[linux-block.git] / net / ipv4 / tcp_offload.c

/*
 *	IPV4 GSO/GRO offload support
 *	Linux INET implementation
 *
 *	This program is free software; you can redistribute it and/or
 *	modify it under the terms of the GNU General Public License
 *	as published by the Free Software Foundation; either version
 *	2 of the License, or (at your option) any later version.
 *
 *	TCPv4 GSO/GRO support
 */

#include <linux/skbuff.h>
#include <net/tcp.h>
#include <net/protocol.h>

static void tcp_gso_tstamp(struct sk_buff *skb, unsigned int ts_seq,
			   unsigned int seq, unsigned int mss)
{
	while (skb) {
		if (before(ts_seq, seq + mss)) {
			skb_shinfo(skb)->tx_flags |= SKBTX_SW_TSTAMP;
			skb_shinfo(skb)->tskey = ts_seq;
			return;
		}

		skb = skb->next;
		seq += mss;
	}
}

static struct sk_buff *tcp4_gso_segment(struct sk_buff *skb,
					netdev_features_t features)
{
	if (!(skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4))
		return ERR_PTR(-EINVAL);

	if (!pskb_may_pull(skb, sizeof(struct tcphdr)))
		return ERR_PTR(-EINVAL);

	if (unlikely(skb->ip_summed != CHECKSUM_PARTIAL)) {
		const struct iphdr *iph = ip_hdr(skb);
		struct tcphdr *th = tcp_hdr(skb);

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

		th->check = 0;
		skb->ip_summed = CHECKSUM_PARTIAL;
		__tcp_v4_send_check(skb, iph->saddr, iph->daddr);
	}

	return tcp_gso_segment(skb, features);
}

struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
				netdev_features_t features)
{
	struct sk_buff *segs = ERR_PTR(-EINVAL);
	unsigned int sum_truesize = 0;
	struct tcphdr *th;
	unsigned int thlen;
	unsigned int seq;
	__be32 delta;
	unsigned int oldlen;
	unsigned int mss;
	struct sk_buff *gso_skb = skb;
	__sum16 newcheck;
	bool ooo_okay, copy_destructor;

	th = tcp_hdr(skb);
	thlen = th->doff * 4;
	if (thlen < sizeof(*th))
		goto out;

	if (!pskb_may_pull(skb, thlen))
		goto out;

	oldlen = (u16)~skb->len;
	__skb_pull(skb, thlen);

	mss = skb_shinfo(skb)->gso_size;
	if (unlikely(skb->len <= mss))
		goto out;

	if (skb_gso_ok(skb, features | NETIF_F_GSO_ROBUST)) {
		/* Packet is from an untrusted source, reset gso_segs. */

		skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss);

		segs = NULL;
		goto out;
	}

	copy_destructor = gso_skb->destructor == tcp_wfree;
	ooo_okay = gso_skb->ooo_okay;
	/* All segments but the first should have ooo_okay cleared */
	skb->ooo_okay = 0;

	segs = skb_segment(skb, features);
	if (IS_ERR(segs))
		goto out;

	/* Only first segment might have ooo_okay set */
	segs->ooo_okay = ooo_okay;

	/* GSO partial and frag_list segmentation only requires splitting
	 * the frame into an MSS multiple and possibly a remainder, both
	 * cases return a GSO skb. So update the mss now.
	 */
	if (skb_is_gso(segs))
		mss *= skb_shinfo(segs)->gso_segs;

	delta = htonl(oldlen + (thlen + mss));

	skb = segs;
	th = tcp_hdr(skb);
	seq = ntohl(th->seq);

	if (unlikely(skb_shinfo(gso_skb)->tx_flags & SKBTX_SW_TSTAMP))
		tcp_gso_tstamp(segs, skb_shinfo(gso_skb)->tskey, seq, mss);

	newcheck = ~csum_fold((__force __wsum)((__force u32)th->check +
					       (__force u32)delta));

	while (skb->next) {
		th->fin = th->psh = 0;
		th->check = newcheck;

		if (skb->ip_summed == CHECKSUM_PARTIAL)
			gso_reset_checksum(skb, ~th->check);
		else
			th->check = gso_make_checksum(skb, ~th->check);

		seq += mss;
		if (copy_destructor) {
			skb->destructor = gso_skb->destructor;
			skb->sk = gso_skb->sk;
			sum_truesize += skb->truesize;
		}
		skb = skb->next;
		th = tcp_hdr(skb);

