tcp_offload.c

  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, struct sk_buff *gso_skb,
 17			   unsigned int seq, unsigned int mss)
 18{
 19	u32 flags = skb_shinfo(gso_skb)->tx_flags & SKBTX_ANY_TSTAMP;
 20	u32 ts_seq = skb_shinfo(gso_skb)->tskey;
 21
 22	while (skb) {
 23		if (before(ts_seq, seq + mss)) {
 24			skb_shinfo(skb)->tx_flags |= flags;
 25			skb_shinfo(skb)->tskey = ts_seq;
 26			return;
 27		}
 28
 29		skb = skb->next;
 30		seq += mss;
 31	}
 32}
 33
 34static void __tcpv4_gso_segment_csum(struct sk_buff *seg,
 35				     __be32 *oldip, __be32 newip,
 36				     __be16 *oldport, __be16 newport)
 37{
 38	struct tcphdr *th;
 39	struct iphdr *iph;
 40
 41	if (*oldip == newip && *oldport == newport)
 42		return;
 43
 44	th = tcp_hdr(seg);
 45	iph = ip_hdr(seg);
 46
 47	inet_proto_csum_replace4(&th->check, seg, *oldip, newip, true);
 48	inet_proto_csum_replace2(&th->check, seg, *oldport, newport, false);
 49	*oldport = newport;
 50
 51	csum_replace4(&iph->check, *oldip, newip);
 52	*oldip = newip;
 53}
 54
 55static struct sk_buff *__tcpv4_gso_segment_list_csum(struct sk_buff *segs)
 56{
 57	const struct tcphdr *th;
 58	const struct iphdr *iph;
 59	struct sk_buff *seg;
 60	struct tcphdr *th2;
 61	struct iphdr *iph2;
 62
 63	seg = segs;
 64	th = tcp_hdr(seg);
 65	iph = ip_hdr(seg);
 66	th2 = tcp_hdr(seg->next);
 67	iph2 = ip_hdr(seg->next);
 68
 69	if (!(*(const u32 *)&th->source ^ *(const u32 *)&th2->source) &&
 70	    iph->daddr == iph2->daddr && iph->saddr == iph2->saddr)
 71		return segs;
 72
 73	while ((seg = seg->next)) {
 74		th2 = tcp_hdr(seg);
 75		iph2 = ip_hdr(seg);
 76
 77		__tcpv4_gso_segment_csum(seg,
 78					 &iph2->saddr, iph->saddr,
 79					 &th2->source, th->source);
 80		__tcpv4_gso_segment_csum(seg,
 81					 &iph2->daddr, iph->daddr,
 82					 &th2->dest, th->dest);
 83	}
 84
 85	return segs;
 86}
 87
 88static struct sk_buff *__tcp4_gso_segment_list(struct sk_buff *skb,
 89					      netdev_features_t features)
 90{
 91	skb = skb_segment_list(skb, features, skb_mac_header_len(skb));
 92	if (IS_ERR(skb))
 93		return skb;
 94
 95	return __tcpv4_gso_segment_list_csum(skb);
 96}
 97
 98static struct sk_buff *tcp4_gso_segment(struct sk_buff *skb,
 99					netdev_features_t features)
100{
101	if (!(skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4))
102		return ERR_PTR(-EINVAL);
103
104	if (!pskb_may_pull(skb, sizeof(struct tcphdr)))
105		return ERR_PTR(-EINVAL);
106
107	if (skb_shinfo(skb)->gso_type & SKB_GSO_FRAGLIST) {
108		struct tcphdr *th = tcp_hdr(skb);
109
110		if ((skb_pagelen(skb) - th->doff * 4 == skb_shinfo(skb)->gso_size) &&
111		    !(skb_shinfo(skb)->gso_type & SKB_GSO_DODGY))
112			return __tcp4_gso_segment_list(skb, features);
113
114		skb->ip_summed = CHECKSUM_NONE;
115	}
116
117	if (unlikely(skb->ip_summed != CHECKSUM_PARTIAL)) {
118		const struct iphdr *iph = ip_hdr(skb);
119		struct tcphdr *th = tcp_hdr(skb);
120
121		/* Set up checksum pseudo header, usually expect stack to
122		 * have done this already.
