contrib/hostapd/src/l2_packet/l2_packet_winpcap.c

   1 /*
   2  * WPA Supplicant - Layer2 packet handling with WinPcap RX thread
   3  * Copyright (c) 2003-2006, Jouni Malinen <j@w1.fi>
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License version 2 as
   7  * published by the Free Software Foundation.
   8  *
   9  * Alternatively, this software may be distributed under the terms of BSD
  10  * license.
  11  *
  12  * See README and COPYING for more details.
  13  *
  14  * This l2_packet implementation is explicitly for WinPcap and Windows events.
  15  * l2_packet_pcap.c has support for WinPcap, but it requires polling to receive
  16  * frames which means relatively long latency for EAPOL RX processing. The
  17  * implementation here uses a separate thread to allow WinPcap to be receiving
  18  * all the time to reduce latency for EAPOL receiving from about 100 ms to 3 ms
  19  * when comparing l2_packet_pcap.c to l2_packet_winpcap.c. Extra sleep of 50 ms
  20  * is added in to receive thread whenever no EAPOL frames has been received for
  21  * a while. Whenever an EAPOL handshake is expected, this sleep is removed.
  22  *
  23  * The RX thread receives a frame and signals main thread through Windows event
  24  * about the availability of a new frame. Processing the received frame is
  25  * synchronized with pair of Windows events so that no extra buffer or queuing
  26  * mechanism is needed. This implementation requires Windows specific event
  27  * loop implementation, i.e., eloop_win.c.
  28  *
  29  * WinPcap has pcap_getevent() that could, in theory at least, be used to
  30  * implement this kind of waiting with a simpler single-thread design. However,
  31  * that event handle is not really signaled immediately when receiving each
  32  * frame, so it does not really work for this kind of use.
  33  */
  34
  35 #include "includes.h"
  36 #include <pcap.h>
  37
  38 #include "common.h"
  39 #include "eloop.h"
  40 #include "l2_packet.h"
  41
  42
  43 static const u8 pae_group_addr[ETH_ALEN] =
  44 { 0x01, 0x80, 0xc2, 0x00, 0x00, 0x03 };
  45
  46 /*
  47  * Number of pcap_dispatch() iterations to do without extra wait after each
  48  * received EAPOL packet or authentication notification. This is used to reduce
  49  * latency for EAPOL receive.
  50  */
  51 static const size_t no_wait_count = 750;
  52
  53 struct l2_packet_data {
  54         pcap_t *pcap;
  55         unsigned int num_fast_poll;
  56         char ifname[100];
  57         u8 own_addr[ETH_ALEN];
  58         void (*rx_callback)(void *ctx, const u8 *src_addr,
  59                             const u8 *buf, size_t len);
  60         void *rx_callback_ctx;
  61         int l2_hdr; /* whether to include layer 2 (Ethernet) header in calls to
  62                      * rx_callback and l2_packet_send() */
  63         int running;
  64         HANDLE rx_avail, rx_done, rx_thread, rx_thread_done, rx_notify;
  65         u8 *rx_buf, *rx_src;
  66         size_t rx_len;
  67         size_t rx_no_wait;
  68 };
  69
  70
  71 int l2_packet_get_own_addr(struct l2_packet_data *l2, u8 *addr)
  72 {
  73         os_memcpy(addr, l2->own_addr, ETH_ALEN);
  74         return 0;
  75 }
  76
  77
  78 int l2_packet_send(struct l2_packet_data *l2, const u8 *dst_addr, u16 proto,
  79                    const u8 *buf, size_t len)
  80 {
  81         int ret;
  82         struct l2_ethhdr *eth;
  83
  84         if (l2 == NULL)
  85                 return -1;
  86
  87         if (l2->l2_hdr) {
  88                 ret = pcap_sendpacket(l2->pcap, buf, len);
  89         } else {
  90                 size_t mlen = sizeof(*eth) + len;
  91                 eth = os_malloc(mlen);
  92                 if (eth == NULL)
  93                         return -1;
  94
  95                 os_memcpy(eth->h_dest, dst_addr, ETH_ALEN);
  96                 os_memcpy(eth->h_source, l2->own_addr, ETH_ALEN);
  97                 eth->h_proto = htons(proto);
  98                 os_memcpy(eth + 1, buf, len);
  99                 ret = pcap_sendpacket(l2->pcap, (u8 *) eth, mlen);
 100                 os_free(eth);
 101         }
 102
 103         return ret;
 104 }
 105
 106
 107 /* pcap_dispatch() callback for the RX thread */
 108 static void l2_packet_receive_cb(u_char *user, const struct pcap_pkthdr *hdr,
 109                                  const u_char *pkt_data)
 110 {
