1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
|
package pppoe
import (
"fmt"
"net"
"os"
"golang.org/x/sys/unix"
)
// PPPoEConn represents a PPPoE discovery connection, allowing
// receipt and transmission of PPPoE discovery packets.
//
// Because raw sockets are used for sending Ethernet frames, it is
// necessary to have root permissions to create PPPoEConn instances.
type PPPoEConn struct {
iface *net.Interface
fd int
file *os.File
}
func newRawSocket(protocol int) (fd int, err error) {
// raw socket since we want to read/write link-level packets
fd, err = unix.Socket(unix.AF_PACKET, unix.SOCK_RAW, protocol)
if err != nil {
return -1, fmt.Errorf("socket: %v", err)
}
// make the socket nonblocking so we can use it with the runtime poller
if err = unix.SetNonblock(fd, true); err != nil {
unix.Close(fd)
return -1, fmt.Errorf("failed to set socket nonblocking: %v", err)
}
// set the socket CLOEXEC to prevent passing it to child processes
flags, err := unix.FcntlInt(uintptr(fd), unix.F_GETFD, 0)
if err != nil {
unix.Close(fd)
return -1, fmt.Errorf("fcntl(F_GETFD): %v", err)
}
_, err = unix.FcntlInt(uintptr(fd), unix.F_SETFD, flags|unix.FD_CLOEXEC)
if err != nil {
unix.Close(fd)
return -1, fmt.Errorf("fcntl(F_SETFD, FD_CLOEXEC): %v", err)
}
// allow broadcast
err = unix.SetsockoptInt(fd, unix.SOL_SOCKET, unix.SO_BROADCAST, 1)
if err != nil {
unix.Close(fd)
return -1, fmt.Errorf("setsockopt(SO_BROADCAST): %v", err)
}
return
}
// NewDiscoveryConnection creates a new PPPoE discovery connection on
// the specified network interface.
func NewDiscoveryConnection(ifname string) (conn *PPPoEConn, err error) {
iface, err := net.InterfaceByName(ifname)
if err != nil {
return nil, fmt.Errorf("failed to obtain details of interface \"%s\": %v", ifname, err)
}
fd, err := newRawSocket(int(ethTypeDiscoveryNetUint16()))
if err != nil {
return nil, fmt.Errorf("failed to create raw socket: %v", err)
}
// bind to the interface specified
sa := unix.SockaddrLinklayer{
Protocol: ethTypeDiscoveryNetUint16(),
Ifindex: iface.Index,
}
err = unix.Bind(fd, &sa)
if err != nil {
unix.Close(fd)
return nil, fmt.Errorf("failed to bind socket: %v", err)
}
// register the socket with the runtime
file := os.NewFile(uintptr(fd), "pppoe")
return &PPPoEConn{
iface: iface,
fd: fd,
file: file,
}, nil
}
// Close closes the discovery connection, releasing allocated resources.
func (c *PPPoEConn) Close() (err error) {
if c.file != nil {
err = c.file.Close()
c.file = nil
}
return
}
// Send sends a frame over the discovery connection.
func (c *PPPoEConn) Send(b []byte) (n int, err error) {
return c.file.Write(b)
}
// Recv receives one or more frames over the discovery connection.
func (c *PPPoEConn) Recv(b []byte) (n int, err error) {
return c.file.Read(b)
}
// HWAddr returns the hardware address of the interface the discovery
// connection is using.
func (c *PPPoEConn) HWAddr() (addr [6]byte) {
if len(c.iface.HardwareAddr) >= 6 {
return [6]byte{
c.iface.HardwareAddr[0],
c.iface.HardwareAddr[1],
c.iface.HardwareAddr[2],
c.iface.HardwareAddr[3],
c.iface.HardwareAddr[4],
c.iface.HardwareAddr[5],
}
}
return [6]byte{}
}
|
