wpa_supplicant二层包收发

添加 wlan 接口时会调用wpa_supplicant_init_iface

\wpa_supplicant\wpa_supplicant.c

\src\l2_packet\l2_packet_linux.c

这里面就是初始化一个 PF_PACKET socket 文件描述符，然后向 eloop 注册读事件，在 bind 时绑定了 wlan 接口地址，因此可以使用这个 socket 文件描述符对指定 wlan 接口收发二层数据包

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;
#ifndef CONFIG_NO_LINUX_PACKET_SOCKET_WAR
	l2->fd_br_rx = -1;
#endif /* CONFIG_NO_LINUX_PACKET_SOCKET_WAR */

	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 (rx_callback &&
	    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);

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

	return l2;
}