hostapd/src/l2_packet/l2_packet_linux.c

/*
 * WPA Supplicant - Layer2 packet handling with Linux packet sockets
 * Copyright (c) 2003-2015, Jouni Malinen <j@w1.fi>
 *
 * This software may be distributed under the terms of the BSD license.
 * See README for more details.
 */

#include "includes.h"
#include <sys/ioctl.h>
#include <netpacket/packet.h>
#include <net/if.h>
#include <linux/filter.h>

#include "common.h"
#include "eloop.h"
#include "l2_packet.h"


struct l2_packet_data {
	int fd; /* packet socket for EAPOL frames */
	char ifname[IFNAMSIZ + 1];
	int ifindex;
	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 data
		     * buffers */

	/* For working around Linux packet socket behavior and regression. */
	int fd_br_rx;
};

/* Generated by 'sudo tcpdump -s 3000 -dd greater 278 and ip and udp and
 * src port bootps and dst port bootpc'
 */
static struct sock_filter dhcp_sock_filter_insns[] = {
	{ 0x80, 0, 0, 0x00000000 },
	{ 0x35, 0, 12, 0x00000116 },
	{ 0x28, 0, 0, 0x0000000c },
	{ 0x15, 0, 10, 0x00000800 },
	{ 0x30, 0, 0, 0x00000017 },
	{ 0x15, 0, 8, 0x00000011 },
	{ 0x28, 0, 0, 0x00000014 },
	{ 0x45, 6, 0, 0x00001fff },
	{ 0xb1, 0, 0, 0x0000000e },
	{ 0x48, 0, 0, 0x0000000e },
	{ 0x15, 0, 3, 0x00000043 },
	{ 0x48, 0, 0, 0x00000010 },
	{ 0x15, 0, 1, 0x00000044 },
	{ 0x6, 0, 0, 0x00000bb8 },
	{ 0x6, 0, 0, 0x00000000 },
};

static const struct sock_fprog dhcp_sock_filter = {
	.len = ARRAY_SIZE(dhcp_sock_filter_insns),
	.filter = dhcp_sock_filter_insns,
};


/* Generated by 'sudo tcpdump -dd -s 1500 multicast and ip6[6]=58' */
static struct sock_filter ndisc_sock_filter_insns[] = {
	{ 0x30, 0, 0, 0x00000000 },
	{ 0x45, 0, 5, 0x00000001 },
	{ 0x28, 0, 0, 0x0000000c },
	{ 0x15, 0, 3, 0x000086dd },
	{ 0x30, 0, 0, 0x00000014 },
	{ 0x15, 0, 1, 0x0000003a },
	{ 0x6, 0, 0, 0x000005dc },
	{ 0x6, 0, 0, 0x00000000 },
};

static const struct sock_fprog ndisc_sock_filter = {
	.len = ARRAY_SIZE(ndisc_sock_filter_insns),
	.filter = ndisc_sock_filter_insns,
};


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;
	if (l2 == NULL)
		return -1;
	if (l2->l2_hdr) {
		ret = send(l2->fd, buf, len, 0);
		if (ret < 0)
			wpa_printf(MSG_ERROR, "l2_packet_send - send: %s",
				   strerror(errno));
	} else {
		struct sockaddr_ll ll;
		os_memset(&ll, 0, sizeof(ll));
		ll.sll_family = AF_PACKET;
		ll.sll_ifindex = l2->ifindex;
		ll.sll_protocol = htons(proto);
		ll.sll_halen = ETH_ALEN;
		os_memcpy(ll.sll_addr, dst_addr, ETH_ALEN);
		ret = sendto(l2->fd, buf, len, 0, (struct sockaddr *) &ll,
			     sizeof(ll));
		if (ret < 0) {
			wpa_printf(MSG_ERROR, "l2_packet_send - sendto: %s",
				   strerror(errno));
		}
	}
	return ret;
}


static void l2_packet_receive(int sock, void *eloop_ctx, void *sock_ctx)
{
	struct l2_packet_data *l2 = eloop_ctx;
	u8 buf[2300];
	int res;
	struct sockaddr_ll ll;
	socklen_t fromlen;

	os_memset(&ll, 0, sizeof(ll));
	fromlen = sizeof(ll);
	res = recvfrom(sock, buf, sizeof(buf), 0, (struct sockaddr *) &ll,
		       &fromlen);
	if (res < 0) {
		wpa_printf(MSG_DEBUG, "l2_packet_receive - recvfrom: %s",
			   strerror(errno));
		return;
	}

