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package netlink
import (
"errors"
"fmt"
"net"
"github.com/vishvananda/netlink/nl"
"golang.org/x/sys/unix"
)
const (
sizeofSocketID = 0x30
sizeofSocketRequest = sizeofSocketID + 0x8
sizeofSocket = sizeofSocketID + 0x18
)
type socketRequest struct {
Family uint8
Protocol uint8
Ext uint8
pad uint8
States uint32
ID SocketID
}
type writeBuffer struct {
Bytes []byte
pos int
}
func (b *writeBuffer) Write(c byte) {
b.Bytes[b.pos] = c
b.pos++
}
func (b *writeBuffer) Next(n int) []byte {
s := b.Bytes[b.pos : b.pos+n]
b.pos += n
return s
}
func (r *socketRequest) Serialize() []byte {
b := writeBuffer{Bytes: make([]byte, sizeofSocketRequest)}
b.Write(r.Family)
b.Write(r.Protocol)
b.Write(r.Ext)
b.Write(r.pad)
native.PutUint32(b.Next(4), r.States)
networkOrder.PutUint16(b.Next(2), r.ID.SourcePort)
networkOrder.PutUint16(b.Next(2), r.ID.DestinationPort)
copy(b.Next(4), r.ID.Source.To4())
b.Next(12)
copy(b.Next(4), r.ID.Destination.To4())
b.Next(12)
native.PutUint32(b.Next(4), r.ID.Interface)
native.PutUint32(b.Next(4), r.ID.Cookie[0])
native.PutUint32(b.Next(4), r.ID.Cookie[1])
return b.Bytes
}
func (r *socketRequest) Len() int { return sizeofSocketRequest }
type readBuffer struct {
Bytes []byte
pos int
}
func (b *readBuffer) Read() byte {
c := b.Bytes[b.pos]
b.pos++
return c
}
func (b *readBuffer) Next(n int) []byte {
s := b.Bytes[b.pos : b.pos+n]
b.pos += n
return s
}
func (s *Socket) deserialize(b []byte) error {
if len(b) < sizeofSocket {
return fmt.Errorf("socket data short read (%d); want %d", len(b), sizeofSocket)
}
rb := readBuffer{Bytes: b}
s.Family = rb.Read()
s.State = rb.Read()
s.Timer = rb.Read()
s.Retrans = rb.Read()
s.ID.SourcePort = networkOrder.Uint16(rb.Next(2))
s.ID.DestinationPort = networkOrder.Uint16(rb.Next(2))
s.ID.Source = net.IPv4(rb.Read(), rb.Read(), rb.Read(), rb.Read())
rb.Next(12)
s.ID.Destination = net.IPv4(rb.Read(), rb.Read(), rb.Read(), rb.Read())
rb.Next(12)
s.ID.Interface = native.Uint32(rb.Next(4))
s.ID.Cookie[0] = native.Uint32(rb.Next(4))
s.ID.Cookie[1] = native.Uint32(rb.Next(4))
s.Expires = native.Uint32(rb.Next(4))
s.RQueue = native.Uint32(rb.Next(4))
s.WQueue = native.Uint32(rb.Next(4))
s.UID = native.Uint32(rb.Next(4))
s.INode = native.Uint32(rb.Next(4))
return nil
}
// SocketGet returns the Socket identified by its local and remote addresses.
func SocketGet(local, remote net.Addr) (*Socket, error) {
localTCP, ok := local.(*net.TCPAddr)
if !ok {
return nil, ErrNotImplemented
}
remoteTCP, ok := remote.(*net.TCPAddr)
if !ok {
return nil, ErrNotImplemented
}
localIP := localTCP.IP.To4()
if localIP == nil {
return nil, ErrNotImplemented
}
remoteIP := remoteTCP.IP.To4()
if remoteIP == nil {
return nil, ErrNotImplemented
}
s, err := nl.Subscribe(unix.NETLINK_INET_DIAG)
if err != nil {
return nil, err
}
defer s.Close()
req := nl.NewNetlinkRequest(nl.SOCK_DIAG_BY_FAMILY, 0)
req.AddData(&socketRequest{
Family: unix.AF_INET,
Protocol: unix.IPPROTO_TCP,
ID: SocketID{
SourcePort: uint16(localTCP.Port),
DestinationPort: uint16(remoteTCP.Port),
Source: localIP,
Destination: remoteIP,
Cookie: [2]uint32{nl.TCPDIAG_NOCOOKIE, nl.TCPDIAG_NOCOOKIE},
},
})
s.Send(req)
msgs, from, err := s.Receive()
if err != nil {
return nil, err
}
if from.Pid != nl.PidKernel {
return nil, fmt.Errorf("Wrong sender portid %d, expected %d", from.Pid, nl.PidKernel)
}
if len(msgs) == 0 {
return nil, errors.New("no message nor error from netlink")
}
if len(msgs) > 2 {
return nil, fmt.Errorf("multiple (%d) matching sockets", len(msgs))
}
sock := &Socket{}
if err := sock.deserialize(msgs[0].Data); err != nil {
return nil, err
}
return sock, nil
}
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