123		 */
124
125		th->check = 0;
126		skb->ip_summed = CHECKSUM_PARTIAL;
127		__tcp_v4_send_check(skb, iph->saddr, iph->daddr);
128	}
129
130	return tcp_gso_segment(skb, features);
131}
132
133struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
134				netdev_features_t features)
135{
136	struct sk_buff *segs = ERR_PTR(-EINVAL);
137	unsigned int sum_truesize = 0;
138	struct tcphdr *th;
139	unsigned int thlen;
140	unsigned int seq;
141	unsigned int oldlen;
142	unsigned int mss;
143	struct sk_buff *gso_skb = skb;
144	__sum16 newcheck;
145	bool ooo_okay, copy_destructor;
146	bool ecn_cwr_mask;
147	__wsum delta;
148
149	th = tcp_hdr(skb);
150	thlen = th->doff * 4;
151	if (thlen < sizeof(*th))
152		goto out;
153
154	if (unlikely(skb_checksum_start(skb) != skb_transport_header(skb)))
155		goto out;
156
157	if (!pskb_may_pull(skb, thlen))
158		goto out;
159
160	oldlen = ~skb->len;
161	__skb_pull(skb, thlen);
162
163	mss = skb_shinfo(skb)->gso_size;
164	if (unlikely(skb->len <= mss))
165		goto out;
166
167	if (skb_gso_ok(skb, features | NETIF_F_GSO_ROBUST)) {
168		/* Packet is from an untrusted source, reset gso_segs. */
169
170		skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss);
171
172		segs = NULL;
173		goto out;
174	}
175
176	copy_destructor = gso_skb->destructor == tcp_wfree;
177	ooo_okay = gso_skb->ooo_okay;
178	/* All segments but the first should have ooo_okay cleared */
179	skb->ooo_okay = 0;
180
181	segs = skb_segment(skb, features);
182	if (IS_ERR(segs))
183		goto out;
184
185	/* Only first segment might have ooo_okay set */
186	segs->ooo_okay = ooo_okay;
187
188	/* GSO partial and frag_list segmentation only requires splitting
189	 * the frame into an MSS multiple and possibly a remainder, both
190	 * cases return a GSO skb. So update the mss now.
191	 */
192	if (skb_is_gso(segs))
193		mss *= skb_shinfo(segs)->gso_segs;
194
195	delta = (__force __wsum)htonl(oldlen + thlen + mss);
196
197	skb = segs;
198	th = tcp_hdr(skb);
199	seq = ntohl(th->seq);
200
201	if (unlikely(skb_shinfo(gso_skb)->tx_flags & SKBTX_ANY_TSTAMP))
202		tcp_gso_tstamp(segs, gso_skb, seq, mss);
203
204	newcheck = ~csum_fold(csum_add(csum_unfold(th->check), delta));
205
206	ecn_cwr_mask = !!(skb_shinfo(gso_skb)->gso_type & SKB_GSO_TCP_ACCECN);
207
208	while (skb->next) {
209		th->fin = th->psh = 0;
210		th->check = newcheck;
211
212		if (skb->ip_summed == CHECKSUM_PARTIAL)
213			gso_reset_checksum(skb, ~th->check);
214		else
215			th->check = gso_make_checksum(skb, ~th->check);
216
217		seq += mss;
218		if (copy_destructor) {
219			skb->destructor = gso_skb->destructor;
220			skb->sk = gso_skb->sk;
221			sum_truesize += skb->truesize;
222		}
223		skb = skb->next;
224		th = tcp_hdr(skb);
225
226		th->seq = htonl(seq);
227
228		th->cwr &= ecn_cwr_mask;
229	}
230
231	/* Following permits TCP Small Queues to work well with GSO :
232	 * The callback to TCP stack will be called at the time last frag
233	 * is freed at TX completion, and not right now when gso_skb
234	 * is freed by GSO engine
235	 */
236	if (copy_destructor) {
237		int delta;
238
239		swap(gso_skb->sk, skb->sk);
240		swap(gso_skb->destructor, skb->destructor);
241		sum_truesize += skb->truesize;
242		delta = sum_truesize - gso_skb->truesize;
243		/* In some pathological cases, delta can be negative.
