hostapd/src/drivers/driver_nl80211_monitor.c

/*
 * Driver interaction with Linux nl80211/cfg80211 - AP monitor interface
 * Copyright (c) 2002-2014, Jouni Malinen <j@w1.fi>
 * Copyright (c) 2003-2004, Instant802 Networks, Inc.
 * Copyright (c) 2005-2006, Devicescape Software, Inc.
 * Copyright (c) 2007, Johannes Berg <johannes@sipsolutions.net>
 * Copyright (c) 2009-2010, Atheros Communications
 *
 * This software may be distributed under the terms of the BSD license.
 * See README for more details.
 */

#include "includes.h"
#include <netpacket/packet.h>
#include <linux/filter.h>

#include "utils/common.h"
#include "utils/eloop.h"
#include "common/ieee802_11_defs.h"
#include "common/ieee802_11_common.h"
#include "linux_ioctl.h"
#include "radiotap_iter.h"
#include "driver_nl80211.h"


static void handle_tx_callback(void *ctx, u8 *buf, size_t len, int ok)
{
	struct ieee80211_hdr *hdr;
	u16 fc;
	union wpa_event_data event;

	hdr = (struct ieee80211_hdr *) buf;
	fc = le_to_host16(hdr->frame_control);

	os_memset(&event, 0, sizeof(event));
	event.tx_status.type = WLAN_FC_GET_TYPE(fc);
	event.tx_status.stype = WLAN_FC_GET_STYPE(fc);
	event.tx_status.dst = hdr->addr1;
	event.tx_status.data = buf;
	event.tx_status.data_len = len;
	event.tx_status.ack = ok;
	wpa_supplicant_event(ctx, EVENT_TX_STATUS, &event);
}


static void from_unknown_sta(struct wpa_driver_nl80211_data *drv,
			     u8 *buf, size_t len)
{
	struct ieee80211_hdr *hdr = (void *)buf;
	u16 fc;
	union wpa_event_data event;

	if (len < sizeof(*hdr))
		return;

	fc = le_to_host16(hdr->frame_control);

	os_memset(&event, 0, sizeof(event));
	event.rx_from_unknown.bssid = get_hdr_bssid(hdr, len);
	event.rx_from_unknown.addr = hdr->addr2;
	event.rx_from_unknown.wds = (fc & (WLAN_FC_FROMDS | WLAN_FC_TODS)) ==
		(WLAN_FC_FROMDS | WLAN_FC_TODS);
	wpa_supplicant_event(drv->ctx, EVENT_RX_FROM_UNKNOWN, &event);
}


static void handle_frame(struct wpa_driver_nl80211_data *drv,
			 u8 *buf, size_t len, int datarate, int ssi_signal)
{
	struct ieee80211_hdr *hdr;
	u16 fc;
	union wpa_event_data event;

	hdr = (struct ieee80211_hdr *) buf;
	fc = le_to_host16(hdr->frame_control);

	switch (WLAN_FC_GET_TYPE(fc)) {
	case WLAN_FC_TYPE_MGMT:
		os_memset(&event, 0, sizeof(event));
		event.rx_mgmt.frame = buf;
		event.rx_mgmt.frame_len = len;
		event.rx_mgmt.datarate = datarate;
		event.rx_mgmt.ssi_signal = ssi_signal;
		wpa_supplicant_event(drv->ctx, EVENT_RX_MGMT, &event);
		break;
	case WLAN_FC_TYPE_CTRL:
		/* can only get here with PS-Poll frames */
		wpa_printf(MSG_DEBUG, "CTRL");
		from_unknown_sta(drv, buf, len);
		break;
	case WLAN_FC_TYPE_DATA:
		from_unknown_sta(drv, buf, len);
		break;
	}
}


static void handle_monitor_read(int sock, void *eloop_ctx, void *sock_ctx)
{
	struct wpa_driver_nl80211_data *drv = eloop_ctx;
	int len;
	unsigned char buf[3000];
	struct ieee80211_radiotap_iterator iter;
	int ret;
	int datarate = 0, ssi_signal = 0;
	int injected = 0, failed = 0, rxflags = 0;

	len = recv(sock, buf, sizeof(buf), 0);
	if (len < 0) {
		wpa_printf(MSG_ERROR, "nl80211: Monitor socket recv failed: %s",
			   strerror(errno));
		return;
	}

	if (ieee80211_radiotap_iterator_init(&iter, (void *) buf, len, NULL)) {
		wpa_printf(MSG_INFO, "nl80211: received invalid radiotap frame");
		return;
	}

