Plumbing for iptables sockopts.

PiperOrigin-RevId: 261413396

pkg/sentry/socket/epsocket/BUILD

@@ -31,6 +31,7 @@ go_library(
         "//pkg/sentry/kernel/time",
         "//pkg/sentry/safemem",
         "//pkg/sentry/socket",
+        "//pkg/sentry/socket/netfilter",
         "//pkg/sentry/unimpl",
         "//pkg/sentry/usermem",
         "//pkg/syserr",
@@ -38,6 +39,7 @@ go_library(
         "//pkg/tcpip",
         "//pkg/tcpip/buffer",
         "//pkg/tcpip/header",
+        "//pkg/tcpip/iptables",
         "//pkg/tcpip/network/ipv4",
         "//pkg/tcpip/network/ipv6",
         "//pkg/tcpip/stack",

pkg/sentry/socket/epsocket/epsocket.go

@@ -43,6 +43,7 @@ import (
 	ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
 	"gvisor.dev/gvisor/pkg/sentry/safemem"
 	"gvisor.dev/gvisor/pkg/sentry/socket"
+	"gvisor.dev/gvisor/pkg/sentry/socket/netfilter"
 	"gvisor.dev/gvisor/pkg/sentry/unimpl"
 	"gvisor.dev/gvisor/pkg/sentry/usermem"
 	"gvisor.dev/gvisor/pkg/syserr"
@@ -624,7 +625,7 @@ func (s *SocketOperations) Shutdown(t *kernel.Task, how int) *syserr.Error {
 
 // GetSockOpt implements the linux syscall getsockopt(2) for sockets backed by
 // tcpip.Endpoint.
-func (s *SocketOperations) GetSockOpt(t *kernel.Task, level, name, outLen int) (interface{}, *syserr.Error) {
+func (s *SocketOperations) GetSockOpt(t *kernel.Task, level, name int, outPtr usermem.Addr, outLen int) (interface{}, *syserr.Error) {
 	// TODO(b/78348848): Unlike other socket options, SO_TIMESTAMP is
 	// implemented specifically for epsocket.SocketOperations rather than
 	// commonEndpoint. commonEndpoint should be extended to support socket
@@ -655,6 +656,33 @@ func (s *SocketOperations) GetSockOpt(t *kernel.Task, level, name, outLen int) (
 		return val, nil
 	}
 
+	if s.skType == linux.SOCK_RAW && level == linux.IPPROTO_IP {
+		switch name {
+		case linux.IPT_SO_GET_INFO:
+			if outLen < linux.SizeOfIPTGetinfo {
+				return nil, syserr.ErrInvalidArgument
+			}
+
+			info, err := netfilter.GetInfo(t, s.Endpoint, outPtr)
+			if err != nil {
+				return nil, err
+			}
+			return info, nil
+
+		case linux.IPT_SO_GET_ENTRIES:
+			if outLen < linux.SizeOfIPTGetEntries {
+				return nil, syserr.ErrInvalidArgument
+			}
+
+			entries, err := netfilter.GetEntries(t, s.Endpoint, outPtr, outLen)
+			if err != nil {
+				return nil, err
+			}
+			return entries, nil
+
+		}
+	}
+
 	return GetSockOpt(t, s, s.Endpoint, s.family, s.skType, level, name, outLen)
 }
 

pkg/sentry/socket/epsocket/stack.go

@@ -18,9 +18,11 @@ import (
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/log"
 	"gvisor.dev/gvisor/pkg/sentry/inet"
+	"gvisor.dev/gvisor/pkg/sentry/socket/netfilter"
 	"gvisor.dev/gvisor/pkg/syserr"
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
+	"gvisor.dev/gvisor/pkg/tcpip/iptables"
 	"gvisor.dev/gvisor/pkg/tcpip/network/ipv4"
 	"gvisor.dev/gvisor/pkg/tcpip/network/ipv6"
 	"gvisor.dev/gvisor/pkg/tcpip/stack"
@@ -188,3 +190,14 @@ func (s *Stack) RouteTable() []inet.Route {
 