244		 * We need to either use refcount_add() or refcount_sub_and_test()
245		 */
246		if (likely(delta >= 0))
247			refcount_add(delta, &skb->sk->sk_wmem_alloc);
248		else
249			WARN_ON_ONCE(refcount_sub_and_test(-delta, &skb->sk->sk_wmem_alloc));
250	}
251
252	delta = (__force __wsum)htonl(oldlen +
253				      (skb_tail_pointer(skb) -
254				       skb_transport_header(skb)) +
255				      skb->data_len);
256	th->check = ~csum_fold(csum_add(csum_unfold(th->check), delta));
257	if (skb->ip_summed == CHECKSUM_PARTIAL)
258		gso_reset_checksum(skb, ~th->check);
259	else
260		th->check = gso_make_checksum(skb, ~th->check);
261out:
262	return segs;
263}
264
265struct sk_buff *tcp_gro_lookup(struct list_head *head, struct tcphdr *th)
266{
267	struct tcphdr *th2;
268	struct sk_buff *p;
269
270	list_for_each_entry(p, head, list) {
271		if (!NAPI_GRO_CB(p)->same_flow)
272			continue;
273
274		th2 = tcp_hdr(p);
275		if (*(u32 *)&th->source ^ *(u32 *)&th2->source) {
276			NAPI_GRO_CB(p)->same_flow = 0;
277			continue;
278		}
279
280		return p;
281	}
282
283	return NULL;
284}
285
286struct sk_buff *tcp_gro_receive(struct list_head *head, struct sk_buff *skb,
287				struct tcphdr *th)
288{
289	unsigned int thlen = th->doff * 4;
290	struct sk_buff *pp = NULL;
291	struct sk_buff *p;
292	struct tcphdr *th2;
293	unsigned int len;
294	__be32 flags;
295	unsigned int mss = 1;
296	int flush = 1;
297	int i;
298
299	len = skb_gro_len(skb);
300	flags = tcp_flag_word(th);
301
302	p = tcp_gro_lookup(head, th);
303	if (!p)
304		goto out_check_final;
305
306	th2 = tcp_hdr(p);
307	flush = (__force int)(flags & TCP_FLAG_CWR);
308	flush |= (__force int)((flags ^ tcp_flag_word(th2)) &
309		  ~(TCP_FLAG_FIN | TCP_FLAG_PSH));
310	flush |= (__force int)(th->ack_seq ^ th2->ack_seq);
311	for (i = sizeof(*th); i < thlen; i += 4)
312		flush |= *(u32 *)((u8 *)th + i) ^
313			 *(u32 *)((u8 *)th2 + i);
314
315	flush |= gro_receive_network_flush(th, th2, p);
316
317	mss = skb_shinfo(p)->gso_size;
318
319	/* If skb is a GRO packet, make sure its gso_size matches prior packet mss.
320	 * If it is a single frame, do not aggregate it if its length
321	 * is bigger than our mss.
322	 */
323	if (unlikely(skb_is_gso(skb)))
324		flush |= (mss != skb_shinfo(skb)->gso_size);
325	else
326		flush |= (len - 1) >= mss;
327
328	flush |= (ntohl(th2->seq) + skb_gro_len(p)) ^ ntohl(th->seq);
329	flush |= skb_cmp_decrypted(p, skb);
330
331	if (unlikely(NAPI_GRO_CB(p)->is_flist)) {
332		flush |= (__force int)(flags ^ tcp_flag_word(th2));
333		flush |= skb->ip_summed != p->ip_summed;
334		flush |= skb->csum_level != p->csum_level;
335		flush |= NAPI_GRO_CB(p)->count >= 64;
336		skb_set_network_header(skb, skb_gro_receive_network_offset(skb));
337
338		if (flush || skb_gro_receive_list(p, skb))
339			mss = 1;
340
341		goto out_check_final;
342	}
343
344	if (flush || skb_gro_receive(p, skb)) {
345		mss = 1;
346		goto out_check_final;
347	}
348
349	tcp_flag_word(th2) |= flags & (TCP_FLAG_FIN | TCP_FLAG_PSH);
350
351out_check_final:
352	/* Force a flush if last segment is smaller than mss. */
353	if (unlikely(skb_is_gso(skb)))
354		flush = len != NAPI_GRO_CB(skb)->count * skb_shinfo(skb)->gso_size;
355	else
356		flush = len < mss;
357
358	flush |= (__force int)(flags & (TCP_FLAG_URG | TCP_FLAG_PSH |
