byte, ipv6 bool) *syserr.Error {
 
 // parseMatchers parses 0 or more matchers from optVal. optVal should contain
 // only the matchers.
-func parseMatchers(filter stack.IPHeaderFilter, optVal []byte) ([]stack.Matcher, error) {
+func parseMatchers(task *kernel.Task, filter stack.IPHeaderFilter, optVal []byte) ([]stack.Matcher, error) {
 	nflog("set entries: parsing matchers of size %d", len(optVal))
 	var matchers []stack.Matcher
 	for len(optVal) > 0 {
@@ -321,13 +319,13 @@ func parseMatchers(filter stack.IPHeaderFilter, optVal []byte) ([]stack.Matcher,
 		}
 
 		// Parse the specific matcher.
-		matcher, err := unmarshalMatcher(match, filter, optVal[linux.SizeOfXTEntryMatch:match.MatchSize])
+		matcher, err := unmarshalMatcher(task, match, filter, optVal[linux.SizeOfXTEntryMatch:match.MatchSize])
 		if err != nil {
 			return nil, fmt.Errorf("failed to create matcher: %v", err)
 		}
 		matchers = append(matchers, matcher)
 
-		// TODO(gvisor.dev/issue/170): Check the revision field.
+		// TODO(gvisor.dev/issue/6167): Check the revision field.
 		optVal = optVal[match.MatchSize:]
 	}
 
diff --git a/pkg/sentry/socket/netfilter/owner_matcher.go b/pkg/sentry/socket/netfilter/owner_matcher.go
index 60845cab3..6eff2ae65 100644
--- a/pkg/sentry/socket/netfilter/owner_matcher.go
+++ b/pkg/sentry/socket/netfilter/owner_matcher.go
@@ -19,6 +19,8 @@ import (
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/marshal"
+	"gvisor.dev/gvisor/pkg/sentry/kernel"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
 	"gvisor.dev/gvisor/pkg/tcpip/stack"
 )
 
@@ -40,8 +42,8 @@ func (ownerMarshaler) name() string {
 func (ownerMarshaler) marshal(mr matcher) []byte {
 	matcher := mr.(*OwnerMatcher)
 	iptOwnerInfo := linux.IPTOwnerInfo{
-		UID: matcher.uid,
-		GID: matcher.gid,
+		UID: uint32(matcher.uid),
+		GID: uint32(matcher.gid),
 	}
 
 	// Support for UID and GID match.
@@ -63,7 +65,7 @@ func (ownerMarshaler) marshal(mr matcher) []byte {
 }
 
 // unmarshal implements matchMaker.unmarshal.
-func (ownerMarshaler) unmarshal(buf []byte, filter stack.IPHeaderFilter) (stack.Matcher, error) {
+func (ownerMarshaler) unmarshal(task *kernel.Task, buf []byte, filter stack.IPHeaderFilter) (stack.Matcher, error) {
 	if len(buf) < linux.SizeOfIPTOwnerInfo {
 		return nil, fmt.Errorf("buf has insufficient size for owner match: %d", len(buf))
 	}
@@ -72,11 +74,12 @@ func (ownerMarshaler) unmarshal(buf []byte, filter stack.IPHeaderFilter) (stack.
 	// exceed what's strictly necessary to hold matchData.
 	var matchData linux.IPTOwnerInfo
 	matchData.UnmarshalUnsafe(buf[:linux.SizeOfIPTOwnerInfo])
-	nflog("parseMatchers: parsed IPTOwnerInfo: %+v", matchData)
+	nflog("parsed IPTOwnerInfo: %+v", matchData)
 
 	var owner OwnerMatcher
-	owner.uid = matchData.UID
-	owner.gid = matchData.GID
+	creds := task.Credentials()
+	owner.uid = creds.UserNamespace.MapToKUID(auth.UID(matchData.UID))
+	owner.gid = creds.UserNamespace.MapToKGID(auth.GID(matchData.GID))
 
 	// Check flags.
 	if matchData.Match&linux.XT_OWNER_UID != 0 {
@@ -97,8 +100,8 @@ func (ownerMarshaler) unmarshal(buf []byte, filter stack.IPHeaderFilter) (stack.
 
