1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 *	IPV4 GSO/GRO offload support
4 *	Linux INET implementation
5 *
6 *	TCPv4 GSO/GRO support
7 */
8
9#include <linux/indirect_call_wrapper.h>
10#include <linux/skbuff.h>
11#include <net/gro.h>
12#include <net/gso.h>
13#include <net/tcp.h>
14#include <net/protocol.h>
15
16static void tcp_gso_tstamp(struct sk_buff *skb, unsigned int ts_seq,
17			   unsigned int seq, unsigned int mss)
18{
19	while (skb) {
20		if (before(ts_seq, seq + mss)) {
21			skb_shinfo(skb)->tx_flags |= SKBTX_SW_TSTAMP;
22			skb_shinfo(skb)->tskey = ts_seq;
23			return;
24		}
25
26		skb = skb->next;
27		seq += mss;
28	}
29}
30
31static struct sk_buff *tcp4_gso_segment(struct sk_buff *skb,
32					netdev_features_t features)
33{
34	if (!(skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4))
35		return ERR_PTR(-EINVAL);
36
37	if (!pskb_may_pull(skb, sizeof(struct tcphdr)))
38		return ERR_PTR(-EINVAL);
39
40	if (unlikely(skb->ip_summed != CHECKSUM_PARTIAL)) {
41		const struct iphdr *iph = ip_hdr(skb);
42		struct tcphdr *th = tcp_hdr(skb);
43
44		/* Set up checksum pseudo header, usually expect stack to
45		 * have done this already.
46		 */
47
48		th->check = 0;
49		skb->ip_summed = CHECKSUM_PARTIAL;
50		__tcp_v4_send_check(skb, iph->saddr, iph->daddr);
51	}
52
53	return tcp_gso_segment(skb, features);
54}
55
56struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
57				netdev_features_t features)
58{
59	struct sk_buff *segs = ERR_PTR(-EINVAL);
60	unsigned int sum_truesize = 0;
61	struct tcphdr *th;
62	unsigned int thlen;
63	unsigned int seq;
64	unsigned int oldlen;
65	unsigned int mss;
66	struct sk_buff *gso_skb = skb;
67	__sum16 newcheck;
68	bool ooo_okay, copy_destructor;
69	__wsum delta;
70
71	th = tcp_hdr(skb);
72	thlen = th->doff * 4;
73	if (thlen < sizeof(*th))
74		goto out;
75
76	if (!pskb_may_pull(skb, thlen))
77		goto out;
78
79	oldlen = ~skb->len;
80	__skb_pull(skb, thlen);
81
82	mss = skb_shinfo(skb)->gso_size;
83	if (unlikely(skb->len <= mss))
84		goto out;
85
86	if (skb_gso_ok(skb, features | NETIF_F_GSO_ROBUST)) {
87		/* Packet is from an untrusted source, reset gso_segs. */
88
89		skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss);
90
91		segs = NULL;
92		goto out;
93	}
94
95	copy_destructor = gso_skb->destructor == tcp_wfree;
96	ooo_okay = gso_skb->ooo_okay;
97	/* All segments but the first should have ooo_okay cleared */
98	skb->ooo_okay = 0;
99
100	segs = skb_segment(skb, features);
101	if (IS_ERR(segs))
102		goto out;
103
104	/* Only first segment might have ooo_okay set */
105	segs->ooo_okay = ooo_okay;
106
107	/* GSO partial and frag_list segmentation only requires splitting
108	 * the frame into an MSS multiple and possibly a remainder, both
109	 * cases return a GSO skb. So update the mss now.