 	return routeTable
 }
+
+// IPTables returns the stack's iptables.
+func (s *Stack) IPTables() (iptables.IPTables, error) {
+	return s.Stack.IPTables(), nil
+}
+
+// FillDefaultIPTables sets the stack's iptables to the default tables, which
+// allow and do not modify all traffic.
+func (s *Stack) FillDefaultIPTables() error {
+	return netfilter.FillDefaultIPTables(s.Stack)
+}

pkg/sentry/socket/hostinet/socket.go

@@ -272,7 +272,7 @@ func (s *socketOperations) Shutdown(t *kernel.Task, how int) *syserr.Error {
 }
 
 // GetSockOpt implements socket.Socket.GetSockOpt.
-func (s *socketOperations) GetSockOpt(t *kernel.Task, level int, name int, outLen int) (interface{}, *syserr.Error) {
+func (s *socketOperations) GetSockOpt(t *kernel.Task, level int, name int, outPtr usermem.Addr, outLen int) (interface{}, *syserr.Error) {
 	if outLen < 0 {
 		return nil, syserr.ErrInvalidArgument
 	}

pkg/sentry/socket/netfilter/BUILD

@@ -0,0 +1,23 @@
+package(licenses = ["notice"])
+
+load("//tools/go_stateify:defs.bzl", "go_library")
+
+go_library(
+    name = "netfilter",
+    srcs = [
+        "netfilter.go",
+    ],
+    importpath = "gvisor.dev/gvisor/pkg/sentry/socket/netfilter",
+    # This target depends on netstack and should only be used by epsocket,
+    # which is allowed to depend on netstack.
+    visibility = ["//pkg/sentry:internal"],
+    deps = [
+        "//pkg/abi/linux",
+        "//pkg/sentry/kernel",
+        "//pkg/sentry/usermem",
+        "//pkg/syserr",
+        "//pkg/tcpip",
+        "//pkg/tcpip/iptables",
+        "//pkg/tcpip/stack",
+    ],
+)

pkg/sentry/socket/netfilter/netfilter.go

@@ -0,0 +1,46 @@
+// Copyright 2019 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package netfilter helps the sentry interact with netstack's netfilter
+// capabilities.
+package netfilter
+
+import (
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/sentry/kernel"
+	"gvisor.dev/gvisor/pkg/sentry/usermem"
+	"gvisor.dev/gvisor/pkg/syserr"
+	"gvisor.dev/gvisor/pkg/tcpip"
+	"gvisor.dev/gvisor/pkg/tcpip/iptables"
+	"gvisor.dev/gvisor/pkg/tcpip/stack"
+)
+
+// GetInfo returns information about iptables.
+func GetInfo(t *kernel.Task, ep tcpip.Endpoint, outPtr usermem.Addr) (linux.IPTGetinfo, *syserr.Error) {
+	// TODO(b/129292233): Implement.
+	return linux.IPTGetinfo{}, syserr.ErrInvalidArgument
+}
+
+// GetEntries returns netstack's iptables rules encoded for the iptables tool.
+func GetEntries(t *kernel.Task, ep tcpip.Endpoint, outPtr usermem.Addr, outLen int) (linux.KernelIPTGetEntries, *syserr.Error) {
+	// TODO(b/129292233): Implement.
+	return linux.KernelIPTGetEntries{}, syserr.ErrInvalidArgument
+}
+
+// FillDefaultIPTables sets stack's IPTables to the default tables and
+// populates them with metadata.
+func FillDefaultIPTables(stack *stack.Stack) error {
+	stack.SetIPTables(iptables.DefaultTables())
+	return nil
+}

pkg/sentry/socket/netlink/socket.go

@@ -289,7 +289,7 @@ func (s *Socket) Shutdown(t *kernel.Task, how int) *syserr.Error {
 }
 
