src/core/loopback-setup.c

   1 /***
   2   This file is part of systemd.
   3
   4   Copyright 2010 Lennart Poettering
   5
   6   systemd is free software; you can redistribute it and/or modify it
   7   under the terms of the GNU Lesser General Public License as published by
   8   the Free Software Foundation; either version 2.1 of the License, or
   9   (at your option) any later version.
  10
  11   systemd is distributed in the hope that it will be useful, but
  12   WITHOUT ANY WARRANTY; without even the implied warranty of
  13   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  14   Lesser General Public License for more details.
  15
  16   You should have received a copy of the GNU Lesser General Public License
  17   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  18 ***/
  19
  20 #include <net/if.h>
  21 #include <stdlib.h>
  22
  23 #include "sd-netlink.h"
  24
  25 #include "loopback-setup.h"
  26 #include "missing.h"
  27 #include "netlink-util.h"
  28
  29 static int start_loopback(sd_netlink *rtnl) {
  30         _cleanup_(sd_netlink_message_unrefp) sd_netlink_message *req = NULL;
  31         int r;
  32
  33         r = sd_rtnl_message_new_link(rtnl, &req, RTM_SETLINK, LOOPBACK_IFINDEX);
  34         if (r < 0)
  35                 return r;
  36
  37         r = sd_rtnl_message_link_set_flags(req, IFF_UP, IFF_UP);
  38         if (r < 0)
  39                 return r;
  40
  41         r = sd_netlink_call(rtnl, req, 0, NULL);
  42         if (r < 0)
  43                 return r;
  44
  45         return 0;
  46 }
  47
  48 static bool check_loopback(sd_netlink *rtnl) {
  49         _cleanup_(sd_netlink_message_unrefp) sd_netlink_message *req = NULL, *reply = NULL;
  50         unsigned flags;
  51         int r;
  52
  53         r = sd_rtnl_message_new_link(rtnl, &req, RTM_GETLINK, LOOPBACK_IFINDEX);
  54         if (r < 0)
  55                 return false;
  56
  57         r = sd_netlink_call(rtnl, req, 0, &reply);
  58         if (r < 0)
  59                 return false;
  60
  61         r = sd_rtnl_message_link_get_flags(reply, &flags);
  62         if (r < 0)
  63                 return false;
  64
  65         return flags & IFF_UP;
  66 }
  67
  68 int loopback_setup(void) {
  69         _cleanup_(sd_netlink_unrefp) sd_netlink *rtnl = NULL;
  70         int r;
  71
  72         r = sd_netlink_open(&rtnl);
  73         if (r < 0)
  74                 return r;
  75
  76         r = start_loopback(rtnl);
  77         if (r < 0) {
  78
  79                 /* If we lack the permissions to configure the
  80                  * loopback device, but we find it to be already
  81                  * configured, let's exit cleanly, in order to
  82                  * supported unprivileged containers. */
  83                 if (r == -EPERM && check_loopback(rtnl))
  84                         return 0;
  85
  86                 return log_warning_errno(r, "Failed to configure loopback device: %m");
  87         }
  88
  89         return 0;
  90 }