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
17static void tcp_gso_tstamp(struct sk_buff *skb, unsigned int ts_seq,
18			   unsigned int seq, unsigned int mss)
19{
20	while (skb) {
21		if (before(ts_seq, seq + mss)) {
22			skb_shinfo(skb)->tx_flags |= SKBTX_SW_TSTAMP;
23			skb_shinfo(skb)->tskey = ts_seq;
24			return;
25		}
26
27		skb = skb->next;
28		seq += mss;
29	}
30}
31
32static struct sk_buff *tcp4_gso_segment(struct sk_buff *skb,
33					netdev_features_t features)
34{
35	if (!pskb_may_pull(skb, sizeof(struct tcphdr)))
36		return ERR_PTR(-EINVAL);
37
38	if (unlikely(skb->ip_summed != CHECKSUM_PARTIAL)) {
39		const struct iphdr *iph = ip_hdr(skb);
40		struct tcphdr *th = tcp_hdr(skb);
41
42		/* Set up checksum pseudo header, usually expect stack to
43		 * have done this already.
44		 */
45
46		th->check = 0;
47		skb->ip_summed = CHECKSUM_PARTIAL;
48		__tcp_v4_send_check(skb, iph->saddr, iph->daddr);
49	}
50
51	return tcp_gso_segment(skb, features);
52}
53
54struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
55				netdev_features_t features)
56{
57	struct sk_buff *segs = ERR_PTR(-EINVAL);
58	unsigned int sum_truesize = 0;
59	struct tcphdr *th;
60	unsigned int thlen;
61	unsigned int seq;
62	__be32 delta;
63	unsigned int oldlen;
64	unsigned int mss;
65	struct sk_buff *gso_skb = skb;
66	__sum16 newcheck;
67	bool ooo_okay, copy_destructor;
68
69	th = tcp_hdr(skb);
70	thlen = th->doff * 4;
71	if (thlen < sizeof(*th))
72		goto out;
73
74	if (!pskb_may_pull(skb, thlen))
75		goto out;
76
77	oldlen = (u16)~skb->len;
78	__skb_pull(skb, thlen);
79
80	mss = skb_shinfo(skb)->gso_size;
81	if (unlikely(skb->len <= mss))
82		goto out;
83
84	if (skb_gso_ok(skb, features | NETIF_F_GSO_ROBUST)) {
85		/* Packet is from an untrusted source, reset gso_segs. */
86		int type = skb_shinfo(skb)->gso_type;
87
88		if (unlikely(type &
89			     ~(SKB_GSO_TCPV4 |
90			       SKB_GSO_DODGY |
91			       SKB_GSO_TCP_ECN |
92			       SKB_GSO_TCPV6 |
93			       SKB_GSO_GRE |
94			       SKB_GSO_GRE_CSUM |
95			       SKB_GSO_IPIP |
96			       SKB_GSO_SIT |
97			       SKB_GSO_UDP_TUNNEL |
98			       SKB_GSO_UDP_TUNNEL_CSUM |
99			       SKB_GSO_TUNNEL_REMCSUM |
100			       0) ||
101			     !(type & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6))))
102			goto out;
103
104		skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss);
105
106		segs = NULL;
107		goto out;
108	}
109
110	copy_destructor = gso_skb->destructor == tcp_wfree;
111	ooo_okay = gso_skb->ooo_okay;
112	/* All segments but the first should have ooo_okay cleared */
113	skb->ooo_okay = 0;
114
115	segs = skb_segment(skb, features);
116	if (IS_ERR(segs))
117		goto out;
118
119	/* Only first segment might have ooo_okay set */
120	segs->ooo_okay = ooo_okay;
121
122	delta = htonl(oldlen + (thlen + mss));
123
124	skb = segs;
125	th = tcp_hdr(skb);
126	seq = ntohl(th->seq);
127
128	if (unlikely(skb_shinfo(gso_skb)->tx_flags & SKBTX_SW_TSTAMP))
129		tcp_gso_tstamp(segs, skb_shinfo(gso_skb)->tskey, seq, mss);
130
131	newcheck = ~csum_fold((__force __wsum)((__force u32)th->check +
132					       (__force u32)delta));
133
134	do {
135		th->fin = th->psh = 0;
136		th->check = newcheck;
137
138		if (skb->ip_summed != CHECKSUM_PARTIAL)
139			th->check = gso_make_checksum(skb, ~th->check);
140
141		seq += mss;
142		if (copy_destructor) {
143			skb->destructor = gso_skb->destructor;
144			skb->sk = gso_skb->sk;
145			sum_truesize += skb->truesize;
146		}
147		skb = skb->next;
148		th = tcp_hdr(skb);
149
150		th->seq = htonl(seq);
151		th->cwr = 0;
152	} while (skb->next);
153
154	/* Following permits TCP Small Queues to work well with GSO :
155	 * The callback to TCP stack will be called at the time last frag
156	 * is freed at TX completion, and not right now when gso_skb
157	 * is freed by GSO engine
158	 */
159	if (copy_destructor) {
160		swap(gso_skb->sk, skb->sk);
161		swap(gso_skb->destructor, skb->destructor);
162		sum_truesize += skb->truesize;
163		atomic_add(sum_truesize - gso_skb->truesize,
164			   &skb->sk->sk_wmem_alloc);
165	}
166
167	delta = htonl(oldlen + (skb_tail_pointer(skb) -
168				skb_transport_header(skb)) +