	while (1) {
		ret = ieee80211_radiotap_iterator_next(&iter);
		if (ret == -ENOENT)
			break;
		if (ret) {
			wpa_printf(MSG_INFO, "nl80211: received invalid radiotap frame (%d)",
				   ret);
			return;
		}
		switch (iter.this_arg_index) {
		case IEEE80211_RADIOTAP_FLAGS:
			if (*iter.this_arg & IEEE80211_RADIOTAP_F_FCS)
				len -= 4;
			break;
		case IEEE80211_RADIOTAP_RX_FLAGS:
			rxflags = 1;
			break;
		case IEEE80211_RADIOTAP_TX_FLAGS:
			injected = 1;
			failed = le_to_host16((*(le16 *) iter.this_arg)) &
					IEEE80211_RADIOTAP_F_TX_FAIL;
			break;
		case IEEE80211_RADIOTAP_DATA_RETRIES:
			break;
		case IEEE80211_RADIOTAP_CHANNEL:
			/* TODO: convert from freq/flags to channel number */
			break;
		case IEEE80211_RADIOTAP_RATE:
			datarate = *iter.this_arg * 5;
			break;
		case IEEE80211_RADIOTAP_DBM_ANTSIGNAL:
			ssi_signal = (s8) *iter.this_arg;
			break;
		}
	}

	if (rxflags && injected)
		return;

	if (!injected)
		handle_frame(drv, buf + iter._max_length,
			     len - iter._max_length, datarate, ssi_signal);
	else
		handle_tx_callback(drv->ctx, buf + iter._max_length,
				   len - iter._max_length, !failed);
}


/*
 * we post-process the filter code later and rewrite
 * this to the offset to the last instruction
 */
#define PASS	0xFF
#define FAIL	0xFE

static struct sock_filter msock_filter_insns[] = {
	/*
	 * do a little-endian load of the radiotap length field
	 */
	/* load lower byte into A */
	BPF_STMT(BPF_LD  | BPF_B | BPF_ABS, 2),
	/* put it into X (== index register) */
	BPF_STMT(BPF_MISC| BPF_TAX, 0),
	/* load upper byte into A */
	BPF_STMT(BPF_LD  | BPF_B | BPF_ABS, 3),
	/* left-shift it by 8 */
	BPF_STMT(BPF_ALU | BPF_LSH | BPF_K, 8),
	/* or with X */
	BPF_STMT(BPF_ALU | BPF_OR | BPF_X, 0),
	/* put result into X */
	BPF_STMT(BPF_MISC| BPF_TAX, 0),

	/*
	 * Allow management frames through, this also gives us those
	 * management frames that we sent ourselves with status
	 */
	/* load the lower byte of the IEEE 802.11 frame control field */
	BPF_STMT(BPF_LD  | BPF_B | BPF_IND, 0),
	/* mask off frame type and version */
	BPF_STMT(BPF_ALU | BPF_AND | BPF_K, 0xF),
	/* accept frame if it's both 0, fall through otherwise */
	BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, 0, PASS, 0),

	/*
	 * TODO: add a bit to radiotap RX flags that indicates
	 * that the sending station is not associated, then
	 * add a filter here that filters on our DA and that flag
	 * to allow us to deauth frames to that bad station.
	 *
	 * For now allow all To DS data frames through.
	 */
	/* load the IEEE 802.11 frame control field */
	BPF_STMT(BPF_LD  | BPF_H | BPF_IND, 0),
	/* mask off frame type, version and DS status */
	BPF_STMT(BPF_ALU | BPF_AND | BPF_K, 0x0F03),
	/* accept frame if version 0, type 2 and To DS, fall through otherwise
	 */
	BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, 0x0801, PASS, 0),

#if 0
	/*
	 * drop non-data frames
	 */
	/* load the lower byte of the frame control field */
	BPF_STMT(BPF_LD   | BPF_B | BPF_IND, 0),
	/* mask off QoS bit */
	BPF_STMT(BPF_ALU  | BPF_AND | BPF_K, 0x0c),
	/* drop non-data frames */
	BPF_JUMP(BPF_JMP  | BPF_JEQ | BPF_K, 8, 0, FAIL),
#endif
	/* load the upper byte of the frame control field */
	BPF_STMT(BPF_LD   | BPF_B | BPF_IND, 1),
	/* mask off toDS/fromDS */
	BPF_STMT(BPF_ALU  | BPF_AND | BPF_K, 0x03),
	/* accept WDS frames */
	BPF_JUMP(BPF_JMP  | BPF_JEQ | BPF_K, 3, PASS, 0),