		th->seq = htonl(seq);
		th->cwr = 0;
	}

	/* Following permits TCP Small Queues to work well with GSO :
	 * The callback to TCP stack will be called at the time last frag
	 * is freed at TX completion, and not right now when gso_skb
	 * is freed by GSO engine
	 */
	if (copy_destructor) {
		int delta;

		swap(gso_skb->sk, skb->sk);
		swap(gso_skb->destructor, skb->destructor);
		sum_truesize += skb->truesize;
		delta = sum_truesize - gso_skb->truesize;
		/* In some pathological cases, delta can be negative.
		 * We need to either use refcount_add() or refcount_sub_and_test()
		 */
		if (likely(delta >= 0))
			refcount_add(delta, &skb->sk->sk_wmem_alloc);
		else
			WARN_ON_ONCE(refcount_sub_and_test(-delta, &skb->sk->sk_wmem_alloc));
	}

	delta = htonl(oldlen + (skb_tail_pointer(skb) -
				skb_transport_header(skb)) +
		      skb->data_len);
	th->check = ~csum_fold((__force __wsum)((__force u32)th->check +
				(__force u32)delta));
	if (skb->ip_summed == CHECKSUM_PARTIAL)
		gso_reset_checksum(skb, ~th->check);
	else
		th->check = gso_make_checksum(skb, ~th->check);
out:
	return segs;
}

struct sk_buff *tcp_gro_receive(struct list_head *head, struct sk_buff *skb)
{
	struct sk_buff *pp = NULL;
	struct sk_buff *p;
	struct tcphdr *th;
	struct tcphdr *th2;
	unsigned int len;
	unsigned int thlen;
	__be32 flags;
	unsigned int mss = 1;
	unsigned int hlen;
	unsigned int off;
	int flush = 1;
	int i;

	off = skb_gro_offset(skb);
	hlen = off + sizeof(*th);
	th = skb_gro_header_fast(skb, off);
	if (skb_gro_header_hard(skb, hlen)) {
		th = skb_gro_header_slow(skb, hlen, off);
		if (unlikely(!th))
			goto out;
	}

	thlen = th->doff * 4;
	if (thlen < sizeof(*th))
		goto out;

	hlen = off + thlen;
	if (skb_gro_header_hard(skb, hlen)) {
		th = skb_gro_header_slow(skb, hlen, off);
		if (unlikely(!th))
			goto out;
	}

	skb_gro_pull(skb, thlen);

	len = skb_gro_len(skb);
	flags = tcp_flag_word(th);

	list_for_each_entry(p, head, list) {
		if (!NAPI_GRO_CB(p)->same_flow)
			continue;

		th2 = tcp_hdr(p);

		if (*(u32 *)&th->source ^ *(u32 *)&th2->source) {
			NAPI_GRO_CB(p)->same_flow = 0;
			continue;
		}

		goto found;
	}
	p = NULL;
	goto out_check_final;

found:
	/* Include the IP ID check below from the inner most IP hdr */
	flush = NAPI_GRO_CB(p)->flush;
	flush |= (__force int)(flags & TCP_FLAG_CWR);
	flush |= (__force int)((flags ^ tcp_flag_word(th2)) &
		  ~(TCP_FLAG_CWR | TCP_FLAG_FIN | TCP_FLAG_PSH));
	flush |= (__force int)(th->ack_seq ^ th2->ack_seq);
	for (i = sizeof(*th); i < thlen; i += 4)
		flush |= *(u32 *)((u8 *)th + i) ^
			 *(u32 *)((u8 *)th2 + i);

	/* When we receive our second frame we can made a decision on if we
	 * continue this flow as an atomic flow with a fixed ID or if we use
	 * an incrementing ID.
	 */
	if (NAPI_GRO_CB(p)->flush_id != 1 ||
	    NAPI_GRO_CB(p)->count != 1 ||
	    !NAPI_GRO_CB(p)->is_atomic)
		flush |= NAPI_GRO_CB(p)->flush_id;
	else
		NAPI_GRO_CB(p)->is_atomic = false;

	mss = skb_shinfo(p)->gso_size;

	flush |= (len - 1) >= mss;
	flush |= (ntohl(th2->seq) + skb_gro_len(p)) ^ ntohl(th->seq);

