net: dsa: generalize overhead for taggers that use both headers and trailers

Some really really weird switches just couldn't decide whether to use a
normal or a tail tagger, so they just did both.

This creates problems for DSA, because we only have the concept of an
'overhead' which can be applied to the headroom or to the tailroom of
the skb (like for example during the central TX reallocation procedure),
depending on the value of bool tail_tag, but not to both.

We need to generalize DSA to cater for these odd switches by
transforming the 'overhead / tail_tag' pair into 'needed_headroom /
needed_tailroom'.

The DSA master's MTU is increased to account for both.

The flow dissector code is modified such that it only calls the DSA
adjustment callback if the tagger has a non-zero header length.

Taggers are trivially modified to declare either needed_headroom or
needed_tailroom, based on the tail_tag value that they currently
declare.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

18 files changed, 34 insertions, 35 deletions

diff --git a/net/dsa/dsa_priv.h b/net/dsa/dsa_priv.h
index 92282de54230..b8b17474b72b 100644
--- a/net/dsa/dsa_priv.h
+++ b/net/dsa/dsa_priv.h
@@ -154,6 +154,11 @@ const struct dsa_device_ops *dsa_find_tagger_by_name(const char *buf);
 bool dsa_schedule_work(struct work_struct *work);
 const char *dsa_tag_protocol_to_str(const struct dsa_device_ops *ops);
 
+static inline int dsa_tag_protocol_overhead(const struct dsa_device_ops *ops)
+{
+	return ops->needed_headroom + ops->needed_tailroom;
+}
+
 /* master.c */
 int dsa_master_setup(struct net_device *dev, struct dsa_port *cpu_dp);
 void dsa_master_teardown(struct net_device *dev);
diff --git a/net/dsa/master.c b/net/dsa/master.c
index 63adbc21a735..3fc90e36772d 100644
--- a/net/dsa/master.c
+++ b/net/dsa/master.c
@@ -346,10 +346,12 @@ static struct lock_class_key dsa_master_addr_list_lock_key;
 
 int dsa_master_setup(struct net_device *dev, struct dsa_port *cpu_dp)
 {
-	int mtu = ETH_DATA_LEN + cpu_dp->tag_ops->overhead;
+	const struct dsa_device_ops *tag_ops = cpu_dp->tag_ops;
 	struct dsa_switch *ds = cpu_dp->ds;
 	struct device_link *consumer_link;
-	int ret;
+	int mtu, ret;
+
+	mtu = ETH_DATA_LEN + dsa_tag_protocol_overhead(tag_ops);
 
 	/* The DSA master must use SET_NETDEV_DEV for this to work. */
 	consumer_link = device_link_add(ds->dev, dev->dev.parent,
diff --git a/net/dsa/slave.c b/net/dsa/slave.c
index d4756b920108..3ca509eb284d 100644
--- a/net/dsa/slave.c
+++ b/net/dsa/slave.c
@@ -1569,7 +1569,7 @@ int dsa_slave_change_mtu(struct net_device *dev, int new_mtu)
 
 	mtu_limit = min_t(int, master->max_mtu, dev->max_mtu);
 	old_master_mtu = master->mtu;
-	new_master_mtu = largest_mtu + cpu_dp->tag_ops->overhead;
+	new_master_mtu = largest_mtu + dsa_tag_protocol_overhead(cpu_dp->tag_ops);
 	if (new_master_mtu > mtu_limit)
 		return -ERANGE;
 
@@ -1605,7 +1605,7 @@ int dsa_slave_change_mtu(struct net_device *dev, int new_mtu)
 out_port_failed:
 	if (new_master_mtu != old_master_mtu)
 		dsa_port_mtu_change(cpu_dp, old_master_mtu -
-				    cpu_dp->tag_ops->overhead,
+				    dsa_tag_protocol_overhead(cpu_dp->tag_ops),
 				    true);
 out_cpu_failed:
 	if (new_master_mtu != old_master_mtu)
@@ -1824,10 +1824,8 @@ void dsa_slave_setup_tagger(struct net_device *slave)
 	const struct dsa_port *cpu_dp = dp->cpu_dp;
 	struct net_device *master = cpu_dp->master;
 
