1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /* Taken & modified from iproute2's libnetlink.c
3 * Authors: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
4 */
5 #include <stdio.h>
6 #include <stdlib.h>
7 #include <unistd.h>
8 #include <errno.h>
9 #include <time.h>
10 #include <sys/socket.h>
11
12 #include "netlink_helpers.h"
13
14 static int rcvbuf = 1024 * 1024;
15
rtnl_close(struct rtnl_handle * rth)16 void rtnl_close(struct rtnl_handle *rth)
17 {
18 if (rth->fd >= 0) {
19 close(rth->fd);
20 rth->fd = -1;
21 }
22 }
23
rtnl_open_byproto(struct rtnl_handle * rth,unsigned int subscriptions,int protocol)24 int rtnl_open_byproto(struct rtnl_handle *rth, unsigned int subscriptions,
25 int protocol)
26 {
27 socklen_t addr_len;
28 int sndbuf = 32768;
29 int one = 1;
30
31 memset(rth, 0, sizeof(*rth));
32 rth->proto = protocol;
33 rth->fd = socket(AF_NETLINK, SOCK_RAW | SOCK_CLOEXEC, protocol);
34 if (rth->fd < 0) {
35 perror("Cannot open netlink socket");
36 return -1;
37 }
38 if (setsockopt(rth->fd, SOL_SOCKET, SO_SNDBUF,
39 &sndbuf, sizeof(sndbuf)) < 0) {
40 perror("SO_SNDBUF");
41 goto err;
42 }
43 if (setsockopt(rth->fd, SOL_SOCKET, SO_RCVBUF,
44 &rcvbuf, sizeof(rcvbuf)) < 0) {
45 perror("SO_RCVBUF");
46 goto err;
47 }
48
49 /* Older kernels may no support extended ACK reporting */
50 setsockopt(rth->fd, SOL_NETLINK, NETLINK_EXT_ACK,
51 &one, sizeof(one));
52
53 memset(&rth->local, 0, sizeof(rth->local));
54 rth->local.nl_family = AF_NETLINK;
55 rth->local.nl_groups = subscriptions;
56
57 if (bind(rth->fd, (struct sockaddr *)&rth->local,
58 sizeof(rth->local)) < 0) {
59 perror("Cannot bind netlink socket");
60 goto err;
61 }
62 addr_len = sizeof(rth->local);
63 if (getsockname(rth->fd, (struct sockaddr *)&rth->local,
64 &addr_len) < 0) {
65 perror("Cannot getsockname");
66 goto err;
67 }
68 if (addr_len != sizeof(rth->local)) {
69 fprintf(stderr, "Wrong address length %d\n", addr_len);
70 goto err;
71 }
72 if (rth->local.nl_family != AF_NETLINK) {
73 fprintf(stderr, "Wrong address family %d\n",
74 rth->local.nl_family);
75 goto err;
76 }
77 rth->seq = time(NULL);
78 return 0;
79 err:
80 rtnl_close(rth);
81 return -1;
82 }
83
rtnl_open(struct rtnl_handle * rth,unsigned int subscriptions)84 int rtnl_open(struct rtnl_handle *rth, unsigned int subscriptions)
85 {
86 return rtnl_open_byproto(rth, subscriptions, NETLINK_ROUTE);
87 }
88
__rtnl_recvmsg(int fd,struct msghdr * msg,int flags)89 static int __rtnl_recvmsg(int fd, struct msghdr *msg, int flags)
90 {
91 int len;
92
93 do {
94 len = recvmsg(fd, msg, flags);
95 } while (len < 0 && (errno == EINTR || errno == EAGAIN));
96 if (len < 0) {
97 fprintf(stderr, "netlink receive error %s (%d)\n",
98 strerror(errno), errno);
99 return -errno;
100 }
101 if (len == 0) {
102 fprintf(stderr, "EOF on netlink\n");
103 return -ENODATA;
104 }
105 return len;
106 }
107
rtnl_recvmsg(int fd,struct msghdr * msg,char ** answer)108 static int rtnl_recvmsg(int fd, struct msghdr *msg, char **answer)
109 {
110 struct iovec *iov = msg->msg_iov;
111 char *buf;
112 int len;
113
114 iov->iov_base = NULL;
115 iov->iov_len = 0;
116
117 len = __rtnl_recvmsg(fd, msg, MSG_PEEK | MSG_TRUNC);
118 if (len < 0)
119 return len;
120 if (len < 32768)
121 len = 32768;
122 buf = malloc(len);
123 if (!buf) {
124 fprintf(stderr, "malloc error: not enough buffer\n");
125 return -ENOMEM;
126 }
127 iov->iov_base = buf;
128 iov->iov_len = len;
129 len = __rtnl_recvmsg(fd, msg, 0);