 // OwnerMatcher matches against a UID and/or GID.
 type OwnerMatcher struct {
-	uid       uint32
-	gid       uint32
+	uid       auth.KUID
+	gid       auth.KGID
 	matchUID  bool
 	matchGID  bool
 	invertUID bool
@@ -113,7 +116,6 @@ func (*OwnerMatcher) name() string {
 // Match implements Matcher.Match.
 func (om *OwnerMatcher) Match(hook stack.Hook, pkt *stack.PacketBuffer, _, _ string) (bool, bool) {
 	// Support only for OUTPUT chain.
-	// TODO(gvisor.dev/issue/170): Need to support for POSTROUTING chain also.
 	if hook != stack.Output {
 		return false, true
 	}
@@ -126,7 +128,7 @@ func (om *OwnerMatcher) Match(hook stack.Hook, pkt *stack.PacketBuffer, _, _ str
 	var matches bool
 	// Check for UID match.
 	if om.matchUID {
-		if pkt.Owner.UID() == om.uid {
+		if auth.KUID(pkt.Owner.KUID()) == om.uid {
 			matches = true
 		}
 		if matches == om.invertUID {
@@ -137,7 +139,7 @@ func (om *OwnerMatcher) Match(hook stack.Hook, pkt *stack.PacketBuffer, _, _ str
 	// Check for GID match.
 	if om.matchGID {
 		matches = false
-		if pkt.Owner.GID() == om.gid {
+		if auth.KGID(pkt.Owner.KGID()) == om.gid {
 			matches = true
 		}
 		if matches == om.invertGID {
diff --git a/pkg/sentry/socket/netfilter/targets.go b/pkg/sentry/socket/netfilter/targets.go
index fa5456eee..7d83e708f 100644
--- a/pkg/sentry/socket/netfilter/targets.go
+++ b/pkg/sentry/socket/netfilter/targets.go
@@ -331,7 +331,6 @@ func (*redirectTargetMaker) unmarshal(buf []byte, filter stack.IPHeaderFilter) (
 		return nil, syserr.ErrInvalidArgument
 	}
 
-	// TODO(gvisor.dev/issue/170): Check if the flags are valid.
 	// Also check if we need to map ports or IP.
 	// For now, redirect target only supports destination port change.
 	// Port range and IP range are not supported yet.
@@ -340,7 +339,6 @@ func (*redirectTargetMaker) unmarshal(buf []byte, filter stack.IPHeaderFilter) (
 		return nil, syserr.ErrInvalidArgument
 	}
 
-	// TODO(gvisor.dev/issue/170): Port range is not supported yet.
 	if nfRange.RangeIPV4.MinPort != nfRange.RangeIPV4.MaxPort {
 		nflog("redirectTargetMaker: MinPort != MaxPort (%d, %d)", nfRange.RangeIPV4.MinPort, nfRange.RangeIPV4.MaxPort)
 		return nil, syserr.ErrInvalidArgument
@@ -502,7 +500,6 @@ func (*snatTargetMakerV4) unmarshal(buf []byte, filter stack.IPHeaderFilter) (ta
 		return nil, syserr.ErrInvalidArgument
 	}
 
-	// TODO(gvisor.dev/issue/170): Port range is not supported yet.
 	if nfRange.RangeIPV4.MinPort != nfRange.RangeIPV4.MaxPort {
 		nflog("snatTargetMakerV4: MinPort != MaxPort (%d, %d)", nfRange.RangeIPV4.MinPort, nfRange.RangeIPV4.MaxPort)
 		return nil, syserr.ErrInvalidArgument
@@ -594,7 +591,6 @@ func (*snatTargetMakerV6) unmarshal(buf []byte, filter stack.IPHeaderFilter) (ta
 // translateToStandardTarget translates from the value in a
 // linux.XTStandardTarget to an stack.Verdict.
 func translateToStandardTarget(val int32, netProto tcpip.NetworkProtocolNumber) (target, *syserr.Error) {
-	// TODO(gvisor.dev/issue/170): Support other verdicts.
 	switch val {
 	case -linux.NF_ACCEPT - 1:
 		return &acceptTarget{stack.AcceptTarget{
diff --git a/pkg/sentry/socket/netfilter/tcp_matcher.go b/pkg/sentry/socket/netfilter/tcp_matcher.go
index 95bb9826e..e5b73a976 100644
--- a/pkg/sentry/socket/netfilter/tcp_matcher.go
+++ b/pkg/sentry/socket/netfilter/tcp_matcher.go
@@ -19,6 +19,7 @@ import (
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/marshal"
+	"gvisor.dev/gvisor/pkg/sentry/kernel"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
 	"gvisor.dev/gvisor/pkg/tcpip/stack"
 )
@@ -50,7 +51,7 @@ func (tcpMarshaler) marshal(mr matcher) []byte {
 }
 
