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 size_t nlmsg_len(const struct nlmsg *nlmsg)
  23 {
  24         return nlmsg->nlmsghdr->nlmsg_len - NLMSG_HDRLEN;
  25 }
  26
  27 void *nlmsg_data(struct nlmsg *nlmsg)
  28 {
  29         char *data;
  30
  31         data = ((char *)nlmsg) + NLMSG_HDRLEN;
  32         if (!nlmsg_len(nlmsg))
  33                 return ret_set_errno(NULL, EINVAL);
  34
  35         return data;
  36 }
  37
  38 static int nla_put(struct nlmsg *nlmsg, int attr,
  39                    const void *data, size_t len)
  40 {
  41         struct rtattr *rta;
  42         size_t rtalen = RTA_LENGTH(len);
  43         size_t tlen = NLMSG_ALIGN(nlmsg->nlmsghdr->nlmsg_len) + RTA_ALIGN(rtalen);
  44
  45         if (tlen > nlmsg->cap)
  46                 return ret_errno(ENOMEM);
  47
  48         rta = NLMSG_TAIL(nlmsg->nlmsghdr);
  49         rta->rta_type = attr;
  50         rta->rta_len = rtalen;
  51         if (data && len)
  52                 memcpy(RTA_DATA(rta), data, len);
  53         nlmsg->nlmsghdr->nlmsg_len = tlen;
  54
  55         return 0;
  56 }
  57
  58 int nla_put_buffer(struct nlmsg *nlmsg, int attr, const void *data, size_t size)
  59 {
  60         return nla_put(nlmsg, attr, data, size);
  61 }
  62
  63 int nla_put_string(struct nlmsg *nlmsg, int attr, const char *string)
  64 {
  65         return nla_put(nlmsg, attr, string, strlen(string) + 1);
  66 }
  67
  68 int nla_put_u32(struct nlmsg *nlmsg, int attr, int value)
  69 {
  70         return nla_put(nlmsg, attr, &value, sizeof(value));
  71 }
  72
  73 int nla_put_u16(struct nlmsg *nlmsg, int attr, unsigned short value)
  74 {
  75         return nla_put(nlmsg, attr, &value, 2);
  76 }
  77
  78 int nla_put_attr(struct nlmsg *nlmsg, int attr)
  79 {
  80         return nla_put(nlmsg, attr, NULL, 0);
  81 }
  82
  83 struct rtattr *nla_begin_nested(struct nlmsg *nlmsg, int attr)
  84 {
  85         struct rtattr *rtattr;
  86
  87         rtattr = NLMSG_TAIL(nlmsg->nlmsghdr);
  88         if (nla_put_attr(nlmsg, attr))
  89                 return ret_set_errno(NULL, ENOMEM);
  90
  91         return rtattr;
  92 }
  93
  94 void nla_end_nested(struct nlmsg *nlmsg, struct rtattr *attr)
  95 {
  96         attr->rta_len = (void *)NLMSG_TAIL(nlmsg->nlmsghdr) - (void *)attr;
  97 }
  98
  99 struct nlmsg *nlmsg_alloc(size_t size)
 100 {
 101         __do_free struct nlmsg *nlmsg = NULL;
 102         size_t len = NLMSG_HDRLEN + NLMSG_ALIGN(size);
 103
 104         nlmsg = malloc(sizeof(struct nlmsg));
 105         if (!nlmsg)
 106                 return ret_set_errno(NULL, ENOMEM);
 107
 108         nlmsg->nlmsghdr = malloc(len);
 109         if (!nlmsg->nlmsghdr)
 110                 return ret_set_errno(NULL, ENOMEM);
 111
 112         memset(nlmsg->nlmsghdr, 0, len);
 113         nlmsg->cap = len;
 114         nlmsg->nlmsghdr->nlmsg_len = NLMSG_HDRLEN;
 115
 116         return move_ptr(nlmsg);
 117 }
 118
 119 void *nlmsg_reserve(struct nlmsg *nlmsg, size_t len)
 120 {
 121         void *buf;
 122         size_t nlmsg_len = nlmsg->nlmsghdr->nlmsg_len;
 123         size_t tlen = NLMSG_ALIGN(len);
 124
 125         if (nlmsg_len + tlen > nlmsg->cap)
 126                 return ret_set_errno(NULL, ENOMEM);
 127
 128         buf = ((char *)(nlmsg->nlmsghdr)) + nlmsg_len;
 129         nlmsg->nlmsghdr->nlmsg_len += tlen;
 130
 131         if (tlen > len)
 132                 memset(buf + len, 0, tlen - len);
 133
 134         return buf;
 135 }
 136
 137 struct nlmsg *nlmsg_alloc_reserve(size_t size)
 138 {
 139         struct nlmsg *nlmsg;
 140
 141         nlmsg = nlmsg_alloc(size);
 142         if (!nlmsg)
 143                 return ret_set_errno(NULL, ENOMEM);
 144
 145         /* Just set message length to cap directly. */
 146         nlmsg->nlmsghdr->nlmsg_len = nlmsg->cap;
 147         return nlmsg;
 148 }
 149
 150 void nlmsg_free(struct nlmsg *nlmsg)
 151 {
 152         if (nlmsg) {
 153                 free(nlmsg->nlmsghdr);
 154                 free(nlmsg);
 155         }
 156 }
 157
 158 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 ret_errno(errno);
 186         }
 187
 188         if (!ret)
 189                 return 0;
 190
 191         if (msg.msg_flags & MSG_TRUNC && (ret == nlmsghdr->nlmsg_len))
 192                 return ret_errno(EMSGSIZE);
 193
 194         return ret;
 195 }
 196
 197 int netlink_rcv(struct nl_handler *handler, struct nlmsg *answer)
