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The Android Open Source Project authored
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_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 }
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