net: dsa: sja1105: Add support for traffic through standalone ports

In order to support this, we are creating a make-shift switch tag out of
a VLAN trunk configured on the CPU port. Termination of normal traffic
on switch ports only works when not under a vlan_filtering bridge.
Termination of management (PTP, BPDU) traffic works under all
circumstances because it uses a different tagging mechanism
(incl_srcpt). We are making use of the generic CONFIG_NET_DSA_TAG_8021Q
code and leveraging it from our own CONFIG_NET_DSA_TAG_SJA1105.

There are two types of traffic: regular and link-local.

The link-local traffic received on the CPU port is trapped from the
switch's regular forwarding decisions because it matched one of the two
DMAC filters for management traffic.

On transmission, the switch requires special massaging for these
link-local frames. Due to a weird implementation of the switching IP, by
default it drops link-local frames that originate on the CPU port.
It needs to be told where to forward them to, through an SPI command
("management route") that is valid for only a single frame.
So when we're sending link-local traffic, we are using the
dsa_defer_xmit mechanism.

Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 141 insertions, 0 deletions

diff --git a/net/dsa/Kconfig b/net/dsa/Kconfig
index fc15a7e1a6df..cf855352a440 100644
--- a/net/dsa/Kconfig
+++ b/net/dsa/Kconfig
@@ -102,6 +102,15 @@ config NET_DSA_TAG_LAN9303
 	  Say Y or M if you want to enable support for tagging frames for the
 	  SMSC/Microchip LAN9303 family of switches.
 
