net: Distributed Switch Architecture protocol support

Distributed Switch Architecture is a protocol for managing hardware
switch chips.  It consists of a set of MII management registers and
commands to configure the switch, and an ethernet header format to
signal which of the ports of the switch a packet was received from
or is intended to be sent to.

The switches that this driver supports are typically embedded in
access points and routers, and a typical setup with a DSA switch
looks something like this:

	+-----------+       +-----------+
	|           | RGMII |           |
	|           +-------+           +------ 1000baseT MDI ("WAN")
	|           |       |  6-port   +------ 1000baseT MDI ("LAN1")
	|    CPU    |       |  ethernet +------ 1000baseT MDI ("LAN2")
	|           |MIImgmt|  switch   +------ 1000baseT MDI ("LAN3")
	|           +-------+  w/5 PHYs +------ 1000baseT MDI ("LAN4")
	|           |       |           |
	+-----------+       +-----------+

The switch driver presents each port on the switch as a separate
network interface to Linux, polls the switch to maintain software
link state of those ports, forwards MII management interface
accesses to those network interfaces (e.g. as done by ethtool) to
the switch, and exposes the switch's hardware statistics counters
via the appropriate Linux kernel interfaces.

This initial patch supports the MII management interface register
layout of the Marvell 88E6123, 88E6161 and 88E6165 switch chips, and
supports the "Ethertype DSA" packet tagging format.

(There is no officially registered ethertype for the Ethertype DSA
packet format, so we just grab a random one.  The ethertype to use
is programmed into the switch, and the switch driver uses the value
of ETH_P_EDSA for this, so this define can be changed at any time in
the future if the one we chose is allocated to another protocol or
if Ethertype DSA gets its own officially registered ethertype, and
everything will continue to work.)

Signed-off-by: Lennert Buytenhek <buytenh@marvell.com>
Tested-by: Nicolas Pitre <nico@marvell.com>
Tested-by: Byron Bradley <byron.bbradley@gmail.com>
Tested-by: Tim Ellis <tim.ellis@mac.com>
Tested-by: Peter van Valderen <linux@ddcrew.com>
Tested-by: Dirk Teurlings <dirk@upexia.nl>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 213 insertions, 0 deletions