-	if (cpu_dp->tag_ops->tail_tag)
-		slave->needed_tailroom = cpu_dp->tag_ops->overhead;
-	else
-		slave->needed_headroom = cpu_dp->tag_ops->overhead;
+	slave->needed_headroom = cpu_dp->tag_ops->needed_headroom;
+	slave->needed_tailroom = cpu_dp->tag_ops->needed_tailroom;
 	/* Try to save one extra realloc later in the TX path (in the master)
 	 * by also inheriting the master's needed headroom and tailroom.
 	 * The 8021q driver also does this.
diff --git a/net/dsa/tag_ar9331.c b/net/dsa/tag_ar9331.c
index 002cf7f952e2..0efae1a372b3 100644
--- a/net/dsa/tag_ar9331.c
+++ b/net/dsa/tag_ar9331.c
@@ -85,7 +85,7 @@ static const struct dsa_device_ops ar9331_netdev_ops = {
 	.proto	= DSA_TAG_PROTO_AR9331,
 	.xmit	= ar9331_tag_xmit,
 	.rcv	= ar9331_tag_rcv,
-	.overhead = AR9331_HDR_LEN,
+	.needed_headroom = AR9331_HDR_LEN,
 };
 
 MODULE_LICENSE("GPL v2");
diff --git a/net/dsa/tag_brcm.c b/net/dsa/tag_brcm.c
index 40e9f3098c8d..0750af951fc9 100644
--- a/net/dsa/tag_brcm.c
+++ b/net/dsa/tag_brcm.c
@@ -205,7 +205,7 @@ static const struct dsa_device_ops brcm_netdev_ops = {
 	.proto	= DSA_TAG_PROTO_BRCM,
 	.xmit	= brcm_tag_xmit,
 	.rcv	= brcm_tag_rcv,
-	.overhead = BRCM_TAG_LEN,
+	.needed_headroom = BRCM_TAG_LEN,
 };
 
 DSA_TAG_DRIVER(brcm_netdev_ops);
@@ -286,7 +286,7 @@ static const struct dsa_device_ops brcm_legacy_netdev_ops = {
 	.proto = DSA_TAG_PROTO_BRCM_LEGACY,
 	.xmit = brcm_leg_tag_xmit,
 	.rcv = brcm_leg_tag_rcv,
-	.overhead = BRCM_LEG_TAG_LEN,
+	.needed_headroom = BRCM_LEG_TAG_LEN,
 };
 
 DSA_TAG_DRIVER(brcm_legacy_netdev_ops);
@@ -314,7 +314,7 @@ static const struct dsa_device_ops brcm_prepend_netdev_ops = {
 	.proto	= DSA_TAG_PROTO_BRCM_PREPEND,
 	.xmit	= brcm_tag_xmit_prepend,
 	.rcv	= brcm_tag_rcv_prepend,
-	.overhead = BRCM_TAG_LEN,
+	.needed_headroom = BRCM_TAG_LEN,
 };
 
 DSA_TAG_DRIVER(brcm_prepend_netdev_ops);
diff --git a/net/dsa/tag_dsa.c b/net/dsa/tag_dsa.c
index 7e7b7decdf39..a822355afc90 100644
--- a/net/dsa/tag_dsa.c
+++ b/net/dsa/tag_dsa.c
@@ -303,7 +303,7 @@ static const struct dsa_device_ops dsa_netdev_ops = {
 	.proto	  = DSA_TAG_PROTO_DSA,
 	.xmit	  = dsa_xmit,
 	.rcv	  = dsa_rcv,
-	.overhead = DSA_HLEN,
+	.needed_headroom = DSA_HLEN,
 };
 
 DSA_TAG_DRIVER(dsa_netdev_ops);
@@ -346,7 +346,7 @@ static const struct dsa_device_ops edsa_netdev_ops = {
 	.proto	  = DSA_TAG_PROTO_EDSA,
 	.xmit	  = edsa_xmit,
 	.rcv	  = edsa_rcv,
-	.overhead = EDSA_HLEN,
+	.needed_headroom = EDSA_HLEN,
 };
 
 DSA_TAG_DRIVER(edsa_netdev_ops);
diff --git a/net/dsa/tag_gswip.c b/net/dsa/tag_gswip.c
index 2f5bd5e338ab..5985dab06ab8 100644
--- a/net/dsa/tag_gswip.c
+++ b/net/dsa/tag_gswip.c
@@ -103,7 +103,7 @@ static const struct dsa_device_ops gswip_netdev_ops = {
 	.proto	= DSA_TAG_PROTO_GSWIP,
 	.xmit = gswip_tag_xmit,
 	.rcv = gswip_tag_rcv,
-	.overhead = GSWIP_RX_HEADER_LEN,
+	.needed_headroom = GSWIP_RX_HEADER_LEN,
 };
 
