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Linux/net/ipv4/tcp_offload.c

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  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 
 17 static 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 
 32 static struct sk_buff *tcp4_gso_segment(struct sk_buff *skb,
 33                                         netdev_features_t features)
 34 {
 35         if (!(skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4))
 36                 return ERR_PTR(-EINVAL);
 37 
 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 
 57 struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
 58                                 netdev_features_t features)
 59 {
 60         struct sk_buff *segs = ERR_PTR(-EINVAL);
 61         unsigned int sum_truesize = 0;
 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 
 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 
 83         mss = skb_shinfo(skb)->gso_size;
 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. */
 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 
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 
115         delta = htonl(oldlen + (thlen + mss));
116 
117         skb = segs;
118         th = tcp_hdr(skb);
119         seq = ntohl(th->seq);
120 
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 
124         newcheck = ~csum_fold((__force __wsum)((__force u32)th->check +
125                                                (__force u32)delta));
126 
127         while (skb->next) {
128                 th->fin = th->psh = 0;
129                 th->check = newcheck;
130 
131                 if (skb->ip_summed == CHECKSUM_PARTIAL)
132                         gso_reset_checksum(skb, ~th->check);
133                 else
134                         th->check = gso_make_checksum(skb, ~th->check);
135 
136                 seq += mss;
137                 if (copy_destructor) {
138                         skb->destructor = gso_skb->destructor;
139                         skb->sk = gso_skb->sk;
140                         sum_truesize += skb->truesize;
141                 }
142                 skb = skb->next;
143                 th = tcp_hdr(skb);
144 
145                 th->seq = htonl(seq);
146                 th->cwr = 0;
147         }
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) {
155                 int delta;
156 
157                 swap(gso_skb->sk, skb->sk);
158                 swap(gso_skb->destructor, skb->destructor);
159                 sum_truesize += skb->truesize;
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));
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));
175         if (skb->ip_summed == CHECKSUM_PARTIAL)
176                 gso_reset_checksum(skb, ~th->check);
177         else
178                 th->check = gso_make_checksum(skb, ~th->check);
179 out:
180         return segs;
181 }
182 
183 struct sk_buff **tcp_gro_receive(struct sk_buff **head, struct sk_buff *skb)
184 {
185         struct sk_buff **pp = NULL;
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 
223         for (; (p = *head); head = &p->next) {
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         }
236 
237         goto out_check_final;
238 
239 found:
240         /* Include the IP ID check below from the inner most IP hdr */
241         flush = NAPI_GRO_CB(p)->flush;
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 
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 
261         mss = skb_shinfo(p)->gso_size;
262 
263         flush |= (len - 1) >= mss;
264         flush |= (ntohl(th2->seq) + skb_gro_len(p)) ^ ntohl(th->seq);
265 
266         if (flush || skb_gro_receive(head, skb)) {
267                 mss = 1;
268                 goto out_check_final;
269         }
270 
271         p = *head;
272         th2 = tcp_hdr(p);
273         tcp_flag_word(th2) |= flags & (TCP_FLAG_FIN | TCP_FLAG_PSH);
274 
275 out_check_final:
276         flush = len < mss;
277         flush |= (__force int)(flags & (TCP_FLAG_URG | TCP_FLAG_PSH |
278                                         TCP_FLAG_RST | TCP_FLAG_SYN |
279                                         TCP_FLAG_FIN));
280 
281         if (p && (!NAPI_GRO_CB(skb)->same_flow || flush))
282                 pp = head;
283 
284 out:
285         NAPI_GRO_CB(skb)->flush |= (flush != 0);
286 
287         return pp;
288 }
289 
290 int tcp_gro_complete(struct sk_buff *skb)
291 {
292         struct tcphdr *th = tcp_hdr(skb);
293 
294         skb->csum_start = (unsigned char *)th - skb->head;
295         skb->csum_offset = offsetof(struct tcphdr, check);
296         skb->ip_summed = CHECKSUM_PARTIAL;
297 
298         skb_shinfo(skb)->gso_segs = NAPI_GRO_CB(skb)->count;
299 
300         if (th->cwr)
301                 skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;
302 
303         return 0;
304 }
305 EXPORT_SYMBOL(tcp_gro_complete);
306 
307 static struct sk_buff **tcp4_gro_receive(struct sk_buff **head, struct sk_buff *skb)
308 {
309         /* Don't bother verifying checksum if we're going to flush anyway. */
310         if (!NAPI_GRO_CB(skb)->flush &&
311             skb_gro_checksum_validate(skb, IPPROTO_TCP,
312                                       inet_gro_compute_pseudo)) {
313                 NAPI_GRO_CB(skb)->flush = 1;
314                 return NULL;
315         }
316 
317         return tcp_gro_receive(head, skb);
318 }
319 
320 static int tcp4_gro_complete(struct sk_buff *skb, int thoff)
321 {
322         const struct iphdr *iph = ip_hdr(skb);
323         struct tcphdr *th = tcp_hdr(skb);
324 
325         th->check = ~tcp_v4_check(skb->len - thoff, iph->saddr,
326                                   iph->daddr, 0);
327         skb_shinfo(skb)->gso_type |= SKB_GSO_TCPV4;
328 
329         if (NAPI_GRO_CB(skb)->is_atomic)
330                 skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_FIXEDID;
331 
332         return tcp_gro_complete(skb);
333 }
334 
335 static const struct net_offload tcpv4_offload = {
336         .callbacks = {
337                 .gso_segment    =       tcp4_gso_segment,
338                 .gro_receive    =       tcp4_gro_receive,
339                 .gro_complete   =       tcp4_gro_complete,
340         },
341 };
342 
343 int __init tcpv4_offload_init(void)
344 {
345         return inet_add_offload(&tcpv4_offload, IPPROTO_TCP);
346 }
347 

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