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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                 int type = skb_shinfo(skb)->gso_type;
 87 
 88                 if (unlikely(type &
 89                              ~(SKB_GSO_TCPV4 |
 90                                SKB_GSO_DODGY |
 91                                SKB_GSO_TCP_ECN |
 92                                SKB_GSO_TCPV6 |
 93                                SKB_GSO_GRE |
 94                                SKB_GSO_GRE_CSUM |
 95                                SKB_GSO_IPIP |
 96                                SKB_GSO_SIT |
 97                                SKB_GSO_UDP_TUNNEL |
 98                                SKB_GSO_UDP_TUNNEL_CSUM |
 99                                SKB_GSO_TUNNEL_REMCSUM |
100                                0) ||
101                              !(type & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6))))
102                         goto out;
103 
104                 skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss);
105 
106                 segs = NULL;
107                 goto out;
108         }
109 
110         copy_destructor = gso_skb->destructor == tcp_wfree;
111         ooo_okay = gso_skb->ooo_okay;
112         /* All segments but the first should have ooo_okay cleared */
113         skb->ooo_okay = 0;
114 
115         segs = skb_segment(skb, features);
116         if (IS_ERR(segs))
117                 goto out;
118 
119         /* Only first segment might have ooo_okay set */
120         segs->ooo_okay = ooo_okay;
121 
122         delta = htonl(oldlen + (thlen + mss));
123 
124         skb = segs;
125         th = tcp_hdr(skb);
126         seq = ntohl(th->seq);
127 
128         if (unlikely(skb_shinfo(gso_skb)->tx_flags & SKBTX_SW_TSTAMP))
129                 tcp_gso_tstamp(segs, skb_shinfo(gso_skb)->tskey, seq, mss);
130 
131         newcheck = ~csum_fold((__force __wsum)((__force u32)th->check +
132                                                (__force u32)delta));
133 
134         do {
135                 th->fin = th->psh = 0;
136                 th->check = newcheck;
137 
138                 if (skb->ip_summed == CHECKSUM_PARTIAL)
139                         gso_reset_checksum(skb, ~th->check);
140                 else
141                         th->check = gso_make_checksum(skb, ~th->check);
142 
143                 seq += mss;
144                 if (copy_destructor) {
145                         skb->destructor = gso_skb->destructor;
146                         skb->sk = gso_skb->sk;
147                         sum_truesize += skb->truesize;
148                 }
149                 skb = skb->next;
150                 th = tcp_hdr(skb);
151 
152                 th->seq = htonl(seq);
153                 th->cwr = 0;
154         } while (skb->next);
155 
156         /* Following permits TCP Small Queues to work well with GSO :
157          * The callback to TCP stack will be called at the time last frag
158          * is freed at TX completion, and not right now when gso_skb
159          * is freed by GSO engine
160          */
161         if (copy_destructor) {
162                 swap(gso_skb->sk, skb->sk);
163                 swap(gso_skb->destructor, skb->destructor);
164                 sum_truesize += skb->truesize;
165                 atomic_add(sum_truesize - gso_skb->truesize,
166                            &skb->sk->sk_wmem_alloc);
167         }
168 
169         delta = htonl(oldlen + (skb_tail_pointer(skb) -
170                                 skb_transport_header(skb)) +
171                       skb->data_len);
172         th->check = ~csum_fold((__force __wsum)((__force u32)th->check +
173                                 (__force u32)delta));
174         if (skb->ip_summed == CHECKSUM_PARTIAL)
175                 gso_reset_checksum(skb, ~th->check);
176         else
177                 th->check = gso_make_checksum(skb, ~th->check);
178 out:
179         return segs;
180 }
