src/lxc/nl.c

   1 /*
   2  * lxc: linux Container library
   3  *
   4  * (C) Copyright IBM Corp. 2007, 2008
   5  *
   6  * Authors:
   7  * Daniel Lezcano <daniel.lezcano at free.fr>
   8  *
   9  * This library is free software; you can redistribute it and/or
  10  * modify it under the terms of the GNU Lesser General Public
  11  * License as published by the Free Software Foundation; either
  12  * version 2.1 of the License, or (at your option) any later version.
  13  *
  14  * This library is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  17  * Lesser General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU Lesser General Public
  20  * License along with this library; if not, write to the Free Software
  21  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  22  */
  23 #include <sys/socket.h>
  24 #include <string.h>
  25 #include <stdio.h>
  26 #include <time.h>
  27 #include <unistd.h>
  28 #include <errno.h>
  29 #include <stdlib.h>
  30 #include <linux/netlink.h>
  31 #include <linux/rtnetlink.h>
  32
  33 #include "nl.h"
  34
  35 #define NLMSG_TAIL(nmsg) \
  36         ((struct rtattr *) (((void *) (nmsg)) + NLMSG_ALIGN((nmsg)->nlmsg_len)))
  37
  38 extern size_t nlmsg_len(const struct nlmsg *nlmsg)
  39 {
  40         return nlmsg->nlmsghdr.nlmsg_len - NLMSG_HDRLEN;
  41 }
  42
  43 extern void *nlmsg_data(struct nlmsg *nlmsg)
  44 {
  45         char *data = ((char *)nlmsg) + NLMSG_ALIGN(sizeof(struct nlmsghdr));
  46         if (!nlmsg_len(nlmsg))
  47                 return NULL;
  48         return data;
  49 }
  50
  51 static int nla_put(struct nlmsg *nlmsg, int attr,
  52                    const void *data, size_t len)
  53 {
  54         struct rtattr *rta;
  55         size_t rtalen = RTA_LENGTH(len);
  56
  57         rta = NLMSG_TAIL(&nlmsg->nlmsghdr);
  58         rta->rta_type = attr;
  59         rta->rta_len = rtalen;
  60         memcpy(RTA_DATA(rta), data, len);
  61         nlmsg->nlmsghdr.nlmsg_len =
  62                 NLMSG_ALIGN(nlmsg->nlmsghdr.nlmsg_len) + RTA_ALIGN(rtalen);
  63         return 0;
  64 }
  65
  66 extern int nla_put_buffer(struct nlmsg *nlmsg, int attr,
  67                           const void *data, size_t size)
  68 {
  69         return nla_put(nlmsg, attr, data, size);
  70 }
  71
  72 extern int nla_put_string(struct nlmsg *nlmsg, int attr, const char *string)
  73 {
  74         return nla_put(nlmsg, attr, string, strlen(string) + 1);
  75 }
  76
  77 extern int nla_put_u32(struct nlmsg *nlmsg, int attr, int value)
  78 {
  79         return nla_put(nlmsg, attr, &value, sizeof(value));
  80 }
  81
  82 extern int nla_put_u16(struct nlmsg *nlmsg, int attr, unsigned short value)
  83 {
  84         return nla_put(nlmsg, attr, &value, 2);
  85 }
  86
  87 extern int nla_put_attr(struct nlmsg *nlmsg, int attr)
  88 {
  89         return nla_put(nlmsg, attr, NULL, 0);
  90 }
  91
  92 struct rtattr *nla_begin_nested(struct nlmsg *nlmsg, int attr)
  93 {
  94         struct rtattr *rtattr = NLMSG_TAIL(&nlmsg->nlmsghdr);
  95
  96         if (nla_put_attr(nlmsg, attr))
  97                 return NULL;
  98
  99         return rtattr;
 100 }
 101
 102 void nla_end_nested(struct nlmsg *nlmsg, struct rtattr *attr)
 103 {
 104         attr->rta_len = (void *)NLMSG_TAIL(&nlmsg->nlmsghdr) - (void *)attr;
 105 }
 106
 107 extern struct nlmsg *nlmsg_alloc(size_t size)
 108 {
 109         struct nlmsg *nlmsg;
 110         size_t len = NLMSG_ALIGN(size) + NLMSG_ALIGN(sizeof(struct nlmsghdr *));
 111
 112         nlmsg = (struct nlmsg *)malloc(len);
 113         if (!nlmsg)
 114                 return NULL;
 115
 116         memset(nlmsg, 0, len);
 117         nlmsg->nlmsghdr.nlmsg_len = NLMSG_ALIGN(size);
 118
 119         return nlmsg;
 120 }
 121
 122 extern void nlmsg_free(struct nlmsg *nlmsg)
 123 {
 124         free(nlmsg);
 125 }
 126
 127 extern int netlink_rcv(struct nl_handler *handler, struct nlmsg *answer)
 128 {
 129         int ret;
 130         struct sockaddr_nl nladdr;
 131         struct iovec iov = {
 132                 .iov_base = answer,
 133                 .iov_len = answer->nlmsghdr.nlmsg_len,