110	 */
111	if (skb_is_gso(segs))
112		mss *= skb_shinfo(segs)->gso_segs;
113
114	delta = (__force __wsum)htonl(oldlen + thlen + mss);
115
116	skb = segs;
117	th = tcp_hdr(skb);
118	seq = ntohl(th->seq);
119
120	if (unlikely(skb_shinfo(gso_skb)->tx_flags & SKBTX_SW_TSTAMP))
121		tcp_gso_tstamp(segs, skb_shinfo(gso_skb)->tskey, seq, mss);
122
123	newcheck = ~csum_fold(csum_add(csum_unfold(th->check), delta));
124
125	while (skb->next) {
126		th->fin = th->psh = 0;
127		th->check = newcheck;
128
129		if (skb->ip_summed == CHECKSUM_PARTIAL)
130			gso_reset_checksum(skb, ~th->check);
131		else
132			th->check = gso_make_checksum(skb, ~th->check);
133
134		seq += mss;
135		if (copy_destructor) {
136			skb->destructor = gso_skb->destructor;
137			skb->sk = gso_skb->sk;
138			sum_truesize += skb->truesize;
139		}
140		skb = skb->next;
141		th = tcp_hdr(skb);
142
143		th->seq = htonl(seq);
144		th->cwr = 0;
145	}
146
147	/* Following permits TCP Small Queues to work well with GSO :
148	 * The callback to TCP stack will be called at the time last frag
149	 * is freed at TX completion, and not right now when gso_skb
150	 * is freed by GSO engine
151	 */
152	if (copy_destructor) {
153		int delta;
154
155		swap(gso_skb->sk, skb->sk);
156		swap(gso_skb->destructor, skb->destructor);
157		sum_truesize += skb->truesize;
158		delta = sum_truesize - gso_skb->truesize;
159		/* In some pathological cases, delta can be negative.
160		 * We need to either use refcount_add() or refcount_sub_and_test()
161		 */
162		if (likely(delta >= 0))
163			refcount_add(delta, &skb->sk->sk_wmem_alloc);
164		else
165			WARN_ON_ONCE(refcount_sub_and_test(-delta, &skb->sk->sk_wmem_alloc));
166	}
167
168	delta = (__force __wsum)htonl(oldlen +
169				      (skb_tail_pointer(skb) -
170				       skb_transport_header(skb)) +
171				      skb->data_len);
172	th->check = ~csum_fold(csum_add(csum_unfold(th->check), delta));
173	if (skb->ip_summed == CHECKSUM_PARTIAL)
174		gso_reset_checksum(skb, ~th->check);
175	else
176		th->check = gso_make_checksum(skb, ~th->check);
177out:
178	return segs;
179}
180
181struct sk_buff *tcp_gro_receive(struct list_head *head, struct sk_buff *skb)
182{
183	struct sk_buff *pp = NULL;
184	struct sk_buff *p;
185	struct tcphdr *th;
186	struct tcphdr *th2;
187	unsigned int len;
188	unsigned int thlen;
189	__be32 flags;
190	unsigned int mss = 1;
191	unsigned int hlen;
192	unsigned int off;
193	int flush = 1;
194	int i;
195
196	off = skb_gro_offset(skb);
197	hlen = off + sizeof(*th);
198	th = skb_gro_header(skb, hlen, off);
199	if (unlikely(!th))
200		goto out;
201
202	thlen = th->doff * 4;
203	if (thlen < sizeof(*th))
204		goto out;
205
206	hlen = off + thlen;
207	if (!skb_gro_may_pull(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	list_for_each_entry(p, head, list) {
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	p = NULL;
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;
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	/* When we receive our second frame we can made a decision on if we
246	 * continue this flow as an atomic flow with a fixed ID or if we use
247	 * an incrementing ID.
248	 */
249	if (NAPI_GRO_CB(p)->flush_id != 1 ||
250	    NAPI_GRO_CB(p)->count != 1 ||
251	    !NAPI_GRO_CB(p)->is_atomic)
252		flush |= NAPI_GRO_CB(p)->flush_id;
253	else
254		NAPI_GRO_CB(p)->is_atomic = false;
255
256	mss = skb_shinfo(p)->gso_size;
257
258	/* If skb is a GRO packet, make sure its gso_size matches prior packet mss.
259	 * If it is a single frame, do not aggregate it if its length
260	 * is bigger than our mss.
