net/ipv6: Drop HBH for BIG TCP on RX side

Complementary to the previous commit, stop inserting HBH when building
BIG TCP GRO SKBs.

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/20260205133925.526371-4-alice.kernel@fastmail.im
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: gentoo-root

net/core/gro.c

@@ -115,8 +115,6 @@ int skb_gro_receive(struct sk_buff *p, struct sk_buff *skb)
 
 	if (unlikely(p->len + len >= GRO_LEGACY_MAX_SIZE)) {
 		if (NAPI_GRO_CB(skb)->proto != IPPROTO_TCP ||
-		    (p->protocol == htons(ETH_P_IPV6) &&
-		     skb_headroom(p) < sizeof(struct hop_jumbo_hdr)) ||
 		    p->encapsulation)
 			return -E2BIG;
 	}

net/ipv6/ip6_offload.c

@@ -336,40 +336,14 @@ INDIRECT_CALLABLE_SCOPE int ipv6_gro_complete(struct sk_buff *skb, int nhoff)
 	const struct net_offload *ops;
 	struct ipv6hdr *iph;
 	int err = -ENOSYS;
-	u32 payload_len;
 
 	if (skb->encapsulation) {
 		skb_set_inner_protocol(skb, cpu_to_be16(ETH_P_IPV6));
 		skb_set_inner_network_header(skb, nhoff);
 	}
 
-	payload_len = skb->len - nhoff - sizeof(*iph);
-	if (unlikely(payload_len > IPV6_MAXPLEN)) {
-		struct hop_jumbo_hdr *hop_jumbo;
-		int hoplen = sizeof(*hop_jumbo);
-
-		/* Move network header left */
-		memmove(skb_mac_header(skb) - hoplen, skb_mac_header(skb),
-			skb->transport_header - skb->mac_header);
-		skb->data -= hoplen;
-		skb->len += hoplen;
-		skb->mac_header -= hoplen;
-		skb->network_header -= hoplen;
-		iph = (struct ipv6hdr *)(skb->data + nhoff);
-		hop_jumbo = (struct hop_jumbo_hdr *)(iph + 1);
-
-		/* Build hop-by-hop options */
-		hop_jumbo->nexthdr = iph->nexthdr;
-		hop_jumbo->hdrlen = 0;
-		hop_jumbo->tlv_type = IPV6_TLV_JUMBO;
-		hop_jumbo->tlv_len = 4;
-		hop_jumbo->jumbo_payload_len = htonl(payload_len + hoplen);
-
-		iph->nexthdr = NEXTHDR_HOP;
-	}
-
 	iph = (struct ipv6hdr *)(skb->data + nhoff);
-	ipv6_set_payload_len(iph, payload_len);
+	ipv6_set_payload_len(iph, skb->len - nhoff - sizeof(*iph));
 
 	nhoff += sizeof(*iph) + ipv6_exthdrs_len(iph, &ops);