1 /*
2  * Copyright (C) 2020 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 #pragma once
18 
19 #include <linux/netlink.h>
20 
21 namespace android::nl::impl {
22 
23 // The following definitions are C++ equivalents of NLMSG_* macros from linux/netlink.h.
24 
25 /**
26  * Equivalent to NLMSG_ALIGNTO.
27  */
28 constexpr size_t alignto = NLMSG_ALIGNTO;
29 static_assert(NLMSG_ALIGNTO == NLA_ALIGNTO);
30 
31 /**
32  * Equivalent to NLMSG_ALIGN(len).
33  */
align(size_t len)34 constexpr size_t align(size_t len) {
35     return (len + alignto - 1) & ~(alignto - 1);
36 }
37 
38 /**
39  * Equivalent to NLMSG_SPACE(len).
40  */
41 template <typename H>
space(size_t len)42 constexpr size_t space(size_t len) {
43     return align(align(sizeof(H)) + len);
44 }
45 
46 /**
47  * Equivalent to NLMSG_DATA(hdr) + NLMSG_ALIGN(offset).
48  */
49 template <typename H, typename D>
50 constexpr D* data(H* header, size_t offset = 0) {
51     return reinterpret_cast<D*>(uintptr_t(header) + space<H>(offset));
52 }
53 
54 }  // namespace android::nl::impl
55