ip6tables: ABI structs and constants

Part of #3549. PiperOrigin-RevId: 326329028
2026-05-22 17:12:49 -07:00 · 2020-08-12 16:20:51 -07:00
parent 252329c1f3
commit d50f2e2c76
5 changed files with 321 additions and 2 deletions
@@ -41,6 +41,7 @@ go_library(
        "mm.go",
        "netdevice.go",
        "netfilter.go",
+        "netfilter_ipv6.go",
        "netlink.go",
        "netlink_route.go",
        "poll.go",
@@ -412,7 +412,7 @@ func (ke *KernelIPTGetEntries) SizeBytes() int {
 func (ke *KernelIPTGetEntries) MarshalBytes(dst []byte) {
 	ke.IPTGetEntries.MarshalBytes(dst)
 	marshalledUntil := ke.IPTGetEntries.SizeBytes()
-	for i := 0; i < len(ke.Entrytable); i++ {
+	for i := range ke.Entrytable {
 		ke.Entrytable[i].MarshalBytes(dst[marshalledUntil:])
 		marshalledUntil += ke.Entrytable[i].SizeBytes()
 	}
@@ -422,7 +422,7 @@ func (ke *KernelIPTGetEntries) MarshalBytes(dst []byte) {
 func (ke *KernelIPTGetEntries) UnmarshalBytes(src []byte) {
 	ke.IPTGetEntries.UnmarshalBytes(src)
 	unmarshalledUntil := ke.IPTGetEntries.SizeBytes()
-	for i := 0; i < len(ke.Entrytable); i++ {
+	for i := range ke.Entrytable {
 		ke.Entrytable[i].UnmarshalBytes(src[unmarshalledUntil:])
 		unmarshalledUntil += ke.Entrytable[i].SizeBytes()
 	}
@@ -0,0 +1,310 @@
+// Copyright 2020 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 linux
+
+import (
+	"io"
+
+	"gvisor.dev/gvisor/pkg/usermem"
+	"gvisor.dev/gvisor/tools/go_marshal/marshal"
+	"gvisor.dev/gvisor/tools/go_marshal/primitive"
+)
+
+// This file contains structures required to support IPv6 netfilter and
+// ip6tables. Some constants and structs are equal to their IPv4 analogues, and
+// are only distinguished by context (e.g. whether used on an IPv4 of IPv6
+// socket).
+
+// Socket options for SOL_SOCLET. These correspond to values in
+// include/uapi/linux/netfilter_ipv6/ip6_tables.h.
+const (
+	IP6T_BASE_CTL            = 64
+	IP6T_SO_SET_REPLACE      = IPT_BASE_CTL
+	IP6T_SO_SET_ADD_COUNTERS = IPT_BASE_CTL + 1
+	IP6T_SO_SET_MAX          = IPT_SO_SET_ADD_COUNTERS
+
+	IP6T_SO_GET_INFO            = IPT_BASE_CTL
+	IP6T_SO_GET_ENTRIES         = IPT_BASE_CTL + 1
+	IP6T_SO_GET_REVISION_MATCH  = IPT_BASE_CTL + 4
+	IP6T_SO_GET_REVISION_TARGET = IPT_BASE_CTL + 5
+	IP6T_SO_GET_MAX             = IP6T_SO_GET_REVISION_TARGET
+)
+
+// IP6T_ORIGINAL_DST is the ip6tables SOL_IPV6 socket option. Corresponds to
+// the value in include/uapi/linux/netfilter_ipv6/ip6_tables.h.
+// TODO(gvisor.dev/issue/3549): Support IPv6 original destination.
+const IP6T_ORIGINAL_DST = 80
+
+// IP6TReplace is the argument for the IP6T_SO_SET_REPLACE sockopt. It
+// corresponds to struct ip6t_replace in
+// include/uapi/linux/netfilter_ipv6/ip6_tables.h.
