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TOMOYO Linux Cross Reference
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/indirect_call_wrapper.h>
 14 #include <linux/skbuff.h>
 15 #include <net/tcp.h>
 16 #include <net/protocol.h>
 17 
 18 static void tcp_gso_tstamp(struct sk_buff *skb, unsigned int ts_seq,
 19                            unsigned int seq, unsigned int mss)
 20 {
 21         while (skb) {
 22                 if (before(ts_seq, seq + mss)) {
 23                         skb_shinfo(skb)->tx_flags |= SKBTX_SW_TSTAMP;
 24                         skb_shinfo(skb)->tskey = ts_seq;
 25                         return;
 26                 }
 27 
 28                 skb = skb->next;
 29                 seq += mss;
 30         }
 31 }
 32 
 33 static struct sk_buff *tcp4_gso_segment(struct sk_buff *skb,
 34                                         netdev_features_t features)
 35 {
 36         if (!(skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4))
 37                 return ERR_PTR(-EINVAL);
 38 
 39         if (!pskb_may_pull(skb, sizeof(struct tcphdr)))
 40                 return ERR_PTR(-EINVAL);
 41 
 42         if (unlikely(skb->ip_summed != CHECKSUM_PARTIAL)) {
 43                 const struct iphdr *iph = ip_hdr(skb);
 44                 struct tcphdr *th = tcp_hdr(skb);
 45 
 46                 /* Set up checksum pseudo header, usually expect stack to
 47                  * have done this already.
 48                  */
 49 
 50                 th->check = 0;
 51                 skb->ip_summed = CHECKSUM_PARTIAL;
 52                 __tcp_v4_send_check(skb, iph->saddr, iph->daddr);
 53         }
 54 
 55         return tcp_gso_segment(skb, features);
 56 }
 57 
 58 struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
 59                                 netdev_features_t features)
 60 {
 61         struct sk_buff *segs = ERR_PTR(-EINVAL);
 62         unsigned int sum_truesize = 0;
 63         struct tcphdr *th;
 64         unsigned int thlen;
 65         unsigned int seq;
 66         __be32 delta;
 67         unsigned int oldlen;
 68         unsigned int mss;
 69         struct sk_buff *gso_skb = skb;
 70         __sum16 newcheck;
 71         bool ooo_okay, copy_destructor;
 72 
 73         th = tcp_hdr(skb);
 74         thlen = th->doff * 4;
 75         if (thlen < sizeof(*th))
 76                 goto out;
 77 
 78         if (!pskb_may_pull(skb, thlen))
 79                 goto out;
 80 
 81         oldlen = (u16)~skb->len;
 82         __skb_pull(skb, thlen);
 83 
 84         mss = skb_shinfo(skb)->gso_size;
 85         if (unlikely(skb->len <= mss))
 86                 goto out;
 87 
 88         if (skb_gso_ok(skb, features | NETIF_F_GSO_ROBUST)) {
 89                 /* Packet is from an untrusted source, reset gso_segs. */
 90 
 91                 skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss);
 92 
 93                 segs = NULL;
 94                 goto out;
 95         }
 96 
 97         copy_destructor = gso_skb->destructor == tcp_wfree;
 98         ooo_okay = gso_skb->ooo_okay;
 99         /* All segments but the first should have ooo_okay cleared */
100         skb->ooo_okay = 0;
101 
102         segs = skb_segment(skb, features);
103         if (IS_ERR(segs))
104                 goto out;
105 
106         /* Only first segment might have ooo_okay set */
107         segs->ooo_okay = ooo_okay;
108 
109         /* GSO partial and frag_list segmentation only requires splitting
110          * the frame into an MSS multiple and possibly a remainder, both
111          * cases return a GSO skb. So update the mss now.
