src/lxc/genl.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 <string.h>
  24 #include <stdio.h>
  25 #include <sys/socket.h>
  26 #include <stdlib.h>
  27 #include <errno.h>
  28 #include <unistd.h>
  29 #include <linux/genetlink.h>
  30 #include <linux/rtnetlink.h>
  31
  32 #include "nl.h"
  33 #include "genl.h"
  34
  35 static int genetlink_resolve_family(const char *family)
  36 {
  37         struct nl_handler handler;
  38         struct nlattr *attr;
  39         struct genlmsg *request, *reply;
  40         struct genlmsghdr *genlmsghdr;
  41
  42         int len, ret;
  43
  44         request = genlmsg_alloc(GENLMSG_GOOD_SIZE);
  45         if (!request)
  46                 return -ENOMEM;
  47
  48         reply = genlmsg_alloc(GENLMSG_GOOD_SIZE);
  49         if (!reply) {
  50                 genlmsg_free(request);
  51                 return -ENOMEM;
  52         }
  53
  54         request->nlmsghdr.nlmsg_len = NLMSG_LENGTH(GENL_HDRLEN);
  55         request->nlmsghdr.nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK;
  56         request->nlmsghdr.nlmsg_type = GENL_ID_CTRL;
  57
  58         genlmsghdr = NLMSG_DATA(&request->nlmsghdr);
  59         genlmsghdr->cmd = CTRL_CMD_GETFAMILY;
  60
  61         ret = netlink_open(&handler, NETLINK_GENERIC);
  62         if (ret)
  63                 goto out;
  64
  65         ret = nla_put_string((struct nlmsg *)&request->nlmsghdr,
  66                              CTRL_ATTR_FAMILY_NAME, family);
  67         if (ret)
  68                 goto out_close;
  69
  70         ret = netlink_transaction(&handler, (struct nlmsg *)&request->nlmsghdr,
  71                                   (struct nlmsg *)&reply->nlmsghdr);
  72         if (ret < 0)
  73                 goto out_close;
  74
  75         genlmsghdr = NLMSG_DATA(&reply->nlmsghdr);
  76         len = reply->nlmsghdr.nlmsg_len;
  77
  78         ret = -ENOMSG;
  79         if (reply->nlmsghdr.nlmsg_type !=  GENL_ID_CTRL)
  80                 goto out_close;
  81
  82         if (genlmsghdr->cmd != CTRL_CMD_NEWFAMILY)
  83                 goto out_close;
  84
  85         ret = -EMSGSIZE;
  86         len -= NLMSG_LENGTH(GENL_HDRLEN);
  87         if (len < 0)
  88                 goto out_close;
  89
  90         attr = (struct nlattr *)GENLMSG_DATA(reply);
  91         attr = (struct nlattr *)((char *)attr + NLA_ALIGN(attr->nla_len));
  92
  93         ret = -ENOMSG;
  94         if (attr->nla_type != CTRL_ATTR_FAMILY_ID)
  95                 goto out_close;
  96
  97         ret =  *(__u16 *) NLA_DATA(attr);
  98 out_close:
  99         netlink_close(&handler);
 100 out:
 101         genlmsg_free(request);
 102         genlmsg_free(reply);
 103         return ret;
 104 }
 105
 106 extern int genetlink_open(struct genl_handler *handler, const char *family)
 107 {
 108         int ret;
 109         handler->family = genetlink_resolve_family(family);
 110         if (handler->family < 0)
 111                 return handler->family;
 112
 113         ret = netlink_open(&handler->nlh, NETLINK_GENERIC);
 114
 115         return ret;
 116 }
 117
 118 extern int genetlink_close(struct genl_handler *handler)
 119 {
 120         return netlink_close(&handler->nlh);
 121 }
 122
 123 extern int genetlink_rcv(struct genl_handler *handler, struct genlmsg *genlmsg)
 124 {
 125         return netlink_rcv(&handler->nlh, (struct nlmsg *)&genlmsg->nlmsghdr);
 126 }
 127
 128 extern int genetlink_send(struct genl_handler *handler, struct genlmsg *genlmsg)
 129 {
 130
 131         return netlink_send(&handler->nlh, (struct nlmsg *)&genlmsg->nlmsghdr);
 132 }
 133
 134 extern int genetlink_transaction(struct genl_handler *handler,
 135                           struct genlmsg *request, struct genlmsg *answer)
 136 {
 137         return netlink_transaction(&handler->nlh, (struct nlmsg *)&request->nlmsghdr,
 138                                    (struct nlmsg *)&answer->nlmsghdr);
 139 }
 140
 141 extern struct genlmsg *genlmsg_alloc(size_t size)
 142 {
 143         size_t len = NLMSG_LENGTH(GENL_HDRLEN) + size;
 144         return  (struct genlmsg *)nlmsg_alloc(len);
 145 }
 146
 147 extern void genlmsg_free(struct genlmsg *genlmsg)
 148 {
 149         free(genlmsg);
 150 }