+//
+// +marshal
+type IP6TReplace struct {
+	Name        TableName
+	ValidHooks  uint32
+	NumEntries  uint32
+	Size        uint32
+	HookEntry   [NF_INET_NUMHOOKS]uint32
+	Underflow   [NF_INET_NUMHOOKS]uint32
+	NumCounters uint32
+	Counters    uint64 // This is really a *XTCounters.
+	// Entries is omitted here because it would cause IP6TReplace to be an
+	// extra byte longer (see http://www.catb.org/esr/structure-packing/).
+	// Entries [0]IP6TEntry
+}
+
+// SizeOfIP6TReplace is the size of an IP6TReplace.
+const SizeOfIP6TReplace = 96
+
+// KernelIP6TGetEntries is identical to IP6TGetEntries, but includes the
+// Entrytable field. This has been manually made marshal.Marshallable since it
+// is dynamically sized.
+type KernelIP6TGetEntries struct {
+	IPTGetEntries
+	Entrytable []KernelIP6TEntry
+}
+
+// SizeBytes implements marshal.Marshallable.SizeBytes.
+func (ke *KernelIP6TGetEntries) SizeBytes() int {
+	res := ke.IPTGetEntries.SizeBytes()
+	for _, entry := range ke.Entrytable {
+		res += entry.SizeBytes()
+	}
+	return res
+}
+
+// MarshalBytes implements marshal.Marshallable.MarshalBytes.
+func (ke *KernelIP6TGetEntries) MarshalBytes(dst []byte) {
+	ke.IPTGetEntries.MarshalBytes(dst)
+	marshalledUntil := ke.IPTGetEntries.SizeBytes()
+	for i := range ke.Entrytable {
+		ke.Entrytable[i].MarshalBytes(dst[marshalledUntil:])
+		marshalledUntil += ke.Entrytable[i].SizeBytes()
+	}
+}
+
+// UnmarshalBytes implements marshal.Marshallable.UnmarshalBytes.
+func (ke *KernelIP6TGetEntries) UnmarshalBytes(src []byte) {
+	ke.IPTGetEntries.UnmarshalBytes(src)
+	unmarshalledUntil := ke.IPTGetEntries.SizeBytes()
+	for i := range ke.Entrytable {
+		ke.Entrytable[i].UnmarshalBytes(src[unmarshalledUntil:])
+		unmarshalledUntil += ke.Entrytable[i].SizeBytes()
+	}
+}
+
+// Packed implements marshal.Marshallable.Packed.
+func (ke *KernelIP6TGetEntries) Packed() bool {
+	// KernelIP6TGetEntries isn't packed because the ke.Entrytable contains
+	// an indirection to the actual data we want to marshal (the slice data
+	// pointer), and the memory for KernelIP6TGetEntries contains the slice
+	// header which we don't want to marshal.
+	return false
+}
+
+// MarshalUnsafe implements marshal.Marshallable.MarshalUnsafe.
+func (ke *KernelIP6TGetEntries) MarshalUnsafe(dst []byte) {
+	// Fall back to safe Marshal because the type in not packed.
+	ke.MarshalBytes(dst)
+}
+
+// UnmarshalUnsafe implements marshal.Marshallable.UnmarshalUnsafe.
+func (ke *KernelIP6TGetEntries) UnmarshalUnsafe(src []byte) {
+	// Fall back to safe Unmarshal because the type in not packed.
+	ke.UnmarshalBytes(src)
+}
+
+// CopyIn implements marshal.Marshallable.CopyIn.
+func (ke *KernelIP6TGetEntries) CopyIn(task marshal.Task, addr usermem.Addr) (int, error) {
+	buf := task.CopyScratchBuffer(ke.SizeBytes()) // escapes: okay.
+	length, err := task.CopyInBytes(addr, buf)    // escapes: okay.
+	// Unmarshal unconditionally. If we had a short copy-in, this results
+	// in a partially unmarshalled struct.
+	ke.UnmarshalBytes(buf) // escapes: fallback.
