1 /*
2 * Copyright (C) 2017 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 #include "netlinkmessage.h"
18
19 #include "log.h"
20
21 #include <linux/netlink.h>
22 #include <linux/rtnetlink.h>
23 #include <sys/types.h>
24 #include <unistd.h>
25
getSpaceForMessageType(uint16_t type)26 size_t getSpaceForMessageType(uint16_t type) {
27 switch (type) {
28 case RTM_NEWLINK:
29 case RTM_GETLINK:
30 return NLMSG_SPACE(sizeof(ifinfomsg));
31 default:
32 return 0;
33 }
34 }
35
NetlinkMessage(uint16_t type,uint32_t sequence)36 NetlinkMessage::NetlinkMessage(uint16_t type,
37 uint32_t sequence)
38 : mData(getSpaceForMessageType(type), 0) {
39
40 auto header = reinterpret_cast<nlmsghdr*>(mData.data());
41 header->nlmsg_len = mData.size();
42 header->nlmsg_flags = NLM_F_REQUEST;
43 header->nlmsg_type = type;
44 header->nlmsg_seq = sequence;
45 header->nlmsg_pid = getpid();
46 }
47
NetlinkMessage(const char * data,size_t size)48 NetlinkMessage::NetlinkMessage(const char* data, size_t size)
49 : mData(data, data + size) {
50 }
51
getAttribute(int attributeId,void * data,size_t size) const52 bool NetlinkMessage::getAttribute(int attributeId, void* data, size_t size) const {
53 const void* value = nullptr;
54 uint16_t attrSize = 0;
55 if (!findAttribute(attributeId, &value, &attrSize)) {
56 return false;
57 }
58 if (size > attrSize) {
59 return false;
60 }
61 memcpy(data, value, size);
62 return true;
63 }
64
type() const65 uint16_t NetlinkMessage::type() const {
66 auto header = reinterpret_cast<const nlmsghdr*>(mData.data());
67 return header->nlmsg_type;
68 }
69
sequence() const70 uint32_t NetlinkMessage::sequence() const {
71 auto header = reinterpret_cast<const nlmsghdr*>(mData.data());
72 return header->nlmsg_seq;
73 }
74
findAttribute(int attributeId,const void ** value,uint16_t * size) const75 bool NetlinkMessage::findAttribute(int attributeId,
76 const void** value,
77 uint16_t* size) const {
78 const uint8_t* end = mData.data() + mData.size();
79 size_t attrOffset = getSpaceForMessageType(type());
80 if (attrOffset == 0) {
81 return false;
82 }
83 const uint8_t* attribute = mData.data() + attrOffset;
84 while (attribute < end) {
85 auto header = reinterpret_cast<const nlattr*>(attribute);
86 if (header->nla_len == 0) {
87 // The length should include the header so the length should always
88 // be greater than zero. If it doesn't we're going to end up looping
89 // forever so ignore this.
90 return false;
91 }
92 if (header->nla_type == attributeId) {
93 *value = attribute + NLA_HDRLEN;
94 *size = header->nla_len;
95 return true;
96 }
97 attribute += header->nla_len;
98 }
99 return false;
100 }
101