src/libsystemd-network/dhcp-identifier.c

   1 /***
   2   This file is part of systemd.
   3
   4   Copyright (C) 2015 Tom Gundersen <teg@jklmen>
   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 "libudev.h"
  21 #include "sd-id128.h"
  22
  23 #include "dhcp-identifier.h"
  24 #include "dhcp6-protocol.h"
  25 #include "network-internal.h"
  26 #include "siphash24.h"
  27 #include "sparse-endian.h"
  28 #include "udev-util.h"
  29 #include "virt.h"
  30
  31 #define SYSTEMD_PEN 43793
  32 #define HASH_KEY SD_ID128_MAKE(80,11,8c,c2,fe,4a,03,ee,3e,d6,0c,6f,36,39,14,09)
  33
  34 int dhcp_identifier_set_duid_en(struct duid *duid, size_t *len) {
  35         sd_id128_t machine_id;
  36         uint64_t hash;
  37         int r;
  38
  39         assert(duid);
  40         assert(len);
  41
  42         r = sd_id128_get_machine(&machine_id);
  43         if (r < 0)
  44                 return r;
  45
  46         unaligned_write_be16(&duid->type, DUID_TYPE_EN);
  47         unaligned_write_be32(&duid->en.pen, SYSTEMD_PEN);
  48
  49         *len = sizeof(duid->type) + sizeof(duid->en);
  50
  51         /* a bit of snake-oil perhaps, but no need to expose the machine-id
  52            directly; duid->en.id might not be aligned, so we need to copy */
  53         hash = htole64(siphash24(&machine_id, sizeof(machine_id), HASH_KEY.bytes));
  54         memcpy(duid->en.id, &hash, sizeof(duid->en.id));
  55
  56         return 0;
  57 }
  58
  59 int dhcp_identifier_set_iaid(int ifindex, uint8_t *mac, size_t mac_len, void *_id) {
  60         /* name is a pointer to memory in the udev_device struct, so must
  61            have the same scope */
  62         _cleanup_udev_device_unref_ struct udev_device *device = NULL;
  63         const char *name = NULL;
  64         uint64_t id;
  65
  66         if (detect_container() <= 0) {
  67                 /* not in a container, udev will be around */
  68                 _cleanup_udev_unref_ struct udev *udev;
  69                 char ifindex_str[2 + DECIMAL_STR_MAX(int)];
  70
  71                 udev = udev_new();
  72                 if (!udev)
  73                         return -ENOMEM;
  74
  75                 sprintf(ifindex_str, "n%d", ifindex);
  76                 device = udev_device_new_from_device_id(udev, ifindex_str);
  77                 if (device) {
  78                         if (udev_device_get_is_initialized(device) <= 0)
  79                                 /* not yet ready */
  80                                 return -EBUSY;
  81
  82                         name = net_get_name(device);
  83                 }
  84         }
  85
  86         if (name)
  87                 id = siphash24(name, strlen(name), HASH_KEY.bytes);
  88         else
  89                 /* fall back to MAC address if no predictable name available */
  90                 id = siphash24(mac, mac_len, HASH_KEY.bytes);
  91
  92         id = htole64(id);
  93
  94         /* fold into 32 bits */
  95         unaligned_write_be32(_id, (id & 0xffffffff) ^ (id >> 32));
  96
  97         return 0;
  98 }