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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 (!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 
 54 struct 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 
 87                 skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss);
 88 
 89                 segs = NULL;
 90                 goto out;
 91         }
 92 
 93         copy_destructor = gso_skb->destructor == tcp_wfree;
 94         ooo_okay = gso_skb->ooo_okay;
 95         /* All segments but the first should have ooo_okay cleared */
 96         skb->ooo_okay = 0;
 97 
 98         segs = skb_segment(skb, features);
 99         if (IS_ERR(segs))
100                 goto out;
101 
102         /* Only first segment might have ooo_okay set */
103         segs->ooo_okay = ooo_okay;
104 
105         /* GSO partial and frag_list segmentation only requires splitting
106          * the frame into an MSS multiple and possibly a remainder, both
107          * cases return a GSO skb. So update the mss now.
108          */
109         if (skb_is_gso(segs))
110                 mss *= skb_shinfo(segs)->gso_segs;
111 
112         delta = htonl(oldlen + (thlen + mss));
113 
114         skb = segs;
115         th = tcp_hdr(skb);
116         seq = ntohl(th->seq);
117 
118         if (unlikely(skb_shinfo(gso_skb)->tx_flags & SKBTX_SW_TSTAMP))
119                 tcp_gso_tstamp(segs, skb_shinfo(gso_skb)->tskey, seq, mss);
120 
121         newcheck = ~csum_fold((__force __wsum)((__force u32)th->check +
122                                                (__force u32)delta));
123 
124         while (skb->next) {
125                 th->fin = th->psh = 0;
126                 th->check = newcheck;
127 
128                 if (skb->ip_summed == CHECKSUM_PARTIAL)
129                         gso_reset_checksum(skb, ~th->check);
130                 else
131                         th->check = gso_make_checksum(skb, ~th->check);
132 
133                 seq += mss;
134                 if (copy_destructor) {
135                         skb->destructor = gso_skb->destructor;
136                         skb->sk = gso_skb->sk;
137                         sum_truesize += skb->truesize;
138                 }
139                 skb = skb->next;
140                 th = tcp_hdr(skb);
141 
142                 th->seq = htonl(seq);
143                 th->cwr = 0;
144         }
145 
146         /* Following permits TCP Small Queues to work well with GSO :
147          * The callback to TCP stack will be called at the time last frag
148          * is freed at TX completion, and not right now when gso_skb
149          * is freed by GSO engine
150          */
151         if (copy_destructor) {
152                 swap(gso_skb->sk, skb->sk);
153                 swap(gso_skb->destructor, skb->destructor);
154                 sum_truesize += skb->truesize;
155                 atomic_add(sum_truesize - gso_skb->truesize,
156                            &skb->sk->sk_wmem_alloc);
157         }
158 
159         delta = htonl(oldlen + (skb_tail_pointer(skb) -
160                                 skb_transport_header(skb)) +
161                       skb->data_len);
162         th->check = ~csum_fold((__force __wsum)((__force u32)th->check +
163                                 (__force u32)delta));
164         if (skb->ip_summed == CHECKSUM_PARTIAL)
165                 gso_reset_checksum(skb, ~th->check);
166         else
167                 th->check = gso_make_checksum(skb, ~th->check);
168 out:
169         return segs;
170 }
171 
172 struct sk_buff **tcp_gro_receive(struct sk_buff **head, struct sk_buff *skb)
173 {
174         struct sk_buff **pp = NULL;
175         struct sk_buff *p;
176         struct tcphdr *th;
177         struct tcphdr *th2;
178         unsigned int len;
179         unsigned int thlen;
180         __be32 flags;
181         unsigned int mss = 1;
182         unsigned int hlen;
183         unsigned int off;
184         int flush = 1;
185         int i;
186 
187         off = skb_gro_offset(skb);
188         hlen = off + sizeof(*th);
189         th = skb_gro_header_fast(skb, off);
190         if (skb_gro_header_hard(skb, hlen)) {
191                 th = skb_gro_header_slow(skb, hlen, off);
192                 if (unlikely(!th))
193                         goto out;
194         }
195 
196         thlen = th->doff * 4;
197         if (thlen < sizeof(*th))
198                 goto out;
199 
200         hlen = off + thlen;
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         skb_gro_pull(skb, thlen);
208 
209         len = skb_gro_len(skb);
210         flags = tcp_flag_word(th);
211 
212         for (; (p = *head); head = &p->next) {
213                 if (!NAPI_GRO_CB(p)->same_flow)
214                         continue;
215 
216                 th2 = tcp_hdr(p);
217 
218                 if (*(u32 *)&th->source ^ *(u32 *)&th2->source) {
219                         NAPI_GRO_CB(p)->same_flow = 0;
220                         continue;
221                 }
222 
223                 goto found;
224         }
225 
226         goto out_check_final;
227 
228 found:
229         /* Include the IP ID check below from the inner most IP hdr */
230         flush = NAPI_GRO_CB(p)->flush;
231         flush |= (__force int)(flags & TCP_FLAG_CWR);
232         flush |= (__force int)((flags ^ tcp_flag_word(th2)) &
233                   ~(TCP_FLAG_CWR | TCP_FLAG_FIN | TCP_FLAG_PSH));
234         flush |= (__force int)(th->ack_seq ^ th2->ack_seq);
235         for (i = sizeof(*th); i < thlen; i += 4)
236                 flush |= *(u32 *)((u8 *)th + i) ^
237                          *(u32 *)((u8 *)th2 + i);
238 
239         /* When we receive our second frame we can made a decision on if we
240          * continue this flow as an atomic flow with a fixed ID or if we use
241          * an incrementing ID.