 198 {
 199         return __netlink_recv(handler, answer->nlmsghdr);
 200 }
 201
 202 int __netlink_send(struct nl_handler *handler, struct nlmsghdr *nlmsghdr)
 203 {
 204         int ret;
 205         struct sockaddr_nl nladdr;
 206         struct iovec iov = {
 207             .iov_base = nlmsghdr,
 208             .iov_len = nlmsghdr->nlmsg_len,
 209         };
 210         struct msghdr msg = {
 211             .msg_name = &nladdr,
 212             .msg_namelen = sizeof(nladdr),
 213             .msg_iov = &iov,
 214             .msg_iovlen = 1,
 215         };
 216
 217         memset(&nladdr, 0, sizeof(nladdr));
 218         nladdr.nl_family = AF_NETLINK;
 219         nladdr.nl_pid = 0;
 220         nladdr.nl_groups = 0;
 221
 222         ret = sendmsg(handler->fd, &msg, MSG_NOSIGNAL);
 223         if (ret < 0)
 224                 return ret_errno(errno);
 225
 226         return ret;
 227 }
 228
 229 extern int netlink_send(struct nl_handler *handler, struct nlmsg *nlmsg)
 230 {
 231         return __netlink_send(handler, nlmsg->nlmsghdr);
 232 }
 233
 234 extern int __netlink_transaction(struct nl_handler *handler,
 235                                  struct nlmsghdr *request,
 236                                  struct nlmsghdr *answer)
 237 {
 238         int ret;
 239
 240         ret = __netlink_send(handler, request);
 241         if (ret < 0)
 242                 return ret;
 243
 244         ret = __netlink_recv(handler, answer);
 245         if (ret < 0)
 246                 return ret;
 247
 248         if (answer->nlmsg_type == NLMSG_ERROR) {
 249                 struct nlmsgerr *err = (struct nlmsgerr *)NLMSG_DATA(answer);
 250                 if (err->error < 0)
 251                         return ret_errno(-err->error);
 252         }
 253
 254         return 0;
 255 }
 256
 257 extern int netlink_transaction(struct nl_handler *handler,
 258                                struct nlmsg *request, struct nlmsg *answer)
 259 {
 260         return __netlink_transaction(handler, request->nlmsghdr,
 261                                      answer->nlmsghdr);
 262 }
 263
 264 extern int netlink_open(struct nl_handler *handler, int protocol)
 265 {
 266         __do_close int fd = -EBADF;
 267         socklen_t socklen;
 268         int sndbuf = 32768;
 269         int rcvbuf = 32768;
 270
 271         memset(handler, 0, sizeof(*handler));
 272         handler->fd = -EBADF;
 273
 274         fd = socket(AF_NETLINK, SOCK_RAW | SOCK_CLOEXEC, protocol);
 275         if (fd < 0)
 276                 return ret_errno(errno);
 277
 278         if (setsockopt(fd, SOL_SOCKET, SO_SNDBUF, &sndbuf, sizeof(sndbuf)) < 0)
 279                 return ret_errno(errno);
 280
 281         if (setsockopt(fd, SOL_SOCKET, SO_RCVBUF, &rcvbuf,sizeof(rcvbuf)) < 0)
 282                 return ret_errno(errno);
 283
 284         memset(&handler->local, 0, sizeof(handler->local));
 285         handler->local.nl_family = AF_NETLINK;
 286         handler->local.nl_groups = 0;
 287
 288         if (bind(fd, (struct sockaddr*)&handler->local, sizeof(handler->local)) < 0)
 289                 return ret_errno(errno);
 290
 291         socklen = sizeof(handler->local);
 292         if (getsockname(fd, (struct sockaddr*)&handler->local, &socklen) < 0)
 293                 return ret_errno(errno);
 294
 295         if (socklen != sizeof(handler->local))
 296                 return ret_errno(EINVAL);
 297
 298         if (handler->local.nl_family != AF_NETLINK)
 299                 return ret_errno(EINVAL);
 300
 301         handler->seq = time(NULL);
 302         handler->fd = move_fd(fd);
 303         return 0;
 304 }
 305
 306 extern void netlink_close(struct nl_handler *handler)
 307 {
 308         close_prot_errno_disarm(handler->fd);
 309 }
 310
 311 int addattr(struct nlmsghdr *n, size_t maxlen, int type, const void *data,
 312             size_t alen)
 313 {
 314         int len = RTA_LENGTH(alen);
 315         struct rtattr *rta;
 316
 317         if (NLMSG_ALIGN(n->nlmsg_len) + RTA_ALIGN(len) > maxlen)
 318                 return ret_errno(EMSGSIZE);
 319
 320         rta = NLMSG_TAIL(n);
 321         rta->rta_type = type;
 322         rta->rta_len = len;
 323         if (alen)
 324                 memcpy(RTA_DATA(rta), data, alen);
 325         n->nlmsg_len = NLMSG_ALIGN(n->nlmsg_len) + RTA_ALIGN(len);
 326
 327         return 0;
 328 }