+	return length, err
+}
+
+// CopyOut implements marshal.Marshallable.CopyOut.
+func (ke *KernelIP6TGetEntries) CopyOut(task marshal.Task, addr usermem.Addr) (int, error) {
+	// Type KernelIP6TGetEntries doesn't have a packed layout in memory,
+	// fall back to MarshalBytes.
+	return task.CopyOutBytes(addr, ke.marshalAll(task))
+}
+
+// CopyOutN implements marshal.Marshallable.CopyOutN.
+func (ke *KernelIP6TGetEntries) CopyOutN(task marshal.Task, addr usermem.Addr, limit int) (int, error) {
+	// Type KernelIP6TGetEntries doesn't have a packed layout in memory, fall
+	// back to MarshalBytes.
+	return task.CopyOutBytes(addr, ke.marshalAll(task)[:limit])
+}
+
+func (ke *KernelIP6TGetEntries) marshalAll(task marshal.Task) []byte {
+	buf := task.CopyScratchBuffer(ke.SizeBytes())
+	ke.MarshalBytes(buf)
+	return buf
+}
+
+// WriteTo implements io.WriterTo.WriteTo.
+func (ke *KernelIP6TGetEntries) WriteTo(w io.Writer) (int64, error) {
+	buf := make([]byte, ke.SizeBytes())
+	ke.MarshalBytes(buf)
+	length, err := w.Write(buf)
+	return int64(length), err
+}
+
+var _ marshal.Marshallable = (*KernelIP6TGetEntries)(nil)
+
+// IP6TEntry is an iptables rule. It corresponds to struct ip6t_entry in
+// include/uapi/linux/netfilter_ipv6/ip6_tables.h.
+//
+// +marshal
+type IP6TEntry struct {
+	// IPv6 is used to filter packets based on the IPv6 header.
+	IPv6 IP6TIP
+
+	// NFCache relates to kernel-internal caching and isn't used by
+	// userspace.
+	NFCache uint32
+
+	// TargetOffset is the byte offset from the beginning of this IPTEntry
+	// to the start of the entry's target.
+	TargetOffset uint16
+
+	// NextOffset is the byte offset from the beginning of this IPTEntry to
+	// the start of the next entry. It is thus also the size of the entry.
+	NextOffset uint16
+
+	// Comeback is a return pointer. It is not used by userspace.
+	Comeback uint32
+
+	_ [4]byte
+
+	// Counters holds the packet and byte counts for this rule.
+	Counters XTCounters
+
+	// Elems holds the data for all this rule's matches followed by the
+	// target. It is variable length -- users have to iterate over any
+	// matches and use TargetOffset and NextOffset to make sense of the
+	// data.
+	//
+	// Elems is omitted here because it would cause IPTEntry to be an extra
+	// byte larger (see http://www.catb.org/esr/structure-packing/).
+	//
+	// Elems [0]byte
+}
+
+// SizeOfIP6TEntry is the size of an IP6TEntry.
+const SizeOfIP6TEntry = 168
+
+// KernelIP6TEntry is identical to IP6TEntry, but includes the Elems field.
+// KernelIP6TEntry itself is not Marshallable but it implements some methods of
+// marshal.Marshallable that help in other implementations of Marshallable.
+type KernelIP6TEntry struct {
+	Entry IP6TEntry
+
+	// Elems holds the data for all this rule's matches followed by the
+	// target. It is variable length -- users have to iterate over any
+	// matches and use TargetOffset and NextOffset to make sense of the
+	// data.
+	Elems primitive.ByteSlice
+}
+
+// SizeBytes implements marshal.Marshallable.SizeBytes.
+func (ke *KernelIP6TEntry) SizeBytes() int {
+	return ke.Entry.SizeBytes() + ke.Elems.SizeBytes()
+}
+
+// MarshalBytes implements marshal.Marshallable.MarshalBytes.