112          */
113         if (skb_is_gso(segs))
114                 mss *= skb_shinfo(segs)->gso_segs;
115 
116         delta = htonl(oldlen + (thlen + mss));
117 
118         skb = segs;
119         th = tcp_hdr(skb);
120         seq = ntohl(th->seq);
121 
122         if (unlikely(skb_shinfo(gso_skb)->tx_flags & SKBTX_SW_TSTAMP))
123                 tcp_gso_tstamp(segs, skb_shinfo(gso_skb)->tskey, seq, mss);
124 
125         newcheck = ~csum_fold((__force __wsum)((__force u32)th->check +
126                                                (__force u32)delta));
127 
128         while (skb->next) {
129                 th->fin = th->psh = 0;
130                 th->check = newcheck;
131 
132                 if (skb->ip_summed == CHECKSUM_PARTIAL)
133                         gso_reset_checksum(skb, ~th->check);
134                 else
135                         th->check = gso_make_checksum(skb, ~th->check);
136 
137                 seq += mss;
138                 if (copy_destructor) {
139                         skb->destructor = gso_skb->destructor;
140                         skb->sk = gso_skb->sk;
141                         sum_truesize += skb->truesize;
142                 }
143                 skb = skb->next;
144                 th = tcp_hdr(skb);
145 
146                 th->seq = htonl(seq);
147                 th->cwr = 0;
148         }
149 
150         /* Following permits TCP Small Queues to work well with GSO :
151          * The callback to TCP stack will be called at the time last frag
152          * is freed at TX completion, and not right now when gso_skb
153          * is freed by GSO engine
154          */
155         if (copy_destructor) {
156                 int delta;
157 
158                 swap(gso_skb->sk, skb->sk);
159                 swap(gso_skb->destructor, skb->destructor);
160                 sum_truesize += skb->truesize;
161                 delta = sum_truesize - gso_skb->truesize;
162                 /* In some pathological cases, delta can be negative.
163                  * We need to either use refcount_add() or refcount_sub_and_test()
164                  */
165                 if (likely(delta >= 0))
166                         refcount_add(delta, &skb->sk->sk_wmem_alloc);
167                 else
168                         WARN_ON_ONCE(refcount_sub_and_test(-delta, &skb->sk->sk_wmem_alloc));
169         }
170 
171         delta = htonl(oldlen + (skb_tail_pointer(skb) -
172                                 skb_transport_header(skb)) +
173                       skb->data_len);
174         th->check = ~csum_fold((__force __wsum)((__force u32)th->check +
175                                 (__force u32)delta));
176         if (skb->ip_summed == CHECKSUM_PARTIAL)
177                 gso_reset_checksum(skb, ~th->check);
178         else
179                 th->check = gso_make_checksum(skb, ~th->check);
180 out:
181         return segs;
182 }
183 
184 struct sk_buff *tcp_gro_receive(struct list_head *head, struct sk_buff *skb)
185 {
186         struct sk_buff *pp = NULL;
187         struct sk_buff *p;
188         struct tcphdr *th;
189         struct tcphdr *th2;
190         unsigned int len;
191         unsigned int thlen;
192         __be32 flags;
193         unsigned int mss = 1;
194         unsigned int hlen;
195         unsigned int off;
196         int flush = 1;
197         int i;
198 
199         off = skb_gro_offset(skb);
200         hlen = off + sizeof(*th);
201         th = skb_gro_header_fast(skb, off);
202         if (skb_gro_header_hard(skb, hlen)) {
203                 th = skb_gro_header_slow(skb, hlen, off);
204                 if (unlikely(!th))
205                         goto out;
206         }
207 
208         thlen = th->doff * 4;
209         if (thlen < sizeof(*th))
210                 goto out;
211 
212         hlen = off + thlen;
213         if (skb_gro_header_hard(skb, hlen)) {
214                 th = skb_gro_header_slow(skb, hlen, off);
215                 if (unlikely(!th))
216                         goto out;
217         }
218 
219         skb_gro_pull(skb, thlen);
220 
221         len = skb_gro_len(skb);
222         flags = tcp_flag_word(th);
223 
224         list_for_each_entry(p, head, list) {
225                 if (!NAPI_GRO_CB(p)->same_flow)
226                         continue;
227 
228                 th2 = tcp_hdr(p);
229 
230                 if (*(u32 *)&th->source ^ *(u32 *)&th2->source) {
231                         NAPI_GRO_CB(p)->same_flow = 0;
232                         continue;
233                 }
234 
235                 goto found;
236         }
237         p = NULL;
238         goto out_check_final;
239 
240 found:
241         /* Include the IP ID check below from the inner most IP hdr */
242         flush = NAPI_GRO_CB(p)->flush;
243         flush |= (__force int)(flags & TCP_FLAG_CWR);
244         flush |= (__force int)((flags ^ tcp_flag_word(th2)) &
245                   ~(TCP_FLAG_CWR | TCP_FLAG_FIN | TCP_FLAG_PSH));
246         flush |= (__force int)(th->ack_seq ^ th2->ack_seq);
247         for (i = sizeof(*th); i < thlen; i += 4)
248                 flush |= *(u32 *)((u8 *)th + i) ^
249                          *(u32 *)((u8 *)th2 + i);
250 
251         /* When we receive our second frame we can made a decision on if we
252          * continue this flow as an atomic flow with a fixed ID or if we use
253          * an incrementing ID.