 // GetSockOpt implements socket.Socket.GetSockOpt.
-func (s *Socket) GetSockOpt(t *kernel.Task, level int, name int, outLen int) (interface{}, *syserr.Error) {
+func (s *Socket) GetSockOpt(t *kernel.Task, level int, name int, outPtr usermem.Addr, outLen int) (interface{}, *syserr.Error) {
 	switch level {
 	case linux.SOL_SOCKET:
 		switch name {

pkg/sentry/socket/rpcinet/socket.go

@@ -395,7 +395,7 @@ func (s *socketOperations) Shutdown(t *kernel.Task, how int) *syserr.Error {
 }
 
 // GetSockOpt implements socket.Socket.GetSockOpt.
-func (s *socketOperations) GetSockOpt(t *kernel.Task, level int, name int, outLen int) (interface{}, *syserr.Error) {
+func (s *socketOperations) GetSockOpt(t *kernel.Task, level int, name int, outPtr usermem.Addr, outLen int) (interface{}, *syserr.Error) {
 	// SO_RCVTIMEO and SO_SNDTIMEO are special because blocking is performed
 	// within the sentry.
 	if level == linux.SOL_SOCKET && name == linux.SO_RCVTIMEO {

pkg/sentry/socket/socket.go

@@ -64,7 +64,7 @@ type Socket interface {
 	Shutdown(t *kernel.Task, how int) *syserr.Error
 
 	// GetSockOpt implements the getsockopt(2) linux syscall.
-	GetSockOpt(t *kernel.Task, level int, name int, outLen int) (interface{}, *syserr.Error)
+	GetSockOpt(t *kernel.Task, level int, name int, outPtr usermem.Addr, outLen int) (interface{}, *syserr.Error)
 
 	// SetSockOpt implements the setsockopt(2) linux syscall.
 	SetSockOpt(t *kernel.Task, level int, name int, opt []byte) *syserr.Error

pkg/sentry/socket/unix/unix.go

@@ -166,7 +166,7 @@ func (s *SocketOperations) Ioctl(ctx context.Context, _ *fs.File, io usermem.IO,
 
 // GetSockOpt implements the linux syscall getsockopt(2) for sockets backed by
 // a transport.Endpoint.
-func (s *SocketOperations) GetSockOpt(t *kernel.Task, level, name, outLen int) (interface{}, *syserr.Error) {
+func (s *SocketOperations) GetSockOpt(t *kernel.Task, level, name int, outPtr usermem.Addr, outLen int) (interface{}, *syserr.Error) {
 	return epsocket.GetSockOpt(t, s, s.ep, linux.AF_UNIX, s.ep.Type(), level, name, outLen)
 }
 

pkg/sentry/syscalls/linux/sys_socket.go

@@ -460,7 +460,7 @@ func GetSockOpt(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sy
 	}
 
 	// Call syscall implementation then copy both value and value len out.
-	v, e := getSockOpt(t, s, int(level), int(name), int(optLen))
+	v, e := getSockOpt(t, s, int(level), int(name), optValAddr, int(optLen))
 	if e != nil {
 		return 0, nil, e.ToError()
 	}
@@ -483,7 +483,7 @@ func GetSockOpt(t *kernel.Task, args arch.SyscallArguments) (uintptr, *kernel.Sy
 
 // getSockOpt tries to handle common socket options, or dispatches to a specific
 // socket implementation.
-func getSockOpt(t *kernel.Task, s socket.Socket, level, name, len int) (interface{}, *syserr.Error) {
+func getSockOpt(t *kernel.Task, s socket.Socket, level, name int, optValAddr usermem.Addr, len int) (interface{}, *syserr.Error) {
 	if level == linux.SOL_SOCKET {
 		switch name {
 		case linux.SO_TYPE, linux.SO_DOMAIN, linux.SO_PROTOCOL:
@@ -505,7 +505,7 @@ func getSockOpt(t *kernel.Task, s socket.Socket, level, name, len int) (interfac
 		}
 	}
 
-	return s.GetSockOpt(t, level, name, len)
+	return s.GetSockOpt(t, level, name, optValAddr, len)
 }
 
 // SetSockOpt implements the linux syscall setsockopt(2).

