// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *	IPV6 GSO/GRO offload support
 *	Linux INET6 implementation
 *
 *      TCPv6 GSO/GRO support
 */
#include <linux/indirect_call_wrapper.h>
#include <linux/skbuff.h>
#include <net/gro.h>
#include <net/protocol.h>
#include <net/tcp.h>
#include <net/ip6_checksum.h>
#include "ip6_offload.h"

INDIRECT_CALLABLE_SCOPE
struct sk_buff *tcp6_gro_receive(struct list_head *head, struct sk_buff *skb)
{
	/* Don't bother verifying checksum if we're going to flush anyway. */
	if (!NAPI_GRO_CB(skb)->flush &&
	    skb_gro_checksum_validate(skb, IPPROTO_TCP,
				      ip6_gro_compute_pseudo)) {
		NAPI_GRO_CB(skb)->flush = 1;
		return NULL;
	}

	return tcp_gro_receive(head, skb);
}

INDIRECT_CALLABLE_SCOPE int tcp6_gro_complete(struct sk_buff *skb, int thoff)
{
	const struct ipv6hdr *iph = ipv6_hdr(skb);
	struct tcphdr *th = tcp_hdr(skb);

	th->check = ~tcp_v6_check(skb->len - thoff, &iph->saddr,
				  &iph->daddr, 0);
	skb_shinfo(skb)->gso_type |= SKB_GSO_TCPV6;

	tcp_gro_complete(skb);
	return 0;
}

static void __tcpv6_gso_segment_csum(struct sk_buff *seg,
				     __be16 *oldport, __be16 newport)
{
	struct tcphdr *th;

	if (*oldport == newport)
		return;

	th = tcp_hdr(seg);
	inet_proto_csum_replace2(&th->check, seg, *oldport, newport, false);
	*oldport = newport;
}

static struct sk_buff *__tcpv6_gso_segment_list_csum(struct sk_buff *segs)
{
	const struct tcphdr *th;
	const struct ipv6hdr *iph;
	struct sk_buff *seg;
	struct tcphdr *th2;
	struct ipv6hdr *iph2;

	seg = segs;
	th = tcp_hdr(seg);
	iph = ipv6_hdr(seg);
	th2 = tcp_hdr(seg->next);
	iph2 = ipv6_hdr(seg->next);

	if (!(*(const u32 *)&th->source ^ *(const u32 *)&th2->source) &&
	    ipv6_addr_equal(&iph->saddr, &iph2->saddr) &&
	    ipv6_addr_equal(&iph->daddr, &iph2->daddr))
		return segs;

	while ((seg = seg->next)) {
		th2 = tcp_hdr(seg);
		iph2 = ipv6_hdr(seg);

		iph2->saddr = iph->saddr;
		iph2->daddr = iph->daddr;
		__tcpv6_gso_segment_csum(seg, &th2->source, th->source);
		__tcpv6_gso_segment_csum(seg, &th2->dest, th->dest);
	}

	return segs;
}

static struct sk_buff *__tcp6_gso_segment_list(struct sk_buff *skb,
					      netdev_features_t features)
{
	skb = skb_segment_list(skb, features, skb_mac_header_len(skb));
	if (IS_ERR(skb))
		return skb;

	return __tcpv6_gso_segment_list_csum(skb);
}

static struct sk_buff *tcp6_gso_segment(struct sk_buff *skb,
					netdev_features_t features)
{
	struct tcphdr *th;

	if (!(skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6))
		return ERR_PTR(-EINVAL);

	if (!pskb_may_pull(skb, sizeof(*th)))
		return ERR_PTR(-EINVAL);

	if (skb_shinfo(skb)->gso_type & SKB_GSO_FRAGLIST) {
		struct tcphdr *th = tcp_hdr(skb);

		if ((skb_pagelen(skb) - th->doff * 4 == skb_shinfo(skb)->gso_size) &&
		    !(skb_shinfo(skb)->gso_type & SKB_GSO_DODGY))
			return __tcp6_gso_segment_list(skb, features);

		skb->ip_summed = CHECKSUM_NONE;
	}

	if (unlikely(skb->ip_summed != CHECKSUM_PARTIAL)) {
		const struct ipv6hdr *ipv6h = ipv6_hdr(skb);
		struct tcphdr *th = tcp_hdr(skb);

		/* Set up pseudo header, usually expect stack to have done
		 * this.
		 */

		th->check = 0;
		skb->ip_summed = CHECKSUM_PARTIAL;
		__tcp_v6_send_check(skb, &ipv6h->saddr, &ipv6h->daddr);
	}

	return tcp_gso_segment(skb, features);
}
static const struct net_offload tcpv6_offload = {
	.callbacks = {
		.gso_segment	=	tcp6_gso_segment,
		.gro_receive	=	tcp6_gro_receive,
		.gro_complete	=	tcp6_gro_complete,
	},
};

int __init tcpv6_offload_init(void)
{
	return inet6_add_offload(&tcpv6_offload, IPPROTO_TCP);
}