[RFC net-next v5 2/2] bnxt: Use generic HBH removal helper in tx path

[Coco Li]

Eric Dumazet implemented Big TCP that allowed bigger TSO/GRO packet sizes
for IPv6 traffic. See patch series:
'commit 89527be8d8d6 ("net: add IFLA_TSO_{MAX_SIZE|SEGS} attributes")'

This reduces the number of packets traversing the networking stack and
should usually improves performance. However, it also inserts a
temporary Hop-by-hop IPv6 extension header.

Using the HBH header removal method in the previous path, the extra header
be removed in bnxt drivers to allow it to send big TCP packets (bigger
TSO packets) as well.

Tested:
Compiled locally

To further test functional correctness, update the GSO/GRO limit on the
physical NIC:

ip link set eth0 gso_max_size 181000
ip link set eth0 gro_max_size 181000

Note that if there are bonding or ipvan devices on top of the physical
NIC, their GSO sizes need to be updated as well.

Then, IPv6/TCP packets with sizes larger than 64k can be observed.

Big TCP functionality is tested by Michael, feature checks not yet.

Tested by Michael:
I've confirmed with our hardware team that this is supported by our
chips, and I've tested it up to gso_max_size of 524280.  Thanks.

Tested-by: Michael Chan <michael.chan@xxxxxxxxxxxx>
Reviewed-by: Michael Chan <michael.chan@xxxxxxxxxxxx>
Signed-off-by: Coco Li <lixiaoyan@xxxxxxxxxx>
---
 drivers/net/ethernet/broadcom/bnxt/bnxt.c | 26 ++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
index 0fe164b42c5d..6ba1cd342a80 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
@@ -389,6 +389,9 @@ static netdev_tx_t bnxt_start_xmit(struct sk_buff *skb, struct net_device *dev)
 			return NETDEV_TX_BUSY;
 	}
 
+	if (unlikely(ipv6_hopopt_jumbo_remove(skb)))
+		goto tx_free;
+
 	length = skb->len;
 	len = skb_headlen(skb);
 	last_frag = skb_shinfo(skb)->nr_frags;
@@ -11315,6 +11318,7 @@ static bool bnxt_exthdr_check(struct bnxt *bp, struct sk_buff *skb, int nw_off,
 			      u8 **nextp)
 {
 	struct ipv6hdr *ip6h = (struct ipv6hdr *)(skb->data + nw_off);
+	struct hop_jumbo_hdr *jhdr;
 	int hdr_count = 0;
 	u8 *nexthdr;
 	int start;
@@ -11342,9 +11346,27 @@ static bool bnxt_exthdr_check(struct bnxt *bp, struct sk_buff *skb, int nw_off,
 
 		if (hdrlen > 64)
 			return false;
+
+		/* The ext header may be a hop-by-hop header inserted for
+		 * big TCP purposes. This will be removed before sending
+		 * from NIC, so do not count it.
+		 */
+		if (*nexthdr == NEXTHDR_HOP) {
+			if (likely(skb->len <= GRO_LEGACY_MAX_SIZE))
+				goto increment_hdr;
+
+			jhdr = (struct hop_jumbo_hdr *)nexthdr;
+			if (jhdr->tlv_type != IPV6_TLV_JUMBO || jhdr->hdrlen != 0 ||
+			    jhdr->nexthdr != IPPROTO_TCP)
+				goto increment_hdr;
+
+			goto next_hdr;
+		}
+increment_hdr:
+		hdr_count++;
+next_hdr:
 		nexthdr = &hp->nexthdr;
 		start += hdrlen;
-		hdr_count++;
 	}
 	if (nextp) {
 		/* Caller will check inner protocol */
@@ -13657,6 +13679,8 @@ static int bnxt_init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
 		dev->features &= ~NETIF_F_LRO;
 	dev->priv_flags |= IFF_UNICAST_FLT;
 
+	netif_set_tso_max_size(dev, GSO_MAX_SIZE);
+
 #ifdef CONFIG_BNXT_SRIOV
 	init_waitqueue_head(&bp->sriov_cfg_wait);
 #endif
-- 
2.39.0.rc0.267.gcb52ba06e7-goog