 MODULE_LICENSE("GPL");
diff --git a/net/dsa/tag_hellcreek.c b/net/dsa/tag_hellcreek.c
index a09805c8e1ab..424130f85f59 100644
--- a/net/dsa/tag_hellcreek.c
+++ b/net/dsa/tag_hellcreek.c
@@ -54,8 +54,7 @@ static const struct dsa_device_ops hellcreek_netdev_ops = {
 	.proto	  = DSA_TAG_PROTO_HELLCREEK,
 	.xmit	  = hellcreek_xmit,
 	.rcv	  = hellcreek_rcv,
-	.overhead = HELLCREEK_TAG_LEN,
-	.tail_tag = true,
+	.needed_tailroom = HELLCREEK_TAG_LEN,
 };
 
 MODULE_LICENSE("Dual MIT/GPL");
diff --git a/net/dsa/tag_ksz.c b/net/dsa/tag_ksz.c
index 4820dbcedfa2..53565f48934c 100644
--- a/net/dsa/tag_ksz.c
+++ b/net/dsa/tag_ksz.c
@@ -77,8 +77,7 @@ static const struct dsa_device_ops ksz8795_netdev_ops = {
 	.proto	= DSA_TAG_PROTO_KSZ8795,
 	.xmit	= ksz8795_xmit,
 	.rcv	= ksz8795_rcv,
-	.overhead = KSZ_INGRESS_TAG_LEN,
-	.tail_tag = true,
+	.needed_tailroom = KSZ_INGRESS_TAG_LEN,
 };
 
 DSA_TAG_DRIVER(ksz8795_netdev_ops);
@@ -149,8 +148,7 @@ static const struct dsa_device_ops ksz9477_netdev_ops = {
 	.proto	= DSA_TAG_PROTO_KSZ9477,
 	.xmit	= ksz9477_xmit,
 	.rcv	= ksz9477_rcv,
-	.overhead = KSZ9477_INGRESS_TAG_LEN,
-	.tail_tag = true,
+	.needed_tailroom = KSZ9477_INGRESS_TAG_LEN,
 };
 
 DSA_TAG_DRIVER(ksz9477_netdev_ops);
@@ -183,8 +181,7 @@ static const struct dsa_device_ops ksz9893_netdev_ops = {
 	.proto	= DSA_TAG_PROTO_KSZ9893,
 	.xmit	= ksz9893_xmit,
 	.rcv	= ksz9477_rcv,
-	.overhead = KSZ_INGRESS_TAG_LEN,
-	.tail_tag = true,
+	.needed_tailroom = KSZ_INGRESS_TAG_LEN,
 };
 
 DSA_TAG_DRIVER(ksz9893_netdev_ops);
diff --git a/net/dsa/tag_lan9303.c b/net/dsa/tag_lan9303.c
index aa1318dccaf0..26207ef39ebc 100644
--- a/net/dsa/tag_lan9303.c
+++ b/net/dsa/tag_lan9303.c
@@ -125,7 +125,7 @@ static const struct dsa_device_ops lan9303_netdev_ops = {
 	.proto	= DSA_TAG_PROTO_LAN9303,
 	.xmit = lan9303_xmit,
 	.rcv = lan9303_rcv,
-	.overhead = LAN9303_TAG_LEN,
+	.needed_headroom = LAN9303_TAG_LEN,
 };
 
 MODULE_LICENSE("GPL");
diff --git a/net/dsa/tag_mtk.c b/net/dsa/tag_mtk.c
index f9b2966d1936..cc3ba864ad5b 100644
--- a/net/dsa/tag_mtk.c
+++ b/net/dsa/tag_mtk.c
@@ -102,7 +102,7 @@ static const struct dsa_device_ops mtk_netdev_ops = {
 	.proto		= DSA_TAG_PROTO_MTK,
 	.xmit		= mtk_tag_xmit,
 	.rcv		= mtk_tag_rcv,
-	.overhead	= MTK_HDR_LEN,
+	.needed_headroom = MTK_HDR_LEN,
 };
 
 MODULE_LICENSE("GPL");
diff --git a/net/dsa/tag_ocelot.c b/net/dsa/tag_ocelot.c
index 91f0fd1242cd..190f4bfd3bef 100644
--- a/net/dsa/tag_ocelot.c
+++ b/net/dsa/tag_ocelot.c
@@ -143,7 +143,7 @@ static const struct dsa_device_ops ocelot_netdev_ops = {
 	.proto			= DSA_TAG_PROTO_OCELOT,
 	.xmit			= ocelot_xmit,
 	.rcv			= ocelot_rcv,
-	.overhead		= OCELOT_TOTAL_TAG_LEN,
+	.needed_headroom	= OCELOT_TOTAL_TAG_LEN,
 	.promisc_on_master	= true,
 };
 