	if (flush || skb_gro_receive(p, skb)) {
		mss = 1;
		goto out_check_final;
	}

	tcp_flag_word(th2) |= flags & (TCP_FLAG_FIN | TCP_FLAG_PSH);

out_check_final:
	flush = len < mss;
	flush |= (__force int)(flags & (TCP_FLAG_URG | TCP_FLAG_PSH |
					TCP_FLAG_RST | TCP_FLAG_SYN |
					TCP_FLAG_FIN));

	if (p && (!NAPI_GRO_CB(skb)->same_flow || flush))
		pp = p;

out:
	NAPI_GRO_CB(skb)->flush |= (flush != 0);

	return pp;
}

int tcp_gro_complete(struct sk_buff *skb)
{
	struct tcphdr *th = tcp_hdr(skb);

	skb->csum_start = (unsigned char *)th - skb->head;
	skb->csum_offset = offsetof(struct tcphdr, check);
	skb->ip_summed = CHECKSUM_PARTIAL;

	skb_shinfo(skb)->gso_segs = NAPI_GRO_CB(skb)->count;

	if (th->cwr)
		skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;

	return 0;
}
EXPORT_SYMBOL(tcp_gro_complete);

static struct sk_buff *tcp4_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,
				      inet_gro_compute_pseudo)) {
		NAPI_GRO_CB(skb)->flush = 1;
		return NULL;
	}

	return tcp_gro_receive(head, skb);
}

static int tcp4_gro_complete(struct sk_buff *skb, int thoff)
{
	const struct iphdr *iph = ip_hdr(skb);
	struct tcphdr *th = tcp_hdr(skb);

	th->check = ~tcp_v4_check(skb->len - thoff, iph->saddr,
				  iph->daddr, 0);
	skb_shinfo(skb)->gso_type |= SKB_GSO_TCPV4;

	if (NAPI_GRO_CB(skb)->is_atomic)
		skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_FIXEDID;

	return tcp_gro_complete(skb);
}

static const struct net_offload tcpv4_offload = {
	.callbacks = {
		.gso_segment	=	tcp4_gso_segment,
		.gro_receive	=	tcp4_gro_receive,
		.gro_complete	=	tcp4_gro_complete,
	},
};

