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  
tcp_gso_tstamp(struct sk_buff * skb,unsigned int ts_seq,unsigned int seq,unsigned int mss)16  static 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  
__tcpv4_gso_segment_csum(struct sk_buff * seg,__be32 * oldip,__be32 newip,__be16 * oldport,__be16 newport)31  static void __tcpv4_gso_segment_csum(struct sk_buff *seg,
32  				     __be32 *oldip, __be32 newip,
33  				     __be16 *oldport, __be16 newport)
34  {
35  	struct tcphdr *th;
36  	struct iphdr *iph;
37  
38  	if (*oldip == newip && *oldport == newport)
39  		return;
40  
41  	th = tcp_hdr(seg);
42  	iph = ip_hdr(seg);
43  
44  	inet_proto_csum_replace4(&th->check, seg, *oldip, newip, true);
45  	inet_proto_csum_replace2(&th->check, seg, *oldport, newport, false);
46  	*oldport = newport;
47  
48  	csum_replace4(&iph->check, *oldip, newip);
49  	*oldip = newip;
50  }
51  
__tcpv4_gso_segment_list_csum(struct sk_buff * segs)52  static struct sk_buff *__tcpv4_gso_segment_list_csum(struct sk_buff *segs)
53  {
54  	const struct tcphdr *th;
55  	const struct iphdr *iph;
56  	struct sk_buff *seg;
57  	struct tcphdr *th2;
58  	struct iphdr *iph2;
59  
60  	seg = segs;
61  	th = tcp_hdr(seg);
62  	iph = ip_hdr(seg);
63  	th2 = tcp_hdr(seg->next);
64  	iph2 = ip_hdr(seg->next);
65  
66  	if (!(*(const u32 *)&th->source ^ *(const u32 *)&th2->source) &&
67  	    iph->daddr == iph2->daddr && iph->saddr == iph2->saddr)
68  		return segs;
69  
70  	while ((seg = seg->next)) {
71  		th2 = tcp_hdr(seg);
72  		iph2 = ip_hdr(seg);
73  
74  		__tcpv4_gso_segment_csum(seg,
75  					 &iph2->saddr, iph->saddr,
76  					 &th2->source, th->source);
77  		__tcpv4_gso_segment_csum(seg,
78  					 &iph2->daddr, iph->daddr,
79  					 &th2->dest, th->dest);
80  	}
81  
82  	return segs;
83  }
84  
__tcp4_gso_segment_list(struct sk_buff * skb,netdev_features_t features)85  static struct sk_buff *__tcp4_gso_segment_list(struct sk_buff *skb,
86  					      netdev_features_t features)
87  {
88  	skb = skb_segment_list(skb, features, skb_mac_header_len(skb));
89  	if (IS_ERR(skb))
90  		return skb;
91  
92  	return __tcpv4_gso_segment_list_csum(skb);
93  }
94  
tcp4_gso_segment(struct sk_buff * skb,netdev_features_t features)95  static struct sk_buff *tcp4_gso_segment(struct sk_buff *skb,
96  					netdev_features_t features)
97  {
98  	if (!(skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4))
99  		return ERR_PTR(-EINVAL);
100  
101  	if (!pskb_may_pull(skb, sizeof(struct tcphdr)))
102  		return ERR_PTR(-EINVAL);
103  
104  	if (skb_shinfo(skb)->gso_type & SKB_GSO_FRAGLIST) {
105  		struct tcphdr *th = tcp_hdr(skb);
106  
107  		if (skb_pagelen(skb) - th->doff * 4 == skb_shinfo(skb)->gso_size)
108  			return __tcp4_gso_segment_list(skb, features);
109  
110  		skb->ip_summed = CHECKSUM_NONE;
111  	}
112  
113  	if (unlikely(skb->ip_summed != CHECKSUM_PARTIAL)) {
114  		const struct iphdr *iph = ip_hdr(skb);
115  		struct tcphdr *th = tcp_hdr(skb);
116  
117  		/* Set up checksum pseudo header, usually expect stack to
118  		 * have done this already.
