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conn.go
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conn.go
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// Copyright 2015 Google Inc. All Rights Reserved.
//
// 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 (
"bufio"
"bytes"
"encoding/binary"
"os"
"syscall"
)
type Connection struct {
// netlink socket
fd int
// cache pid to use in every netlink request.
pid uint32
// sequence number for netlink messages.
seq uint32
addr syscall.SockaddrNetlink
rbuf *bufio.Reader
}
// Create and bind a new netlink socket.
func newConnection() (*Connection, error) {
fd, err := syscall.Socket(syscall.AF_NETLINK, syscall.SOCK_DGRAM, syscall.NETLINK_GENERIC)
if err != nil {
return nil, err
}
conn := new(Connection)
conn.fd = fd
conn.seq = 0
conn.pid = uint32(os.Getpid())
conn.addr.Family = syscall.AF_NETLINK
conn.rbuf = bufio.NewReader(conn)
err = syscall.Bind(fd, &conn.addr)
if err != nil {
syscall.Close(fd)
return nil, err
}
return conn, err
}
func (self *Connection) Read(b []byte) (n int, err error) {
n, _, err = syscall.Recvfrom(self.fd, b, 0)
return n, err
}
func (self *Connection) Write(b []byte) (n int, err error) {
err = syscall.Sendto(self.fd, b, 0, &self.addr)
return len(b), err
}
func (self *Connection) Close() error {
return syscall.Close(self.fd)
}
func (self *Connection) WriteMessage(msg syscall.NetlinkMessage) error {
w := bytes.NewBuffer(nil)
msg.Header.Len = uint32(syscall.NLMSG_HDRLEN + len(msg.Data))
msg.Header.Seq = self.seq
self.seq++
msg.Header.Pid = self.pid
binary.Write(w, binary.LittleEndian, msg.Header)
_, err := w.Write(msg.Data)
if err != nil {
return err
}
_, err = self.Write(w.Bytes())
return err
}
func (self *Connection) ReadMessage() (msg syscall.NetlinkMessage, err error) {
err = binary.Read(self.rbuf, binary.LittleEndian, &msg.Header)
if err != nil {
return msg, err
}
msg.Data = make([]byte, msg.Header.Len-syscall.NLMSG_HDRLEN)
_, err = self.rbuf.Read(msg.Data)
return msg, err
}