130 if (len < 0) {
131 free(buf);
132 return len;
133 }
134 if (answer)
135 *answer = buf;
136 else
137 free(buf);
138 return len;
139 }
140
rtnl_talk_error(struct nlmsghdr * h,struct nlmsgerr * err,nl_ext_ack_fn_t errfn)141 static void rtnl_talk_error(struct nlmsghdr *h, struct nlmsgerr *err,
142 nl_ext_ack_fn_t errfn)
143 {
144 fprintf(stderr, "RTNETLINK answers: %s\n",
145 strerror(-err->error));
146 }
147
__rtnl_talk_iov(struct rtnl_handle * rtnl,struct iovec * iov,size_t iovlen,struct nlmsghdr ** answer,bool show_rtnl_err,nl_ext_ack_fn_t errfn)148 static int __rtnl_talk_iov(struct rtnl_handle *rtnl, struct iovec *iov,
149 size_t iovlen, struct nlmsghdr **answer,
150 bool show_rtnl_err, nl_ext_ack_fn_t errfn)
151 {
152 struct sockaddr_nl nladdr = { .nl_family = AF_NETLINK };
153 struct iovec riov;
154 struct msghdr msg = {
155 .msg_name = &nladdr,
156 .msg_namelen = sizeof(nladdr),
157 .msg_iov = iov,
158 .msg_iovlen = iovlen,
159 };
160 unsigned int seq = 0;
161 struct nlmsghdr *h;
162 int i, status;
163 char *buf;
164
165 for (i = 0; i < iovlen; i++) {
166 h = iov[i].iov_base;
167 h->nlmsg_seq = seq = ++rtnl->seq;
168 if (answer == NULL)
169 h->nlmsg_flags |= NLM_F_ACK;
170 }
171 status = sendmsg(rtnl->fd, &msg, 0);
172 if (status < 0) {
173 perror("Cannot talk to rtnetlink");
174 return -1;
175 }
176 /* change msg to use the response iov */
177 msg.msg_iov = &riov;
178 msg.msg_iovlen = 1;
179 i = 0;
180 while (1) {
181 next:
182 status = rtnl_recvmsg(rtnl->fd, &msg, &buf);
183 ++i;
184 if (status < 0)
185 return status;
186 if (msg.msg_namelen != sizeof(nladdr)) {
187 fprintf(stderr,
188 "Sender address length == %d!\n",
189 msg.msg_namelen);
190 exit(1);
191 }
192 for (h = (struct nlmsghdr *)buf; status >= sizeof(*h); ) {
193 int len = h->nlmsg_len;
194 int l = len - sizeof(*h);
195
196 if (l < 0 || len > status) {
197 if (msg.msg_flags & MSG_TRUNC) {
198 fprintf(stderr, "Truncated message!\n");
199 free(buf);
200 return -1;
201 }
202 fprintf(stderr,
203 "Malformed message: len=%d!\n",
204 len);
205 exit(1);
206 }
207 if (nladdr.nl_pid != 0 ||
208 h->nlmsg_pid != rtnl->local.nl_pid ||
209 h->nlmsg_seq > seq || h->nlmsg_seq < seq - iovlen) {
210 /* Don't forget to skip that message. */
211 status -= NLMSG_ALIGN(len);
212 h = (struct nlmsghdr *)((char *)h + NLMSG_ALIGN(len));
213 continue;
214 }
215 if (h->nlmsg_type == NLMSG_ERROR) {
216 struct nlmsgerr *err = (struct nlmsgerr *)NLMSG_DATA(h);
217 int error = err->error;
218
219 if (l < sizeof(struct nlmsgerr)) {
220 fprintf(stderr, "ERROR truncated\n");
221 free(buf);
222 return -1;
223 }
224 if (error) {
225 errno = -error;
226 if (rtnl->proto != NETLINK_SOCK_DIAG &&
227 show_rtnl_err)
228 rtnl_talk_error(h, err, errfn);
229 }
230 if (i < iovlen) {
231 free(buf);
232 goto next;
233 }
234 if (error) {
235 free(buf);
236 return -i;
237 }
238 if (answer)
239 *answer = (struct nlmsghdr *)buf;
240 else
241 free(buf);
242 return 0;
243 }
244 if (answer) {
245 *answer = (struct nlmsghdr *)buf;
246 return 0;
247 }
248 fprintf(stderr, "Unexpected reply!\n");
249 status -= NLMSG_ALIGN(len);
250 h = (struct nlmsghdr *)((char *)h + NLMSG_ALIGN(len));
251 }
252 free(buf);
253 if (msg.msg_flags & MSG_TRUNC) {
254 fprintf(stderr, "Message truncated!\n");
255 continue;
256 }
257 if (status) {
258 fprintf(stderr, "Remnant of size %d!\n", status);
259 exit(1);
260 }
261 }
262 }
263