int __init tcpv4_offload_init(void)
{
	return inet_add_offload(&tcpv4_offload, IPPROTO_TCP);
}
Commit	Line	Data
28850dc7 DB	1	/*
	2	* IPV4 GSO/GRO offload support
	3	* Linux INET implementation
	4	*
	5	* This program is free software; you can redistribute it and/or
	6	* modify it under the terms of the GNU General Public License
	7	* as published by the Free Software Foundation; either version
	8	* 2 of the License, or (at your option) any later version.
	9	*
	10	* TCPv4 GSO/GRO support
	11	*/
	12
	13	#include <linux/skbuff.h>
	14	#include <net/tcp.h>
	15	#include <net/protocol.h>
	16
f066e2b0 WB	17	static void tcp_gso_tstamp(struct sk_buff *skb, unsigned int ts_seq,
f066e2b0 WB	18	unsigned int seq, unsigned int mss)
4ed2d765 WB	19	{
4ed2d765 WB	20	while (skb) {
f066e2b0 WB	21	if (before(ts_seq, seq + mss)) {
f066e2b0 WB	22	skb_shinfo(skb)->tx_flags \|= SKBTX_SW_TSTAMP;
4ed2d765 WB	23	skb_shinfo(skb)->tskey = ts_seq;
	24	return;
	25	}
	26
	27	skb = skb->next;
	28	seq += mss;
	29	}
	30	}
	31
74abc20c ED	32	static struct sk_buff tcp4_gso_segment(struct sk_buff skb,
74abc20c ED	33	netdev_features_t features)
d020f8f7	34	{
121d57af WB	35	if (!(skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4))
	36	return ERR_PTR(-EINVAL);
	37
d020f8f7 TH	38	if (!pskb_may_pull(skb, sizeof(struct tcphdr)))
	39	return ERR_PTR(-EINVAL);
	40
	41	if (unlikely(skb->ip_summed != CHECKSUM_PARTIAL)) {
	42	const struct iphdr *iph = ip_hdr(skb);
	43	struct tcphdr *th = tcp_hdr(skb);
	44
	45	/* Set up checksum pseudo header, usually expect stack to
	46	* have done this already.
	47	*/
	48
	49	th->check = 0;
	50	skb->ip_summed = CHECKSUM_PARTIAL;
	51	__tcp_v4_send_check(skb, iph->saddr, iph->daddr);
	52	}
	53
	54	return tcp_gso_segment(skb, features);
	55	}
	56
28be6e07	57	struct sk_buff tcp_gso_segment(struct sk_buff skb,
28850dc7 DB	58	netdev_features_t features)
	59	{
	60	struct sk_buff *segs = ERR_PTR(-EINVAL);
0d08c42c	61	unsigned int sum_truesize = 0;
28850dc7 DB	62	struct tcphdr *th;
	63	unsigned int thlen;
	64	unsigned int seq;
	65	__be32 delta;
	66	unsigned int oldlen;
	67	unsigned int mss;
	68	struct sk_buff *gso_skb = skb;
	69	__sum16 newcheck;
	70	bool ooo_okay, copy_destructor;
	71
28850dc7 DB	72	th = tcp_hdr(skb);
	73	thlen = th->doff * 4;
	74	if (thlen < sizeof(*th))
	75	goto out;
	76
	77	if (!pskb_may_pull(skb, thlen))
	78	goto out;
	79
	80	oldlen = (u16)~skb->len;
	81	__skb_pull(skb, thlen);
	82
a7eea416	83	mss = skb_shinfo(skb)->gso_size;
28850dc7 DB	84	if (unlikely(skb->len <= mss))
	85	goto out;
	86
	87	if (skb_gso_ok(skb, features \| NETIF_F_GSO_ROBUST)) {
	88	/* Packet is from an untrusted source, reset gso_segs. */
28850dc7 DB	89
	90	skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss);
	91
	92	segs = NULL;
	93	goto out;
	94	}
	95
	96	copy_destructor = gso_skb->destructor == tcp_wfree;
	97	ooo_okay = gso_skb->ooo_okay;
	98	/* All segments but the first should have ooo_okay cleared */
	99	skb->ooo_okay = 0;
	100
	101	segs = skb_segment(skb, features);
	102	if (IS_ERR(segs))
	103	goto out;
	104
	105	/* Only first segment might have ooo_okay set */
	106	segs->ooo_okay = ooo_okay;
	107
07b26c94 SK	108	/* GSO partial and frag_list segmentation only requires splitting
	109	* the frame into an MSS multiple and possibly a remainder, both
	110	* cases return a GSO skb. So update the mss now.
	111	*/
	112	if (skb_is_gso(segs))
	113	mss *= skb_shinfo(segs)->gso_segs;
	114
28850dc7 DB	115	delta = htonl(oldlen + (thlen + mss));
	116
	117	skb = segs;
