src/lxc/nl.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2
   3 #ifndef _GNU_SOURCE
   4 #define _GNU_SOURCE 1
   5 #endif
   6 #include <errno.h>
   7 #include <linux/netlink.h>
   8 #include <linux/rtnetlink.h>
   9 #include <stdio.h>
  10 #include <stdlib.h>
  11 #include <string.h>
  12 #include <sys/socket.h>
  13 #include <time.h>
  14 #include <unistd.h>
  15
  16 #include "config.h"
  17 #include "log.h"
  18 #include "nl.h"
  19
  20 lxc_log_define(nl, lxc);
  21
  22 extern size_t nlmsg_len(const struct nlmsg *nlmsg)
  23 {
  24         return nlmsg->nlmsghdr->nlmsg_len - NLMSG_HDRLEN;
  25 }
  26
  27 extern void *nlmsg_data(struct nlmsg *nlmsg)
  28 {
  29         char *data = ((char *)nlmsg) + NLMSG_HDRLEN;
  30         if (!nlmsg_len(nlmsg))
  31                 return NULL;
  32         return data;
  33 }
  34
  35 static int nla_put(struct nlmsg *nlmsg, int attr,
  36                    const void *data, size_t len)
  37 {
  38         struct rtattr *rta;
  39         size_t rtalen = RTA_LENGTH(len);
  40         size_t tlen = NLMSG_ALIGN(nlmsg->nlmsghdr->nlmsg_len) + RTA_ALIGN(rtalen);
  41
  42         if (tlen > nlmsg->cap)
  43                 return -ENOMEM;
  44
  45         rta = NLMSG_TAIL(nlmsg->nlmsghdr);
  46         rta->rta_type = attr;
  47         rta->rta_len = rtalen;
  48         if (data && len)
  49                 memcpy(RTA_DATA(rta), data, len);
  50         nlmsg->nlmsghdr->nlmsg_len = tlen;
  51         return 0;
  52 }
  53
  54 extern int nla_put_buffer(struct nlmsg *nlmsg, int attr,
  55                           const void *data, size_t size)
  56 {
  57         return nla_put(nlmsg, attr, data, size);
  58 }
  59
  60 extern int nla_put_string(struct nlmsg *nlmsg, int attr, const char *string)
  61 {
  62         return nla_put(nlmsg, attr, string, strlen(string) + 1);
  63 }
  64
  65 extern int nla_put_u32(struct nlmsg *nlmsg, int attr, int value)
  66 {
  67         return nla_put(nlmsg, attr, &value, sizeof(value));
  68 }
  69
  70 extern int nla_put_u16(struct nlmsg *nlmsg, int attr, unsigned short value)
  71 {
  72         return nla_put(nlmsg, attr, &value, 2);
  73 }
  74
  75 extern int nla_put_attr(struct nlmsg *nlmsg, int attr)
  76 {
  77         return nla_put(nlmsg, attr, NULL, 0);
  78 }
  79
  80 struct rtattr *nla_begin_nested(struct nlmsg *nlmsg, int attr)
  81 {
  82         struct rtattr *rtattr = NLMSG_TAIL(nlmsg->nlmsghdr);
  83
  84         if (nla_put_attr(nlmsg, attr))
  85                 return NULL;
  86
  87         return rtattr;
  88 }
  89
  90 void nla_end_nested(struct nlmsg *nlmsg, struct rtattr *attr)
  91 {
  92         attr->rta_len = (void *)NLMSG_TAIL(nlmsg->nlmsghdr) - (void *)attr;
  93 }
  94
  95 extern struct nlmsg *nlmsg_alloc(size_t size)
  96 {
  97         struct nlmsg *nlmsg;
  98         size_t len = NLMSG_HDRLEN + NLMSG_ALIGN(size);
  99
 100         nlmsg = (struct nlmsg *)malloc(sizeof(struct nlmsg));
 101         if (!nlmsg)
 102                 return NULL;
 103
 104         nlmsg->nlmsghdr = (struct nlmsghdr *)malloc(len);
 105         if (!nlmsg->nlmsghdr)
 106                 goto errout;
 107
 108         memset(nlmsg->nlmsghdr, 0, len);
 109         nlmsg->cap = len;
 110         nlmsg->nlmsghdr->nlmsg_len = NLMSG_HDRLEN;
 111
 112         return nlmsg;
 113 errout:
 114         free(nlmsg);
 115         return NULL;
 116 }
 117
 118 extern void *nlmsg_reserve(struct nlmsg *nlmsg, size_t len)
 119 {
 120         void *buf;
