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/*
* WPA Supplicant - Layer2 packet handling with WinPcap RX thread
* Copyright (c) 2003-2006, Jouni Malinen <j@w1.fi>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* Alternatively, this software may be distributed under the terms of BSD
* license.
*
* See README and COPYING for more details.
*
* This l2_packet implementation is explicitly for WinPcap and Windows events.
* l2_packet_pcap.c has support for WinPcap, but it requires polling to receive
* frames which means relatively long latency for EAPOL RX processing. The
* implementation here uses a separate thread to allow WinPcap to be receiving
* all the time to reduce latency for EAPOL receiving from about 100 ms to 3 ms
* when comparing l2_packet_pcap.c to l2_packet_winpcap.c. Extra sleep of 50 ms
* is added in to receive thread whenever no EAPOL frames has been received for
* a while. Whenever an EAPOL handshake is expected, this sleep is removed.
*
* The RX thread receives a frame and signals main thread through Windows event
* about the availability of a new frame. Processing the received frame is
* synchronized with pair of Windows events so that no extra buffer or queuing
* mechanism is needed. This implementation requires Windows specific event
* loop implementation, i.e., eloop_win.c.
*
* WinPcap has pcap_getevent() that could, in theory at least, be used to
* implement this kind of waiting with a simpler single-thread design. However,
* that event handle is not really signaled immediately when receiving each
* frame, so it does not really work for this kind of use.
*/
#include "includes.h"
#include <pcap.h>
#include "common.h"
#include "eloop.h"
#include "l2_packet.h"
static const u8 pae_group_addr[ETH_ALEN] =
{ 0x01, 0x80, 0xc2, 0x00, 0x00, 0x03 };
/*
* Number of pcap_dispatch() iterations to do without extra wait after each
* received EAPOL packet or authentication notification. This is used to reduce
* latency for EAPOL receive.
*/
static const size_t no_wait_count = 750;
struct l2_packet_data {
pcap_t *pcap;
unsigned int num_fast_poll;
char ifname[100];
u8 own_addr[ETH_ALEN];
void (*rx_callback)(void *ctx, const u8 *src_addr,
const u8 *buf, size_t len);
void *rx_callback_ctx;
int l2_hdr; /* whether to include layer 2 (Ethernet) header in calls to
* rx_callback and l2_packet_send() */
int running;
HANDLE rx_avail, rx_done, rx_thread, rx_thread_done, rx_notify;
u8 *rx_buf, *rx_src;
size_t rx_len;
size_t rx_no_wait;
};
int l2_packet_get_own_addr(struct l2_packet_data *l2, u8 *addr)
{
os_memcpy(addr, l2->own_addr, ETH_ALEN);
return 0;
}
int l2_packet_send(struct l2_packet_data *l2, const u8 *dst_addr, u16 proto,
const u8 *buf, size_t len)
{
int ret;
struct l2_ethhdr *eth;
if (l2 == NULL)
return -1;
if (l2->l2_hdr) {
ret = pcap_sendpacket(l2->pcap, buf, len);
} else {
size_t mlen = sizeof(*eth) + len;
eth = os_malloc(mlen);
if (eth == NULL)
return -1;
os_memcpy(eth->h_dest, dst_addr, ETH_ALEN);