diff --git a/net/dsa/tag_edsa.c b/net/dsa/tag_edsa.c
new file mode 100644
index 000000000000..f985ea993843
--- /dev/null
+++ b/net/dsa/tag_edsa.c
@@ -0,0 +1,213 @@
+/*
+ * net/dsa/tag_edsa.c - Ethertype DSA tagging
+ * Copyright (c) 2008 Marvell Semiconductor
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#include <linux/etherdevice.h>
+#include <linux/list.h>
+#include <linux/netdevice.h>
+#include "dsa_priv.h"
+
+#define DSA_HLEN	4
+#define EDSA_HLEN	8
+
+int edsa_xmit(struct sk_buff *skb, struct net_device *dev)
+{
+	struct dsa_slave_priv *p = netdev_priv(dev);
+	u8 *edsa_header;
+
+	dev->stats.tx_packets++;
+	dev->stats.tx_bytes += skb->len;
+
+	/*
+	 * Convert the outermost 802.1q tag to a DSA tag and prepend
+	 * a DSA ethertype field is the packet is tagged, or insert
+	 * a DSA ethertype plus DSA tag between the addresses and the
+	 * current ethertype field if the packet is untagged.
+	 */
+	if (skb->protocol == htons(ETH_P_8021Q)) {
+		if (skb_cow_head(skb, DSA_HLEN) < 0)
+			goto out_free;
+		skb_push(skb, DSA_HLEN);
+
+		memmove(skb->data, skb->data + DSA_HLEN, 2 * ETH_ALEN);
+
+		/*
+		 * Construct tagged FROM_CPU DSA tag from 802.1q tag.
+		 */
+		edsa_header = skb->data + 2 * ETH_ALEN;
+		edsa_header[0] = (ETH_P_EDSA >> 8) & 0xff;
+		edsa_header[1] = ETH_P_EDSA & 0xff;
+		edsa_header[2] = 0x00;
+		edsa_header[3] = 0x00;
+		edsa_header[4] = 0x60;
+		edsa_header[5] = p->port << 3;
+
+		/*
+		 * Move CFI field from byte 6 to byte 5.
+		 */
+		if (edsa_header[6] & 0x10) {
+			edsa_header[5] |= 0x01;
+			edsa_header[6] &= ~0x10;
+		}
+	} else {
+		if (skb_cow_head(skb, EDSA_HLEN) < 0)
+			goto out_free;
+		skb_push(skb, EDSA_HLEN);
+
+		memmove(skb->data, skb->data + EDSA_HLEN, 2 * ETH_ALEN);
+
+		/*
+		 * Construct untagged FROM_CPU DSA tag.
+		 */
+		edsa_header = skb->data + 2 * ETH_ALEN;
+		edsa_header[0] = (ETH_P_EDSA >> 8) & 0xff;
+		edsa_header[1] = ETH_P_EDSA & 0xff;
+		edsa_header[2] = 0x00;
+		edsa_header[3] = 0x00;
+		edsa_header[4] = 0x40;
+		edsa_header[5] = p->port << 3;
+		edsa_header[6] = 0x00;
+		edsa_header[7] = 0x00;
+	}
+
+	skb->protocol = htons(ETH_P_EDSA);
+
+	skb->dev = p->parent->master_netdev;
+	dev_queue_xmit(skb);
+
+	return NETDEV_TX_OK;
+
+out_free:
+	kfree_skb(skb);
+	return NETDEV_TX_OK;
+}
+
+static int edsa_rcv(struct sk_buff *skb, struct net_device *dev,
+		    struct packet_type *pt, struct net_device *orig_dev)
+{
+	struct dsa_switch *ds = dev->dsa_ptr;
+	u8 *edsa_header;
+	int source_port;
+
+	if (unlikely(ds == NULL))
+		goto out_drop;
+
+	skb = skb_unshare(skb, GFP_ATOMIC);
+	if (skb == NULL)
+		goto out;
+
+	if (unlikely(!pskb_may_pull(skb, EDSA_HLEN)))
+		goto out_drop;
+
+	/*
+	 * Skip the two null bytes after the ethertype.
+	 */
+	edsa_header = skb->data + 2;
+
+	/*
+	 * Check that frame type is either TO_CPU or FORWARD, and
+	 * that the source device is zero.
+	 */
+	if ((edsa_header[0] & 0xdf) != 0x00 && (edsa_header[0] & 0xdf) != 0xc0)
+		goto out_drop;
+
+	/*
+	 * Check that the source port is a registered DSA port.
+	 */
+	source_port = (edsa_header[1] >> 3) & 0x1f;
+	if (source_port >= DSA_MAX_PORTS || ds->ports[source_port] == NULL)
+		goto out_drop;
+
+	/*
+	 * If the 'tagged' bit is set, convert the DSA tag to a 802.1q
+	 * tag and delete the ethertype part.  If the 'tagged' bit is
+	 * clear, delete the ethertype and the DSA tag parts.
+	 */
+	if (edsa_header[0] & 0x20) {
+		u8 new_header[4];
+
+		/*
+		 * Insert 802.1q ethertype and copy the VLAN-related
+		 * fields, but clear the bit that will hold CFI (since
+		 * DSA uses that bit location for another purpose).
+		 */
+		new_header[0] = (ETH_P_8021Q >> 8) & 0xff;
+		new_header[1] = ETH_P_8021Q & 0xff;
+		new_header[2] = edsa_header[2] & ~0x10;
+		new_header[3] = edsa_header[3];
+
+		/*
+		 * Move CFI bit from its place in the DSA header to
+		 * its 802.1q-designated place.
+		 */
+		if (edsa_header[1] & 0x01)
+			new_header[2] |= 0x10;
+
+		skb_pull_rcsum(skb, DSA_HLEN);
+
+		/*
+		 * Update packet checksum if skb is CHECKSUM_COMPLETE.
+		 */
+		if (skb->ip_summed == CHECKSUM_COMPLETE) {
+			__wsum c = skb->csum;
+			c = csum_add(c, csum_partial(new_header + 2, 2, 0));
+			c = csum_sub(c, csum_partial(edsa_header + 2, 2, 0));
+			skb->csum = c;
+		}
+
+		memcpy(edsa_header, new_header, DSA_HLEN);
+
+		memmove(skb->data - ETH_HLEN,
+			skb->data - ETH_HLEN - DSA_HLEN,
+			2 * ETH_ALEN);
+	} else {
+		/*
+		 * Remove DSA tag and update checksum.
+		 */
+		skb_pull_rcsum(skb, EDSA_HLEN);
+		memmove(skb->data - ETH_HLEN,
+			skb->data - ETH_HLEN - EDSA_HLEN,
+			2 * ETH_ALEN);
+	}
+
+	skb->dev = ds->ports[source_port];
+	skb_push(skb, ETH_HLEN);
+	skb->protocol = eth_type_trans(skb, skb->dev);
+
+	skb->dev->last_rx = jiffies;
+	skb->dev->stats.rx_packets++;
+	skb->dev->stats.rx_bytes += skb->len;
+
+	netif_receive_skb(skb);
+
+	return 0;
+
+out_drop:
+	kfree_skb(skb);
+out:
+	return 0;
+}
+
+static struct packet_type edsa_packet_type = {
+	.type	= __constant_htons(ETH_P_EDSA),
+	.func	= edsa_rcv,
+};
+
+static int __init edsa_init_module(void)
+{
+	dev_add_pack(&edsa_packet_type);
+	return 0;
+}
+module_init(edsa_init_module);
+
+static void __exit edsa_cleanup_module(void)
+{
+	dev_remove_pack(&edsa_packet_type);
+}
+module_exit(edsa_cleanup_module);