tx.c

static const unsigned char pkt[] = {
// ethernet header
0xa0, 0x36, 0x9f, 0x18, 0x50, 0xe5,
0x00, 0x1c, 0x7e, 0x6a, 0xba, 0xd1,
0x08, 0x00,
// IPv4 header
0x45, 0x00, 0x00, 0x4e,
0x00, 0x00, 0x40, 0x00,
0x40, 0x11, 0xfb, 0x32,
0x0a, 0x00, 0x00, 0x6e,
0x0a, 0x00, 0x00, 0x02,
// payload
0x04, 0x04, 0x00, 0x89, 0x00, 0x3a, 0x38, 0x03,
0x10, 0xfd, 0x01, 0x10, 0x00, 0x01, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x20, 0x46, 0x45, 0x45,
0x4e, 0x45, 0x42, 0x46, 0x45, 0x46, 0x44, 0x46,
0x46, 0x46, 0x4a, 0x45, 0x42, 0x43, 0x4e, 0x45,
0x49, 0x46, 0x41, 0x43, 0x41, 0x43, 0x41, 0x43,
0x41, 0x43, 0x41, 0x43, 0x41, 0x00, 0x00, 0x20,
0x00, 0x01
};
static const unsigned short pktlen = sizeof(pkt) / sizeof(pkt[0]);

static int packet_direct_xmit(struct sk_buff *skb)
{
	struct net_device *dev = skb->dev;
	const struct net_device_ops *ops = dev->netdev_ops;
	netdev_features_t features;
	struct netdev_queue *txq;
	int ret = NETDEV_TX_BUSY;
	u16 queue_map;

	if (unlikely(!netif_running(dev) || !netif_carrier_ok(dev)))
		goto drop;

	features = netif_skb_features(skb);
	if (skb_needs_linearize(skb, features) && __skb_linearize(skb))
		goto drop;

	queue_map = skb_get_queue_mapping(skb);
	txq = netdev_get_tx_queue(dev, queue_map);

	local_bh_disable();

	HARD_TX_LOCK(dev, txq, smp_processor_id());

	if (!netif_xmit_frozen_or_drv_stopped(txq)) {
		ret = ops->ndo_start_xmit(skb, dev);
		if (ret == NETDEV_TX_OK)
			txq_trans_update(txq);
	}
	HARD_TX_UNLOCK(dev, txq);

	local_bh_enable();

	if (!dev_xmit_complete(ret))
		kfree_skb(skb);

	return ret;
drop:
	atomic_long_inc(&dev->tx_dropped);
	kfree_skb(skb);
	return NET_XMIT_DROP;
}

static ssize_t tx_write(struct file *filp, const char __user *buf,
			    size_t count, loff_t *ppos)
{
	int ret;
	struct sk_buff *tx_skb = NULL;

	pr_info( "pktlen: %d\n", pktlen );

	tx_skb = netdev_alloc_skb(device, pktlen);
	if (likely(tx_skb)) {
		tx_skb->dev = device;

		skb_put(tx_skb, pktlen);
		memcpy(tx_skb->data, pkt, pktlen);

		ret = packet_direct_xmit(tx_skb);
		if (ret) {
			pr_info( "fail packet_direct_xmit=%d\n", ret );
		}
	}

	return count;
}