242          */
243         if (NAPI_GRO_CB(p)->flush_id != 1 ||
244             NAPI_GRO_CB(p)->count != 1 ||
245             !NAPI_GRO_CB(p)->is_atomic)
246                 flush |= NAPI_GRO_CB(p)->flush_id;
247         else
248                 NAPI_GRO_CB(p)->is_atomic = false;
249 
250         mss = skb_shinfo(p)->gso_size;
251 
252         flush |= (len - 1) >= mss;
253         flush |= (ntohl(th2->seq) + skb_gro_len(p)) ^ ntohl(th->seq);
254 
255         if (flush || skb_gro_receive(head, skb)) {
256                 mss = 1;
257                 goto out_check_final;
258         }
259 
260         p = *head;
261         th2 = tcp_hdr(p);
262         tcp_flag_word(th2) |= flags & (TCP_FLAG_FIN | TCP_FLAG_PSH);
263 
264 out_check_final:
265         flush = len < mss;
266         flush |= (__force int)(flags & (TCP_FLAG_URG | TCP_FLAG_PSH |
267                                         TCP_FLAG_RST | TCP_FLAG_SYN |
268                                         TCP_FLAG_FIN));
269 
270         if (p && (!NAPI_GRO_CB(skb)->same_flow || flush))
271                 pp = head;
272 
273 out:
274         NAPI_GRO_CB(skb)->flush |= (flush != 0);
275 
276         return pp;
277 }
278 
279 int tcp_gro_complete(struct sk_buff *skb)
280 {
281         struct tcphdr *th = tcp_hdr(skb);
282 
283         skb->csum_start = (unsigned char *)th - skb->head;
284         skb->csum_offset = offsetof(struct tcphdr, check);
285         skb->ip_summed = CHECKSUM_PARTIAL;
286 
287         skb_shinfo(skb)->gso_segs = NAPI_GRO_CB(skb)->count;
288 
289         if (th->cwr)
290                 skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;
291 
292         return 0;
293 }
294 EXPORT_SYMBOL(tcp_gro_complete);
295 
296 static struct sk_buff **tcp4_gro_receive(struct sk_buff **head, struct sk_buff *skb)
297 {
298         /* Don't bother verifying checksum if we're going to flush anyway. */
299         if (!NAPI_GRO_CB(skb)->flush &&
300             skb_gro_checksum_validate(skb, IPPROTO_TCP,
301                                       inet_gro_compute_pseudo)) {
302                 NAPI_GRO_CB(skb)->flush = 1;
303                 return NULL;
304         }
305 
306         return tcp_gro_receive(head, skb);
307 }
308 
309 static int tcp4_gro_complete(struct sk_buff *skb, int thoff)
310 {
311         const struct iphdr *iph = ip_hdr(skb);
312         struct tcphdr *th = tcp_hdr(skb);
313 
314         th->check = ~tcp_v4_check(skb->len - thoff, iph->saddr,
315                                   iph->daddr, 0);
316         skb_shinfo(skb)->gso_type |= SKB_GSO_TCPV4;
317 
318         if (NAPI_GRO_CB(skb)->is_atomic)
319                 skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_FIXEDID;
320 
321         return tcp_gro_complete(skb);
322 }
323 
324 static const struct net_offload tcpv4_offload = {
325         .callbacks = {
326                 .gso_segment    =       tcp4_gso_segment,
327                 .gro_receive    =       tcp4_gro_receive,
328                 .gro_complete   =       tcp4_gro_complete,
329         },
330 };
331 
332 int __init tcpv4_offload_init(void)
333 {
334         return inet_add_offload(&tcpv4_offload, IPPROTO_TCP);
335 }
336 

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