In case an adapter advertises NETIF_F_HW_SWITCH_RX_TAG, proceed with
extracting the 4-bytes Broadcom tag directly from skb->cb[] and utilize
that instead of copying and memmoving() data around.
To establish a contract between the Ethernet MAC advertisign
NETIF_F_HW_SWITCH_RX_TAG and the Broadcom tag DSA parsing code,
introduce a helper function to copy such a tag into skb->cb[] at a
pre-defined offset which is checked against other parts of the kernel we
compete with: NAPI GRO cb.
Signed-off-by: Florian Fainelli <f.faine...@gmail.com>
---
include/linux/netdevice.h | 13 +++++++++++++
include/net/dsa.h | 5 +++++
net/dsa/tag_brcm.c | 38 +++++++++++++++++++++++---------------
3 files changed, 41 insertions(+), 15 deletions(-)
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 607b5f41f46f..02790c6acdb8 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2004,6 +2004,19 @@ struct napi_gro_cb {
#define NAPI_GRO_CB(skb) ((struct napi_gro_cb *)(skb)->cb)
+/* We compete with napi_gro_cb when an Ethernet adapter wants to put a 4-bytes
+ * Broadcom tag into skb->cb since this will typically be done before the call
+ * to napi_gro_receive, so assert a build time that we have enough room to make
+ * this possible
+ */
+#define DSA_BRCM_TAG_OFF (sizeof(((struct sk_buff *)0)->cb) -
BRCM_TAG_LEN)
+
+static inline void dsa_copy_brcm_tag(struct sk_buff *skb, const void *tag)
+{
+ BUILD_BUG_ON(sizeof(skb->cb) - sizeof(struct napi_gro_cb) <
BRCM_TAG_LEN);
+ memcpy(&skb->cb[DSA_BRCM_TAG_OFF], tag, BRCM_TAG_LEN);
+}
+
struct packet_type {
__be16 type; /* This is really htons(ether_type). */
struct net_device *dev; /* NULL is wildcarded here */
diff --git a/include/net/dsa.h b/include/net/dsa.h
index fbca63ba8f73..d8bf698d5189 100644
--- a/include/net/dsa.h
+++ b/include/net/dsa.h
@@ -31,6 +31,11 @@ enum dsa_tag_protocol {
#define DSA_MAX_SWITCHES 4
#define DSA_MAX_PORTS 12
+/* This tag length is 4 bytes, older ones were 6 bytes, we do not
+ * handle them
+ */
+#define BRCM_TAG_LEN 4
+
struct dsa_chip_data {
/*
* How to access the switch configuration registers.
diff --git a/net/dsa/tag_brcm.c b/net/dsa/tag_brcm.c
index 83d3572cdb20..6c006524540f 100644
--- a/net/dsa/tag_brcm.c
+++ b/net/dsa/tag_brcm.c
@@ -14,11 +14,6 @@
#include <linux/slab.h>
#include "dsa_priv.h"
-/* This tag length is 4 bytes, older ones were 6 bytes, we do not
- * handle them
- */
-#define BRCM_TAG_LEN 4
-
/* Tag is constructed and desconstructed using byte by byte access
* because the tag is placed after the MAC Source Address, which does
* not make it 4-bytes aligned, so this might cause unaligned accesses
@@ -105,6 +100,7 @@ static int brcm_tag_rcv(struct sk_buff *skb, struct
net_device *dev,
{
struct dsa_switch_tree *dst = dev->dsa_ptr;
struct dsa_switch *ds;
+ bool hw_accel = false;
int source_port;
u8 *brcm_tag;
@@ -117,11 +113,17 @@ static int brcm_tag_rcv(struct sk_buff *skb, struct
net_device *dev,
if (skb == NULL)
goto out;
- if (unlikely(!pskb_may_pull(skb, BRCM_TAG_LEN)))
- goto out_drop;
+ /* Verify if the underlying device supports automatic tag extraction */
+ hw_accel = !!(orig_dev->features & NETIF_F_HW_SWITCH_TAG_RX);
+ if (hw_accel) {
+ brcm_tag = (u8 *)&skb->cb[DSA_BRCM_TAG_OFF];
+ } else {
+ if (unlikely(!pskb_may_pull(skb, BRCM_TAG_LEN)))
+ goto out_drop;
- /* skb->data points to the EtherType, the tag is right before it */
- brcm_tag = skb->data - 2;
+ /* skb->data points to the EtherType, the tag is right before
it */
+ brcm_tag = skb->data - 2;
+ }
/* The opcode should never be different than 0b000 */
if (unlikely((brcm_tag[0] >> BRCM_OPCODE_SHIFT) & BRCM_OPCODE_MASK))
@@ -139,14 +141,20 @@ static int brcm_tag_rcv(struct sk_buff *skb, struct
net_device *dev,
if (source_port >= DSA_MAX_PORTS || ds->ports[source_port] == NULL)
goto out_drop;
- /* Remove Broadcom tag and update checksum */
- skb_pull_rcsum(skb, BRCM_TAG_LEN);
+ if (!hw_accel) {
+ /* Remove Broadcom tag and update checksum */
+ skb_pull_rcsum(skb, BRCM_TAG_LEN);
- /* Move the Ethernet DA and SA */
- memmove(skb->data - ETH_HLEN,
- skb->data - ETH_HLEN - BRCM_TAG_LEN,
- 2 * ETH_ALEN);
+ /* Move the Ethernet DA and SA */
+ memmove(skb->data - ETH_HLEN,
+ skb->data - ETH_HLEN - BRCM_TAG_LEN,
+ 2 * ETH_ALEN);
+ }
+
+ /* With or without hardware acceleration, the initial eth_type_trans
+ * will have pulled the SKB by ETH_HLEN, reset that here
+ */
skb_push(skb, ETH_HLEN);
skb->pkt_type = PACKET_HOST;
skb->dev = ds->ports[source_port];
--
2.1.0
--
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