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 <linux/nl80211.h>
  19 #include <libnl3/netlink/genl/genl.h>
  20 #include <libnl3/netlink/genl/family.h>
  21 #include <libnl3/netlink/genl/ctrl.h>
  22 #include <libnl3/netlink/msg.h>
  23 #include <libnl3/netlink/attr.h>
  24
  25 #include "die.h"
  26 #include "str.h"
  27 #include "xutils.h"
  28 #include "mac80211.h"
  29 #include "xmalloc.h"
  30 #include "built_in.h"
  31
  32 struct nl80211_state {
  33         struct nl_sock *nl_sock;
  34         struct nl_cache *nl_cache;
  35         struct genl_family *nl80211;
  36 };
  37
  38 static void get_mac80211_phydev(const char *device, char *phydev_path,
  39                                 size_t phydev_len)
  40 {
  41         int ret;
  42         char *pathstr;
  43         ssize_t num;
  44
  45         ret = asprintf(&pathstr, "/sys/class/net/%s/phy80211", device);
  46         if (ret < 0)
  47                 panic("Can't generate path name string for /sys/class/net device");
  48
  49         num = readlink(pathstr, phydev_path, phydev_len);
  50         if (num < 0) {
  51                 if (errno == ENOENT || errno == EINVAL)
  52                         panic("It's probably not a mac80211 device!\n");
  53                 panic("Can't readlink %s: %s!\n", pathstr, strerror(errno));
  54         }
  55
  56         xfree(pathstr);
  57         phydev_path[min(num, phydev_len - 1)] = 0;
  58 }
  59
  60 static inline struct nl_msg *nl80211_nlmsg_xalloc(void)
  61 {
  62         struct nl_msg *ret = nlmsg_alloc();
  63         if (!ret)
  64                 panic("Cannot allocate nlmsg memory!\n");
  65         return ret;
  66 }
  67
  68 static inline struct nl_sock *nl80211_nl_socket_xalloc(void)
  69 {
  70         struct nl_sock *ret = nl_socket_alloc();
  71         if (!ret)
  72                 panic("Cannot allocate nl socket memory!\n");
  73         return ret;
  74 }
  75
  76 static void nl80211_init(struct nl80211_state *state, const char *device)
  77 {
  78         int ret;
  79
  80         state->nl_sock = nl80211_nl_socket_xalloc();
  81
  82         ret = genl_connect(state->nl_sock);
  83         if (ret)
  84                 panic("Cannot connect generic netlink!\n");
  85
  86         ret = genl_ctrl_alloc_cache(state->nl_sock, &state->nl_cache);
  87         if (ret < 0)
  88                 panic("Failed to allocate generic netlink cache: %s!",
  89                       nl_geterror(-ret));
  90
  91         state->nl80211 = genl_ctrl_search_by_name(state->nl_cache, "nl80211");
  92         if (!state->nl80211)
  93                 panic("nl80211 not found in netlink cache!\n");
  94 }
  95
  96 static void nl80211_cleanup(struct nl80211_state *state)
  97 {
  98         genl_family_put(state->nl80211);
  99
 100         nl_cache_free(state->nl_cache);
 101         nl_socket_free(state->nl_sock);
 102 }
 103
 104 static int nl80211_wait_handler(struct nl_msg *msg, void *arg)
 105 {
 106         int *finished = arg;
 107
 108         *finished = 1;
 109
 110         return NL_STOP;
 111 }
 112
 113 static int nl80211_error_handler(struct sockaddr_nl *nla,
 114                                  struct nlmsgerr *err,
 115                                  void *arg)
 116 {
 117         panic("nl80211 returned with error %d\n", err->error);
 118 }
 119
 120 static int nl80211_add_mon_if(struct nl80211_state *state, const char *device,
 121                               const char *mondevice)
 122 {
 123         int ifindex, ret;
 124         struct nl_msg *msg;
 125         struct nl_cb *cb = NULL;
 126         int finished = 0;
 127
 128         ifindex = device_ifindex(device);
 129
 130         msg = nl80211_nlmsg_xalloc();
 131
 132         genlmsg_put(msg, 0, 0, genl_family_get_id(state->nl80211), 0,
 133                     0, NL80211_CMD_NEW_INTERFACE, 0);
 134
 135         NLA_PUT_U32(msg, NL80211_ATTR_IFINDEX, ifindex);
 136         NLA_PUT_STRING(msg, NL80211_ATTR_IFNAME, mondevice);