119  		 */
120  
121  		th->check = 0;
122  		skb->ip_summed = CHECKSUM_PARTIAL;
123  		__tcp_v4_send_check(skb, iph->saddr, iph->daddr);
124  	}
125  
126  	return tcp_gso_segment(skb, features);
127  }
128  
tcp_gso_segment(struct sk_buff * skb,netdev_features_t features)129  struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
130  				netdev_features_t features)
131  {
132  	struct sk_buff *segs = ERR_PTR(-EINVAL);
133  	unsigned int sum_truesize = 0;
134  	struct tcphdr *th;
135  	unsigned int thlen;
136  	unsigned int seq;
137  	unsigned int oldlen;
138  	unsigned int mss;
139  	struct sk_buff *gso_skb = skb;
140  	__sum16 newcheck;
141  	bool ooo_okay, copy_destructor;
142  	__wsum delta;
143  
144  	th = tcp_hdr(skb);
145  	thlen = th->doff * 4;
146  	if (thlen < sizeof(*th))
147  		goto out;
148  
149  	if (unlikely(skb_checksum_start(skb) != skb_transport_header(skb)))
150  		goto out;
151  
152  	if (!pskb_may_pull(skb, thlen))
153  		goto out;
154  
155  	oldlen = ~skb->len;
156  	__skb_pull(skb, thlen);
157  
158  	mss = skb_shinfo(skb)->gso_size;
159  	if (unlikely(skb->len <= mss))
160  		goto out;
161  
162  	if (skb_gso_ok(skb, features | NETIF_F_GSO_ROBUST)) {
163  		/* Packet is from an untrusted source, reset gso_segs. */
164  
165  		skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss);
166  
167  		segs = NULL;
168  		goto out;
169  	}
170  
171  	copy_destructor = gso_skb->destructor == tcp_wfree;
172  	ooo_okay = gso_skb->ooo_okay;
173  	/* All segments but the first should have ooo_okay cleared */
174  	skb->ooo_okay = 0;
175  
176  	segs = skb_segment(skb, features);
177  	if (IS_ERR(segs))
178  		goto out;
179  
180  	/* Only first segment might have ooo_okay set */
181  	segs->ooo_okay = ooo_okay;
182  
183  	/* GSO partial and frag_list segmentation only requires splitting
184  	 * the frame into an MSS multiple and possibly a remainder, both
185  	 * cases return a GSO skb. So update the mss now.
186  	 */
187  	if (skb_is_gso(segs))
188  		mss *= skb_shinfo(segs)->gso_segs;
189  
190  	delta = (__force __wsum)htonl(oldlen + thlen + mss);
191  
192  	skb = segs;
193  	th = tcp_hdr(skb);
194  	seq = ntohl(th->seq);
195  
196  	if (unlikely(skb_shinfo(gso_skb)->tx_flags & SKBTX_SW_TSTAMP))
197  		tcp_gso_tstamp(segs, skb_shinfo(gso_skb)->tskey, seq, mss);
198  
199  	newcheck = ~csum_fold(csum_add(csum_unfold(th->check), delta));
200  
201  	while (skb->next) {
202  		th->fin = th->psh = 0;
203  		th->check = newcheck;
204  
205  		if (skb->ip_summed == CHECKSUM_PARTIAL)
206  			gso_reset_checksum(skb, ~th->check);
207  		else
208  			th->check = gso_make_checksum(skb, ~th->check);
209  
210  		seq += mss;
211  		if (copy_destructor) {
212  			skb->destructor = gso_skb->destructor;
213  			skb->sk = gso_skb->sk;
214  			sum_truesize += skb->truesize;
215  		}
216  		skb = skb->next;
217  		th = tcp_hdr(skb);
218  
219  		th->seq = htonl(seq);
220  		th->cwr = 0;
221  	}
222  
223  	/* Following permits TCP Small Queues to work well with GSO :
224  	 * The callback to TCP stack will be called at the time last frag
225  	 * is freed at TX completion, and not right now when gso_skb
226  	 * is freed by GSO engine
227  	 */
228  	if (copy_destructor) {
229  		int delta;
230  
231  		swap(gso_skb->sk, skb->sk);
232  		swap(gso_skb->destructor, skb->destructor);
233  		sum_truesize += skb->truesize;
234  		delta = sum_truesize - gso_skb->truesize;
235  		/* In some pathological cases, delta can be negative.