 121         size_t nlmsg_len = nlmsg->nlmsghdr->nlmsg_len;
 122         size_t tlen = NLMSG_ALIGN(len);
 123
 124         if (nlmsg_len + tlen > nlmsg->cap)
 125                 return NULL;
 126
 127         buf = ((char *)(nlmsg->nlmsghdr)) + nlmsg_len;
 128         nlmsg->nlmsghdr->nlmsg_len += tlen;
 129
 130         if (tlen > len)
 131                 memset(buf + len, 0, tlen - len);
 132
 133         return buf;
 134 }
 135
 136 extern struct nlmsg *nlmsg_alloc_reserve(size_t size)
 137 {
 138         struct nlmsg *nlmsg;
 139
 140         nlmsg = nlmsg_alloc(size);
 141         if (!nlmsg)
 142                 return NULL;
 143
 144         /* Just set message length to cap directly. */
 145         nlmsg->nlmsghdr->nlmsg_len = nlmsg->cap;
 146         return nlmsg;
 147 }
 148
 149 extern void nlmsg_free(struct nlmsg *nlmsg)
 150 {
 151         if (!nlmsg)
 152                 return;
 153
 154         free(nlmsg->nlmsghdr);
 155         free(nlmsg);
 156 }
 157
 158 extern int __netlink_recv(struct nl_handler *handler, struct nlmsghdr *nlmsghdr)
 159 {
 160         int ret;
 161         struct sockaddr_nl nladdr;
 162         struct iovec iov = {
 163             .iov_base = nlmsghdr,
 164             .iov_len = nlmsghdr->nlmsg_len,
 165         };
 166
 167         struct msghdr msg = {
 168             .msg_name = &nladdr,
 169             .msg_namelen = sizeof(nladdr),
 170             .msg_iov = &iov,
 171             .msg_iovlen = 1,
 172         };
 173
 174         memset(&nladdr, 0, sizeof(nladdr));
 175         nladdr.nl_family = AF_NETLINK;
 176         nladdr.nl_pid = 0;
 177         nladdr.nl_groups = 0;
 178
 179 again:
 180         ret = recvmsg(handler->fd, &msg, 0);
 181         if (ret < 0) {
 182                 if (errno == EINTR)
 183                         goto again;
 184
 185                 return -1;
 186         }
 187
 188         if (!ret)
 189                 return 0;
 190
 191         if (msg.msg_flags & MSG_TRUNC && (ret == nlmsghdr->nlmsg_len)) {
 192                 errno = EMSGSIZE;
 193                 ret = -1;
 194         }
 195
 196         return ret;
 197 }
 198
 199 extern int netlink_rcv(struct nl_handler *handler, struct nlmsg *answer)
 200 {
 201         return __netlink_recv(handler, answer->nlmsghdr);
 202 }
 203
 204 extern int __netlink_send(struct nl_handler *handler, struct nlmsghdr *nlmsghdr)
 205 {
 206         int ret;
 207         struct sockaddr_nl nladdr;
 208         struct iovec iov = {
 209             .iov_base = nlmsghdr,
 210             .iov_len = nlmsghdr->nlmsg_len,
 211         };
 212         struct msghdr msg = {
 213             .msg_name = &nladdr,
 214             .msg_namelen = sizeof(nladdr),
 215             .msg_iov = &iov,
 216             .msg_iovlen = 1,
 217         };
 218
 219         memset(&nladdr, 0, sizeof(nladdr));
 220         nladdr.nl_family = AF_NETLINK;
 221         nladdr.nl_pid = 0;
 222         nladdr.nl_groups = 0;
 223
 224         ret = sendmsg(handler->fd, &msg, MSG_NOSIGNAL);
 225         if (ret < 0)
 226                 return -1;
 227
 228         return ret;
 229 }
 230
 231 extern int netlink_send(struct nl_handler *handler, struct nlmsg *nlmsg)
 232 {
 233         return __netlink_send(handler, nlmsg->nlmsghdr);
 234 }
 235
 236 extern int __netlink_transaction(struct nl_handler *handler,
 237                                  struct nlmsghdr *request,
 238                                  struct nlmsghdr *answer)