254          */
255         if (NAPI_GRO_CB(p)->flush_id != 1 ||
256             NAPI_GRO_CB(p)->count != 1 ||
257             !NAPI_GRO_CB(p)->is_atomic)
258                 flush |= NAPI_GRO_CB(p)->flush_id;
259         else
260                 NAPI_GRO_CB(p)->is_atomic = false;
261 
262         mss = skb_shinfo(p)->gso_size;
263 
264         flush |= (len - 1) >= mss;
265         flush |= (ntohl(th2->seq) + skb_gro_len(p)) ^ ntohl(th->seq);
266 #ifdef CONFIG_TLS_DEVICE
267         flush |= p->decrypted ^ skb->decrypted;
268 #endif
269 
270         if (flush || skb_gro_receive(p, skb)) {
271                 mss = 1;
272                 goto out_check_final;
273         }
274 
275         tcp_flag_word(th2) |= flags & (TCP_FLAG_FIN | TCP_FLAG_PSH);
276 
277 out_check_final:
278         flush = len < mss;
279         flush |= (__force int)(flags & (TCP_FLAG_URG | TCP_FLAG_PSH |
280                                         TCP_FLAG_RST | TCP_FLAG_SYN |
281                                         TCP_FLAG_FIN));
282 
283         if (p && (!NAPI_GRO_CB(skb)->same_flow || flush))
284                 pp = p;
285 
286 out:
287         NAPI_GRO_CB(skb)->flush |= (flush != 0);
288 
289         return pp;
290 }
291 
292 int tcp_gro_complete(struct sk_buff *skb)
293 {
294         struct tcphdr *th = tcp_hdr(skb);
295 
296         skb->csum_start = (unsigned char *)th - skb->head;
297         skb->csum_offset = offsetof(struct tcphdr, check);
298         skb->ip_summed = CHECKSUM_PARTIAL;
299 
300         skb_shinfo(skb)->gso_segs = NAPI_GRO_CB(skb)->count;
301 
302         if (th->cwr)
303                 skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;
304 
305         return 0;
306 }
307 EXPORT_SYMBOL(tcp_gro_complete);
308 
309 INDIRECT_CALLABLE_SCOPE
310 struct sk_buff *tcp4_gro_receive(struct list_head *head, struct sk_buff *skb)
311 {
312         /* Don't bother verifying checksum if we're going to flush anyway. */
313         if (!NAPI_GRO_CB(skb)->flush &&
314             skb_gro_checksum_validate(skb, IPPROTO_TCP,
315                                       inet_gro_compute_pseudo)) {
316                 NAPI_GRO_CB(skb)->flush = 1;
317                 return NULL;
318         }
319 
320         return tcp_gro_receive(head, skb);
321 }
322 
323 INDIRECT_CALLABLE_SCOPE int tcp4_gro_complete(struct sk_buff *skb, int thoff)
324 {
325         const struct iphdr *iph = ip_hdr(skb);
326         struct tcphdr *th = tcp_hdr(skb);
327 
328         th->check = ~tcp_v4_check(skb->len - thoff, iph->saddr,
329                                   iph->daddr, 0);
330         skb_shinfo(skb)->gso_type |= SKB_GSO_TCPV4;
331 
332         if (NAPI_GRO_CB(skb)->is_atomic)
333                 skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_FIXEDID;
334 
335         return tcp_gro_complete(skb);
336 }
337 
338 static const struct net_offload tcpv4_offload = {
339         .callbacks = {
340                 .gso_segment    =       tcp4_gso_segment,
341                 .gro_receive    =       tcp4_gro_receive,
342                 .gro_complete   =       tcp4_gro_complete,
343         },
344 };
345 
346 int __init tcpv4_offload_init(void)
347 {
348         return inet_add_offload(&tcpv4_offload, IPPROTO_TCP);
349 }
350 

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