169		      skb->data_len);
170	th->check = ~csum_fold((__force __wsum)((__force u32)th->check +
171				(__force u32)delta));
172	if (skb->ip_summed != CHECKSUM_PARTIAL)
173		th->check = gso_make_checksum(skb, ~th->check);
174out:
175	return segs;
176}
177
178struct sk_buff **tcp_gro_receive(struct sk_buff **head, struct sk_buff *skb)
179{
180	struct sk_buff **pp = NULL;
181	struct sk_buff *p;
182	struct tcphdr *th;
183	struct tcphdr *th2;
184	unsigned int len;
185	unsigned int thlen;
186	__be32 flags;
187	unsigned int mss = 1;
188	unsigned int hlen;
189	unsigned int off;
190	int flush = 1;
191	int i;
192
193	off = skb_gro_offset(skb);
194	hlen = off + sizeof(*th);
195	th = skb_gro_header_fast(skb, off);
196	if (skb_gro_header_hard(skb, hlen)) {
197		th = skb_gro_header_slow(skb, hlen, off);
198		if (unlikely(!th))
199			goto out;
200	}
201
202	thlen = th->doff * 4;
203	if (thlen < sizeof(*th))
204		goto out;
205
206	hlen = off + thlen;
207	if (skb_gro_header_hard(skb, hlen)) {
208		th = skb_gro_header_slow(skb, hlen, off);
209		if (unlikely(!th))
210			goto out;
211	}
212
213	skb_gro_pull(skb, thlen);
214
215	len = skb_gro_len(skb);
216	flags = tcp_flag_word(th);
217
218	for (; (p = *head); head = &p->next) {
219		if (!NAPI_GRO_CB(p)->same_flow)
220			continue;
221
222		th2 = tcp_hdr(p);
223
224		if (*(u32 *)&th->source ^ *(u32 *)&th2->source) {
225			NAPI_GRO_CB(p)->same_flow = 0;
226			continue;
227		}
228
229		goto found;
230	}
231
232	goto out_check_final;
233
234found:
235	/* Include the IP ID check below from the inner most IP hdr */
236	flush = NAPI_GRO_CB(p)->flush | NAPI_GRO_CB(p)->flush_id;
237	flush |= (__force int)(flags & TCP_FLAG_CWR);
238	flush |= (__force int)((flags ^ tcp_flag_word(th2)) &
239		  ~(TCP_FLAG_CWR | TCP_FLAG_FIN | TCP_FLAG_PSH));
240	flush |= (__force int)(th->ack_seq ^ th2->ack_seq);
241	for (i = sizeof(*th); i < thlen; i += 4)
242		flush |= *(u32 *)((u8 *)th + i) ^
243			 *(u32 *)((u8 *)th2 + i);
244
245	mss = skb_shinfo(p)->gso_size;
246
247	flush |= (len - 1) >= mss;
248	flush |= (ntohl(th2->seq) + skb_gro_len(p)) ^ ntohl(th->seq);
249
250	if (flush || skb_gro_receive(head, skb)) {
251		mss = 1;
252		goto out_check_final;
253	}
254
255	p = *head;
256	th2 = tcp_hdr(p);
257	tcp_flag_word(th2) |= flags & (TCP_FLAG_FIN | TCP_FLAG_PSH);
258
259out_check_final:
260	flush = len < mss;
261	flush |= (__force int)(flags & (TCP_FLAG_URG | TCP_FLAG_PSH |
262					TCP_FLAG_RST | TCP_FLAG_SYN |
263					TCP_FLAG_FIN));
264
265	if (p && (!NAPI_GRO_CB(skb)->same_flow || flush))
266		pp = head;
267
268out:
269	NAPI_GRO_CB(skb)->flush |= (flush != 0);
270
271	return pp;
272}
273
274int tcp_gro_complete(struct sk_buff *skb)
275{
276	struct tcphdr *th = tcp_hdr(skb);
277
278	skb->csum_start = (unsigned char *)th - skb->head;
279	skb->csum_offset = offsetof(struct tcphdr, check);
280	skb->ip_summed = CHECKSUM_PARTIAL;
281
282	skb_shinfo(skb)->gso_segs = NAPI_GRO_CB(skb)->count;
283
284	if (th->cwr)
285		skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;
286
287	return 0;
288}
289EXPORT_SYMBOL(tcp_gro_complete);
290
291static struct sk_buff **tcp4_gro_receive(struct sk_buff **head, struct sk_buff *skb)
292{
293	/* Don't bother verifying checksum if we're going to flush anyway. */
294	if (!NAPI_GRO_CB(skb)->flush &&
295	    skb_gro_checksum_validate(skb, IPPROTO_TCP,
296				      inet_gro_compute_pseudo)) {
297		NAPI_GRO_CB(skb)->flush = 1;
298		return NULL;
299	}
300
301	return tcp_gro_receive(head, skb);
302}
303
304static int tcp4_gro_complete(struct sk_buff *skb, int thoff)
305{
306	const struct iphdr *iph = ip_hdr(skb);
307	struct tcphdr *th = tcp_hdr(skb);
308
309	th->check = ~tcp_v4_check(skb->len - thoff, iph->saddr,
310				  iph->daddr, 0);
311	skb_shinfo(skb)->gso_type |= SKB_GSO_TCPV4;
312
313	return tcp_gro_complete(skb);
314}
315
316static const struct net_offload tcpv4_offload = {
317	.callbacks = {
318		.gso_segment	=	tcp4_gso_segment,
319		.gro_receive	=	tcp4_gro_receive,
320		.gro_complete	=	tcp4_gro_complete,
321	},
322};
323
324int __init tcpv4_offload_init(void)
325{
326	return inet_add_offload(&tcpv4_offload, IPPROTO_TCP);
327}
328