261	 */
262	if (unlikely(skb_is_gso(skb)))
263		flush |= (mss != skb_shinfo(skb)->gso_size);
264	else
265		flush |= (len - 1) >= mss;
266
267	flush |= (ntohl(th2->seq) + skb_gro_len(p)) ^ ntohl(th->seq);
268#ifdef CONFIG_TLS_DEVICE
269	flush |= p->decrypted ^ skb->decrypted;
270#endif
271
272	if (flush || skb_gro_receive(p, skb)) {
273		mss = 1;
274		goto out_check_final;
275	}
276
277	tcp_flag_word(th2) |= flags & (TCP_FLAG_FIN | TCP_FLAG_PSH);
278
279out_check_final:
280	/* Force a flush if last segment is smaller than mss. */
281	if (unlikely(skb_is_gso(skb)))
282		flush = len != NAPI_GRO_CB(skb)->count * skb_shinfo(skb)->gso_size;
283	else
284		flush = len < mss;
285
286	flush |= (__force int)(flags & (TCP_FLAG_URG | TCP_FLAG_PSH |
287					TCP_FLAG_RST | TCP_FLAG_SYN |
288					TCP_FLAG_FIN));
289
290	if (p && (!NAPI_GRO_CB(skb)->same_flow || flush))
291		pp = p;
292
293out:
294	NAPI_GRO_CB(skb)->flush |= (flush != 0);
295
296	return pp;
297}
298
299void tcp_gro_complete(struct sk_buff *skb)
300{
301	struct tcphdr *th = tcp_hdr(skb);
302	struct skb_shared_info *shinfo;
303
304	if (skb->encapsulation)
305		skb->inner_transport_header = skb->transport_header;
306
307	skb->csum_start = (unsigned char *)th - skb->head;
308	skb->csum_offset = offsetof(struct tcphdr, check);
309	skb->ip_summed = CHECKSUM_PARTIAL;
310
311	shinfo = skb_shinfo(skb);
312	shinfo->gso_segs = NAPI_GRO_CB(skb)->count;
313
314	if (th->cwr)
315		shinfo->gso_type |= SKB_GSO_TCP_ECN;
316}
317EXPORT_SYMBOL(tcp_gro_complete);
318
319INDIRECT_CALLABLE_SCOPE
320struct sk_buff *tcp4_gro_receive(struct list_head *head, struct sk_buff *skb)
321{
322	/* Don't bother verifying checksum if we're going to flush anyway. */
323	if (!NAPI_GRO_CB(skb)->flush &&
324	    skb_gro_checksum_validate(skb, IPPROTO_TCP,
325				      inet_gro_compute_pseudo)) {
326		NAPI_GRO_CB(skb)->flush = 1;
327		return NULL;
328	}
329
330	return tcp_gro_receive(head, skb);
331}
332
333INDIRECT_CALLABLE_SCOPE int tcp4_gro_complete(struct sk_buff *skb, int thoff)
334{
335	const struct iphdr *iph = ip_hdr(skb);
336	struct tcphdr *th = tcp_hdr(skb);
337
338	th->check = ~tcp_v4_check(skb->len - thoff, iph->saddr,
339				  iph->daddr, 0);
340
341	skb_shinfo(skb)->gso_type |= SKB_GSO_TCPV4 |
342			(NAPI_GRO_CB(skb)->is_atomic * SKB_GSO_TCP_FIXEDID);
343
344	tcp_gro_complete(skb);
345	return 0;
346}
347
348int __init tcpv4_offload_init(void)
349{
350	net_hotdata.tcpv4_offload = (struct net_offload) {
351		.callbacks = {
352			.gso_segment	=	tcp4_gso_segment,
353			.gro_receive	=	tcp4_gro_receive,
354			.gro_complete	=	tcp4_gro_complete,
355		},
356	};
357	return inet_add_offload(&net_hotdata.tcpv4_offload, IPPROTO_TCP);
358}
359