src/mac80211.c

   1 /*
   2  * netsniff-ng - the packet sniffing beast
   3  * By Daniel Borkmann <daniel@netsniff-ng.org>
   4  * Copyright 2012 Daniel Borkmann.
   5  * Subject to the GPL, version 2.
   6  * Parts derived from iw, subject to ISC license.
   7  * Copyright 2007, 2008 Johannes Berg
   8  * Copyright 2007 Andy Lutomirski
   9  * Copyright 2007 Mike Kershaw
  10  * Copyright 2008-2009 Luis R. Rodriguez
  11  */
  12
  13 #define _GNU_SOURCE
  14 #include <stdio.h>
  15 #include <stdlib.h>
  16 #include <errno.h>
  17 #include <string.h>
  18 #include <limits.h>
  19 #include <linux/nl80211.h>
  20 #include <libnl3/netlink/genl/genl.h>
  21 #include <libnl3/netlink/genl/family.h>
  22 #include <libnl3/netlink/genl/ctrl.h>
  23 #include <libnl3/netlink/msg.h>
  24 #include <libnl3/netlink/attr.h>
  25
  26 #include "die.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_add_mon_if(struct nl80211_state *state, const char *device,
 105                               const char *mondevice)
 106 {
 107         int ifindex, ret;
 108         struct nl_msg *msg;
 109
 110         ifindex = device_ifindex(device);
 111
 112         msg = nl80211_nlmsg_xalloc();
 113
 114         genlmsg_put(msg, 0, 0, genl_family_get_id(state->nl80211), 0,
 115                     0, NL80211_CMD_NEW_INTERFACE, 0);
 116
 117         NLA_PUT_U32(msg, NL80211_ATTR_IFINDEX, ifindex);
 118         NLA_PUT_STRING(msg, NL80211_ATTR_IFNAME, mondevice);
 119         NLA_PUT_U32(msg, NL80211_ATTR_IFTYPE, NL80211_IFTYPE_MONITOR);
 120
 121         ret = nl_send_auto_complete(state->nl_sock, msg);
 122         if (ret < 0) {
 123                 if (ret == -ENFILE) {
 124                         nlmsg_free(msg);
 125                         return -EBUSY;
 126                 }
 127
 128                 panic("Cannot send_auto_complete!\n");
 129         }
 130
 131         ret = nl_wait_for_ack(state->nl_sock);
 132         if (ret < 0) {
 133                 if (ret == -ENFILE) {
 134                         nlmsg_free(msg);
 135                         return -EBUSY;
 136                 }
 137
 138                 panic("Waiting for netlink ack failed!\n");
 139         }
 140
 141         nlmsg_free(msg);
 142         return 0;
 143
 144 nla_put_failure:
 145         panic("nla put failure!\n");
 146         return -EIO; /* dummy */
 147 }
 148
 149 static int nl80211_del_mon_if(struct nl80211_state *state, const char *device,
 150                               const char *mondevice)
 151 {
 152         int ifindex, ret;
 153         struct nl_msg *msg;
 154
 155         ifindex = device_ifindex(mondevice);
 156
 157         msg = nl80211_nlmsg_xalloc();
 158
 159         genlmsg_put(msg, 0, 0, genl_family_get_id(state->nl80211), 0,
 160                     0, NL80211_CMD_DEL_INTERFACE, 0);
 161
 162         NLA_PUT_U32(msg, NL80211_ATTR_IFINDEX, ifindex);
 163
 164         ret = nl_send_auto_complete(state->nl_sock, msg);
 165         if (ret < 0)
 166                 panic("Cannot send_auto_complete!\n");
 167
 168         ret = nl_wait_for_ack(state->nl_sock);
 169         if (ret < 0)
 170                 panic("Waiting for netlink ack failed!\n");
 171
 172         nlmsg_free(msg);
 173         return 0;
 174
 175 nla_put_failure:
 176         panic("nla put failure!\n");
 177         return -EIO; /* dummy */
 178 }
 179
 180 void enter_rfmon_mac80211(const char *device, char **mondev)
 181 {
 182         int ret;
 183         short flags;
 184         uint32_t n;
 185         char phydev_path[256];
 186         struct nl80211_state nlstate;
 187
 188         /* XXX: is this already a monN device? */
 189         get_mac80211_phydev(device, phydev_path, sizeof(phydev_path));
 190         nl80211_init(&nlstate, device);
 191
 192         for (n = 0; n < UINT_MAX; n++) {
 193                 char mondevice[32];
 194
 195                 slprintf(mondevice, sizeof(mondevice), "mon%u", n);
 196                 ret = nl80211_add_mon_if(&nlstate, device, mondevice);
 197                 if (ret == 0) {
 198                         *mondev = xstrdup(mondevice);
 199
 200                         flags = device_get_flags(*mondev);
 201                         flags |= IFF_UP | IFF_RUNNING;
 202                         device_set_flags(*mondev, flags);
 203
 204                         nl80211_cleanup(&nlstate);
 205                         return;
 206                 }
 207         }
 208
 209         panic("No free monN interfaces!\n");
 210 }
 211
 212 void leave_rfmon_mac80211(const char *device, const char *mondev)
 213 {
 214         short flags;
 215         struct nl80211_state nlstate;
 216
 217         flags = device_get_flags(mondev);
 218         flags &= ~(IFF_UP | IFF_RUNNING);
 219         device_set_flags(mondev, flags);
 220
 221         nl80211_init(&nlstate, device);
 222         nl80211_del_mon_if(&nlstate, device, mondev);
 223         nl80211_cleanup(&nlstate);
 224 }