pkg/tcpip/BUILD

@@ -12,6 +12,7 @@ go_library(
     visibility = ["//visibility:public"],
     deps = [
         "//pkg/tcpip/buffer",
+        "//pkg/tcpip/iptables",
         "//pkg/waiter",
     ],
 )

pkg/tcpip/iptables/BUILD

@@ -11,8 +11,5 @@ go_library(
     ],
     importpath = "gvisor.dev/gvisor/pkg/tcpip/iptables",
     visibility = ["//visibility:public"],
-    deps = [
-        "//pkg/tcpip",
-        "//pkg/tcpip/buffer",
-    ],
+    deps = ["//pkg/tcpip/buffer"],
 )

pkg/tcpip/iptables/iptables.go

@@ -32,8 +32,8 @@ const (
 
 // DefaultTables returns a default set of tables. Each chain is set to accept
 // all packets.
-func DefaultTables() *IPTables {
-	return &IPTables{
+func DefaultTables() IPTables {
+	return IPTables{
 		Tables: map[string]Table{
 			tablenameNat: Table{
 				BuiltinChains: map[Hook]Chain{

pkg/tcpip/iptables/types.go

@@ -15,7 +15,6 @@
 package iptables
 
 import (
-	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 )
 
@@ -128,15 +127,29 @@ type Table struct {
 	// UserChains, and its purpose is to make looking up tables by name
 	// fast.
 	Chains map[string]*Chain
+
+	// Metadata holds information about the Table that is useful to users
+	// of IPTables, but not to the netstack IPTables code itself.
+	metadata interface{}
 }
 
 // ValidHooks returns a bitmap of the builtin hooks for the given table.
-func (table *Table) ValidHooks() (uint32, *tcpip.Error) {
+func (table *Table) ValidHooks() uint32 {
 	hooks := uint32(0)
 	for hook, _ := range table.BuiltinChains {
 		hooks |= 1 << hook
 	}
-	return hooks, nil
+	return hooks
+}
+
+// Metadata returns the metadata object stored in table.
+func (table *Table) Metadata() interface{} {
+	return table.metadata
+}
+
+// SetMetadata sets the metadata object stored in table.
+func (table *Table) SetMetadata(metadata interface{}) {
+	table.metadata = metadata
 }
 
 // A Chain defines a list of rules for packet processing. When a packet

pkg/tcpip/stack/BUILD

@@ -24,6 +24,7 @@ go_library(
         "//pkg/tcpip/buffer",
         "//pkg/tcpip/hash/jenkins",
         "//pkg/tcpip/header",
+        "//pkg/tcpip/iptables",
         "//pkg/tcpip/ports",
         "//pkg/tcpip/seqnum",
         "//pkg/waiter",
@@ -42,6 +43,7 @@ go_test(
         "//pkg/tcpip",
         "//pkg/tcpip/buffer",
         "//pkg/tcpip/header",
+        "//pkg/tcpip/iptables",
         "//pkg/tcpip/link/channel",
         "//pkg/tcpip/link/loopback",
         "//pkg/waiter",

pkg/tcpip/stack/stack.go

@@ -32,6 +32,7 @@ import (
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
+	"gvisor.dev/gvisor/pkg/tcpip/iptables"
 	"gvisor.dev/gvisor/pkg/tcpip/ports"
 	"gvisor.dev/gvisor/pkg/tcpip/seqnum"
 	"gvisor.dev/gvisor/pkg/waiter"
@@ -372,6 +373,9 @@ type Stack struct {
 
 	// handleLocal allows non-loopback interfaces to loop packets.
 	handleLocal bool
+
+	// tables are the iptables packet filtering and manipulation rules.
+	tables iptables.IPTables
 }
 
