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// Copyright 2018 Google Inc.
//
// 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 route provides a NETLINK_ROUTE socket protocol.
package route
import (
"bytes"
"gvisor.googlesource.com/gvisor/pkg/abi/linux"
"gvisor.googlesource.com/gvisor/pkg/sentry/context"
"gvisor.googlesource.com/gvisor/pkg/sentry/inet"
"gvisor.googlesource.com/gvisor/pkg/sentry/kernel"
"gvisor.googlesource.com/gvisor/pkg/sentry/kernel/auth"
"gvisor.googlesource.com/gvisor/pkg/sentry/socket/netlink"
"gvisor.googlesource.com/gvisor/pkg/syserr"
)
// commandKind describes the operational class of a message type.
//
// The route message types use the lower 2 bits of the type to describe class
// of command.
type commandKind int
const (
kindNew commandKind = 0x0
kindDel = 0x1
kindGet = 0x2
kindSet = 0x3
)
func typeKind(typ uint16) commandKind {
return commandKind(typ & 0x3)
}
// Protocol implements netlink.Protocol.
//
// +stateify savable
type Protocol struct{}
var _ netlink.Protocol = (*Protocol)(nil)
// NewProtocol creates a NETLINK_ROUTE netlink.Protocol.
func NewProtocol(t *kernel.Task) (netlink.Protocol, *syserr.Error) {
return &Protocol{}, nil
}
// Protocol implements netlink.Protocol.Protocol.
func (p *Protocol) Protocol() int {
return linux.NETLINK_ROUTE
}
// dumpLinks handles RTM_GETLINK + NLM_F_DUMP requests.
func (p *Protocol) dumpLinks(ctx context.Context, hdr linux.NetlinkMessageHeader, data []byte, ms *netlink.MessageSet) *syserr.Error {
// NLM_F_DUMP + RTM_GETLINK messages are supposed to include an
// ifinfomsg. However, Linux <3.9 only checked for rtgenmsg, and some
// userspace applications (including glibc) still include rtgenmsg.
// Linux has a workaround based on the total message length.
//
// We don't bother to check for either, since we don't support any
// extra attributes that may be included anyways.
//
// The message may also contain netlink attribute IFLA_EXT_MASK, which
// we don't support.
// The RTM_GETLINK dump response is a set of messages each containing
// an InterfaceInfoMessage followed by a set of netlink attributes.
// We always send back an NLMSG_DONE.
ms.Multi = true
stack := inet.StackFromContext(ctx)
if stack == nil {
// No network devices.
return nil
}
for id, i := range stack.Interfaces() {
m := ms.AddMessage(linux.NetlinkMessageHeader{
Type: linux.RTM_NEWLINK,
})
m.Put(linux.InterfaceInfoMessage{
Family: linux.AF_UNSPEC,
Type: i.DeviceType,
Index: id,
Flags: i.Flags,
})
m.PutAttrString(linux.IFLA_IFNAME, i.Name)
m.PutAttr(linux.IFLA_MTU, i.MTU)
mac := make([]byte, 6)
brd := mac
if len(i.Addr) > 0 {
mac = i.Addr
brd = bytes.Repeat([]byte{0xff}, len(i.Addr))
}
m.PutAttr(linux.IFLA_ADDRESS, mac)
m.PutAttr(linux.IFLA_BROADCAST, brd)
// TODO: There are many more attributes.
}
return nil
}
// dumpAddrs handles RTM_GETADDR + NLM_F_DUMP requests.
func (p *Protocol) dumpAddrs(ctx context.Context, hdr linux.NetlinkMessageHeader, data []byte, ms *netlink.MessageSet) *syserr.Error {
// RTM_GETADDR dump requests need not contain anything more than the
// netlink header and 1 byte protocol family common to all
// NETLINK_ROUTE requests.
//
// TODO: Filter output by passed protocol family.
// The RTM_GETADDR dump response is a set of RTM_NEWADDR messages each
// containing an InterfaceAddrMessage followed by a set of netlink
// attributes.
// We always send back an NLMSG_DONE.
ms.Multi = true
stack := inet.StackFromContext(ctx)
if stack == nil {
// No network devices.
return nil
}
for id, as := range stack.InterfaceAddrs() {
for _, a := range as {
m := ms.AddMessage(linux.NetlinkMessageHeader{
Type: linux.RTM_NEWADDR,
})
m.Put(linux.InterfaceAddrMessage{
Family: a.Family,
PrefixLen: a.PrefixLen,
Index: uint32(id),
})
m.PutAttr(linux.IFA_ADDRESS, []byte(a.Addr))
// TODO: There are many more attributes.
}
}
return nil
}
// ProcessMessage implements netlink.Protocol.ProcessMessage.
func (p *Protocol) ProcessMessage(ctx context.Context, hdr linux.NetlinkMessageHeader, data []byte, ms *netlink.MessageSet) *syserr.Error {
// All messages start with a 1 byte protocol family.
if len(data) < 1 {
// Linux ignores messages missing the protocol family. See
// net/core/rtnetlink.c:rtnetlink_rcv_msg.
return nil
}
// Non-GET message types require CAP_NET_ADMIN.
if typeKind(hdr.Type) != kindGet {
creds := auth.CredentialsFromContext(ctx)
if !creds.HasCapability(linux.CAP_NET_ADMIN) {
return syserr.ErrPermissionDenied
}
}
// TODO: Only the dump variant of the types below are
// supported.
if hdr.Flags&linux.NLM_F_DUMP != linux.NLM_F_DUMP {
return syserr.ErrNotSupported
}
switch hdr.Type {
case linux.RTM_GETLINK:
return p.dumpLinks(ctx, hdr, data, ms)
case linux.RTM_GETADDR:
return p.dumpAddrs(ctx, hdr, data, ms)
default:
return syserr.ErrNotSupported
}
}
// init registers the NETLINK_ROUTE provider.
func init() {
netlink.RegisterProvider(linux.NETLINK_ROUTE, NewProtocol)
}
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