net/mlx4: Remove jumbo_remove step from TX path

Now that the kernel doesn't insert HBH for BIG TCP IPv6 packets, remove
unnecessary steps from the mlx4 TX path, that used to check and remove
HBH.

Signed-off-by: Alice Mikityanska <alice@isovalent.com>
Acked-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20260205133925.526371-7-alice.kernel@fastmail.im
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: gentoo-root

drivers/net/ethernet/mellanox/mlx4/en_tx.c

@@ -636,28 +636,20 @@ static int get_real_size(const struct sk_buff *skb,
 			 struct net_device *dev,
 			 int *lso_header_size,
 			 bool *inline_ok,
-			 void **pfrag,
-			 int *hopbyhop)
+			 void **pfrag)
 {
 	struct mlx4_en_priv *priv = netdev_priv(dev);
 	int real_size;
 
 	if (shinfo->gso_size) {
 		*inline_ok = false;
-		*hopbyhop = 0;
 		if (skb->encapsulation) {
 			*lso_header_size = skb_inner_tcp_all_headers(skb);
 		} else {
-			/* Detects large IPV6 TCP packets and prepares for removal of
-			 * HBH header that has been pushed by ip6_xmit(),
-			 * mainly so that tcpdump can dissect them.
-			 */
-			if (ipv6_has_hopopt_jumbo(skb))
-				*hopbyhop = sizeof(struct hop_jumbo_hdr);
 			*lso_header_size = skb_tcp_all_headers(skb);
 		}
 		real_size = CTRL_SIZE + shinfo->nr_frags * DS_SIZE +
-			ALIGN(*lso_header_size - *hopbyhop + 4, DS_SIZE);
+			ALIGN(*lso_header_size + 4, DS_SIZE);
 		if (unlikely(*lso_header_size != skb_headlen(skb))) {
 			/* We add a segment for the skb linear buffer only if
 			 * it contains data */
@@ -884,7 +876,6 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev)
 	int desc_size;
 	int real_size;
 	u32 index, bf_index;
-	struct ipv6hdr *h6;
 	__be32 op_own;
 	int lso_header_size;
 	void *fragptr = NULL;
@@ -893,7 +884,6 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev)
 	bool stop_queue;
 	bool inline_ok;
 	u8 data_offset;
-	int hopbyhop;
 	bool bf_ok;
 
 	tx_ind = skb_get_queue_mapping(skb);
@@ -903,7 +893,7 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev)
 		goto tx_drop;
 
 	real_size = get_real_size(skb, shinfo, dev, &lso_header_size,
-				  &inline_ok, &fragptr, &hopbyhop);
+				  &inline_ok, &fragptr);
 	if (unlikely(!real_size))
 		goto tx_drop_count;
 
@@ -956,7 +946,7 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev)
 		data = &tx_desc->data;
 		data_offset = offsetof(struct mlx4_en_tx_desc, data);
 	} else {
-		int lso_align = ALIGN(lso_header_size - hopbyhop + 4, DS_SIZE);
+		int lso_align = ALIGN(lso_header_size + 4, DS_SIZE);
 
 		data = (void *)&tx_desc->lso + lso_align;
 		data_offset = offsetof(struct mlx4_en_tx_desc, lso) + lso_align;
@@ -1021,31 +1011,15 @@ netdev_tx_t mlx4_en_xmit(struct sk_buff *skb, struct net_device *dev)
 			((ring->prod & ring->size) ?
 				cpu_to_be32(MLX4_EN_BIT_DESC_OWN) : 0);
 
-		lso_header_size -= hopbyhop;
 		/* Fill in the LSO prefix */
 		tx_desc->lso.mss_hdr_size = cpu_to_be32(
 			shinfo->gso_size << 16 | lso_header_size);
 
+		/* Copy headers;
+		 * note that we already verified that it is linear
+		 */
+		memcpy(tx_desc->lso.header, skb->data, lso_header_size);
 
-		if (unlikely(hopbyhop)) {
-			/* remove the HBH header.
-			 * Layout: [Ethernet header][IPv6 header][HBH][TCP header]
-			 */
-			memcpy(tx_desc->lso.header, skb->data, ETH_HLEN + sizeof(*h6));
-			h6 = (struct ipv6hdr *)((char *)tx_desc->lso.header + ETH_HLEN);
-			h6->nexthdr = IPPROTO_TCP;
-			/* Copy the TCP header after the IPv6 one */
-			memcpy(h6 + 1,
-			       skb->data + ETH_HLEN + sizeof(*h6) +
-					sizeof(struct hop_jumbo_hdr),
-			       tcp_hdrlen(skb));
-			/* Leave ipv6 payload_len set to 0, as LSO v2 specs request. */
-		} else {
-			/* Copy headers;
-			 * note that we already verified that it is linear
-			 */
-			memcpy(tx_desc->lso.header, skb->data, lso_header_size);
-		}
 		ring->tso_packets++;
 
 		i = shinfo->gso_segs;