+config NET_DSA_TAG_SJA1105
+	tristate "Tag driver for NXP SJA1105 switches"
+	select NET_DSA_TAG_8021Q
+	help
+	  Say Y or M if you want to enable support for tagging frames with the
+	  NXP SJA1105 switch family. Both the native tagging protocol (which
+	  is only for link-local traffic) as well as non-native tagging (based
+	  on a custom 802.1Q VLAN header) are available.
+
 config NET_DSA_TAG_TRAILER
 	tristate "Tag driver for switches using a trailer tag"
 	help
diff --git a/net/dsa/Makefile b/net/dsa/Makefile
index e97c794ec57b..c342f54715ba 100644
--- a/net/dsa/Makefile
+++ b/net/dsa/Makefile
@@ -13,4 +13,5 @@ obj-$(CONFIG_NET_DSA_TAG_KSZ_COMMON) += tag_ksz.o
 obj-$(CONFIG_NET_DSA_TAG_LAN9303) += tag_lan9303.o
 obj-$(CONFIG_NET_DSA_TAG_MTK) += tag_mtk.o
 obj-$(CONFIG_NET_DSA_TAG_QCA) += tag_qca.o
+obj-$(CONFIG_NET_DSA_TAG_SJA1105) += tag_sja1105.o
 obj-$(CONFIG_NET_DSA_TAG_TRAILER) += tag_trailer.o
diff --git a/net/dsa/tag_sja1105.c b/net/dsa/tag_sja1105.c
new file mode 100644
index 000000000000..969402c7dbf1
--- /dev/null
+++ b/net/dsa/tag_sja1105.c
@@ -0,0 +1,131 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2019, Vladimir Oltean <olteanv@gmail.com>
+ */
+#include <linux/if_vlan.h>
+#include <linux/dsa/sja1105.h>
+#include <linux/dsa/8021q.h>
+#include <linux/packing.h>
+#include "dsa_priv.h"
+
+/* Similar to is_link_local_ether_addr(hdr->h_dest) but also covers PTP */
+static inline bool sja1105_is_link_local(const struct sk_buff *skb)
+{
+	const struct ethhdr *hdr = eth_hdr(skb);
+	u64 dmac = ether_addr_to_u64(hdr->h_dest);
+
+	if ((dmac & SJA1105_LINKLOCAL_FILTER_A_MASK) ==
+		    SJA1105_LINKLOCAL_FILTER_A)
+		return true;
+	if ((dmac & SJA1105_LINKLOCAL_FILTER_B_MASK) ==
+		    SJA1105_LINKLOCAL_FILTER_B)
+		return true;
+	return false;
+}
+
+/* This is the first time the tagger sees the frame on RX.
+ * Figure out if we can decode it, and if we can, annotate skb->cb with how we
+ * plan to do that, so we don't need to check again in the rcv function.
+ */
+static bool sja1105_filter(const struct sk_buff *skb, struct net_device *dev)
+{
+	if (sja1105_is_link_local(skb)) {
+		SJA1105_SKB_CB(skb)->type = SJA1105_FRAME_TYPE_LINK_LOCAL;
+		return true;
+	}
+	if (!dsa_port_is_vlan_filtering(dev->dsa_ptr)) {
+		SJA1105_SKB_CB(skb)->type = SJA1105_FRAME_TYPE_NORMAL;
+		return true;
+	}
+	return false;
+}
+
+static struct sk_buff *sja1105_xmit(struct sk_buff *skb,
+				    struct net_device *netdev)
+{
+	struct dsa_port *dp = dsa_slave_to_port(netdev);
+	struct dsa_switch *ds = dp->ds;
+	u16 tx_vid = dsa_8021q_tx_vid(ds, dp->index);
+	u8 pcp = skb->priority;
+
+	/* Transmitting management traffic does not rely upon switch tagging,
+	 * but instead SPI-installed management routes. Part 2 of this
+	 * is the .port_deferred_xmit driver callback.
+	 */
+	if (unlikely(sja1105_is_link_local(skb)))
+		return dsa_defer_xmit(skb, netdev);
+
+	/* If we are under a vlan_filtering bridge, IP termination on
+	 * switch ports based on 802.1Q tags is simply too brittle to
+	 * be passable. So just defer to the dsa_slave_notag_xmit
+	 * implementation.
+	 */
+	if (dsa_port_is_vlan_filtering(dp))
+		return skb;
+
+	return dsa_8021q_xmit(skb, netdev, ETH_P_SJA1105,
+			     ((pcp << VLAN_PRIO_SHIFT) | tx_vid));
+}
+
+static struct sk_buff *sja1105_rcv(struct sk_buff *skb,
+				   struct net_device *netdev,
+				   struct packet_type *pt)
+{
+	struct ethhdr *hdr = eth_hdr(skb);
+	u64 source_port, switch_id;
+	struct sk_buff *nskb;
+	u16 tpid, vid, tci;
+	bool is_tagged;
+
+	nskb = dsa_8021q_rcv(skb, netdev, pt, &tpid, &tci);
+	is_tagged = (nskb && tpid == ETH_P_SJA1105);
+
+	skb->priority = (tci & VLAN_PRIO_MASK) >> VLAN_PRIO_SHIFT;
+	vid = tci & VLAN_VID_MASK;
+
+	skb->offload_fwd_mark = 1;
+
+	if (SJA1105_SKB_CB(skb)->type == SJA1105_FRAME_TYPE_LINK_LOCAL) {
+		/* Management traffic path. Switch embeds the switch ID and
+		 * port ID into bytes of the destination MAC, courtesy of
+		 * the incl_srcpt options.
+		 */
+		source_port = hdr->h_dest[3];
+		switch_id = hdr->h_dest[4];
+		/* Clear the DMAC bytes that were mangled by the switch */
+		hdr->h_dest[3] = 0;
+		hdr->h_dest[4] = 0;
+	} else {
+		/* Normal traffic path. */
+		source_port = dsa_8021q_rx_source_port(vid);
+		switch_id = dsa_8021q_rx_switch_id(vid);
+	}
+
+	skb->dev = dsa_master_find_slave(netdev, switch_id, source_port);
+	if (!skb->dev) {
+		netdev_warn(netdev, "Couldn't decode source port\n");
+		return NULL;
+	}
+
+	/* Delete/overwrite fake VLAN header, DSA expects to not find
+	 * it there, see dsa_switch_rcv: skb_push(skb, ETH_HLEN).
+	 */
+	if (is_tagged)
+		memmove(skb->data - ETH_HLEN, skb->data - ETH_HLEN - VLAN_HLEN,
+			ETH_HLEN - VLAN_HLEN);
+
+	return skb;
+}
+
+static struct dsa_device_ops sja1105_netdev_ops = {
+	.name = "sja1105",
+	.proto = DSA_TAG_PROTO_SJA1105,
+	.xmit = sja1105_xmit,
+	.rcv = sja1105_rcv,
+	.filter = sja1105_filter,
+	.overhead = VLAN_HLEN,
+};
+
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_SJA1105);
+
+module_dsa_tag_driver(sja1105_netdev_ops);