__rtnl_talk(struct rtnl_handle * rtnl,struct nlmsghdr * n,struct nlmsghdr ** answer,bool show_rtnl_err,nl_ext_ack_fn_t errfn)264 static int __rtnl_talk(struct rtnl_handle *rtnl, struct nlmsghdr *n,
265 struct nlmsghdr **answer, bool show_rtnl_err,
266 nl_ext_ack_fn_t errfn)
267 {
268 struct iovec iov = {
269 .iov_base = n,
270 .iov_len = n->nlmsg_len,
271 };
272
273 return __rtnl_talk_iov(rtnl, &iov, 1, answer, show_rtnl_err, errfn);
274 }
275
rtnl_talk(struct rtnl_handle * rtnl,struct nlmsghdr * n,struct nlmsghdr ** answer)276 int rtnl_talk(struct rtnl_handle *rtnl, struct nlmsghdr *n,
277 struct nlmsghdr **answer)
278 {
279 return __rtnl_talk(rtnl, n, answer, true, NULL);
280 }
281
addattr(struct nlmsghdr * n,int maxlen,int type)282 int addattr(struct nlmsghdr *n, int maxlen, int type)
283 {
284 return addattr_l(n, maxlen, type, NULL, 0);
285 }
286
addattr8(struct nlmsghdr * n,int maxlen,int type,__u8 data)287 int addattr8(struct nlmsghdr *n, int maxlen, int type, __u8 data)
288 {
289 return addattr_l(n, maxlen, type, &data, sizeof(__u8));
290 }
291
addattr16(struct nlmsghdr * n,int maxlen,int type,__u16 data)292 int addattr16(struct nlmsghdr *n, int maxlen, int type, __u16 data)
293 {
294 return addattr_l(n, maxlen, type, &data, sizeof(__u16));
295 }
296
addattr32(struct nlmsghdr * n,int maxlen,int type,__u32 data)297 int addattr32(struct nlmsghdr *n, int maxlen, int type, __u32 data)
298 {
299 return addattr_l(n, maxlen, type, &data, sizeof(__u32));
300 }
301
addattr64(struct nlmsghdr * n,int maxlen,int type,__u64 data)302 int addattr64(struct nlmsghdr *n, int maxlen, int type, __u64 data)
303 {
304 return addattr_l(n, maxlen, type, &data, sizeof(__u64));
305 }
306
addattrstrz(struct nlmsghdr * n,int maxlen,int type,const char * str)307 int addattrstrz(struct nlmsghdr *n, int maxlen, int type, const char *str)
308 {
309 return addattr_l(n, maxlen, type, str, strlen(str)+1);
310 }
311
addattr_l(struct nlmsghdr * n,int maxlen,int type,const void * data,int alen)312 int addattr_l(struct nlmsghdr *n, int maxlen, int type, const void *data,
313 int alen)
314 {
315 int len = RTA_LENGTH(alen);
316 struct rtattr *rta;
317
318 if (NLMSG_ALIGN(n->nlmsg_len) + RTA_ALIGN(len) > maxlen) {
319 fprintf(stderr, "%s: Message exceeded bound of %d\n",
320 __func__, maxlen);
321 return -1;
322 }
323 rta = NLMSG_TAIL(n);
324 rta->rta_type = type;
325 rta->rta_len = len;
326 if (alen)
327 memcpy(RTA_DATA(rta), data, alen);
328 n->nlmsg_len = NLMSG_ALIGN(n->nlmsg_len) + RTA_ALIGN(len);
329 return 0;
330 }
331
addraw_l(struct nlmsghdr * n,int maxlen,const void * data,int len)332 int addraw_l(struct nlmsghdr *n, int maxlen, const void *data, int len)
333 {
334 if (NLMSG_ALIGN(n->nlmsg_len) + NLMSG_ALIGN(len) > maxlen) {
335 fprintf(stderr, "%s: Message exceeded bound of %d\n",
336 __func__, maxlen);
337 return -1;
338 }
339
340 memcpy(NLMSG_TAIL(n), data, len);
341 memset((void *) NLMSG_TAIL(n) + len, 0, NLMSG_ALIGN(len) - len);
342 n->nlmsg_len = NLMSG_ALIGN(n->nlmsg_len) + NLMSG_ALIGN(len);
343 return 0;
344 }
345
addattr_nest(struct nlmsghdr * n,int maxlen,int type)346 struct rtattr *addattr_nest(struct nlmsghdr *n, int maxlen, int type)
347 {
348 struct rtattr *nest = NLMSG_TAIL(n);
349
350 addattr_l(n, maxlen, type, NULL, 0);
351 return nest;
352 }
353
addattr_nest_end(struct nlmsghdr * n,struct rtattr * nest)354 int addattr_nest_end(struct nlmsghdr *n, struct rtattr *nest)
355 {
356 nest->rta_len = (void *)NLMSG_TAIL(n) - (void *)nest;
357 return n->nlmsg_len;
358 }
359