l2_packet_winpcap.c
Go to the documentation of this file.
00001 /*
00002  * WPA Supplicant - Layer2 packet handling with WinPcap RX thread
00003  * Copyright (c) 2003-2006, Jouni Malinen <j@w1.fi>
00004  *
00005  * This program is free software; you can redistribute it and/or modify
00006  * it under the terms of the GNU General Public License version 2 as
00007  * published by the Free Software Foundation.
00008  *
00009  * Alternatively, this software may be distributed under the terms of BSD
00010  * license.
00011  *
00012  * See README and COPYING for more details.
00013  *
00014  * This l2_packet implementation is explicitly for WinPcap and Windows events.
00015  * l2_packet_pcap.c has support for WinPcap, but it requires polling to receive
00016  * frames which means relatively long latency for EAPOL RX processing. The
00017  * implementation here uses a separate thread to allow WinPcap to be receiving
00018  * all the time to reduce latency for EAPOL receiving from about 100 ms to 3 ms
00019  * when comparing l2_packet_pcap.c to l2_packet_winpcap.c. Extra sleep of 50 ms
00020  * is added in to receive thread whenever no EAPOL frames has been received for
00021  * a while. Whenever an EAPOL handshake is expected, this sleep is removed.
00022  *
00023  * The RX thread receives a frame and signals main thread through Windows event
00024  * about the availability of a new frame. Processing the received frame is
00025  * synchronized with pair of Windows events so that no extra buffer or queuing
00026  * mechanism is needed. This implementation requires Windows specific event
00027  * loop implementation, i.e., eloop_win.c.
00028  *
00029  * WinPcap has pcap_getevent() that could, in theory at least, be used to
00030  * implement this kind of waiting with a simpler single-thread design. However,
00031  * that event handle is not really signaled immediately when receiving each
00032  * frame, so it does not really work for this kind of use.
00033  */
00034 
00035 #include "includes.h"
00036 #include <pcap.h>
00037 
00038 #include "common.h"
00039 #include "eloop.h"
00040 #include "l2_packet.h"
00041 
00042 
00043 static const u8 pae_group_addr[ETH_ALEN] =
00044 { 0x01, 0x80, 0xc2, 0x00, 0x00, 0x03 };
00045 
00046 /*
00047  * Number of pcap_dispatch() iterations to do without extra wait after each
00048  * received EAPOL packet or authentication notification. This is used to reduce
00049  * latency for EAPOL receive.
00050  */
00051 static const size_t no_wait_count = 750;
00052 
00053 struct l2_packet_data {
00054         pcap_t *pcap;
00055         unsigned int num_fast_poll;
00056         char ifname[100];
00057         u8 own_addr[ETH_ALEN];
00058         void (*rx_callback)(void *ctx, const u8 *src_addr,
00059                             const u8 *buf, size_t len);
00060         void *rx_callback_ctx;
00061         int l2_hdr; /* whether to include layer 2 (Ethernet) header in calls to
00062                      * rx_callback and l2_packet_send() */
00063         int running;
00064         HANDLE rx_avail, rx_done, rx_thread, rx_thread_done, rx_notify;
00065         u8 *rx_buf, *rx_src;
00066         size_t rx_len;
00067         size_t rx_no_wait;
00068 };
00069 
00070 
00071 int l2_packet_get_own_addr(struct l2_packet_data *l2, u8 *addr)
00072 {
00073         os_memcpy(addr, l2->own_addr, ETH_ALEN);
00074         return 0;
00075 }
00076 
00077 
00078 int l2_packet_send(struct l2_packet_data *l2, const u8 *dst_addr, u16 proto,
00079                    const u8 *buf, size_t len)
00080 {
00081         int ret;
00082         struct l2_ethhdr *eth;
00083 
00084         if (l2 == NULL)
00085                 return -1;
00086 
00087         if (l2->l2_hdr) {
00088                 ret = pcap_sendpacket(l2->pcap, buf, len);
00089         } else {
00090                 size_t mlen = sizeof(*eth) + len;
00091                 eth = os_malloc(mlen);
00092                 if (eth == NULL)
00093                         return -1;
00094 
00095                 os_memcpy(eth->h_dest, dst_addr, ETH_ALEN);
00096                 os_memcpy(eth->h_source, l2->own_addr, ETH_ALEN);
00097                 eth->h_proto = htons(proto);
00098                 os_memcpy(eth + 1, buf, len);
00099                 ret = pcap_sendpacket(l2->pcap, (u8 *) eth, mlen);
00100                 os_free(eth);
00101         }
00102 
00103         return ret;
00104 }
00105 
00106 
00107 /* pcap_dispatch() callback for the RX thread */
00108 static void l2_packet_receive_cb(u_char *user, const struct pcap_pkthdr *hdr,
00109                                  const u_char *pkt_data)
00110 {