 239 {
 240         int ret;
 241
 242         ret = __netlink_send(handler, request);
 243         if (ret < 0)
 244                 return -1;
 245
 246         ret = __netlink_recv(handler, answer);
 247         if (ret < 0)
 248                 return -1;
 249
 250         ret = 0;
 251         if (answer->nlmsg_type == NLMSG_ERROR) {
 252                 struct nlmsgerr *err = (struct nlmsgerr *)NLMSG_DATA(answer);
 253                 errno = -err->error;
 254                 if (err->error < 0)
 255                         ret = -1;
 256         }
 257
 258         return ret;
 259 }
 260
 261 extern int netlink_transaction(struct nl_handler *handler,
 262                                struct nlmsg *request, struct nlmsg *answer)
 263 {
 264         return __netlink_transaction(handler, request->nlmsghdr,
 265                                      answer->nlmsghdr);
 266 }
 267
 268 extern int netlink_open(struct nl_handler *handler, int protocol)
 269 {
 270         socklen_t socklen;
 271         int sndbuf = 32768;
 272         int rcvbuf = 32768;
 273         int err;
 274
 275         memset(handler, 0, sizeof(*handler));
 276
 277         handler->fd = socket(AF_NETLINK, SOCK_RAW | SOCK_CLOEXEC, protocol);
 278         if (handler->fd < 0)
 279                 return -errno;
 280
 281         if (setsockopt(handler->fd, SOL_SOCKET, SO_SNDBUF,
 282                        &sndbuf, sizeof(sndbuf)) < 0)
 283                 goto err_with_errno;
 284
 285         if (setsockopt(handler->fd, SOL_SOCKET, SO_RCVBUF,
 286                        &rcvbuf,sizeof(rcvbuf)) < 0)
 287                 goto err_with_errno;
 288
 289         memset(&handler->local, 0, sizeof(handler->local));
 290         handler->local.nl_family = AF_NETLINK;
 291         handler->local.nl_groups = 0;
 292
 293         if (bind(handler->fd, (struct sockaddr*)&handler->local,
 294                  sizeof(handler->local)) < 0)
 295                 goto err_with_errno;
 296
 297         socklen = sizeof(handler->local);
 298         if (getsockname(handler->fd, (struct sockaddr*)&handler->local,
 299                         &socklen) < 0)
 300                 goto err_with_errno;
 301
 302         if (socklen != sizeof(handler->local)) {
 303                 err = -EINVAL;
 304                 goto errclose;
 305         }
 306
 307         if (handler->local.nl_family != AF_NETLINK) {
 308                 err = -EINVAL;
 309                 goto errclose;
 310         }
 311
 312         handler->seq = time(NULL);
 313
 314         return 0;
 315 err_with_errno:
 316         err = -errno;
 317 errclose:
 318         close(handler->fd);
 319         return err;
 320 }
 321
 322 extern int netlink_close(struct nl_handler *handler)
 323 {
 324         close(handler->fd);
 325         handler->fd = -1;
 326         return 0;
 327 }
 328
 329 int addattr(struct nlmsghdr *n, size_t maxlen, int type, const void *data,
 330             size_t alen)
 331 {
 332         int len = RTA_LENGTH(alen);
 333         struct rtattr *rta;
 334
 335         errno = EMSGSIZE;
 336         if (NLMSG_ALIGN(n->nlmsg_len) + RTA_ALIGN(len) > maxlen)
 337                 return -1;
 338
 339         rta = NLMSG_TAIL(n);
 340         rta->rta_type = type;
 341         rta->rta_len = len;
 342         if (alen)
 343                 memcpy(RTA_DATA(rta), data, alen);
 344         n->nlmsg_len = NLMSG_ALIGN(n->nlmsg_len) + RTA_ALIGN(len);
 345
 346         return 0;
 347 }