	118	th = tcp_hdr(skb);
	119	seq = ntohl(th->seq);
	120
4ed2d765 WB	121	if (unlikely(skb_shinfo(gso_skb)->tx_flags & SKBTX_SW_TSTAMP))
	122	tcp_gso_tstamp(segs, skb_shinfo(gso_skb)->tskey, seq, mss);
	123
28850dc7 DB	124	newcheck = ~csum_fold((__force __wsum)((__force u32)th->check +
	125	(__force u32)delta));
	126
802ab55a	127	while (skb->next) {
28850dc7 DB	128	th->fin = th->psh = 0;
	129	th->check = newcheck;
	130
08b64fcc AD	131	if (skb->ip_summed == CHECKSUM_PARTIAL)
	132	gso_reset_checksum(skb, ~th->check);
	133	else
e9c3a24b	134	th->check = gso_make_checksum(skb, ~th->check);
28850dc7 DB	135
	136	seq += mss;
	137	if (copy_destructor) {
	138	skb->destructor = gso_skb->destructor;
	139	skb->sk = gso_skb->sk;
0d08c42c	140	sum_truesize += skb->truesize;
28850dc7 DB	141	}
	142	skb = skb->next;
	143	th = tcp_hdr(skb);
	144
	145	th->seq = htonl(seq);
	146	th->cwr = 0;
802ab55a	147	}
28850dc7 DB	148
	149	/* Following permits TCP Small Queues to work well with GSO :
	150	* The callback to TCP stack will be called at the time last frag
	151	* is freed at TX completion, and not right now when gso_skb
	152	* is freed by GSO engine
	153	*/
	154	if (copy_destructor) {
7ec318fe ED	155	int delta;
7ec318fe ED	156
28850dc7 DB	157	swap(gso_skb->sk, skb->sk);
28850dc7 DB	158	swap(gso_skb->destructor, skb->destructor);
0d08c42c	159	sum_truesize += skb->truesize;
7ec318fe ED	160	delta = sum_truesize - gso_skb->truesize;
	161	/* In some pathological cases, delta can be negative.
	162	* We need to either use refcount_add() or refcount_sub_and_test()
	163	*/
	164	if (likely(delta >= 0))
	165	refcount_add(delta, &skb->sk->sk_wmem_alloc);
	166	else
	167	WARN_ON_ONCE(refcount_sub_and_test(-delta, &skb->sk->sk_wmem_alloc));
28850dc7 DB	168	}
	169
	170	delta = htonl(oldlen + (skb_tail_pointer(skb) -
	171	skb_transport_header(skb)) +
	172	skb->data_len);
	173	th->check = ~csum_fold((__force __wsum)((__force u32)th->check +
	174	(__force u32)delta));
08b64fcc AD	175	if (skb->ip_summed == CHECKSUM_PARTIAL)
	176	gso_reset_checksum(skb, ~th->check);
	177	else
e9c3a24b	178	th->check = gso_make_checksum(skb, ~th->check);
28850dc7 DB	179	out:
	180	return segs;
	181	}
28850dc7	182
d4546c25	183	struct sk_buff tcp_gro_receive(struct list_head head, struct sk_buff *skb)
28850dc7	184	{
d4546c25	185	struct sk_buff *pp = NULL;
28850dc7 DB	186	struct sk_buff *p;
	187	struct tcphdr *th;
	188	struct tcphdr *th2;
	189	unsigned int len;
	190	unsigned int thlen;
	191	__be32 flags;
	192	unsigned int mss = 1;
	193	unsigned int hlen;
	194	unsigned int off;
	195	int flush = 1;
	196	int i;
	197
	198	off = skb_gro_offset(skb);
	199	hlen = off + sizeof(*th);
	200	th = skb_gro_header_fast(skb, off);
	201	if (skb_gro_header_hard(skb, hlen)) {
	202	th = skb_gro_header_slow(skb, hlen, off);
	203	if (unlikely(!th))
	204	goto out;
	205	}
	206
	207	thlen = th->doff * 4;
	208	if (thlen < sizeof(*th))
	209	goto out;
	210
	211	hlen = off + thlen;
	212	if (skb_gro_header_hard(skb, hlen)) {
	213	th = skb_gro_header_slow(skb, hlen, off);
	214	if (unlikely(!th))
	215	goto out;
	216	}
	217
	218	skb_gro_pull(skb, thlen);
	219
	220	len = skb_gro_len(skb);
	221	flags = tcp_flag_word(th);
	222
d4546c25	223	list_for_each_entry(p, head, list) {
28850dc7 DB	224	if (!NAPI_GRO_CB(p)->same_flow)
	225	continue;
	226
	227	th2 = tcp_hdr(p);
	228
	229	if ((u32 )&th->source ^ (u32 )&th2->source) {
	230	NAPI_GRO_CB(p)->same_flow = 0;
	231	continue;
	232	}
	233
	234	goto found;
	235	}
d4546c25	236	p = NULL;