 // Options contains optional Stack configuration.
@@ -1166,3 +1170,13 @@ func (s *Stack) LeaveGroup(protocol tcpip.NetworkProtocolNumber, nicID tcpip.NIC
 	}
 	return tcpip.ErrUnknownNICID
 }
+
+// IPTables returns the stack's iptables.
+func (s *Stack) IPTables() iptables.IPTables {
+	return s.tables
+}
+
+// SetIPTables sets the stack's iptables.
+func (s *Stack) SetIPTables(ipt iptables.IPTables) {
+	s.tables = ipt
+}

pkg/tcpip/stack/transport_test.go

@@ -19,6 +19,7 @@ import (
 
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
+	"gvisor.dev/gvisor/pkg/tcpip/iptables"
 	"gvisor.dev/gvisor/pkg/tcpip/link/channel"
 	"gvisor.dev/gvisor/pkg/tcpip/link/loopback"
 	"gvisor.dev/gvisor/pkg/tcpip/stack"
@@ -200,6 +201,10 @@ func (f *fakeTransportEndpoint) State() uint32 {
 func (f *fakeTransportEndpoint) ModerateRecvBuf(copied int) {
 }
 
+func (f *fakeTransportEndpoint) IPTables() (iptables.IPTables, error) {
+	return iptables.IPTables{}, nil
+}
+
 type fakeTransportGoodOption bool
 
 type fakeTransportBadOption bool

pkg/tcpip/tcpip.go

@@ -39,6 +39,7 @@ import (
 	"time"
 
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
+	"gvisor.dev/gvisor/pkg/tcpip/iptables"
 	"gvisor.dev/gvisor/pkg/waiter"
 )
 
@@ -403,6 +404,9 @@ type Endpoint interface {
 	//
 	// NOTE: This method is a no-op for sockets other than TCP.
 	ModerateRecvBuf(copied int)
+
+	// IPTables returns the iptables for this endpoint's stack.
+	IPTables() (iptables.IPTables, error)
 }
 
 // WriteOptions contains options for Endpoint.Write.

pkg/tcpip/transport/icmp/BUILD

@@ -31,6 +31,7 @@ go_library(
         "//pkg/tcpip",
         "//pkg/tcpip/buffer",
         "//pkg/tcpip/header",
+        "//pkg/tcpip/iptables",
         "//pkg/tcpip/stack",
         "//pkg/tcpip/transport/raw",
         "//pkg/tcpip/transport/tcp",

pkg/tcpip/transport/icmp/endpoint.go

@@ -21,6 +21,7 @@ import (
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
+	"gvisor.dev/gvisor/pkg/tcpip/iptables"
 	"gvisor.dev/gvisor/pkg/tcpip/stack"
 	"gvisor.dev/gvisor/pkg/waiter"
 )
@@ -130,6 +131,11 @@ func (e *endpoint) Close() {
 // ModerateRecvBuf implements tcpip.Endpoint.ModerateRecvBuf.
 func (e *endpoint) ModerateRecvBuf(copied int) {}
 
+// IPTables implements tcpip.Endpoint.IPTables.
+func (e *endpoint) IPTables() (iptables.IPTables, error) {
+	return e.stack.IPTables(), nil
+}
+
 // Read reads data from the endpoint. This method does not block if
 // there is no data pending.
 func (e *endpoint) Read(addr *tcpip.FullAddress) (buffer.View, tcpip.ControlMessages, *tcpip.Error) {

pkg/tcpip/transport/raw/BUILD

@@ -32,6 +32,7 @@ go_library(
         "//pkg/tcpip",
         "//pkg/tcpip/buffer",
         "//pkg/tcpip/header",
+        "//pkg/tcpip/iptables",
         "//pkg/tcpip/stack",
         "//pkg/waiter",
     ],

pkg/tcpip/transport/raw/endpoint.go

@@ -32,6 +32,7 @@ import (
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
+	"gvisor.dev/gvisor/pkg/tcpip/iptables"
 	"gvisor.dev/gvisor/pkg/tcpip/stack"
 	"gvisor.dev/gvisor/pkg/waiter"
 )
@@ -168,6 +169,11 @@ func (ep *endpoint) Close() {
 // ModerateRecvBuf implements tcpip.Endpoint.ModerateRecvBuf.
 func (ep *endpoint) ModerateRecvBuf(copied int) {}
 