@@ -155,7 +155,7 @@ static const struct dsa_device_ops seville_netdev_ops = {
 	.proto			= DSA_TAG_PROTO_SEVILLE,
 	.xmit			= seville_xmit,
 	.rcv			= ocelot_rcv,
-	.overhead		= OCELOT_TOTAL_TAG_LEN,
+	.needed_headroom	= OCELOT_TOTAL_TAG_LEN,
 	.promisc_on_master	= true,
 };
 
diff --git a/net/dsa/tag_ocelot_8021q.c b/net/dsa/tag_ocelot_8021q.c
index 62a93303bd63..663b74793cfc 100644
--- a/net/dsa/tag_ocelot_8021q.c
+++ b/net/dsa/tag_ocelot_8021q.c
@@ -73,7 +73,7 @@ static const struct dsa_device_ops ocelot_8021q_netdev_ops = {
 	.proto			= DSA_TAG_PROTO_OCELOT_8021Q,
 	.xmit			= ocelot_xmit,
 	.rcv			= ocelot_rcv,
-	.overhead		= VLAN_HLEN,
+	.needed_headroom	= VLAN_HLEN,
 	.promisc_on_master	= true,
 };
 
diff --git a/net/dsa/tag_qca.c b/net/dsa/tag_qca.c
index 88181b52f480..693bda013065 100644
--- a/net/dsa/tag_qca.c
+++ b/net/dsa/tag_qca.c
@@ -91,7 +91,7 @@ static const struct dsa_device_ops qca_netdev_ops = {
 	.proto	= DSA_TAG_PROTO_QCA,
 	.xmit	= qca_tag_xmit,
 	.rcv	= qca_tag_rcv,
-	.overhead = QCA_HDR_LEN,
+	.needed_headroom = QCA_HDR_LEN,
 };
 
 MODULE_LICENSE("GPL");
diff --git a/net/dsa/tag_rtl4_a.c b/net/dsa/tag_rtl4_a.c
index cf8ac316f4c7..57c46b4ab2b3 100644
--- a/net/dsa/tag_rtl4_a.c
+++ b/net/dsa/tag_rtl4_a.c
@@ -124,7 +124,7 @@ static const struct dsa_device_ops rtl4a_netdev_ops = {
 	.proto	= DSA_TAG_PROTO_RTL4_A,
 	.xmit	= rtl4a_tag_xmit,
 	.rcv	= rtl4a_tag_rcv,
-	.overhead = RTL4_A_HDR_LEN,
+	.needed_headroom = RTL4_A_HDR_LEN,
 };
 module_dsa_tag_driver(rtl4a_netdev_ops);
 
diff --git a/net/dsa/tag_sja1105.c b/net/dsa/tag_sja1105.c
index 50496013cdb7..ff4a81eae16f 100644
--- a/net/dsa/tag_sja1105.c
+++ b/net/dsa/tag_sja1105.c
@@ -362,7 +362,7 @@ static const struct dsa_device_ops sja1105_netdev_ops = {
 	.xmit = sja1105_xmit,
 	.rcv = sja1105_rcv,
 	.filter = sja1105_filter,
-	.overhead = VLAN_HLEN,
+	.needed_headroom = VLAN_HLEN,
 	.flow_dissect = sja1105_flow_dissect,
 	.promisc_on_master = true,
 };
diff --git a/net/dsa/tag_trailer.c b/net/dsa/tag_trailer.c
index 5b97ede56a0f..ba73804340a5 100644
--- a/net/dsa/tag_trailer.c
+++ b/net/dsa/tag_trailer.c
@@ -55,8 +55,7 @@ static const struct dsa_device_ops trailer_netdev_ops = {
 	.proto	= DSA_TAG_PROTO_TRAILER,
 	.xmit	= trailer_xmit,
 	.rcv	= trailer_rcv,
-	.overhead = 4,
-	.tail_tag = true,
+	.needed_tailroom = 4,
 };
 
 MODULE_LICENSE("GPL");
diff --git a/net/dsa/tag_xrs700x.c b/net/dsa/tag_xrs700x.c
index 858cdf9d2913..a31ff7fcb45f 100644
--- a/net/dsa/tag_xrs700x.c
+++ b/net/dsa/tag_xrs700x.c
@@ -56,8 +56,7 @@ static const struct dsa_device_ops xrs700x_netdev_ops = {
 	.proto	= DSA_TAG_PROTO_XRS700X,
 	.xmit	= xrs700x_xmit,
 	.rcv	= xrs700x_rcv,
-	.overhead = 1,
-	.tail_tag = true,
+	.needed_tailroom = 1,
 };
 
 MODULE_LICENSE("GPL");