net/dsa/tag_lan9303.c

Source file repositories/reference/linux-study-clean/net/dsa/tag_lan9303.c

File Facts

System
Linux kernel
Corpus path
net/dsa/tag_lan9303.c
Extension
.c
Size
3691 bytes
Lines
127
Domain
Networking Core
Bucket
Sockets, Protocols, Packet Path, And Network Policy
Inferred role
Networking Core: implementation source
Status
source implementation candidate

Why This File Exists

Networking stack implementation surface: socket APIs, protocol dispatch, packet flow, routing, filtering, and network namespaces.

Dependency Surface

Detected Declarations

Annotated Snippet

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2017 Pengutronix, Juergen Borleis <jbe@pengutronix.de>
 */
#include <linux/dsa/lan9303.h>
#include <linux/etherdevice.h>
#include <linux/list.h>
#include <linux/slab.h>

#include "tag.h"

/* To define the outgoing port and to discover the incoming port a regular
 * VLAN tag is used by the LAN9303. But its VID meaning is 'special':
 *
 *       Dest MAC       Src MAC        TAG    Type
 * ...| 1 2 3 4 5 6 | 1 2 3 4 5 6 | 1 2 3 4 | 1 2 |...
 *                                |<------->|
 * TAG:
 *    |<------------->|
 *    |  1  2 | 3  4  |
 *      TPID    VID
 *     0x8100
 *
 * VID bit 3 indicates a request for an ALR lookup.
 *
 * If VID bit 3 is zero, then bits 0 and 1 specify the destination port
 * (0, 1, 2) or broadcast (3) or the source port (1, 2).
 *
 * VID bit 4 is used to specify if the STP port state should be overridden.
 * Required when no forwarding between the external ports should happen.
 */

#define LAN9303_NAME "lan9303"

#define LAN9303_TAG_LEN 4
# define LAN9303_TAG_TX_USE_ALR BIT(3)
# define LAN9303_TAG_TX_STP_OVERRIDE BIT(4)
# define LAN9303_TAG_RX_IGMP BIT(3)
# define LAN9303_TAG_RX_STP BIT(4)
# define LAN9303_TAG_RX_TRAPPED_TO_CPU (LAN9303_TAG_RX_IGMP | \
					LAN9303_TAG_RX_STP)

/* Decide whether to transmit using ALR lookup, or transmit directly to
 * port using tag. ALR learning is performed only when using ALR lookup.
 * If the two external ports are bridged and the frame is unicast,
 * then use ALR lookup to allow ALR learning on CPU port.
 * Otherwise transmit directly to port with STP state override.
 * See also: lan9303_separate_ports() and lan9303.pdf 6.4.10.1
 */
static int lan9303_xmit_use_arl(struct dsa_port *dp, u8 *dest_addr)
{
	struct lan9303 *chip = dp->ds->priv;

	return chip->is_bridged && !is_multicast_ether_addr(dest_addr);
}

static struct sk_buff *lan9303_xmit(struct sk_buff *skb, struct net_device *dev)
{
	struct dsa_port *dp = dsa_user_to_port(dev);
	__be16 *lan9303_tag;
	u16 tag;

	/* provide 'LAN9303_TAG_LEN' bytes additional space */
	skb_push(skb, LAN9303_TAG_LEN);

	/* make room between MACs and Ether-Type */
	dsa_alloc_etype_header(skb, LAN9303_TAG_LEN);

	lan9303_tag = dsa_etype_header_pos_tx(skb);

	tag = lan9303_xmit_use_arl(dp, skb->data) ?
		LAN9303_TAG_TX_USE_ALR :
		dp->index | LAN9303_TAG_TX_STP_OVERRIDE;
	lan9303_tag[0] = htons(ETH_P_8021Q);
	lan9303_tag[1] = htons(tag);

	return skb;
}

static struct sk_buff *lan9303_rcv(struct sk_buff *skb, struct net_device *dev)
{
	u16 lan9303_tag1;
	unsigned int source_port;

	if (unlikely(!pskb_may_pull(skb, LAN9303_TAG_LEN))) {
		dev_warn_ratelimited(&dev->dev,
				     "Dropping packet, cannot pull\n");
		return NULL;
	}

Annotation

Implementation Notes