236  		 * We need to either use refcount_add() or refcount_sub_and_test()
237  		 */
238  		if (likely(delta >= 0))
239  			refcount_add(delta, &skb->sk->sk_wmem_alloc);
240  		else
241  			WARN_ON_ONCE(refcount_sub_and_test(-delta, &skb->sk->sk_wmem_alloc));
242  	}
243  
244  	delta = (__force __wsum)htonl(oldlen +
245  				      (skb_tail_pointer(skb) -
246  				       skb_transport_header(skb)) +
247  				      skb->data_len);
248  	th->check = ~csum_fold(csum_add(csum_unfold(th->check), delta));
249  	if (skb->ip_summed == CHECKSUM_PARTIAL)
250  		gso_reset_checksum(skb, ~th->check);
251  	else
252  		th->check = gso_make_checksum(skb, ~th->check);
253  out:
254  	return segs;
255  }
256  
tcp_gro_lookup(struct list_head * head,struct tcphdr * th)257  struct sk_buff *tcp_gro_lookup(struct list_head *head, struct tcphdr *th)
258  {
259  	struct tcphdr *th2;
260  	struct sk_buff *p;
261  
262  	list_for_each_entry(p, head, list) {
263  		if (!NAPI_GRO_CB(p)->same_flow)
264  			continue;
265  
266  		th2 = tcp_hdr(p);
267  		if (*(u32 *)&th->source ^ *(u32 *)&th2->source) {
268  			NAPI_GRO_CB(p)->same_flow = 0;
269  			continue;
270  		}
271  
272  		return p;
273  	}
274  
275  	return NULL;
276  }
277  
tcp_gro_pull_header(struct sk_buff * skb)278  struct tcphdr *tcp_gro_pull_header(struct sk_buff *skb)
279  {
280  	unsigned int thlen, hlen, off;
281  	struct tcphdr *th;
282  
283  	off = skb_gro_offset(skb);
284  	hlen = off + sizeof(*th);
285  	th = skb_gro_header(skb, hlen, off);
286  	if (unlikely(!th))
287  		return NULL;
288  
289  	thlen = th->doff * 4;
290  	if (thlen < sizeof(*th))
291  		return NULL;
292  
293  	hlen = off + thlen;
294  	if (!skb_gro_may_pull(skb, hlen)) {
295  		th = skb_gro_header_slow(skb, hlen, off);
296  		if (unlikely(!th))
297  			return NULL;
298  	}
299  
300  	skb_gro_pull(skb, thlen);
301  
302  	return th;
303  }
304  
tcp_gro_receive(struct list_head * head,struct sk_buff * skb,struct tcphdr * th)305  struct sk_buff *tcp_gro_receive(struct list_head *head, struct sk_buff *skb,
306  				struct tcphdr *th)
307  {
308  	unsigned int thlen = th->doff * 4;
309  	struct sk_buff *pp = NULL;
310  	struct sk_buff *p;
311  	struct tcphdr *th2;
312  	unsigned int len;
313  	__be32 flags;
314  	unsigned int mss = 1;
315  	int flush = 1;
316  	int i;
317  
318  	len = skb_gro_len(skb);
319  	flags = tcp_flag_word(th);
320  
321  	p = tcp_gro_lookup(head, th);
322  	if (!p)
323  		goto out_check_final;
324  
325  	th2 = tcp_hdr(p);
326  	flush = (__force int)(flags & TCP_FLAG_CWR);
327  	flush |= (__force int)((flags ^ tcp_flag_word(th2)) &
328  		  ~(TCP_FLAG_CWR | TCP_FLAG_FIN | TCP_FLAG_PSH));
329  	flush |= (__force int)(th->ack_seq ^ th2->ack_seq);
330  	for (i = sizeof(*th); i < thlen; i += 4)
331  		flush |= *(u32 *)((u8 *)th + i) ^
332  			 *(u32 *)((u8 *)th2 + i);
333  
334  	flush |= gro_receive_network_flush(th, th2, p);
335  
336  	mss = skb_shinfo(p)->gso_size;
337  
338  	/* If skb is a GRO packet, make sure its gso_size matches prior packet mss.
