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
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
|
// Copyright 2021 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//go:build linux
// +build linux
package unix
import (
"bytes"
"unsafe"
)
// Helpers for dealing with ifreq since it contains a union and thus requires a
// lot of unsafe.Pointer casts to use properly.
// An Ifreq is a type-safe wrapper around the raw ifreq struct. An Ifreq
// contains an interface name and a union of arbitrary data which can be
// accessed using the Ifreq's methods. To create an Ifreq, use the NewIfreq
// function.
//
// Use the Name method to access the stored interface name. The union data
// fields can be get and set using the following methods:
// - Uint16/SetUint16: flags
// - Uint32/SetUint32: ifindex, metric, mtu
type Ifreq struct{ raw ifreq }
// NewIfreq creates an Ifreq with the input network interface name after
// validating the name does not exceed IFNAMSIZ-1 (trailing NULL required)
// bytes.
func NewIfreq(name string) (*Ifreq, error) {
// Leave room for terminating NULL byte.
if len(name) >= IFNAMSIZ {
return nil, EINVAL
}
var ifr ifreq
copy(ifr.Ifrn[:], name)
return &Ifreq{raw: ifr}, nil
}
// TODO(mdlayher): get/set methods for hardware address sockaddr, char array, etc.
// Name returns the interface name associated with the Ifreq.
func (ifr *Ifreq) Name() string {
// BytePtrToString requires a NULL terminator or the program may crash. If
// one is not present, just return the empty string.
if !bytes.Contains(ifr.raw.Ifrn[:], []byte{0x00}) {
return ""
}
return BytePtrToString(&ifr.raw.Ifrn[0])
}
// According to netdevice(7), only AF_INET addresses are returned for numerous
// sockaddr ioctls. For convenience, we expose these as Inet4Addr since the Port
// field and other data is always empty.
// Inet4Addr returns the Ifreq union data from an embedded sockaddr as a C
// in_addr/Go []byte (4-byte IPv4 address) value. If the sockaddr family is not
// AF_INET, an error is returned.
func (ifr *Ifreq) Inet4Addr() ([]byte, error) {
raw := *(*RawSockaddrInet4)(unsafe.Pointer(&ifr.raw.Ifru[:SizeofSockaddrInet4][0]))
if raw.Family != AF_INET {
// Cannot safely interpret raw.Addr bytes as an IPv4 address.
return nil, EINVAL
}
return raw.Addr[:], nil
}
// SetInet4Addr sets a C in_addr/Go []byte (4-byte IPv4 address) value in an
// embedded sockaddr within the Ifreq's union data. v must be 4 bytes in length
// or an error will be returned.
func (ifr *Ifreq) SetInet4Addr(v []byte) error {
if len(v) != 4 {
return EINVAL
}
var addr [4]byte
copy(addr[:], v)
ifr.clear()
*(*RawSockaddrInet4)(
unsafe.Pointer(&ifr.raw.Ifru[:SizeofSockaddrInet4][0]),
) = RawSockaddrInet4{
// Always set IP family as ioctls would require it anyway.
Family: AF_INET,
Addr: addr,
}
return nil
}
// Uint16 returns the Ifreq union data as a C short/Go uint16 value.
func (ifr *Ifreq) Uint16() uint16 {
return *(*uint16)(unsafe.Pointer(&ifr.raw.Ifru[:2][0]))
}
// SetUint16 sets a C short/Go uint16 value as the Ifreq's union data.
func (ifr *Ifreq) SetUint16(v uint16) {
ifr.clear()
*(*uint16)(unsafe.Pointer(&ifr.raw.Ifru[:2][0])) = v
}
// Uint32 returns the Ifreq union data as a C int/Go uint32 value.
func (ifr *Ifreq) Uint32() uint32 {
return *(*uint32)(unsafe.Pointer(&ifr.raw.Ifru[:4][0]))
}
// SetUint32 sets a C int/Go uint32 value as the Ifreq's union data.
func (ifr *Ifreq) SetUint32(v uint32) {
ifr.clear()
*(*uint32)(unsafe.Pointer(&ifr.raw.Ifru[:4][0])) = v
}
// clear zeroes the ifreq's union field to prevent trailing garbage data from
// being sent to the kernel if an ifreq is reused.
func (ifr *Ifreq) clear() {
for i := range ifr.raw.Ifru {
ifr.raw.Ifru[i] = 0
}
}
// TODO(mdlayher): export as IfreqData? For now we can provide helpers such as
// IoctlGetEthtoolDrvinfo which use these APIs under the hood.
// An ifreqData is an Ifreq which carries pointer data. To produce an ifreqData,
// use the Ifreq.withData method.
type ifreqData struct {
name [IFNAMSIZ]byte
// A type separate from ifreq is required in order to comply with the
// unsafe.Pointer rules since the "pointer-ness" of data would not be
// preserved if it were cast into the byte array of a raw ifreq.
data unsafe.Pointer
// Pad to the same size as ifreq.
_ [len(ifreq{}.Ifru) - SizeofPtr]byte
}
// withData produces an ifreqData with the pointer p set for ioctls which require
// arbitrary pointer data.
func (ifr Ifreq) withData(p unsafe.Pointer) ifreqData {
return ifreqData{
name: ifr.raw.Ifrn,
data: p,
}
}
|