00111         struct l2_packet_data *l2 = (struct l2_packet_data *) user;
00112         struct l2_ethhdr *ethhdr;
00113 
00114         if (pkt_data == NULL || hdr->caplen < sizeof(*ethhdr))
00115                 return;
00116 
00117         ethhdr = (struct l2_ethhdr *) pkt_data;
00118         if (l2->l2_hdr) {
00119                 l2->rx_buf = (u8 *) ethhdr;
00120                 l2->rx_len = hdr->caplen;
00121         } else {
00122                 l2->rx_buf = (u8 *) (ethhdr + 1);
00123                 l2->rx_len = hdr->caplen - sizeof(*ethhdr);
00124         }
00125         l2->rx_src = ethhdr->h_source;
00126         SetEvent(l2->rx_avail);
00127         WaitForSingleObject(l2->rx_done, INFINITE);
00128         ResetEvent(l2->rx_done);
00129         l2->rx_no_wait = no_wait_count;
00130 }
00131 
00132 
00133 /* main RX loop that is running in a separate thread */
00134 static DWORD WINAPI l2_packet_receive_thread(LPVOID arg)
00135 {
00136         struct l2_packet_data *l2 = arg;
00137 
00138         while (l2->running) {
00139                 pcap_dispatch(l2->pcap, 1, l2_packet_receive_cb,
00140                               (u_char *) l2);
00141                 if (l2->rx_no_wait > 0)
00142                         l2->rx_no_wait--;
00143                 if (WaitForSingleObject(l2->rx_notify,
00144                                         l2->rx_no_wait ? 0 : 50) ==
00145                     WAIT_OBJECT_0) {
00146                         l2->rx_no_wait = no_wait_count;
00147                         ResetEvent(l2->rx_notify);
00148                 }
00149         }
00150         SetEvent(l2->rx_thread_done);
00151         ExitThread(0);
00152         return 0;
00153 }
00154 
00155 
00156 /* main thread RX event handler */
00157 static void l2_packet_rx_event(void *eloop_data, void *user_data)
00158 {
00159         struct l2_packet_data *l2 = eloop_data;
00160         l2->rx_callback(l2->rx_callback_ctx, l2->rx_src, l2->rx_buf,
00161                         l2->rx_len);
00162         ResetEvent(l2->rx_avail);
00163         SetEvent(l2->rx_done);
00164 }
00165 
00166 
00167 static int l2_packet_init_libpcap(struct l2_packet_data *l2,
00168                                   unsigned short protocol)
00169 {
00170         bpf_u_int32 pcap_maskp, pcap_netp;
00171         char pcap_filter[200], pcap_err[PCAP_ERRBUF_SIZE];
00172         struct bpf_program pcap_fp;
00173 
00174         pcap_lookupnet(l2->ifname, &pcap_netp, &pcap_maskp, pcap_err);
00175         l2->pcap = pcap_open_live(l2->ifname, 2500, 0, 1, pcap_err);
00176         if (l2->pcap == NULL) {
00177                 fprintf(stderr, "pcap_open_live: %s\n", pcap_err);
00178                 fprintf(stderr, "ifname='%s'\n", l2->ifname);
00179                 return -1;
00180         }
00181         os_snprintf(pcap_filter, sizeof(pcap_filter),
00182                     "not ether src " MACSTR " and "
00183                     "( ether dst " MACSTR " or ether dst " MACSTR " ) and "
00184                     "ether proto 0x%x",
00185                     MAC2STR(l2->own_addr), /* do not receive own packets */
00186                     MAC2STR(l2->own_addr), MAC2STR(pae_group_addr),
00187                     protocol);
00188         if (pcap_compile(l2->pcap, &pcap_fp, pcap_filter, 1, pcap_netp) < 0) {
00189                 fprintf(stderr, "pcap_compile: %s\n", pcap_geterr(l2->pcap));
00190                 return -1;
00191         }
00192 
00193         if (pcap_setfilter(l2->pcap, &pcap_fp) < 0) {
00194                 fprintf(stderr, "pcap_setfilter: %s\n", pcap_geterr(l2->pcap));
00195                 return -1;
00196         }
00197 
00198         pcap_freecode(&pcap_fp);
00199 
00200         return 0;
00201 }
00202 
00203 
00204 struct l2_packet_data * l2_packet_init(
00205         const char *ifname, const u8 *own_addr, unsigned short protocol,
00206         void (*rx_callback)(void *ctx, const u8 *src_addr,
00207                             const u8 *buf, size_t len),
00208         void *rx_callback_ctx, int l2_hdr)
00209 {
00210         struct l2_packet_data *l2;
00211         DWORD thread_id;
00212 
00213         l2 = os_zalloc(sizeof(struct l2_packet_data));
00214         if (l2 == NULL)
00215                 return NULL;
00216         if (os_strncmp(ifname, "\\Device\\NPF_", 12) == 0)
00217                 os_strlcpy(l2->ifname, ifname, sizeof(l2->ifname));
00218         else
00219                 os_snprintf(l2->ifname, sizeof(l2->ifname), "\\Device\\NPF_%s",
00220                             ifname);
00221         l2->rx_callback = rx_callback;
00222         l2->rx_callback_ctx = rx_callback_ctx;