 137         NLA_PUT_U32(msg, NL80211_ATTR_IFTYPE, NL80211_IFTYPE_MONITOR);
 138
 139         ret = nl_send_auto_complete(state->nl_sock, msg);
 140         if (ret < 0) {
 141                 if (ret == -ENFILE) {
 142                         nlmsg_free(msg);
 143                         return -EBUSY;
 144                 }
 145
 146                 panic("Cannot send_auto_complete!\n");
 147         }
 148
 149         cb = nl_cb_alloc(NL_CB_CUSTOM);
 150         if (!cb)
 151                 panic("Cannot alloc nl_cb!\n");
 152
 153         nl_cb_set(cb, NL_CB_ACK, NL_CB_CUSTOM, nl80211_wait_handler, &finished);
 154         nl_cb_err(cb, NL_CB_CUSTOM, nl80211_error_handler, NULL);
 155
 156         nl_recvmsgs(state->nl_sock, cb);
 157
 158         if (!finished) {
 159                 ret = nl_wait_for_ack(state->nl_sock);
 160                 if (ret < 0) {
 161                         if (ret == -ENFILE) {
 162                                 nlmsg_free(msg);
 163                                 return -EBUSY;
 164                         }
 165
 166                         panic("Waiting for netlink ack failed!\n");
 167                 }
 168         }
 169
 170         nl_cb_put(cb);
 171         nlmsg_free(msg);
 172         return 0;
 173
 174 nla_put_failure:
 175         panic("nla put failure!\n");
 176         return -EIO; /* dummy */
 177 }
 178
 179 static int nl80211_del_mon_if(struct nl80211_state *state, const char *device,
 180                               const char *mondevice)
 181 {
 182         int ifindex, ret;
 183         struct nl_msg *msg;
 184
 185         ifindex = device_ifindex(mondevice);
 186
 187         msg = nl80211_nlmsg_xalloc();
 188
 189         genlmsg_put(msg, 0, 0, genl_family_get_id(state->nl80211), 0,
 190                     0, NL80211_CMD_DEL_INTERFACE, 0);
 191
 192         NLA_PUT_U32(msg, NL80211_ATTR_IFINDEX, ifindex);
 193
 194         ret = nl_send_auto_complete(state->nl_sock, msg);
 195         if (ret < 0)
 196                 panic("Cannot send_auto_complete!\n");
 197
 198         ret = nl_wait_for_ack(state->nl_sock);
 199         if (ret < 0)
 200                 panic("Waiting for netlink ack failed!\n");
 201
 202         nlmsg_free(msg);
 203         return 0;
 204
 205 nla_put_failure:
 206         panic("nla put failure!\n");
 207         return -EIO; /* dummy */
 208 }
 209
 210 void enter_rfmon_mac80211(const char *device, char **mondev)
 211 {
 212         int ret;
 213         short flags;
 214         uint32_t n;
 215         char phydev_path[256];
 216         struct nl80211_state nlstate;
 217
 218         /* XXX: is this already a monN device? */
 219         get_mac80211_phydev(device, phydev_path, sizeof(phydev_path));
 220         nl80211_init(&nlstate, device);
 221
 222         for (n = 0; n < UINT_MAX; n++) {
 223                 char mondevice[32];
 224
 225                 slprintf(mondevice, sizeof(mondevice), "mon%u", n);
 226                 ret = nl80211_add_mon_if(&nlstate, device, mondevice);
 227                 if (ret == 0) {
 228                         *mondev = xstrdup(mondevice);
 229
 230                         flags = device_get_flags(*mondev);
 231                         flags |= IFF_UP | IFF_RUNNING;
 232                         device_set_flags(*mondev, flags);
 233
 234                         nl80211_cleanup(&nlstate);
 235                         return;
 236                 }
 237         }
 238
 239         panic("No free monN interfaces!\n");
 240 }
 241
 242 void leave_rfmon_mac80211(const char *device, const char *mondev)
 243 {
 244         short flags;
 245         struct nl80211_state nlstate;
 246
 247         flags = device_get_flags(mondev);
 248         flags &= ~(IFF_UP | IFF_RUNNING);
 249         device_set_flags(mondev, flags);
 250
 251         nl80211_init(&nlstate, device);
 252         nl80211_del_mon_if(&nlstate, device, mondev);
 253         nl80211_cleanup(&nlstate);
 254 }