359					TCP_FLAG_RST | TCP_FLAG_SYN |
360					TCP_FLAG_FIN));
361
362	if (p && (!NAPI_GRO_CB(skb)->same_flow || flush))
363		pp = p;
364
365	NAPI_GRO_CB(skb)->flush |= (flush != 0);
366
367	return pp;
368}
369
370void tcp_gro_complete(struct sk_buff *skb)
371{
372	struct tcphdr *th = tcp_hdr(skb);
373	struct skb_shared_info *shinfo;
374
375	if (skb->encapsulation)
376		skb->inner_transport_header = skb->transport_header;
377
378	skb->csum_start = (unsigned char *)th - skb->head;
379	skb->csum_offset = offsetof(struct tcphdr, check);
380	skb->ip_summed = CHECKSUM_PARTIAL;
381
382	shinfo = skb_shinfo(skb);
383	shinfo->gso_segs = NAPI_GRO_CB(skb)->count;
384
385	if (th->cwr)
386		shinfo->gso_type |= SKB_GSO_TCP_ACCECN;
387}
388EXPORT_SYMBOL(tcp_gro_complete);
389
390static void tcp4_check_fraglist_gro(struct list_head *head, struct sk_buff *skb,
391				    struct tcphdr *th)
392{
393	const struct iphdr *iph;
394	struct sk_buff *p;
395	struct sock *sk;
396	struct net *net;
397	int iif, sdif;
398
399	if (likely(!(skb->dev->features & NETIF_F_GRO_FRAGLIST)))
400		return;
401
402	p = tcp_gro_lookup(head, th);
403	if (p) {
404		NAPI_GRO_CB(skb)->is_flist = NAPI_GRO_CB(p)->is_flist;
405		return;
406	}
407
408	inet_get_iif_sdif(skb, &iif, &sdif);
409	iph = skb_gro_network_header(skb);
410	net = dev_net_rcu(skb->dev);
411	sk = __inet_lookup_established(net, iph->saddr, th->source,
412				       iph->daddr, ntohs(th->dest),
413				       iif, sdif);
414	NAPI_GRO_CB(skb)->is_flist = !sk;
415	if (sk)
416		sock_gen_put(sk);
417}
418
419INDIRECT_CALLABLE_SCOPE
420struct sk_buff *tcp4_gro_receive(struct list_head *head, struct sk_buff *skb)
421{
422	struct tcphdr *th;
423
424	/* Don't bother verifying checksum if we're going to flush anyway. */
425	if (!NAPI_GRO_CB(skb)->flush &&
426	    skb_gro_checksum_validate(skb, IPPROTO_TCP,
427				      inet_gro_compute_pseudo))
428		goto flush;
429
430	th = tcp_gro_pull_header(skb);
431	if (!th)
432		goto flush;
433
434	tcp4_check_fraglist_gro(head, skb, th);
435
436	return tcp_gro_receive(head, skb, th);
437
438flush:
439	NAPI_GRO_CB(skb)->flush = 1;
440	return NULL;
441}
442
443INDIRECT_CALLABLE_SCOPE int tcp4_gro_complete(struct sk_buff *skb, int thoff)
444{
445	const u16 offset = NAPI_GRO_CB(skb)->network_offsets[skb->encapsulation];
446	const struct iphdr *iph = (struct iphdr *)(skb->data + offset);
447	struct tcphdr *th = tcp_hdr(skb);
448
449	if (unlikely(NAPI_GRO_CB(skb)->is_flist)) {
450		skb_shinfo(skb)->gso_type |= SKB_GSO_FRAGLIST | SKB_GSO_TCPV4;
451		skb_shinfo(skb)->gso_segs = NAPI_GRO_CB(skb)->count;
452
453		__skb_incr_checksum_unnecessary(skb);
454
455		return 0;
456	}
457
458	th->check = ~tcp_v4_check(skb->len - thoff, iph->saddr,
459				  iph->daddr, 0);
460
461	BUILD_BUG_ON(SKB_GSO_TCP_FIXEDID << 1 != SKB_GSO_TCP_FIXEDID_INNER);
462	skb_shinfo(skb)->gso_type |= SKB_GSO_TCPV4 |
463			(NAPI_GRO_CB(skb)->ip_fixedid * SKB_GSO_TCP_FIXEDID);
464
465	tcp_gro_complete(skb);
466	return 0;
467}
468
469int __init tcpv4_offload_init(void)
470{
471	net_hotdata.tcpv4_offload = (struct net_offload) {
472		.callbacks = {
473			.gso_segment	=	tcp4_gso_segment,
474			.gro_receive	=	tcp4_gro_receive,
475			.gro_complete	=	tcp4_gro_complete,
476		},
477	};
478	return inet_add_offload(&net_hotdata.tcpv4_offload, IPPROTO_TCP);
479}