 134         };
 135
 136         struct msghdr msg = {
 137                 .msg_name = &nladdr,
 138                 .msg_namelen = sizeof(nladdr),
 139                 .msg_iov = &iov,
 140                 .msg_iovlen = 1,
 141         };
 142
 143         memset(&nladdr, 0, sizeof(nladdr));
 144         nladdr.nl_family = AF_NETLINK;
 145         nladdr.nl_pid = 0;
 146         nladdr.nl_groups = 0;
 147
 148 again:
 149         ret = recvmsg(handler->fd, &msg, 0);
 150         if (ret < 0) {
 151                 if (errno == EINTR)
 152                         goto again;
 153                 return -errno;
 154         }
 155
 156         if (!ret)
 157                 return 0;
 158
 159         if (msg.msg_flags & MSG_TRUNC &&
 160             ret == answer->nlmsghdr.nlmsg_len)
 161                 return -EMSGSIZE;
 162
 163         return ret;
 164 }
 165
 166 extern int netlink_send(struct nl_handler *handler, struct nlmsg *nlmsg)
 167 {
 168         struct sockaddr_nl nladdr;
 169         struct iovec iov = {
 170                 .iov_base = (void*)nlmsg,
 171                 .iov_len = nlmsg->nlmsghdr.nlmsg_len,
 172         };
 173         struct msghdr msg = {
 174                 .msg_name = &nladdr,
 175                 .msg_namelen = sizeof(nladdr),
 176                 .msg_iov = &iov,
 177                 .msg_iovlen = 1,
 178         };
 179         int ret;
 180
 181         memset(&nladdr, 0, sizeof(nladdr));
 182         nladdr.nl_family = AF_NETLINK;
 183         nladdr.nl_pid = 0;
 184         nladdr.nl_groups = 0;
 185
 186         ret = sendmsg(handler->fd, &msg, 0);
 187         if (ret < 0)
 188                 return -errno;
 189
 190         return ret;
 191 }
 192
 193 #ifndef NLMSG_ERROR
 194 #define NLMSG_ERROR                0x2
 195 #endif
 196 extern int netlink_transaction(struct nl_handler *handler,
 197                                struct nlmsg *request, struct nlmsg *answer)
 198 {
 199         int ret;
 200
 201         ret = netlink_send(handler, request);
 202         if (ret < 0)
 203                 return ret;
 204
 205         ret = netlink_rcv(handler, answer);
 206         if (ret < 0)
 207                 return ret;
 208
 209         if (answer->nlmsghdr.nlmsg_type == NLMSG_ERROR) {
 210                 struct nlmsgerr *err = (struct nlmsgerr*)NLMSG_DATA(answer);
 211                 return err->error;
 212         }
 213
 214         return 0;
 215 }
 216
 217 extern int netlink_open(struct nl_handler *handler, int protocol)
 218 {
 219         socklen_t socklen;
 220         int sndbuf = 32768;
 221         int rcvbuf = 32768;
 222
 223         memset(handler, 0, sizeof(*handler));
 224
 225         handler->fd = socket(AF_NETLINK, SOCK_RAW, protocol);
 226         if (handler->fd < 0)
 227                 return -errno;
 228
 229         if (setsockopt(handler->fd, SOL_SOCKET, SO_SNDBUF,
 230                        &sndbuf, sizeof(sndbuf)) < 0)
 231                 return -errno;
 232
 233         if (setsockopt(handler->fd, SOL_SOCKET, SO_RCVBUF,
 234                        &rcvbuf,sizeof(rcvbuf)) < 0)
 235                 return -errno;
 236
 237         memset(&handler->local, 0, sizeof(handler->local));
 238         handler->local.nl_family = AF_NETLINK;
 239         handler->local.nl_groups = 0;
 240
 241         if (bind(handler->fd, (struct sockaddr*)&handler->local,
 242                  sizeof(handler->local)) < 0)
 243                 return -errno;
 244
 245         socklen = sizeof(handler->local);
 246         if (getsockname(handler->fd, (struct sockaddr*)&handler->local,
 247                         &socklen) < 0)
 248                 return -errno;
 249
 250         if (socklen != sizeof(handler->local))
 251                 return -EINVAL;
 252
 253         if (handler->local.nl_family != AF_NETLINK)
 254                 return -EINVAL;
 255
 256         handler->seq = time(NULL);
 257
 258         return 0;
 259 }
 260
 261 extern int netlink_close(struct nl_handler *handler)
 262 {
 263         close(handler->fd);
 264         handler->fd = -1;
 265         return 0;
 266 }
 267