	if (l2->fd_br_rx >= 0) {
		wpa_printf(MSG_DEBUG, "l2_packet_receive: Main packet socket for %s seems to have working RX - close workaround bridge socket",
			   l2->ifname);
		eloop_unregister_read_sock(l2->fd_br_rx);
		close(l2->fd_br_rx);
		l2->fd_br_rx = -1;
	}

	l2->rx_callback(l2->rx_callback_ctx, ll.sll_addr, buf, res);
}


static void l2_packet_receive_br(int sock, void *eloop_ctx, void *sock_ctx)
{
	struct l2_packet_data *l2 = eloop_ctx;
	u8 buf[2300];
	int res;
	struct sockaddr_ll ll;
	socklen_t fromlen;

	os_memset(&ll, 0, sizeof(ll));
	fromlen = sizeof(ll);
	res = recvfrom(sock, buf, sizeof(buf), 0, (struct sockaddr *) &ll,
		       &fromlen);
	if (res < 0) {
		wpa_printf(MSG_DEBUG, "l2_packet_receive_br - recvfrom: %s",
			   strerror(errno));
		return;
	}

	l2->rx_callback(l2->rx_callback_ctx, ll.sll_addr, buf, res);
}


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;
	struct ifreq ifr;
	struct sockaddr_ll ll;

	l2 = os_zalloc(sizeof(struct l2_packet_data));
	if (l2 == NULL)
		return NULL;
	os_strlcpy(l2->ifname, ifname, sizeof(l2->ifname));
	l2->rx_callback = rx_callback;
	l2->rx_callback_ctx = rx_callback_ctx;
	l2->l2_hdr = l2_hdr;
	l2->fd_br_rx = -1;

	l2->fd = socket(PF_PACKET, l2_hdr ? SOCK_RAW : SOCK_DGRAM,
			htons(protocol));
	if (l2->fd < 0) {
		wpa_printf(MSG_ERROR, "%s: socket(PF_PACKET): %s",
			   __func__, strerror(errno));
		os_free(l2);
		return NULL;
	}
	os_memset(&ifr, 0, sizeof(ifr));
	os_strlcpy(ifr.ifr_name, l2->ifname, sizeof(ifr.ifr_name));
	if (ioctl(l2->fd, SIOCGIFINDEX, &ifr) < 0) {
		wpa_printf(MSG_ERROR, "%s: ioctl[SIOCGIFINDEX]: %s",
			   __func__, strerror(errno));
		close(l2->fd);
		os_free(l2);
		return NULL;
	}
	l2->ifindex = ifr.ifr_ifindex;

	os_memset(&ll, 0, sizeof(ll));
	ll.sll_family = PF_PACKET;
	ll.sll_ifindex = ifr.ifr_ifindex;
	ll.sll_protocol = htons(protocol);
	if (bind(l2->fd, (struct sockaddr *) &ll, sizeof(ll)) < 0) {
		wpa_printf(MSG_ERROR, "%s: bind[PF_PACKET]: %s",
			   __func__, strerror(errno));
		close(l2->fd);
		os_free(l2);
		return NULL;
	}

	if (ioctl(l2->fd, SIOCGIFHWADDR, &ifr) < 0) {
		wpa_printf(MSG_ERROR, "%s: ioctl[SIOCGIFHWADDR]: %s",
			   __func__, strerror(errno));
		close(l2->fd);
		os_free(l2);
		return NULL;
	}
	os_memcpy(l2->own_addr, ifr.ifr_hwaddr.sa_data, ETH_ALEN);

	eloop_register_read_sock(l2->fd, l2_packet_receive, l2, NULL);

	return l2;
}


struct l2_packet_data * l2_packet_init_bridge(
	const char *br_ifname, 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;
	struct sock_filter ethertype_sock_filter_insns[] = {
		/* Load ethertype */
		BPF_STMT(BPF_LD | BPF_H | BPF_ABS, 2 * ETH_ALEN),
		/* Jump over next statement if ethertype does not match */
		BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, protocol, 0, 1),
		/* Ethertype match - return all */
		BPF_STMT(BPF_RET | BPF_K, ~0),
		/* No match - drop */
		BPF_STMT(BPF_RET | BPF_K, 0)
	};
	const struct sock_fprog ethertype_sock_filter = {
		.len = ARRAY_SIZE(ethertype_sock_filter_insns),
		.filter = ethertype_sock_filter_insns,
	};
	struct sockaddr_ll ll;

	l2 = l2_packet_init(br_ifname, own_addr, protocol, rx_callback,
			    rx_callback_ctx, l2_hdr);
	if (!l2)
		return NULL;

