TX path

Linux 6.18.37 LTS: net/core/dev.c
Linux 6.18.37 LTS: net/sched/sch_generic.c
Linux 6.18.37 LTS: net/ipv4/ip_output.c

	skb_set_queue_mapping(skb, queue_index);
	return netdev_get_tx_queue(dev, queue_index);
}

/**
 * __dev_queue_xmit() - transmit a buffer
 * @skb:	buffer to transmit
 * @sb_dev:	suboordinate device used for L2 forwarding offload
 *
 * Queue a buffer for transmission to a network device. The caller must
 * have set the device and priority and built the buffer before calling
 * this function. The function can be called from an interrupt.
 *
 * When calling this method, interrupts MUST be enabled. This is because
 * the BH enable code must have IRQs enabled so that it will not deadlock.
 *
 * Regardless of the return value, the skb is consumed, so it is currently
 * difficult to retry a send to this method. (You can bump the ref count
 * before sending to hold a reference for retry if you are careful.)
 *
 * Return:
 * * 0				- buffer successfully transmitted
 * * positive qdisc return code	- NET_XMIT_DROP etc.
 * * negative errno		- other errors
 */
int __dev_queue_xmit(struct sk_buff *skb, struct net_device *sb_dev)
{
	struct net_device *dev = skb->dev;
	struct netdev_queue *txq = NULL;
	struct Qdisc *q;
	int rc = -ENOMEM;
	bool again = false;

	skb_reset_mac_header(skb);
	skb_assert_len(skb);

	if (unlikely(skb_shinfo(skb)->tx_flags & SKBTX_SCHED_TSTAMP))
		__skb_tstamp_tx(skb, NULL, NULL, skb->sk, SCM_TSTAMP_SCHED);

	/* Disable soft irqs for various locks below. Also

	trace_net_dev_xmit(skb, rc, dev, len);

	return rc;
}

struct sk_buff *dev_hard_start_xmit(struct sk_buff *first, struct net_device *dev,
				    struct netdev_queue *txq, int *ret)
{
	struct sk_buff *skb = first;
	int rc = NETDEV_TX_OK;

	while (skb) {
		struct sk_buff *next = skb->next;

		skb_mark_not_on_list(skb);
		rc = xmit_one(skb, dev, txq, next != NULL);
		if (unlikely(!dev_xmit_complete(rc))) {
			skb->next = next;
			goto out;
		}

		skb = next;
		if (netif_tx_queue_stopped(txq) && skb) {
			rc = NETDEV_TX_BUSY;
			break;
		}
	}

out:
	*ret = rc;
	return skb;
}

static struct sk_buff *validate_xmit_vlan(struct sk_buff *skb,
					  netdev_features_t features)
{
	if (skb_vlan_tag_present(skb) &&
	    !vlan_hw_offload_capable(features, skb->vlan_proto))
		skb = __vlan_hwaccel_push_inside(skb);
	return skb;