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