mac80211.c

   1 /*
   2  * netsniff-ng - the packet sniffing beast
   3  * Copyright 2012 Daniel Borkmann.
   4  * Subject to the GPL, version 2.
   5  * Parts derived from iw, subject to ISC license.
   6  * Copyright 2007, 2008 Johannes Berg
   7  * Copyright 2007 Andy Lutomirski
   8  * Copyright 2007 Mike Kershaw
   9  * Copyright 2008-2009 Luis R. Rodriguez
  10  */
  11
  12 #define _GNU_SOURCE
  13 #include <stdio.h>
  14 #include <stdlib.h>
  15 #include <errno.h>
  16 #include <string.h>
  17 #include <limits.h>
  18 #include <sys/socket.h>
  19 #include <linux/if.h>
  20 #include <linux/nl80211.h>
  21 #include <netlink/genl/genl.h>
  22 #include <netlink/genl/family.h>
  23 #include <netlink/genl/ctrl.h>
  24 #include <netlink/msg.h>
  25 #include <netlink/attr.h>
  26
  27 #include "str.h"
  28 #include "dev.h"
  29 #include "mac80211.h"
  30 #include "xmalloc.h"
  31 #include "built_in.h"
  32
  33 struct nl80211_state {
  34         struct nl_sock *nl_sock;
  35         struct nl_cache *nl_cache;
  36         struct genl_family *nl80211;
  37 };
  38
  39 static void get_mac80211_phydev(const char *device, char *phydev_path,
  40                                 size_t phydev_len)
  41 {
  42         int ret;
  43         char *pathstr;
  44         ssize_t num;
  45
  46         ret = asprintf(&pathstr, "/sys/class/net/%s/phy80211", device);
  47         if (ret < 0)
  48                 panic("Can't generate path name string for /sys/class/net device");
  49
  50         num = readlink(pathstr, phydev_path, phydev_len);
  51         if (num < 0) {
  52                 if (errno == ENOENT || errno == EINVAL)
  53                         panic("It's probably not a mac80211 device!\n");
  54                 panic("Can't readlink %s: %s!\n", pathstr, strerror(errno));
  55         }
  56
  57         xfree(pathstr);
  58         phydev_path[min_t(size_t, num, phydev_len - 1)] = 0;
  59 }
  60
  61 static inline struct nl_msg *nl80211_nlmsg_xalloc(void)
  62 {
  63         struct nl_msg *ret = nlmsg_alloc();
  64         if (!ret)
  65                 panic("Cannot allocate nlmsg memory!\n");
  66         return ret;
  67 }
  68
  69 static inline struct nl_sock *nl80211_nl_socket_xalloc(void)
  70 {
  71         struct nl_sock *ret = nl_socket_alloc();
  72         if (!ret)
  73                 panic("Cannot allocate nl socket memory!\n");
  74         return ret;
  75 }
  76
  77 static void nl80211_init(struct nl80211_state *state)
  78 {
  79         int ret;
  80
  81         state->nl_sock = nl80211_nl_socket_xalloc();
  82
  83         ret = genl_connect(state->nl_sock);
  84         if (ret)
  85                 panic("Cannot connect generic netlink!\n");
  86
  87         ret = genl_ctrl_alloc_cache(state->nl_sock, &state->nl_cache);
  88         if (ret < 0)
  89                 panic("Failed to allocate generic netlink cache: %s!",
  90                       nl_geterror(-ret));
  91
  92         state->nl80211 = genl_ctrl_search_by_name(state->nl_cache, "nl80211");
  93         if (!state->nl80211)
  94                 panic("nl80211 not found in netlink cache!\n");
  95 }
  96
  97 static void nl80211_cleanup(struct nl80211_state *state)
  98 {
  99         genl_family_put(state->nl80211);
 100
 101         nl_cache_free(state->nl_cache);
 102         nl_socket_free(state->nl_sock);
 103 }
 104
 105 static int nl80211_wait_handler(struct nl_msg *msg __maybe_unused, void *arg)
 106 {
 107         int *finished = arg;
 108
 109         *finished = 1;
 110
 111         return NL_STOP;
 112 }
 113
 114 static int nl80211_error_handler(struct sockaddr_nl *nla __maybe_unused,
 115                                  struct nlmsgerr *err,
 116                                  void *arg __maybe_unused)
 117 {
 118         panic("nl80211 returned with error (%d): %s\n", err->error,
 119               nl_geterror(err->error));
 120 }
 121
 122 static int nl80211_add_mon_if(struct nl80211_state *state, const char *device,
 123                               const char *mondevice)
 124 {
 125         int ifindex, ret;
 126         struct nl_msg *msg;
 127         struct nl_cb *cb = NULL;
 128         int finished = 0;
 129
 130         ifindex = device_ifindex(device);
 131
 132         msg = nl80211_nlmsg_xalloc();
