1 /* 2 * WPA Supplicant - Layer2 packet handling with WinPcap RX thread 3 * Copyright (c) 2003-2006, Jouni Malinen <j (at) 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_strncpy(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_snprintf(buf, len, "%s", 323 inet_ntoa(saddr->sin_addr)); 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 SetEvent(l2->rx_notify); 340 } 341