 111         struct l2_packet_data *l2 = (struct l2_packet_data *) user;
 112         struct l2_ethhdr *ethhdr;
 113
 114         if (pkt_data == NULL || hdr->caplen < sizeof(*ethhdr))
 115                 return;
 116
 117         ethhdr = (struct l2_ethhdr *) pkt_data;
 118         if (l2->l2_hdr) {
 119                 l2->rx_buf = (u8 *) ethhdr;
 120                 l2->rx_len = hdr->caplen;
 121         } else {
 122                 l2->rx_buf = (u8 *) (ethhdr + 1);
 123                 l2->rx_len = hdr->caplen - sizeof(*ethhdr);
 124         }
 125         l2->rx_src = ethhdr->h_source;
 126         SetEvent(l2->rx_avail);
 127         WaitForSingleObject(l2->rx_done, INFINITE);
 128         ResetEvent(l2->rx_done);
 129         l2->rx_no_wait = no_wait_count;
 130 }
 131
 132
 133 /* main RX loop that is running in a separate thread */
 134 static DWORD WINAPI l2_packet_receive_thread(LPVOID arg)
 135 {
 136         struct l2_packet_data *l2 = arg;
 137
 138         while (l2->running) {
 139                 pcap_dispatch(l2->pcap, 1, l2_packet_receive_cb,
 140                               (u_char *) l2);
 141                 if (l2->rx_no_wait > 0)
 142                         l2->rx_no_wait--;
 143                 if (WaitForSingleObject(l2->rx_notify,
 144                                         l2->rx_no_wait ? 0 : 50) ==
 145                     WAIT_OBJECT_0) {
 146                         l2->rx_no_wait = no_wait_count;
 147                         ResetEvent(l2->rx_notify);
 148                 }
 149         }
 150         SetEvent(l2->rx_thread_done);
 151         ExitThread(0);
 152         return 0;
 153 }
 154
 155
 156 /* main thread RX event handler */
 157 static void l2_packet_rx_event(void *eloop_data, void *user_data)
 158 {
 159         struct l2_packet_data *l2 = eloop_data;
 160         l2->rx_callback(l2->rx_callback_ctx, l2->rx_src, l2->rx_buf,
 161                         l2->rx_len);
 162         ResetEvent(l2->rx_avail);
 163         SetEvent(l2->rx_done);
 164 }
 165
 166
 167 static int l2_packet_init_libpcap(struct l2_packet_data *l2,
 168                                   unsigned short protocol)
 169 {
 170         bpf_u_int32 pcap_maskp, pcap_netp;
 171         char pcap_filter[200], pcap_err[PCAP_ERRBUF_SIZE];
 172         struct bpf_program pcap_fp;
 173
 174         pcap_lookupnet(l2->ifname, &pcap_netp, &pcap_maskp, pcap_err);
 175         l2->pcap = pcap_open_live(l2->ifname, 2500, 0, 1, pcap_err);
 176         if (l2->pcap == NULL) {
 177                 fprintf(stderr, "pcap_open_live: %s\n", pcap_err);
 178                 fprintf(stderr, "ifname='%s'\n", l2->ifname);
 179                 return -1;
 180         }
 181         os_snprintf(pcap_filter, sizeof(pcap_filter),
 182                     "not ether src " MACSTR " and "
 183                     "( ether dst " MACSTR " or ether dst " MACSTR " ) and "
 184                     "ether proto 0x%x",
 185                     MAC2STR(l2->own_addr), /* do not receive own packets */
 186                     MAC2STR(l2->own_addr), MAC2STR(pae_group_addr),
 187                     protocol);
 188         if (pcap_compile(l2->pcap, &pcap_fp, pcap_filter, 1, pcap_netp) < 0) {
 189                 fprintf(stderr, "pcap_compile: %s\n", pcap_geterr(l2->pcap));
 190                 return -1;
 191         }
 192
 193         if (pcap_setfilter(l2->pcap, &pcap_fp) < 0) {
 194                 fprintf(stderr, "pcap_setfilter: %s\n", pcap_geterr(l2->pcap));
 195                 return -1;
 196         }
 197
 198         pcap_freecode(&pcap_fp);
 199
 200         return 0;
 201 }
 202
 203
 204 struct l2_packet_data * l2_packet_init(
 205         const char *ifname, const u8 *own_addr, unsigned short protocol,
 206         void (*rx_callback)(void *ctx, const u8 *src_addr,
 207                             const u8 *buf, size_t len),
 208         void *rx_callback_ctx, int l2_hdr)
 209 {
 210         struct l2_packet_data *l2;
 211         DWORD thread_id;
 212
 213         l2 = os_zalloc(sizeof(struct l2_packet_data));
 214         if (l2 == NULL)
 215                 return NULL;
 216         if (os_strncmp(ifname, "\\Device\\NPF_", 12) == 0)
 217                 os_strlcpy(l2->ifname, ifname, sizeof(l2->ifname));
 218         else
 219                 os_snprintf(l2->ifname, sizeof(l2->ifname), "\\Device\\NPF_%s",
 220                             ifname);
 221         l2->rx_callback = rx_callback;