+// IPTables implements tcpip.Endpoint.IPTables.
+func (ep *endpoint) IPTables() (iptables.IPTables, error) {
+	return ep.stack.IPTables(), nil
+}
+
 // Read implements tcpip.Endpoint.Read.
 func (ep *endpoint) Read(addr *tcpip.FullAddress) (buffer.View, tcpip.ControlMessages, *tcpip.Error) {
 	if !ep.associated {
@@ -484,7 +490,7 @@ func (ep *endpoint) Readiness(mask waiter.EventMask) waiter.EventMask {
 
 // SetSockOpt implements tcpip.Endpoint.SetSockOpt.
 func (ep *endpoint) SetSockOpt(opt interface{}) *tcpip.Error {
-	return nil
+	return tcpip.ErrUnknownProtocolOption
 }
 
 // GetSockOptInt implements tcpip.Endpoint.GetSockOptInt.

pkg/tcpip/transport/tcp/BUILD

@@ -48,6 +48,7 @@ go_library(
         "//pkg/tcpip",
         "//pkg/tcpip/buffer",
         "//pkg/tcpip/header",
+        "//pkg/tcpip/iptables",
         "//pkg/tcpip/seqnum",
         "//pkg/tcpip/stack",
         "//pkg/tcpip/transport/raw",

pkg/tcpip/transport/tcp/endpoint.go

@@ -27,6 +27,7 @@ import (
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
+	"gvisor.dev/gvisor/pkg/tcpip/iptables"
 	"gvisor.dev/gvisor/pkg/tcpip/seqnum"
 	"gvisor.dev/gvisor/pkg/tcpip/stack"
 	"gvisor.dev/gvisor/pkg/tmutex"
@@ -683,6 +684,11 @@ func (e *endpoint) ModerateRecvBuf(copied int) {
 	e.rcvListMu.Unlock()
 }
 
+// IPTables implements tcpip.Endpoint.IPTables.
+func (e *endpoint) IPTables() (iptables.IPTables, error) {
+	return e.stack.IPTables(), nil
+}
+
 // Read reads data from the endpoint.
 func (e *endpoint) Read(*tcpip.FullAddress) (buffer.View, tcpip.ControlMessages, *tcpip.Error) {
 	e.mu.RLock()

pkg/tcpip/transport/udp/BUILD

@@ -32,6 +32,7 @@ go_library(
         "//pkg/tcpip",
         "//pkg/tcpip/buffer",
         "//pkg/tcpip/header",
+        "//pkg/tcpip/iptables",
         "//pkg/tcpip/stack",
         "//pkg/tcpip/transport/raw",
         "//pkg/waiter",

pkg/tcpip/transport/udp/endpoint.go

@@ -21,6 +21,7 @@ import (
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
+	"gvisor.dev/gvisor/pkg/tcpip/iptables"
 	"gvisor.dev/gvisor/pkg/tcpip/stack"
 	"gvisor.dev/gvisor/pkg/waiter"
 )
@@ -172,6 +173,11 @@ func (e *endpoint) Close() {
 // ModerateRecvBuf implements tcpip.Endpoint.ModerateRecvBuf.
 func (e *endpoint) ModerateRecvBuf(copied int) {}
 
+// IPTables implements tcpip.Endpoint.IPTables.
+func (e *endpoint) IPTables() (iptables.IPTables, error) {
+	return e.stack.IPTables(), nil
+}
+
 // Read reads data from the endpoint. This method does not block if
 // there is no data pending.
 func (e *endpoint) Read(addr *tcpip.FullAddress) (buffer.View, tcpip.ControlMessages, *tcpip.Error) {

runsc/boot/loader.go

@@ -933,6 +933,8 @@ func newEmptyNetworkStack(conf *Config, clock tcpip.Clock) (inet.Stack, error) {
 			return nil, fmt.Errorf("SetTransportProtocolOption failed: %v", err)
 		}
 
+		s.FillDefaultIPTables()
+
 		return &s, nil
 
 	default: