net: dsa: tag_dsa: Unify regular and ethertype DSA taggers

Ethertype DSA encodes exactly the same information in the DSA tag as
the non-ethertype variety. So refactor out the common parts and reuse
them for both protocols.

This is ensures tag parsing and generation is always consistent across
all mv88e6xxx chips.

While we are at it, explicitly deal with all possible CPU codes on
receive, making sure to set offload_fwd_mark as appropriate.

Signed-off-by: Tobias Waldekranz <tobias@waldekranz.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 246 insertions, 59 deletions

diff --git a/net/dsa/tag_dsa.c b/net/dsa/tag_dsa.c
index af340a4945dc..04646dd71c6c 100644
--- a/net/dsa/tag_dsa.c
+++ b/net/dsa/tag_dsa.c
@@ -1,7 +1,48 @@
 // SPDX-License-Identifier: GPL-2.0+
 /*
- * net/dsa/tag_dsa.c - (Non-ethertype) DSA tagging
+ * Regular and Ethertype DSA tagging
  * Copyright (c) 2008-2009 Marvell Semiconductor
+ *
+ * Regular DSA
+ * -----------
+
+ * For untagged (in 802.1Q terms) packets, the switch will splice in
+ * the tag between the SA and the ethertype of the original
+ * packet. Tagged frames will instead have their outermost .1Q tag
+ * converted to a DSA tag. It expects the same layout when receiving
+ * packets from the CPU.
+ *
+ * Example:
+ *
+ *     .----.----.----.---------
+ * Pu: | DA | SA | ET | Payload ...
+ *     '----'----'----'---------
+ *       6    6    2       N
+ *     .----.----.--------.-----.----.---------
+ * Pt: | DA | SA | 0x8100 | TCI | ET | Payload ...
+ *     '----'----'--------'-----'----'---------
+ *       6    6       2      2    2       N
+ *     .----.----.-----.----.---------
+ * Pd: | DA | SA | DSA | ET | Payload ...
+ *     '----'----'-----'----'---------
+ *       6    6     4    2       N
+ *
+ * No matter if a packet is received untagged (Pu) or tagged (Pt),
+ * they will both have the same layout (Pd) when they are sent to the
+ * CPU. This is done by ignoring 802.3, replacing the ethertype field
+ * with more metadata, among which is a bit to signal if the original
+ * packet was tagged or not.
+ *
+ * Ethertype DSA
+ * -------------
+ * Uses the exact same tag format as regular DSA, but also includes a
+ * proper ethertype field (which the mv88e6xxx driver sets to
+ * ETH_P_EDSA/0xdada) followed by two zero bytes:
+ *
+ * .----.----.--------.--------.-----.----.---------
+ * | DA | SA | 0xdada | 0x0000 | DSA | ET | Payload ...
+ * '----'----'--------'--------'-----'----'---------
+ *   6    6       2        2      4    2       N
  */
 
 #include <linux/etherdevice.h>
@@ -12,27 +53,92 @@
 
 #define DSA_HLEN	4
 
-#define FRAME_TYPE_TO_CPU	0x00
-#define FRAME_TYPE_FORWARD	0x03
+/**
+ * enum dsa_cmd - DSA Command
+ * @DSA_CMD_TO_CPU: Set on packets that were trapped or mirrored to
+ *     the CPU port. This is needed to implement control protocols,
+ *     e.g. STP and LLDP, that must not allow those control packets to
+ *     be switched according to the normal rules.
+ * @DSA_CMD_FROM_CPU: Used by the CPU to send a packet to a specific
+ *     port, ignoring all the barriers that the switch normally
+ *     enforces (VLANs, STP port states etc.). No source address
+ *     learning takes place. "sudo send packet"
+ * @DSA_CMD_TO_SNIFFER: Set on the copies of packets that matched some
+ *     user configured ingress or egress monitor criteria. These are
+ *     forwarded by the switch tree to the user configured ingress or
+ *     egress monitor port, which can be set to the CPU port or a
+ *     regular port. If the destination is a regular port, the tag
+ *     will be removed before egressing the port. If the destination
+ *     is the CPU port, the tag will not be removed.
+ * @DSA_CMD_FORWARD: This tag is used on all bulk traffic passing
+ *     through the switch tree, including the flows that are directed
+ *     towards the CPU. Its device/port tuple encodes the original
+ *     source port on which the packet ingressed. It can also be used
+ *     on transmit by the CPU to defer the forwarding decision to the
+ *     hardware, based on the current config of PVT/VTU/ATU
+ *     etc. Source address learning takes places if enabled on the
+ *     receiving DSA/CPU port.
+ */
+enum dsa_cmd {
+	DSA_CMD_TO_CPU     = 0,
+	DSA_CMD_FROM_CPU   = 1,
+	DSA_CMD_TO_SNIFFER = 2,
+	DSA_CMD_FORWARD    = 3
+};
 
-#define TO_CPU_CODE_IGMP_MLD_TRAP	0x02
+/**
+ * enum dsa_code - TO_CPU Code
+ *
+ * @DSA_CODE_MGMT_TRAP: DA was classified as a management
+ *     address. Typical examples include STP BPDUs and LLDP.
+ * @DSA_CODE_FRAME2REG: Response to a "remote management" request.
+ * @DSA_CODE_IGMP_MLD_TRAP: IGMP/MLD signaling.
+ * @DSA_CODE_POLICY_TRAP: Frame matched some policy configuration on
+ *     the device. Typical examples are matching on DA/SA/VID and DHCP
+ *     snooping.
+ * @DSA_CODE_ARP_MIRROR: The name says it all really.
+ * @DSA_CODE_POLICY_MIRROR: Same as @DSA_CODE_POLICY_TRAP, but the
+ *     particular policy was set to trigger a mirror instead of a
+ *     trap.
+ * @DSA_CODE_RESERVED_6: Unused on all devices up to at least 6393X.
+ * @DSA_CODE_RESERVED_7: Unused on all devices up to at least 6393X.
+ *
+ * A 3-bit code is used to relay why a particular frame was sent to
+ * the CPU. We only use this to determine if the packet was mirrored
+ * or trapped, i.e. whether the packet has been forwarded by hardware
+ * or not.
+ *
+ * This is the superset of all possible codes. Any particular device
+ * may only implement a subset.
+ */
+enum dsa_code {
+	DSA_CODE_MGMT_TRAP     = 0,
+	DSA_CODE_FRAME2REG     = 1,
+	DSA_CODE_IGMP_MLD_TRAP = 2,
+	DSA_CODE_POLICY_TRAP   = 3,
+	DSA_CODE_ARP_MIRROR    = 4,
+	DSA_CODE_POLICY_MIRROR = 5,
+	DSA_CODE_RESERVED_6    = 6,
+	DSA_CODE_RESERVED_7    = 7
+};
 
-static struct sk_buff *dsa_xmit(struct sk_buff *skb, struct net_device *dev)
+static struct sk_buff *dsa_xmit_ll(struct sk_buff *skb, struct net_device *dev,
+				   u8 extra)
 {
 	struct dsa_port *dp = dsa_slave_to_port(dev);
 	u8 *dsa_header;
 
-	/*
-	 * Convert the outermost 802.1q tag to a DSA tag for tagged
-	 * packets, or insert a DSA tag between the addresses and
-	 * the ethertype field for untagged packets.
-	 */
 	if (skb->protocol == htons(ETH_P_8021Q)) {
 		/*
 		 * Construct tagged FROM_CPU DSA tag from 802.1q tag.
 		 */
-		dsa_header = skb->data + 2 * ETH_ALEN;
-		dsa_header[0] = 0x60 | dp->ds->index;
+		if (extra) {
+			skb_push(skb, extra);
+			memmove(skb->data, skb->data + extra, 2 * ETH_ALEN);
+		}
+
+		dsa_header = skb->data + 2 * ETH_ALEN + extra;
+		dsa_header[0] = (DSA_CMD_FROM_CPU << 6) | 0x20 | dp->ds->index;
 		dsa_header[1] = dp->index << 3;
 
 		/*
@@ -43,15 +149,14 @@ static struct sk_buff *dsa_xmit(struct sk_buff *skb, struct net_device *dev)
 			dsa_header[2] &= ~0x10;
 		}
 	} else {
-		skb_push(skb, DSA_HLEN);
-
-		memmove(skb->data, skb->data + DSA_HLEN, 2 * ETH_ALEN);
+		skb_push(skb, DSA_HLEN + extra);
+		memmove(skb->data, skb->data + DSA_HLEN + extra, 2 * ETH_ALEN);
 
 		/*
 		 * Construct untagged FROM_CPU DSA tag.
 		 */
-		dsa_header = skb->data + 2 * ETH_ALEN;
-		dsa_header[0] = 0x40 | dp->ds->index;
+		dsa_header = skb->data + 2 * ETH_ALEN + extra;
+		dsa_header[0] = (DSA_CMD_FROM_CPU << 6) | dp->ds->index;
 		dsa_header[1] = dp->index << 3;
 		dsa_header[2] = 0x00;
 		dsa_header[3] = 0x00;
@@ -60,53 +165,62 @@ static struct sk_buff *dsa_xmit(struct sk_buff *skb, struct net_device *dev)
 	return skb;
 }
 
-static struct sk_buff *dsa_rcv(struct sk_buff *skb, struct net_device *dev,
-			       struct packet_type *pt)
+static struct sk_buff *dsa_rcv_ll(struct sk_buff *skb, struct net_device *dev,
+				  u8 extra)
 {
+	int source_device, source_port;
+	enum dsa_code code;
+	enum dsa_cmd cmd;
 	u8 *dsa_header;
-	int source_device;
-	int source_port;
-	int frame_type;
-	int code;
-
-	if (unlikely(!pskb_may_pull(skb, DSA_HLEN)))
-		return NULL;
 
 	/*
 	 * The ethertype field is part of the DSA header.
 	 */
 	dsa_header = skb->data - 2;
 
-	/*
-	 * Check that frame type is either TO_CPU or FORWARD.
-	 */
-	frame_type = dsa_header[0] >> 6;
+	cmd = dsa_header[0] >> 6;
+	switch (cmd) {
+	case DSA_CMD_FORWARD:
+		skb->offload_fwd_mark = 1;
+		break;
 
-	switch (frame_type) {
-	case FRAME_TYPE_TO_CPU:
+	case DSA_CMD_TO_CPU:
 		code = (dsa_header[1] & 0x6) | ((dsa_header[2] >> 4) & 1);
 
-		/*
-		 * Mark the frame to never egress on any port of the same switch
-		 * unless it's a trapped IGMP/MLD packet, in which case the
-		 * bridge might want to forward it.
-		 */
-		if (code != TO_CPU_CODE_IGMP_MLD_TRAP)
+		switch (code) {
+		case DSA_CODE_FRAME2REG:
+			/* Remote management is not implemented yet,
+			 * drop.
+			 */
+			return NULL;
+		case DSA_CODE_ARP_MIRROR:
+		case DSA_CODE_POLICY_MIRROR:
+			/* Mark mirrored packets to notify any upper
+			 * device (like a bridge) that forwarding has
+			 * already been done by hardware.
+			 */
 			skb->offload_fwd_mark = 1;
+			break;
+		case DSA_CODE_MGMT_TRAP:
+		case DSA_CODE_IGMP_MLD_TRAP:
+		case DSA_CODE_POLICY_TRAP:
+			/* Traps have, by definition, not been
+			 * forwarded by hardware, so don't mark them.
+			 */
+			break;
+		default:
+			/* Reserved code, this could be anything. Drop
+			 * seems like the safest option.
+			 */
+			return NULL;
+		}
 
 		break;
 
-	case FRAME_TYPE_FORWARD:
-		skb->offload_fwd_mark = 1;
-		break;
-
 	default:
 		return NULL;
 	}
 
-	/*
-	 * Determine source device and port.
-	 */
 	source_device = dsa_header[0] & 0x1f;
 	source_port = (dsa_header[1] >> 3) & 0x1f;
 
@@ -114,10 +228,10 @@ static struct sk_buff *dsa_rcv(struct sk_buff *skb, struct net_device *dev,
 	if (!skb->dev)
 		return NULL;
 