339  	 * If it is a single frame, do not aggregate it if its length
340  	 * is bigger than our mss.
341  	 */
342  	if (unlikely(skb_is_gso(skb)))
343  		flush |= (mss != skb_shinfo(skb)->gso_size);
344  	else
345  		flush |= (len - 1) >= mss;
346  
347  	flush |= (ntohl(th2->seq) + skb_gro_len(p)) ^ ntohl(th->seq);
348  	flush |= skb_cmp_decrypted(p, skb);
349  
350  	if (unlikely(NAPI_GRO_CB(p)->is_flist)) {
351  		flush |= (__force int)(flags ^ tcp_flag_word(th2));
352  		flush |= skb->ip_summed != p->ip_summed;
353  		flush |= skb->csum_level != p->csum_level;
354  		flush |= NAPI_GRO_CB(p)->count >= 64;
355  
356  		if (flush || skb_gro_receive_list(p, skb))
357  			mss = 1;
358  
359  		goto out_check_final;
360  	}
361  
362  	if (flush || skb_gro_receive(p, skb)) {
363  		mss = 1;
364  		goto out_check_final;
365  	}
366  
367  	tcp_flag_word(th2) |= flags & (TCP_FLAG_FIN | TCP_FLAG_PSH);
368  
369  out_check_final:
370  	/* Force a flush if last segment is smaller than mss. */
371  	if (unlikely(skb_is_gso(skb)))
372  		flush = len != NAPI_GRO_CB(skb)->count * skb_shinfo(skb)->gso_size;
373  	else
374  		flush = len < mss;
375  
376  	flush |= (__force int)(flags & (TCP_FLAG_URG | TCP_FLAG_PSH |
377  					TCP_FLAG_RST | TCP_FLAG_SYN |
378  					TCP_FLAG_FIN));
379  
380  	if (p && (!NAPI_GRO_CB(skb)->same_flow || flush))
381  		pp = p;
382  
383  	NAPI_GRO_CB(skb)->flush |= (flush != 0);
384  
385  	return pp;
386  }
387  
tcp_gro_complete(struct sk_buff * skb)388  void tcp_gro_complete(struct sk_buff *skb)
389  {
390  	struct tcphdr *th = tcp_hdr(skb);
391  	struct skb_shared_info *shinfo;
392  
393  	if (skb->encapsulation)
394  		skb->inner_transport_header = skb->transport_header;
395  
396  	skb->csum_start = (unsigned char *)th - skb->head;
397  	skb->csum_offset = offsetof(struct tcphdr, check);
398  	skb->ip_summed = CHECKSUM_PARTIAL;
399  
400  	shinfo = skb_shinfo(skb);
401  	shinfo->gso_segs = NAPI_GRO_CB(skb)->count;
402  
403  	if (th->cwr)
404  		shinfo->gso_type |= SKB_GSO_TCP_ECN;
405  }
406  EXPORT_SYMBOL(tcp_gro_complete);
407  
tcp4_check_fraglist_gro(struct list_head * head,struct sk_buff * skb,struct tcphdr * th)408  static void tcp4_check_fraglist_gro(struct list_head *head, struct sk_buff *skb,
409  				    struct tcphdr *th)
410  {
411  	const struct iphdr *iph;
412  	struct sk_buff *p;
413  	struct sock *sk;
414  	struct net *net;
415  	int iif, sdif;
416  
417  	if (likely(!(skb->dev->features & NETIF_F_GRO_FRAGLIST)))