00223         l2->l2_hdr = l2_hdr;
00224 
00225         if (own_addr)
00226                 os_memcpy(l2->own_addr, own_addr, ETH_ALEN);
00227 
00228         if (l2_packet_init_libpcap(l2, protocol)) {
00229                 os_free(l2);
00230                 return NULL;
00231         }
00232 
00233         l2->rx_avail = CreateEvent(NULL, TRUE, FALSE, NULL);
00234         l2->rx_done = CreateEvent(NULL, TRUE, FALSE, NULL);
00235         l2->rx_notify = CreateEvent(NULL, TRUE, FALSE, NULL);
00236         if (l2->rx_avail == NULL || l2->rx_done == NULL ||
00237             l2->rx_notify == NULL) {
00238                 CloseHandle(l2->rx_avail);
00239                 CloseHandle(l2->rx_done);
00240                 CloseHandle(l2->rx_notify);
00241                 pcap_close(l2->pcap);
00242                 os_free(l2);
00243                 return NULL;
00244         }
00245 
00246         eloop_register_event(l2->rx_avail, sizeof(l2->rx_avail),
00247                              l2_packet_rx_event, l2, NULL);
00248 
00249         l2->running = 1;
00250         l2->rx_thread = CreateThread(NULL, 0, l2_packet_receive_thread, l2, 0,
00251                                      &thread_id);
00252 
00253         return l2;
00254 }
00255 
00256 
00257 static void l2_packet_deinit_timeout(void *eloop_ctx, void *timeout_ctx)
00258 {
00259         struct l2_packet_data *l2 = eloop_ctx;
00260 
00261         if (l2->rx_thread_done &&
00262             WaitForSingleObject(l2->rx_thread_done, 2000) != WAIT_OBJECT_0) {
00263                 wpa_printf(MSG_DEBUG, "l2_packet_winpcap: RX thread did not "
00264                            "exit - kill it\n");
00265                 TerminateThread(l2->rx_thread, 0);
00266         }
00267         CloseHandle(l2->rx_thread_done);
00268         CloseHandle(l2->rx_thread);
00269         if (l2->pcap)
00270                 pcap_close(l2->pcap);
00271         eloop_unregister_event(l2->rx_avail, sizeof(l2->rx_avail));
00272         CloseHandle(l2->rx_avail);
00273         CloseHandle(l2->rx_done);
00274         CloseHandle(l2->rx_notify);
00275         os_free(l2);
00276 }
00277 
00278 
00279 void l2_packet_deinit(struct l2_packet_data *l2)
00280 {
00281         if (l2 == NULL)
00282                 return;
00283 
00284         l2->rx_thread_done = CreateEvent(NULL, TRUE, FALSE, NULL);
00285 
00286         l2->running = 0;
00287         pcap_breakloop(l2->pcap);
00288 
00289         /*
00290          * RX thread may be waiting in l2_packet_receive_cb() for l2->rx_done
00291          * event and this event is set in l2_packet_rx_event(). However,
00292          * l2_packet_deinit() may end up being called from l2->rx_callback(),
00293          * so we need to return from here and complete deinitialization in
00294          * a registered timeout to avoid having to forcefully kill the RX
00295          * thread.
00296          */
00297         eloop_register_timeout(0, 0, l2_packet_deinit_timeout, l2, NULL);
00298 }
00299 
00300 
00301 int l2_packet_get_ip_addr(struct l2_packet_data *l2, char *buf, size_t len)
00302 {
00303         pcap_if_t *devs, *dev;
00304         struct pcap_addr *addr;
00305         struct sockaddr_in *saddr;
00306         int found = 0;
00307         char err[PCAP_ERRBUF_SIZE + 1];
00308 
00309         if (pcap_findalldevs(&devs, err) < 0) {
00310                 wpa_printf(MSG_DEBUG, "pcap_findalldevs: %s\n", err);
00311                 return -1;
00312         }
00313 
00314         for (dev = devs; dev && !found; dev = dev->next) {
00315                 if (os_strcmp(dev->name, l2->ifname) != 0)
00316                         continue;
00317 
00318                 addr = dev->addresses;
00319                 while (addr) {
00320                         saddr = (struct sockaddr_in *) addr->addr;
00321                         if (saddr && saddr->sin_family == AF_INET) {
00322                                 os_strlcpy(buf, inet_ntoa(saddr->sin_addr),
00323                                            len);
00324                                 found = 1;
00325                                 break;
00326                         }
00327                         addr = addr->next;
00328                 }
00329         }
00330 
00331         pcap_freealldevs(devs);
00332 
00333         return found ? 0 : -1;
00334 }
00335 
00336 
00337 void l2_packet_notify_auth_start(struct l2_packet_data *l2)
00338 {
00339         if (l2)
00340                 SetEvent(l2->rx_notify);
00341 }


wpa_supplicant_node
Author(s): Package maintained by Blaise Gassend
autogenerated on Thu Jan 2 2014 11:25:14