 133
 134         genlmsg_put(msg, 0, 0, genl_family_get_id(state->nl80211), 0,
 135                     0, NL80211_CMD_NEW_INTERFACE, 0);
 136
 137         NLA_PUT_U32(msg, NL80211_ATTR_IFINDEX, ifindex);
 138         NLA_PUT_STRING(msg, NL80211_ATTR_IFNAME, mondevice);
 139         NLA_PUT_U32(msg, NL80211_ATTR_IFTYPE, NL80211_IFTYPE_MONITOR);
 140
 141         ret = nl_send_auto_complete(state->nl_sock, msg);
 142         if (ret < 0) {
 143                 if (ret == -ENFILE) {
 144                         nlmsg_free(msg);
 145                         return -EBUSY;
 146                 }
 147
 148                 panic("Cannot send_auto_complete!\n");
 149         }
 150
 151         cb = nl_cb_alloc(NL_CB_CUSTOM);
 152         if (!cb)
 153                 panic("Cannot alloc nl_cb!\n");
 154
 155         nl_cb_set(cb, NL_CB_ACK, NL_CB_CUSTOM, nl80211_wait_handler, &finished);
 156         nl_cb_err(cb, NL_CB_CUSTOM, nl80211_error_handler, NULL);
 157
 158         nl_recvmsgs(state->nl_sock, cb);
 159
 160         if (!finished) {
 161                 ret = nl_wait_for_ack(state->nl_sock);
 162                 if (ret < 0) {
 163                         if (ret == -ENFILE) {
 164                                 nlmsg_free(msg);
 165                                 return -EBUSY;
 166                         }
 167
 168                         panic("Waiting for netlink ack failed!\n");
 169                 }
 170         }
 171
 172         nl_cb_put(cb);
 173         nlmsg_free(msg);
 174         return 0;
 175
 176 nla_put_failure:
 177         panic("nla put failure!\n");
 178         return -EIO; /* dummy */
 179 }
 180
 181 static int nl80211_del_mon_if(struct nl80211_state *state,
 182                               const char *mondevice)
 183 {
 184         int ifindex, ret;
 185         struct nl_msg *msg;
 186
 187         ifindex = device_ifindex(mondevice);
 188
 189         msg = nl80211_nlmsg_xalloc();
 190
 191         genlmsg_put(msg, 0, 0, genl_family_get_id(state->nl80211), 0,
 192                     0, NL80211_CMD_DEL_INTERFACE, 0);
 193
 194         NLA_PUT_U32(msg, NL80211_ATTR_IFINDEX, ifindex);
 195
 196         ret = nl_send_auto_complete(state->nl_sock, msg);
 197         if (ret < 0)
 198                 panic("Cannot send_auto_complete!\n");
 199
 200         ret = nl_wait_for_ack(state->nl_sock);
 201         if (ret < 0)
 202                 panic("Waiting for netlink ack failed!\n");
 203
 204         nlmsg_free(msg);
 205         return 0;
 206
 207 nla_put_failure:
 208         panic("nla put failure!\n");
 209         return -EIO; /* dummy */
 210 }
 211
 212 void enter_rfmon_mac80211(const char *device, char **mondev)
 213 {
 214         int ret;
 215         short flags;
 216         uint32_t n;
 217         char phydev_path[256];
 218         struct nl80211_state nlstate;
 219
 220         /* XXX: is this already a monN device? */
 221         get_mac80211_phydev(device, phydev_path, sizeof(phydev_path));
 222         nl80211_init(&nlstate);
 223
 224         for (n = 0; n < UINT_MAX; n++) {
 225                 char mondevice[32];
 226
 227                 slprintf(mondevice, sizeof(mondevice), "mon%u", n);
 228
 229                 if (__device_ifindex(mondevice) > 0)
 230                         continue;
 231
 232                 ret = nl80211_add_mon_if(&nlstate, device, mondevice);
 233                 if (ret == 0) {
 234                         *mondev = xstrdup(mondevice);
 235
 236                         flags = device_get_flags(*mondev);
 237                         flags |= IFF_UP | IFF_RUNNING;
 238                         device_set_flags(*mondev, flags);
 239
 240                         nl80211_cleanup(&nlstate);
 241                         return;
 242                 }
 243         }
 244
 245         panic("No free monN interfaces!\n");
 246 }
 247
 248 void leave_rfmon_mac80211(const char *mondev)
 249 {
 250         short flags;
 251         struct nl80211_state nlstate;
 252
 253         flags = device_get_flags(mondev);
 254         flags &= ~(IFF_UP | IFF_RUNNING);
 255         device_set_flags(mondev, flags);
 256
 257         nl80211_init(&nlstate);
 258         nl80211_del_mon_if(&nlstate, mondev);
 259         nl80211_cleanup(&nlstate);
 260 }