418  		return;
419  
420  	p = tcp_gro_lookup(head, th);
421  	if (p) {
422  		NAPI_GRO_CB(skb)->is_flist = NAPI_GRO_CB(p)->is_flist;
423  		return;
424  	}
425  
426  	inet_get_iif_sdif(skb, &iif, &sdif);
427  	iph = skb_gro_network_header(skb);
428  	net = dev_net(skb->dev);
429  	sk = __inet_lookup_established(net, net->ipv4.tcp_death_row.hashinfo,
430  				       iph->saddr, th->source,
431  				       iph->daddr, ntohs(th->dest),
432  				       iif, sdif);
433  	NAPI_GRO_CB(skb)->is_flist = !sk;
434  	if (sk)
435  		sock_put(sk);
436  }
437  
438  INDIRECT_CALLABLE_SCOPE
tcp4_gro_receive(struct list_head * head,struct sk_buff * skb)439  struct sk_buff *tcp4_gro_receive(struct list_head *head, struct sk_buff *skb)
440  {
441  	struct tcphdr *th;
442  
443  	/* Don't bother verifying checksum if we're going to flush anyway. */
444  	if (!NAPI_GRO_CB(skb)->flush &&
445  	    skb_gro_checksum_validate(skb, IPPROTO_TCP,
446  				      inet_gro_compute_pseudo))
447  		goto flush;
448  
449  	th = tcp_gro_pull_header(skb);
450  	if (!th)
451  		goto flush;
452  
453  	tcp4_check_fraglist_gro(head, skb, th);
454  
455  	return tcp_gro_receive(head, skb, th);
456  
457  flush:
458  	NAPI_GRO_CB(skb)->flush = 1;
459  	return NULL;
460  }
461  
tcp4_gro_complete(struct sk_buff * skb,int thoff)462  INDIRECT_CALLABLE_SCOPE int tcp4_gro_complete(struct sk_buff *skb, int thoff)
463  {
464  	const u16 offset = NAPI_GRO_CB(skb)->network_offsets[skb->encapsulation];
465  	const struct iphdr *iph = (struct iphdr *)(skb->data + offset);
466  	struct tcphdr *th = tcp_hdr(skb);
467  
468  	if (unlikely(NAPI_GRO_CB(skb)->is_flist)) {
469  		skb_shinfo(skb)->gso_type |= SKB_GSO_FRAGLIST | SKB_GSO_TCPV4;
470  		skb_shinfo(skb)->gso_segs = NAPI_GRO_CB(skb)->count;
471  
472  		__skb_incr_checksum_unnecessary(skb);
473  
474  		return 0;
475  	}
476  
477  	th->check = ~tcp_v4_check(skb->len - thoff, iph->saddr,
478  				  iph->daddr, 0);
479  
480  	skb_shinfo(skb)->gso_type |= SKB_GSO_TCPV4 |
481  			(NAPI_GRO_CB(skb)->ip_fixedid * SKB_GSO_TCP_FIXEDID);
482  
483  	tcp_gro_complete(skb);
484  	return 0;
485  }
486  
tcpv4_offload_init(void)487  int __init tcpv4_offload_init(void)
488  {
489  	net_hotdata.tcpv4_offload = (struct net_offload) {
490  		.callbacks = {
491  			.gso_segment	=	tcp4_gso_segment,
492  			.gro_receive	=	tcp4_gro_receive,
493  			.gro_complete	=	tcp4_gro_complete,
494  		},
495  	};
496  	return inet_add_offload(&net_hotdata.tcpv4_offload, IPPROTO_TCP);
497  }
498