28850dc7 DB	237	goto out_check_final;
	238
	239	found:
bf5a755f	240	/* Include the IP ID check below from the inner most IP hdr */
1530545e	241	flush = NAPI_GRO_CB(p)->flush;
28850dc7 DB	242	flush \|= (__force int)(flags & TCP_FLAG_CWR);
	243	flush \|= (__force int)((flags ^ tcp_flag_word(th2)) &
	244	~(TCP_FLAG_CWR \| TCP_FLAG_FIN \| TCP_FLAG_PSH));
	245	flush \|= (__force int)(th->ack_seq ^ th2->ack_seq);
	246	for (i = sizeof(*th); i < thlen; i += 4)
	247	flush \|= (u32 )((u8 *)th + i) ^
	248	(u32 )((u8 *)th2 + i);
	249
1530545e AD	250	/* When we receive our second frame we can made a decision on if we
	251	* continue this flow as an atomic flow with a fixed ID or if we use
	252	* an incrementing ID.
	253	*/
	254	if (NAPI_GRO_CB(p)->flush_id != 1 \|\|
	255	NAPI_GRO_CB(p)->count != 1 \|\|
	256	!NAPI_GRO_CB(p)->is_atomic)
	257	flush \|= NAPI_GRO_CB(p)->flush_id;
	258	else
	259	NAPI_GRO_CB(p)->is_atomic = false;
	260
a7eea416	261	mss = skb_shinfo(p)->gso_size;
28850dc7 DB	262
	263	flush \|= (len - 1) >= mss;
	264	flush \|= (ntohl(th2->seq) + skb_gro_len(p)) ^ ntohl(th->seq);
	265
d4546c25	266	if (flush \|\| skb_gro_receive(p, skb)) {
28850dc7 DB	267	mss = 1;
	268	goto out_check_final;
	269	}
	270
28850dc7 DB	271	tcp_flag_word(th2) \|= flags & (TCP_FLAG_FIN \| TCP_FLAG_PSH);
	272
	273	out_check_final:
	274	flush = len < mss;
	275	flush \|= (__force int)(flags & (TCP_FLAG_URG \| TCP_FLAG_PSH \|
	276	TCP_FLAG_RST \| TCP_FLAG_SYN \|
	277	TCP_FLAG_FIN));
	278
	279	if (p && (!NAPI_GRO_CB(skb)->same_flow \|\| flush))
d4546c25	280	pp = p;
28850dc7 DB	281
28850dc7 DB	282	out:
bf5a755f	283	NAPI_GRO_CB(skb)->flush \|= (flush != 0);
28850dc7 DB	284
	285	return pp;
	286	}
28850dc7 DB	287
	288	int tcp_gro_complete(struct sk_buff *skb)
	289	{
	290	struct tcphdr *th = tcp_hdr(skb);
	291
299603e8	292	skb->csum_start = (unsigned char *)th - skb->head;
28850dc7 DB	293	skb->csum_offset = offsetof(struct tcphdr, check);
	294	skb->ip_summed = CHECKSUM_PARTIAL;
	295
	296	skb_shinfo(skb)->gso_segs = NAPI_GRO_CB(skb)->count;
	297
	298	if (th->cwr)
	299	skb_shinfo(skb)->gso_type \|= SKB_GSO_TCP_ECN;
	300
	301	return 0;
	302	}
	303	EXPORT_SYMBOL(tcp_gro_complete);
	304
d4546c25	305	static struct sk_buff tcp4_gro_receive(struct list_head head, struct sk_buff *skb)
28850dc7	306	{
cc5c00bb	307	/* Don't bother verifying checksum if we're going to flush anyway. */
149d0774 TH	308	if (!NAPI_GRO_CB(skb)->flush &&
	309	skb_gro_checksum_validate(skb, IPPROTO_TCP,
	310	inet_gro_compute_pseudo)) {
28850dc7 DB	311	NAPI_GRO_CB(skb)->flush = 1;
28850dc7 DB	312	return NULL;
28850dc7 DB	313	}
	314
	315	return tcp_gro_receive(head, skb);
	316	}
	317
299603e8	318	static int tcp4_gro_complete(struct sk_buff *skb, int thoff)
28850dc7 DB	319	{
	320	const struct iphdr *iph = ip_hdr(skb);
	321	struct tcphdr *th = tcp_hdr(skb);
	322
299603e8 JC	323	th->check = ~tcp_v4_check(skb->len - thoff, iph->saddr,
299603e8 JC	324	iph->daddr, 0);
c3caf119	325	skb_shinfo(skb)->gso_type \|= SKB_GSO_TCPV4;
28850dc7	326
1530545e AD	327	if (NAPI_GRO_CB(skb)->is_atomic)
	328	skb_shinfo(skb)->gso_type \|= SKB_GSO_TCP_FIXEDID;
	329
28850dc7 DB	330	return tcp_gro_complete(skb);
	331	}
	332
	333	static const struct net_offload tcpv4_offload = {
	334	.callbacks = {
d020f8f7	335	.gso_segment = tcp4_gso_segment,
28850dc7 DB	336	.gro_receive = tcp4_gro_receive,
	337	.gro_complete = tcp4_gro_complete,
	338	},
	339	};
	340
	341	int __init tcpv4_offload_init(void)
	342	{
	343	return inet_add_offload(&tcpv4_offload, IPPROTO_TCP);
	344	}