	/*
	 * add header length to index
	 */
	/* load the lower byte of the frame control field */
	BPF_STMT(BPF_LD   | BPF_B | BPF_IND, 0),
	/* mask off QoS bit */
	BPF_STMT(BPF_ALU  | BPF_AND | BPF_K, 0x80),
	/* right shift it by 6 to give 0 or 2 */
	BPF_STMT(BPF_ALU  | BPF_RSH | BPF_K, 6),
	/* add data frame header length */
	BPF_STMT(BPF_ALU  | BPF_ADD | BPF_K, 24),
	/* add index, was start of 802.11 header */
	BPF_STMT(BPF_ALU  | BPF_ADD | BPF_X, 0),
	/* move to index, now start of LL header */
	BPF_STMT(BPF_MISC | BPF_TAX, 0),

	/*
	 * Accept empty data frames, we use those for
	 * polling activity.
	 */
	BPF_STMT(BPF_LD  | BPF_W | BPF_LEN, 0),
	BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_X, 0, PASS, 0),

	/*
	 * Accept EAPOL frames
	 */
	BPF_STMT(BPF_LD  | BPF_W | BPF_IND, 0),
	BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, 0xAAAA0300, 0, FAIL),
	BPF_STMT(BPF_LD  | BPF_W | BPF_IND, 4),
	BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, 0x0000888E, PASS, FAIL),

	/* keep these last two statements or change the code below */
	/* return 0 == "DROP" */
	BPF_STMT(BPF_RET | BPF_K, 0),
	/* return ~0 == "keep all" */
	BPF_STMT(BPF_RET | BPF_K, ~0),
};

static struct sock_fprog msock_filter = {
	.len = ARRAY_SIZE(msock_filter_insns),
	.filter = msock_filter_insns,
};


static int add_monitor_filter(int s)
{
	int idx;

	/* rewrite all PASS/FAIL jump offsets */
	for (idx = 0; idx < msock_filter.len; idx++) {
		struct sock_filter *insn = &msock_filter_insns[idx];

		if (BPF_CLASS(insn->code) == BPF_JMP) {
			if (insn->code == (BPF_JMP|BPF_JA)) {
				if (insn->k == PASS)
					insn->k = msock_filter.len - idx - 2;
				else if (insn->k == FAIL)
					insn->k = msock_filter.len - idx - 3;
			}

			if (insn->jt == PASS)
				insn->jt = msock_filter.len - idx - 2;
			else if (insn->jt == FAIL)
				insn->jt = msock_filter.len - idx - 3;

			if (insn->jf == PASS)
				insn->jf = msock_filter.len - idx - 2;
			else if (insn->jf == FAIL)
				insn->jf = msock_filter.len - idx - 3;
		}
	}

	if (setsockopt(s, SOL_SOCKET, SO_ATTACH_FILTER,
		       &msock_filter, sizeof(msock_filter))) {
		wpa_printf(MSG_ERROR, "nl80211: setsockopt(SO_ATTACH_FILTER) failed: %s",
			   strerror(errno));
		return -1;
	}

	return 0;
}


void nl80211_remove_monitor_interface(struct wpa_driver_nl80211_data *drv)
{
	if (drv->monitor_refcount > 0)
		drv->monitor_refcount--;
	wpa_printf(MSG_DEBUG, "nl80211: Remove monitor interface: refcount=%d",
		   drv->monitor_refcount);
	if (drv->monitor_refcount > 0)
		return;

	if (drv->monitor_ifidx >= 0) {
		nl80211_remove_iface(drv, drv->monitor_ifidx);
		drv->monitor_ifidx = -1;
	}
	if (drv->monitor_sock >= 0) {
		eloop_unregister_read_sock(drv->monitor_sock);
		close(drv->monitor_sock);
		drv->monitor_sock = -1;
	}
}


int nl80211_create_monitor_interface(struct wpa_driver_nl80211_data *drv)
{
	char buf[IFNAMSIZ];
	struct sockaddr_ll ll;
	int optval;
	socklen_t optlen;

	if (drv->monitor_ifidx >= 0) {
		drv->monitor_refcount++;
		wpa_printf(MSG_DEBUG, "nl80211: Re-use existing monitor interface: refcount=%d",
			   drv->monitor_refcount);
		return 0;
	}

	if (os_strncmp(drv->first_bss->ifname, "p2p-", 4) == 0) {
		/*
		 * P2P interface name is of the format p2p-%s-%d. For monitor
		 * interface name corresponding to P2P GO, replace "p2p-" with
		 * "mon-" to retain the same interface name length and to
		 * indicate that it is a monitor interface.
		 */
		snprintf(buf, IFNAMSIZ, "mon-%s", drv->first_bss->ifname + 4);
	} else {
		/* Non-P2P interface with AP functionality. */
		snprintf(buf, IFNAMSIZ, "mon.%s", drv->first_bss->ifname);
	}