	/*
	 * The Linux packet socket behavior has changed over the years and there
	 * is an inconvenient regression in it that breaks RX for a specific
	 * protocol from interfaces in a bridge when that interface is not in
	 * fully operation state (i.e., when in station mode and not completed
	 * authorization). To work around this, register ETH_P_ALL version of
	 * the packet socket bound to the real netdev and use socket filter to
	 * match the ethertype value. This version is less efficient, but
	 * required for functionality with many kernel version. If the main
	 * packet socket is found to be working, this less efficient version
	 * gets closed automatically.
	 */

	l2->fd_br_rx = socket(PF_PACKET, l2_hdr ? SOCK_RAW : SOCK_DGRAM,
			      htons(ETH_P_ALL));
	if (l2->fd_br_rx < 0) {
		wpa_printf(MSG_DEBUG, "%s: socket(PF_PACKET-fd_br_rx): %s",
			   __func__, strerror(errno));
		/* try to continue without the workaround RX socket */
		return l2;
	}

	os_memset(&ll, 0, sizeof(ll));
	ll.sll_family = PF_PACKET;
	ll.sll_ifindex = if_nametoindex(ifname);
	ll.sll_protocol = htons(ETH_P_ALL);
	if (bind(l2->fd_br_rx, (struct sockaddr *) &ll, sizeof(ll)) < 0) {
		wpa_printf(MSG_DEBUG, "%s: bind[PF_PACKET-fd_br_rx]: %s",
			   __func__, strerror(errno));
		/* try to continue without the workaround RX socket */
		close(l2->fd_br_rx);
		l2->fd_br_rx = -1;
		return l2;
	}

	if (setsockopt(l2->fd_br_rx, SOL_SOCKET, SO_ATTACH_FILTER,
		       &ethertype_sock_filter, sizeof(struct sock_fprog))) {
		wpa_printf(MSG_DEBUG,
			   "l2_packet_linux: setsockopt(SO_ATTACH_FILTER) failed: %s",
			   strerror(errno));
		/* try to continue without the workaround RX socket */
		close(l2->fd_br_rx);
		l2->fd_br_rx = -1;
		return l2;
	}

	eloop_register_read_sock(l2->fd_br_rx, l2_packet_receive_br, l2, NULL);

	return l2;
}


void l2_packet_deinit(struct l2_packet_data *l2)
{
	if (l2 == NULL)
		return;

	if (l2->fd >= 0) {
		eloop_unregister_read_sock(l2->fd);
		close(l2->fd);
	}

	if (l2->fd_br_rx >= 0) {
		eloop_unregister_read_sock(l2->fd_br_rx);
		close(l2->fd_br_rx);
	}

	os_free(l2);
}


int l2_packet_get_ip_addr(struct l2_packet_data *l2, char *buf, size_t len)
{
	int s;
	struct ifreq ifr;
	struct sockaddr_in *saddr;
	size_t res;

	s = socket(PF_INET, SOCK_DGRAM, 0);
	if (s < 0) {
		wpa_printf(MSG_ERROR, "%s: socket: %s",
			   __func__, strerror(errno));
		return -1;
	}
	os_memset(&ifr, 0, sizeof(ifr));
	os_strlcpy(ifr.ifr_name, l2->ifname, sizeof(ifr.ifr_name));
	if (ioctl(s, SIOCGIFADDR, &ifr) < 0) {
		if (errno != EADDRNOTAVAIL)
			wpa_printf(MSG_ERROR, "%s: ioctl[SIOCGIFADDR]: %s",
				   __func__, strerror(errno));
		close(s);
		return -1;
	}
	close(s);
	saddr = aliasing_hide_typecast(&ifr.ifr_addr, struct sockaddr_in);
	if (saddr->sin_family != AF_INET)
		return -1;
	res = os_strlcpy(buf, inet_ntoa(saddr->sin_addr), len);
	if (res >= len)
		return -1;
	return 0;
}


void l2_packet_notify_auth_start(struct l2_packet_data *l2)
{
}


int l2_packet_set_packet_filter(struct l2_packet_data *l2,
				enum l2_packet_filter_type type)
{
	const struct sock_fprog *sock_filter;

	switch (type) {
	case L2_PACKET_FILTER_DHCP:
		sock_filter = &dhcp_sock_filter;
		break;
	case L2_PACKET_FILTER_NDISC:
		sock_filter = &ndisc_sock_filter;
		break;
	default:
		return -1;
	}

	if (setsockopt(l2->fd, SOL_SOCKET, SO_ATTACH_FILTER,
		       sock_filter, sizeof(struct sock_fprog))) {
		wpa_printf(MSG_ERROR,
			   "l2_packet_linux: setsockopt(SO_ATTACH_FILTER) failed: %s",
			   strerror(errno));
		return -1;
	}

	return 0;
}