 // unmarshal implements matchMaker.unmarshal.
-func (tcpMarshaler) unmarshal(buf []byte, filter stack.IPHeaderFilter) (stack.Matcher, error) {
+func (tcpMarshaler) unmarshal(_ *kernel.Task, buf []byte, filter stack.IPHeaderFilter) (stack.Matcher, error) {
 	if len(buf) < linux.SizeOfXTTCP {
 		return nil, fmt.Errorf("buf has insufficient size for TCP match: %d", len(buf))
 	}
@@ -95,8 +96,6 @@ func (*TCPMatcher) name() string {
 
 // Match implements Matcher.Match.
 func (tm *TCPMatcher) Match(hook stack.Hook, pkt *stack.PacketBuffer, _, _ string) (bool, bool) {
-	// TODO(gvisor.dev/issue/170): Proto checks should ultimately be moved
-	// into the stack.Check codepath as matchers are added.
 	switch pkt.NetworkProtocolNumber {
 	case header.IPv4ProtocolNumber:
 		netHeader := header.IPv4(pkt.NetworkHeader().View())
diff --git a/pkg/sentry/socket/netfilter/udp_matcher.go b/pkg/sentry/socket/netfilter/udp_matcher.go
index fb8be27e6..aa72ee70c 100644
--- a/pkg/sentry/socket/netfilter/udp_matcher.go
+++ b/pkg/sentry/socket/netfilter/udp_matcher.go
@@ -19,6 +19,7 @@ import (
 
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/marshal"
+	"gvisor.dev/gvisor/pkg/sentry/kernel"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
 	"gvisor.dev/gvisor/pkg/tcpip/stack"
 )
@@ -50,7 +51,7 @@ func (udpMarshaler) marshal(mr matcher) []byte {
 }
 
 // unmarshal implements matchMaker.unmarshal.
-func (udpMarshaler) unmarshal(buf []byte, filter stack.IPHeaderFilter) (stack.Matcher, error) {
+func (udpMarshaler) unmarshal(_ *kernel.Task, buf []byte, filter stack.IPHeaderFilter) (stack.Matcher, error) {
 	if len(buf) < linux.SizeOfXTUDP {
 		return nil, fmt.Errorf("buf has insufficient size for UDP match: %d", len(buf))
 	}
@@ -92,8 +93,6 @@ func (*UDPMatcher) name() string {
 
 // Match implements Matcher.Match.
 func (um *UDPMatcher) Match(hook stack.Hook, pkt *stack.PacketBuffer, _, _ string) (bool, bool) {
-	// TODO(gvisor.dev/issue/170): Proto checks should ultimately be moved
-	// into the stack.Check codepath as matchers are added.
 	switch pkt.NetworkProtocolNumber {
 	case header.IPv4ProtocolNumber:
 		netHeader := header.IPv4(pkt.NetworkHeader().View())
diff --git a/pkg/sentry/socket/netstack/netstack.go b/pkg/sentry/socket/netstack/netstack.go
index d4b1bad67..11ba80497 100644
--- a/pkg/sentry/socket/netstack/netstack.go
+++ b/pkg/sentry/socket/netstack/netstack.go
@@ -2105,10 +2105,10 @@ func setSockOptIPv6(t *kernel.Task, s socket.SocketOps, ep commonEndpoint, name
 			return syserr.ErrNoDevice
 		}
 		// Stack must be a netstack stack.
-		return netfilter.SetEntries(stack.(*Stack).Stack, optVal, true)
+		return netfilter.SetEntries(t, stack.(*Stack).Stack, optVal, true)
 
 	case linux.IP6T_SO_SET_ADD_COUNTERS:
-		// TODO(gvisor.dev/issue/170): Counter support.
+		log.Infof("IP6T_SO_SET_ADD_COUNTERS is not supported")
 		return nil
 
 	default:
@@ -2348,10 +2348,10 @@ func setSockOptIP(t *kernel.Task, s socket.SocketOps, ep commonEndpoint, name in
 			return syserr.ErrNoDevice
 		}
 		// Stack must be a netstack stack.
-		return netfilter.SetEntries(stack.(*Stack).Stack, optVal, false)
+		return netfilter.SetEntries(t, stack.(*Stack).Stack, optVal, false)
 
 	case linux.IPT_SO_SET_ADD_COUNTERS:
-		// TODO(gvisor.dev/issue/170): Counter support.
+		log.Infof("IPT_SO_SET_ADD_COUNTERS is not supported")
 		return nil
 
 	case linux.IP_ADD_SOURCE_MEMBERSHIP,