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