	buf[IFNAMSIZ - 1] = '\0';

	drv->monitor_ifidx =
		nl80211_create_iface(drv, buf, NL80211_IFTYPE_MONITOR, NULL,
				     0, NULL, NULL, 0);

	if (drv->monitor_ifidx == -EOPNOTSUPP) {
		/*
		 * This is backward compatibility for a few versions of
		 * the kernel only that didn't advertise the right
		 * attributes for the only driver that then supported
		 * AP mode w/o monitor -- ath6kl.
		 */
		wpa_printf(MSG_DEBUG, "nl80211: Driver does not support "
			   "monitor interface type - try to run without it");
		drv->device_ap_sme = 1;
	}

	if (drv->monitor_ifidx < 0)
		return -1;

	if (linux_set_iface_flags(drv->global->ioctl_sock, buf, 1))
		goto error;

	memset(&ll, 0, sizeof(ll));
	ll.sll_family = AF_PACKET;
	ll.sll_ifindex = drv->monitor_ifidx;
	drv->monitor_sock = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL));
	if (drv->monitor_sock < 0) {
		wpa_printf(MSG_ERROR, "nl80211: socket[PF_PACKET,SOCK_RAW] failed: %s",
			   strerror(errno));
		goto error;
	}

	if (add_monitor_filter(drv->monitor_sock)) {
		wpa_printf(MSG_INFO, "Failed to set socket filter for monitor "
			   "interface; do filtering in user space");
		/* This works, but will cost in performance. */
	}

	if (bind(drv->monitor_sock, (struct sockaddr *) &ll, sizeof(ll)) < 0) {
		wpa_printf(MSG_ERROR, "nl80211: monitor socket bind failed: %s",
			   strerror(errno));
		goto error;
	}

	optlen = sizeof(optval);
	optval = 20;
	if (setsockopt
	    (drv->monitor_sock, SOL_SOCKET, SO_PRIORITY, &optval, optlen)) {
		wpa_printf(MSG_ERROR, "nl80211: Failed to set socket priority: %s",
			   strerror(errno));
		goto error;
	}

	if (eloop_register_read_sock(drv->monitor_sock, handle_monitor_read,
				     drv, NULL)) {
		wpa_printf(MSG_INFO, "nl80211: Could not register monitor read socket");
		goto error;
	}

	drv->monitor_refcount++;
	return 0;
 error:
	nl80211_remove_monitor_interface(drv);
	return -1;
}


int nl80211_send_monitor(struct wpa_driver_nl80211_data *drv,
			 const void *data, size_t len,
			 int encrypt, int noack)
{
	__u8 rtap_hdr[] = {
		0x00, 0x00, /* radiotap version */
		0x0e, 0x00, /* radiotap length */
		0x02, 0xc0, 0x00, 0x00, /* bmap: flags, tx and rx flags */
		IEEE80211_RADIOTAP_F_FRAG, /* F_FRAG (fragment if required) */
		0x00,       /* padding */
		0x00, 0x00, /* RX and TX flags to indicate that */
		0x00, 0x00, /* this is the injected frame directly */
	};
	struct iovec iov[2] = {
		{
			.iov_base = &rtap_hdr,
			.iov_len = sizeof(rtap_hdr),
		},
		{
			.iov_base = (void *) data,
			.iov_len = len,
		}
	};
	struct msghdr msg = {
		.msg_name = NULL,
		.msg_namelen = 0,
		.msg_iov = iov,
		.msg_iovlen = 2,
		.msg_control = NULL,
		.msg_controllen = 0,
		.msg_flags = 0,
	};
	int res;
	u16 txflags = 0;

	if (encrypt)
		rtap_hdr[8] |= IEEE80211_RADIOTAP_F_WEP;

	if (drv->monitor_sock < 0) {
		wpa_printf(MSG_DEBUG, "nl80211: No monitor socket available "
			   "for %s", __func__);
		return -1;
	}

	if (noack)
		txflags |= IEEE80211_RADIOTAP_F_TX_NOACK;
	WPA_PUT_LE16(&rtap_hdr[12], txflags);

	res = sendmsg(drv->monitor_sock, &msg, 0);
	if (res < 0) {
		wpa_printf(MSG_INFO, "nl80211: sendmsg: %s", strerror(errno));
		return -1;
	}
	return 0;
}