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 "router.h"
18
19 #include <linux/rtnetlink.h>
20 #include <stddef.h>
21 #include <string.h>
22
23 #include "address.h"
24 #include "log.h"
25
26 template<class Request>
addRouterAttribute(Request & r,int type,const void * data,size_t size)27 static void addRouterAttribute(Request& r,
28 int type,
29 const void* data,
30 size_t size) {
31 // Calculate the offset into the character buffer where the RTA data lives
32 // We use offsetof on the buffer to get it. This avoids undefined behavior
33 // by casting the buffer (which is safe because it's char) instead of the
34 // Request struct.(which is undefined because of aliasing)
35 size_t offset = NLMSG_ALIGN(r.hdr.nlmsg_len) - offsetof(Request, buf);
36 auto attr = reinterpret_cast<struct rtattr*>(r.buf + offset);
37 attr->rta_type = type;
38 attr->rta_len = RTA_LENGTH(size);
39 memcpy(RTA_DATA(attr), data, size);
40
41 // Update the message length to include the router attribute.
42 r.hdr.nlmsg_len = NLMSG_ALIGN(r.hdr.nlmsg_len) + RTA_ALIGN(attr->rta_len);
43 }
44
init()45 bool Router::init() {
46 // Create a netlink socket to the router
47 Result res = mSocket.open(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
48 if (!res) {
49 loge("Unable to open netlink socket: %s\n", res.c_str());
50 return false;
51 }
52 return true;
53 }
54
addNeighbor(const struct in6_addr & address,unsigned int interfaceIndex)55 bool Router::addNeighbor(const struct in6_addr& address,
56 unsigned int interfaceIndex) {
57 struct Request {
58 struct nlmsghdr hdr;
59 struct ndmsg msg;
60 char buf[256];
61 } request;
62
63 memset(&request, 0, sizeof(request));
64
65 unsigned short msgLen = NLMSG_LENGTH(sizeof(request.msg));
66 // Set up a request to create a new neighbor
67 request.hdr.nlmsg_len = msgLen;
68 request.hdr.nlmsg_type = RTM_NEWNEIGH;
69 request.hdr.nlmsg_flags = NLM_F_REQUEST | NLM_F_CREATE;
70
71 // The neighbor is a permanent IPv6 proxy
72 request.msg.ndm_family = AF_INET6;
73 request.msg.ndm_state = NUD_PERMANENT;
74 request.msg.ndm_flags = NTF_PROXY;
75 request.msg.ndm_ifindex = interfaceIndex;
76
77 addRouterAttribute(request, NDA_DST, &address, sizeof(address));
78
79 return sendNetlinkMessage(&request, request.hdr.nlmsg_len);
80 }
81
addRoute(const struct in6_addr & address,uint8_t bits,uint32_t ifaceIndex)82 bool Router::addRoute(const struct in6_addr& address,
83 uint8_t bits,
84 uint32_t ifaceIndex) {
85 struct Request {
86 struct nlmsghdr hdr;
87 struct rtmsg msg;
88 char buf[256];
89 } request;
90
91 memset(&request, 0, sizeof(request));
92
93 // Set up a request to create a new route
94 request.hdr.nlmsg_len = NLMSG_LENGTH(sizeof(request.msg));
95 request.hdr.nlmsg_type = RTM_NEWROUTE;
96 request.hdr.nlmsg_flags = NLM_F_REQUEST | NLM_F_CREATE;
97
98 request.msg.rtm_family = AF_INET6;
99 request.msg.rtm_dst_len = bits;
100 request.msg.rtm_table = RT_TABLE_MAIN;
101 request.msg.rtm_protocol = RTPROT_RA;
102 request.msg.rtm_scope = RT_SCOPE_UNIVERSE;
103 request.msg.rtm_type = RTN_UNICAST;
104
105 addRouterAttribute(request, RTA_DST, &address, sizeof(address));
106 addRouterAttribute(request, RTA_OIF, &ifaceIndex, sizeof(ifaceIndex));
107
108 return sendNetlinkMessage(&request, request.hdr.nlmsg_len);
109 }
110
setDefaultGateway(const struct in6_addr & address,unsigned int ifaceIndex)111 bool Router::setDefaultGateway(const struct in6_addr& address,
112 unsigned int ifaceIndex) {
113 struct Request {
114 struct nlmsghdr hdr;
115 struct rtmsg msg;
116 char buf[256];
117 } request;
118
119 memset(&request, 0, sizeof(request));
120
121 // Set up a request to create a new route
122 request.hdr.nlmsg_len = NLMSG_LENGTH(sizeof(request.msg));
123 request.hdr.nlmsg_type = RTM_NEWROUTE;
124 request.hdr.nlmsg_flags = NLM_F_REQUEST | NLM_F_CREATE;
125
126 request.msg.rtm_family = AF_INET6;
127 request.msg.rtm_dst_len = 0;
128 request.msg.rtm_src_len = 0;
129 request.msg.rtm_table = RT_TABLE_MAIN;
130 request.msg.rtm_protocol = RTPROT_RA;
131 request.msg.rtm_scope = RT_SCOPE_UNIVERSE;
132 request.msg.rtm_type = RTN_UNICAST;
133
134 struct in6_addr anyAddress;
135 memset(&anyAddress, 0, sizeof(anyAddress));
136 addRouterAttribute(request, RTA_GATEWAY, &address, sizeof(address));
137 addRouterAttribute(request, RTA_OIF, &ifaceIndex, sizeof(ifaceIndex));
138 addRouterAttribute(request, RTA_SRC, &anyAddress, sizeof(anyAddress));
139
140 return sendNetlinkMessage(&request, request.hdr.nlmsg_len);
141 }
142
sendNetlinkMessage(const void * data,size_t size)143 bool Router::sendNetlinkMessage(const void* data, size_t size) {
144 struct sockaddr_nl netlinkAddress;
145 memset(&netlinkAddress, 0, sizeof(netlinkAddress));
146 netlinkAddress.nl_family = AF_NETLINK;
147 Result res = mSocket.sendTo(netlinkAddress, data, size);
148 if (!res) {
149 loge("Unable to send on netlink socket: %s\n", res.c_str());
150 return false;
151 }
152 return true;
153 }
154
155