os_memcpy(eth->h_source, l2->own_addr, ETH_ALEN);
eth->h_proto = htons(proto);
os_memcpy(eth + 1, buf, len);
ret = pcap_sendpacket(l2->pcap, (u8 *) eth, mlen);
os_free(eth);
}
return ret;
}
/* pcap_dispatch() callback for the RX thread */
static void l2_packet_receive_cb(u_char *user, const struct pcap_pkthdr *hdr,
const u_char *pkt_data)
{
struct l2_packet_data *l2 = (struct l2_packet_data *) user;
struct l2_ethhdr *ethhdr;
if (pkt_data == NULL || hdr->caplen < sizeof(*ethhdr))
return;
ethhdr = (struct l2_ethhdr *) pkt_data;
if (l2->l2_hdr) {
l2->rx_buf = (u8 *) ethhdr;
l2->rx_len = hdr->caplen;
} else {
l2->rx_buf = (u8 *) (ethhdr + 1);
l2->rx_len = hdr->caplen - sizeof(*ethhdr);
}
l2->rx_src = ethhdr->h_source;
SetEvent(l2->rx_avail);
WaitForSingleObject(l2->rx_done, INFINITE);
ResetEvent(l2->rx_done);
l2->rx_no_wait = no_wait_count;
}
/* main RX loop that is running in a separate thread */
static DWORD WINAPI l2_packet_receive_thread(LPVOID arg)
{
struct l2_packet_data *l2 = arg;
while (l2->running) {
pcap_dispatch(l2->pcap, 1, l2_packet_receive_cb,
(u_char *) l2);
if (l2->rx_no_wait > 0)
l2->rx_no_wait--;
if (WaitForSingleObject(l2->rx_notify,
l2->rx_no_wait ? 0 : 50) ==
WAIT_OBJECT_0) {
l2->rx_no_wait = no_wait_count;
ResetEvent(l2->rx_notify);
}
}
SetEvent(l2->rx_thread_done);
ExitThread(0);
return 0;
}
/* main thread RX event handler */
static void l2_packet_rx_event(void *eloop_data, void *user_data)
{
struct l2_packet_data *l2 = eloop_data;
l2->rx_callback(l2->rx_callback_ctx, l2->rx_src, l2->rx_buf,
l2->rx_len);
ResetEvent(l2->rx_avail);
SetEvent(l2->rx_done);
}
static int l2_packet_init_libpcap(struct l2_packet_data *l2,
unsigned short protocol)
{
bpf_u_int32 pcap_maskp, pcap_netp;
char pcap_filter[200], pcap_err[PCAP_ERRBUF_SIZE];
struct bpf_program pcap_fp;
pcap_lookupnet(l2->ifname, &pcap_netp, &pcap_maskp, pcap_err);
l2->pcap = pcap_open_live(l2->ifname, 2500, 0, 1, pcap_err);
if (l2->pcap == NULL) {
fprintf(stderr, "pcap_open_live: %s\n", pcap_err);
fprintf(stderr, "ifname='%s'\n", l2->ifname);
return -1;
}
os_snprintf(pcap_filter, sizeof(pcap_filter),
"not ether src " MACSTR " and "
"( ether dst " MACSTR " or ether dst " MACSTR " ) and "
"ether proto 0x%x",
MAC2STR(l2->own_addr), /* do not receive own packets */
MAC2STR(l2->own_addr), MAC2STR(pae_group_addr),
protocol);
if (pcap_compile(l2->pcap, &pcap_fp, pcap_filter, 1, pcap_netp) < 0) {
fprintf(stderr, "pcap_compile: %s\n", pcap_geterr(l2->pcap));
return -1;
}
if (pcap_setfilter(l2->pcap, &pcap_fp) < 0) {
fprintf(stderr, "pcap_setfilter: %s\n", pcap_geterr(l2->pcap));
return -1;
}
pcap_freecode(&pcap_fp);
return 0;
}
struct l2_packet_data * l2_packet_init(
const char *ifname, const u8 *own_addr, unsigned short protocol,
void (*rx_callback)(void *ctx, const u8 *src_addr,
const u8 *buf, size_t len),
void *rx_callback_ctx, int l2_hdr)
{
struct l2_packet_data *l2;
DWORD thread_id;
l2 = os_zalloc(sizeof(struct l2_packet_data));
if (l2 == NULL)
return NULL;