-	/*
-	 * Convert the DSA header to an 802.1q header if the 'tagged'
-	 * bit in the DSA header is set.  If the 'tagged' bit is clear,
-	 * delete the DSA header entirely.
+	/* If the 'tagged' bit is set; convert the DSA tag to a 802.1Q
+	 * tag, and delete the ethertype (extra) if applicable. If the
+	 * 'tagged' bit is cleared; delete the DSA tag, and ethertype
+	 * if applicable.
 	 */
 	if (dsa_header[0] & 0x20) {
 		u8 new_header[4];
@@ -150,28 +264,101 @@ static struct sk_buff *dsa_rcv(struct sk_buff *skb, struct net_device *dev,
 		}
 
 		memcpy(dsa_header, new_header, DSA_HLEN);
+
+		if (extra)
+			memmove(skb->data - ETH_HLEN,
+				skb->data - ETH_HLEN - extra,
+				2 * ETH_ALEN);
 	} else {
-		/*
-		 * Remove DSA tag and update checksum.
-		 */
 		skb_pull_rcsum(skb, DSA_HLEN);
 		memmove(skb->data - ETH_HLEN,
-			skb->data - ETH_HLEN - DSA_HLEN,
+			skb->data - ETH_HLEN - DSA_HLEN - extra,
 			2 * ETH_ALEN);
 	}
 
 	return skb;
 }
 
+#if IS_ENABLED(CONFIG_NET_DSA_TAG_DSA)
+
+static struct sk_buff *dsa_xmit(struct sk_buff *skb, struct net_device *dev)
+{
+	return dsa_xmit_ll(skb, dev, 0);
+}
+
+static struct sk_buff *dsa_rcv(struct sk_buff *skb, struct net_device *dev,
+			       struct packet_type *pt)
+{
+	if (unlikely(!pskb_may_pull(skb, DSA_HLEN)))
+		return NULL;
+
+	return dsa_rcv_ll(skb, dev, 0);
+}
+
 static const struct dsa_device_ops dsa_netdev_ops = {
-	.name	= "dsa",
-	.proto	= DSA_TAG_PROTO_DSA,
-	.xmit	= dsa_xmit,
-	.rcv	= dsa_rcv,
+	.name	  = "dsa",
+	.proto	  = DSA_TAG_PROTO_DSA,
+	.xmit	  = dsa_xmit,
+	.rcv	  = dsa_rcv,
 	.overhead = DSA_HLEN,
 };
 
-MODULE_LICENSE("GPL");
+DSA_TAG_DRIVER(dsa_netdev_ops);
 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_DSA);
+#endif	/* CONFIG_NET_DSA_TAG_DSA */
+
+#if IS_ENABLED(CONFIG_NET_DSA_TAG_EDSA)
+
+#define EDSA_HLEN 8
+
+static struct sk_buff *edsa_xmit(struct sk_buff *skb, struct net_device *dev)
+{
+	u8 *edsa_header;
+
+	skb = dsa_xmit_ll(skb, dev, EDSA_HLEN - DSA_HLEN);
+	if (!skb)
+		return NULL;
 
-module_dsa_tag_driver(dsa_netdev_ops);
+	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;
+	return skb;
+}
+
+static struct sk_buff *edsa_rcv(struct sk_buff *skb, struct net_device *dev,
+				struct packet_type *pt)
+{
+	if (unlikely(!pskb_may_pull(skb, EDSA_HLEN)))
+		return NULL;
+
+	skb_pull_rcsum(skb, EDSA_HLEN - DSA_HLEN);
+
+	return dsa_rcv_ll(skb, dev, EDSA_HLEN - DSA_HLEN);
+}
+
+static const struct dsa_device_ops edsa_netdev_ops = {
+	.name	  = "edsa",
+	.proto	  = DSA_TAG_PROTO_EDSA,
+	.xmit	  = edsa_xmit,
+	.rcv	  = edsa_rcv,
+	.overhead = EDSA_HLEN,
+};
+
+DSA_TAG_DRIVER(edsa_netdev_ops);
+MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_EDSA);
+#endif	/* CONFIG_NET_DSA_TAG_EDSA */
+
+static struct dsa_tag_driver *dsa_tag_drivers[] = {
+#if IS_ENABLED(CONFIG_NET_DSA_TAG_DSA)
+	&DSA_TAG_DRIVER_NAME(dsa_netdev_ops),
+#endif
+#if IS_ENABLED(CONFIG_NET_DSA_TAG_EDSA)
+	&DSA_TAG_DRIVER_NAME(edsa_netdev_ops),
+#endif
+};
+
+module_dsa_tag_drivers(dsa_tag_drivers);
+
+MODULE_LICENSE("GPL");