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// Copyright 2018 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 netlink
import (
"fmt"
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/context"
"gvisor.dev/gvisor/pkg/sentry/fs"
"gvisor.dev/gvisor/pkg/sentry/kernel"
"gvisor.dev/gvisor/pkg/sentry/socket"
"gvisor.dev/gvisor/pkg/syserr"
)
// Protocol is the implementation of a netlink socket protocol.
type Protocol interface {
// Protocol returns the Linux netlink protocol value.
Protocol() int
// CanSend returns true if this protocol may ever send messages.
//
// TODO(gvisor.dev/issue/1119): This is a workaround to allow
// advertising support for otherwise unimplemented features on sockets
// that will never send messages, thus making those features no-ops.
CanSend() bool
// ProcessMessage processes a single message from userspace.
//
// If err == nil, any messages added to ms will be sent back to the
// other end of the socket. Setting ms.Multi will cause an NLMSG_DONE
// message to be sent even if ms contains no messages.
ProcessMessage(ctx context.Context, msg *Message, ms *MessageSet) *syserr.Error
}
// Provider is a function that creates a new Protocol for a specific netlink
// protocol.
//
// Note that this is distinct from socket.Provider, which is used for all
// socket families.
type Provider func(t *kernel.Task) (Protocol, *syserr.Error)
// protocols holds a map of all known address protocols and their provider.
var protocols = make(map[int]Provider)
// RegisterProvider registers the provider of a given address protocol so that
// netlink sockets of that type can be created via socket(2).
//
// Preconditions: May only be called before any netlink sockets are created.
func RegisterProvider(protocol int, provider Provider) {
if p, ok := protocols[protocol]; ok {
panic(fmt.Sprintf("Netlink protocol %d already provided by %+v", protocol, p))
}
protocols[protocol] = provider
}
// socketProvider implements socket.Provider.
type socketProvider struct {
}
// Socket implements socket.Provider.Socket.
func (*socketProvider) Socket(t *kernel.Task, stype linux.SockType, protocol int) (*fs.File, *syserr.Error) {
// Netlink sockets must be specified as datagram or raw, but they
// behave the same regardless of type.
if stype != linux.SOCK_DGRAM && stype != linux.SOCK_RAW {
return nil, syserr.ErrSocketNotSupported
}
provider, ok := protocols[protocol]
if !ok {
return nil, syserr.ErrProtocolNotSupported
}
p, err := provider(t)
if err != nil {
return nil, err
}
s, err := NewSocket(t, stype, p)
if err != nil {
return nil, err
}
d := socket.NewDirent(t, netlinkSocketDevice)
defer d.DecRef()
return fs.NewFile(t, d, fs.FileFlags{Read: true, Write: true, NonSeekable: true}, s), nil
}
// Pair implements socket.Provider.Pair by returning an error.
func (*socketProvider) Pair(*kernel.Task, linux.SockType, int) (*fs.File, *fs.File, *syserr.Error) {
// Netlink sockets never supports creating socket pairs.
return nil, nil, syserr.ErrNotSupported
}
// init registers the socket provider.
func init() {
socket.RegisterProvider(linux.AF_NETLINK, &socketProvider{})
}
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