if (os_strncmp(ifname, "\\Device\\NPF_", 12) == 0)
os_strncpy(l2->ifname, ifname, sizeof(l2->ifname));
else
os_snprintf(l2->ifname, sizeof(l2->ifname), "\\Device\\NPF_%s",
ifname);
l2->rx_callback = rx_callback;
l2->rx_callback_ctx = rx_callback_ctx;
l2->l2_hdr = l2_hdr;
if (own_addr)
os_memcpy(l2->own_addr, own_addr, ETH_ALEN);
if (l2_packet_init_libpcap(l2, protocol)) {
os_free(l2);
return NULL;
}
l2->rx_avail = CreateEvent(NULL, TRUE, FALSE, NULL);
l2->rx_done = CreateEvent(NULL, TRUE, FALSE, NULL);
l2->rx_notify = CreateEvent(NULL, TRUE, FALSE, NULL);
if (l2->rx_avail == NULL || l2->rx_done == NULL ||
l2->rx_notify == NULL) {
CloseHandle(l2->rx_avail);
CloseHandle(l2->rx_done);
CloseHandle(l2->rx_notify);
pcap_close(l2->pcap);
os_free(l2);
return NULL;
}
eloop_register_event(l2->rx_avail, sizeof(l2->rx_avail),
l2_packet_rx_event, l2, NULL);
l2->running = 1;
l2->rx_thread = CreateThread(NULL, 0, l2_packet_receive_thread, l2, 0,
&thread_id);
return l2;
}
static void l2_packet_deinit_timeout(void *eloop_ctx, void *timeout_ctx)
{
struct l2_packet_data *l2 = eloop_ctx;
if (l2->rx_thread_done &&
WaitForSingleObject(l2->rx_thread_done, 2000) != WAIT_OBJECT_0) {
wpa_printf(MSG_DEBUG, "l2_packet_winpcap: RX thread did not "
"exit - kill it\n");
TerminateThread(l2->rx_thread, 0);
}
CloseHandle(l2->rx_thread_done);
CloseHandle(l2->rx_thread);
if (l2->pcap)
pcap_close(l2->pcap);
eloop_unregister_event(l2->rx_avail, sizeof(l2->rx_avail));
CloseHandle(l2->rx_avail);
CloseHandle(l2->rx_done);
CloseHandle(l2->rx_notify);
os_free(l2);
}
void l2_packet_deinit(struct l2_packet_data *l2)
{
if (l2 == NULL)
return;
l2->rx_thread_done = CreateEvent(NULL, TRUE, FALSE, NULL);
l2->running = 0;
pcap_breakloop(l2->pcap);
/*
* RX thread may be waiting in l2_packet_receive_cb() for l2->rx_done
* event and this event is set in l2_packet_rx_event(). However,
* l2_packet_deinit() may end up being called from l2->rx_callback(),
* so we need to return from here and complete deinitialization in
* a registered timeout to avoid having to forcefully kill the RX
* thread.
*/
eloop_register_timeout(0, 0, l2_packet_deinit_timeout, l2, NULL);
}
int l2_packet_get_ip_addr(struct l2_packet_data *l2, char *buf, size_t len)
{
pcap_if_t *devs, *dev;
struct pcap_addr *addr;
struct sockaddr_in *saddr;
int found = 0;
char err[PCAP_ERRBUF_SIZE + 1];
if (pcap_findalldevs(&devs, err) < 0) {
wpa_printf(MSG_DEBUG, "pcap_findalldevs: %s\n", err);
return -1;
}
for (dev = devs; dev && !found; dev = dev->next) {
if (os_strcmp(dev->name, l2->ifname) != 0)
continue;
addr = dev->addresses;
while (addr) {
saddr = (struct sockaddr_in *) addr->addr;
if (saddr && saddr->sin_family == AF_INET) {
os_snprintf(buf, len, "%s",
inet_ntoa(saddr->sin_addr));
found = 1;
break;
}
addr = addr->next;
}
}
pcap_freealldevs(devs);
return found ? 0 : -1;
}
void l2_packet_notify_auth_start(struct l2_packet_data *l2)
{
SetEvent(l2->rx_notify);
}
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