 222         l2->rx_callback_ctx = rx_callback_ctx;
 223         l2->l2_hdr = l2_hdr;
 224
 225         if (own_addr)
 226                 os_memcpy(l2->own_addr, own_addr, ETH_ALEN);
 227
 228         if (l2_packet_init_libpcap(l2, protocol)) {
 229                 os_free(l2);
 230                 return NULL;
 231         }
 232
 233         l2->rx_avail = CreateEvent(NULL, TRUE, FALSE, NULL);
 234         l2->rx_done = CreateEvent(NULL, TRUE, FALSE, NULL);
 235         l2->rx_notify = CreateEvent(NULL, TRUE, FALSE, NULL);
 236         if (l2->rx_avail == NULL || l2->rx_done == NULL ||
 237             l2->rx_notify == NULL) {
 238                 CloseHandle(l2->rx_avail);
 239                 CloseHandle(l2->rx_done);
 240                 CloseHandle(l2->rx_notify);
 241                 pcap_close(l2->pcap);
 242                 os_free(l2);
 243                 return NULL;
 244         }
 245
 246         eloop_register_event(l2->rx_avail, sizeof(l2->rx_avail),
 247                              l2_packet_rx_event, l2, NULL);
 248
 249         l2->running = 1;
 250         l2->rx_thread = CreateThread(NULL, 0, l2_packet_receive_thread, l2, 0,
 251                                      &thread_id);
 252
 253         return l2;
 254 }
 255
 256
 257 static void l2_packet_deinit_timeout(void *eloop_ctx, void *timeout_ctx)
 258 {
 259         struct l2_packet_data *l2 = eloop_ctx;
 260
 261         if (l2->rx_thread_done &&
 262             WaitForSingleObject(l2->rx_thread_done, 2000) != WAIT_OBJECT_0) {
 263                 wpa_printf(MSG_DEBUG, "l2_packet_winpcap: RX thread did not "
 264                            "exit - kill it\n");
 265                 TerminateThread(l2->rx_thread, 0);
 266         }
 267         CloseHandle(l2->rx_thread_done);
 268         CloseHandle(l2->rx_thread);
 269         if (l2->pcap)
 270                 pcap_close(l2->pcap);
 271         eloop_unregister_event(l2->rx_avail, sizeof(l2->rx_avail));
 272         CloseHandle(l2->rx_avail);
 273         CloseHandle(l2->rx_done);
 274         CloseHandle(l2->rx_notify);
 275         os_free(l2);
 276 }
 277
 278
 279 void l2_packet_deinit(struct l2_packet_data *l2)
 280 {
 281         if (l2 == NULL)
 282                 return;
 283
 284         l2->rx_thread_done = CreateEvent(NULL, TRUE, FALSE, NULL);
 285
 286         l2->running = 0;
 287         pcap_breakloop(l2->pcap);
 288
 289         /*
 290          * RX thread may be waiting in l2_packet_receive_cb() for l2->rx_done
 291          * event and this event is set in l2_packet_rx_event(). However,
 292          * l2_packet_deinit() may end up being called from l2->rx_callback(),
 293          * so we need to return from here and complete deinitialization in
 294          * a registered timeout to avoid having to forcefully kill the RX
 295          * thread.
 296          */
 297         eloop_register_timeout(0, 0, l2_packet_deinit_timeout, l2, NULL);
 298 }
 299
 300
 301 int l2_packet_get_ip_addr(struct l2_packet_data *l2, char *buf, size_t len)
 302 {
 303         pcap_if_t *devs, *dev;
 304         struct pcap_addr *addr;
 305         struct sockaddr_in *saddr;
 306         int found = 0;
 307         char err[PCAP_ERRBUF_SIZE + 1];
 308
 309         if (pcap_findalldevs(&devs, err) < 0) {
 310                 wpa_printf(MSG_DEBUG, "pcap_findalldevs: %s\n", err);
 311                 return -1;
 312         }
 313
 314         for (dev = devs; dev && !found; dev = dev->next) {
 315                 if (os_strcmp(dev->name, l2->ifname) != 0)
 316                         continue;
 317
 318                 addr = dev->addresses;
 319                 while (addr) {
 320                         saddr = (struct sockaddr_in *) addr->addr;
 321                         if (saddr && saddr->sin_family == AF_INET) {
 322                                 os_strlcpy(buf, inet_ntoa(saddr->sin_addr),
 323                                            len);
 324                                 found = 1;
 325                                 break;
 326                         }
 327                         addr = addr->next;
 328                 }
 329         }
 330
 331         pcap_freealldevs(devs);
 332
 333         return found ? 0 : -1;
 334 }
 335
 336
 337 void l2_packet_notify_auth_start(struct l2_packet_data *l2)
 338 {
 339         if (l2)
 340                 SetEvent(l2->rx_notify);
 341 }