+func (ke *KernelIP6TEntry) MarshalBytes(dst []byte) {
+	ke.Entry.MarshalBytes(dst)
+	ke.Elems.MarshalBytes(dst[ke.Entry.SizeBytes():])
+}
+
+// UnmarshalBytes implements marshal.Marshallable.UnmarshalBytes.
+func (ke *KernelIP6TEntry) UnmarshalBytes(src []byte) {
+	ke.Entry.UnmarshalBytes(src)
+	ke.Elems.UnmarshalBytes(src[ke.Entry.SizeBytes():])
+}
+
+// IP6TIP contains information for matching a packet's IP header.
+// It corresponds to struct ip6t_ip6 in
+// include/uapi/linux/netfilter_ipv6/ip6_tables.h.
+//
+// +marshal
+type IP6TIP struct {
+	// Src is the source IP address.
+	Src Inet6Addr
+
+	// Dst is the destination IP address.
+	Dst Inet6Addr
+
+	// SrcMask is the source IP mask.
+	SrcMask Inet6Addr
+
+	// DstMask is the destination IP mask.
+	DstMask Inet6Addr
+
+	// InputInterface is the input network interface.
+	InputInterface [IFNAMSIZ]byte
+
+	// OutputInterface is the output network interface.
+	OutputInterface [IFNAMSIZ]byte
+
+	// InputInterfaceMask is the input interface mask.
+	InputInterfaceMask [IFNAMSIZ]byte
+
+	// OuputInterfaceMask is the output interface mask.
+	OutputInterfaceMask [IFNAMSIZ]byte
+
+	// Protocol is the transport protocol.
+	Protocol uint16
+
+	// TOS matches TOS flags when Flags indicates filtering by TOS.
+	TOS uint8
+
+	// Flags define matching behavior for the IP header.
+	Flags uint8
+
+	// InverseFlags invert the meaning of fields in struct IPTIP. See the
+	// IP6T_INV_* flags.
+	InverseFlags uint8
+
+	// Linux defines in6_addr (Inet6Addr for us) as the union of a
+	// 16-element byte array and a 4-element 32-bit integer array, so the
+	// whole struct is 4-byte aligned.
+	_ [3]byte
+}
+
+const SizeOfIP6TIP = 136
+
+// Flags in IP6TIP.InverseFlags. Corresponding constants are in
+// include/uapi/linux/netfilter_ipv6/ip6_tables.h.
+const (
+	// Invert the meaning of InputInterface.
+	IP6T_INV_VIA_IN = 0x01
+	// Invert the meaning of OutputInterface.
+	IP6T_INV_VIA_OUT = 0x02
+	// Invert the meaning of TOS.
+	IP6T_INV_TOS = 0x04
+	// Invert the meaning of Src.
+	IP6T_INV_SRCIP = 0x08
+	// Invert the meaning of Dst.
+	IP6T_INV_DSTIP = 0x10
+	// Invert the meaning of the IPT_F_FRAG flag.
+	IP6T_INV_FRAG = 0x20
+	// Enable all flags.
+	IP6T_INV_MASK = 0x7F
+)
@@ -36,6 +36,9 @@ func TestSizes(t *testing.T) {
 		{XTEntryTarget{}, SizeOfXTEntryTarget},
 		{XTErrorTarget{}, SizeOfXTErrorTarget},
 		{XTStandardTarget{}, SizeOfXTStandardTarget},
+		{IP6TReplace{}, SizeOfIP6TReplace},
+		{IP6TEntry{}, SizeOfIP6TEntry},
+		{IP6TIP{}, SizeOfIP6TIP},
 	}

 	for _, tc := range testCases {
@@ -259,6 +259,11 @@ type InetMulticastRequestWithNIC struct {
 	InterfaceIndex int32
 }

+// Inet6Addr is struct in6_addr, from uapi/linux/in6.h.
+//
+// +marshal
+type Inet6Addr [16]byte
+
 // SockAddrInet6 is struct sockaddr_in6, from uapi/linux/in6.h.
 type SockAddrInet6 struct {
 	Family   uint16