181 
182 struct sk_buff **tcp_gro_receive(struct sk_buff **head, struct sk_buff *skb)
183 {
184         struct sk_buff **pp = NULL;
185         struct sk_buff *p;
186         struct tcphdr *th;
187         struct tcphdr *th2;
188         unsigned int len;
189         unsigned int thlen;
190         __be32 flags;
191         unsigned int mss = 1;
192         unsigned int hlen;
193         unsigned int off;
194         int flush = 1;
195         int i;
196 
197         off = skb_gro_offset(skb);
198         hlen = off + sizeof(*th);
199         th = skb_gro_header_fast(skb, off);
200         if (skb_gro_header_hard(skb, hlen)) {
201                 th = skb_gro_header_slow(skb, hlen, off);
202                 if (unlikely(!th))
203                         goto out;
204         }
205 
206         thlen = th->doff * 4;
207         if (thlen < sizeof(*th))
208                 goto out;
209 
210         hlen = off + thlen;
211         if (skb_gro_header_hard(skb, hlen)) {
212                 th = skb_gro_header_slow(skb, hlen, off);
213                 if (unlikely(!th))
214                         goto out;
215         }
216 
217         skb_gro_pull(skb, thlen);
218 
219         len = skb_gro_len(skb);
220         flags = tcp_flag_word(th);
221 
222         for (; (p = *head); head = &p->next) {
223                 if (!NAPI_GRO_CB(p)->same_flow)
224                         continue;
225 
226                 th2 = tcp_hdr(p);
227 
228                 if (*(u32 *)&th->source ^ *(u32 *)&th2->source) {
229                         NAPI_GRO_CB(p)->same_flow = 0;
230                         continue;
231                 }
232 
233                 goto found;
234         }
235 
236         goto out_check_final;
237 
238 found:
239         /* Include the IP ID check below from the inner most IP hdr */
240         flush = NAPI_GRO_CB(p)->flush | NAPI_GRO_CB(p)->flush_id;
241         flush |= (__force int)(flags & TCP_FLAG_CWR);
242         flush |= (__force int)((flags ^ tcp_flag_word(th2)) &
243                   ~(TCP_FLAG_CWR | TCP_FLAG_FIN | TCP_FLAG_PSH));
244         flush |= (__force int)(th->ack_seq ^ th2->ack_seq);
245         for (i = sizeof(*th); i < thlen; i += 4)
246                 flush |= *(u32 *)((u8 *)th + i) ^
247                          *(u32 *)((u8 *)th2 + i);
248 
249         mss = skb_shinfo(p)->gso_size;
250 
251         flush |= (len - 1) >= mss;
252         flush |= (ntohl(th2->seq) + skb_gro_len(p)) ^ ntohl(th->seq);
253 
254         if (flush || skb_gro_receive(head, skb)) {
255                 mss = 1;
256                 goto out_check_final;
257         }
258 
259         p = *head;
260         th2 = tcp_hdr(p);
261         tcp_flag_word(th2) |= flags & (TCP_FLAG_FIN | TCP_FLAG_PSH);
262 
263 out_check_final:
264         flush = len < mss;
265         flush |= (__force int)(flags & (TCP_FLAG_URG | TCP_FLAG_PSH |
266                                         TCP_FLAG_RST | TCP_FLAG_SYN |
267                                         TCP_FLAG_FIN));
268 
269         if (p && (!NAPI_GRO_CB(skb)->same_flow || flush))
270                 pp = head;
271 
272 out:
273         NAPI_GRO_CB(skb)->flush |= (flush != 0);
274 
275         return pp;
276 }
277 
278 int tcp_gro_complete(struct sk_buff *skb)
279 {
280         struct tcphdr *th = tcp_hdr(skb);
281 
282         skb->csum_start = (unsigned char *)th - skb->head;
283         skb->csum_offset = offsetof(struct tcphdr, check);
284         skb->ip_summed = CHECKSUM_PARTIAL;
285 
286         skb_shinfo(skb)->gso_segs = NAPI_GRO_CB(skb)->count;
287 
288         if (th->cwr)
289                 skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;
290 
291         return 0;
292 }
293 EXPORT_SYMBOL(tcp_gro_complete);
294 
295 static struct sk_buff **tcp4_gro_receive(struct sk_buff **head, struct sk_buff *skb)
296 {
297         /* Don't bother verifying checksum if we're going to flush anyway. */
298         if (!NAPI_GRO_CB(skb)->flush &&
299             skb_gro_checksum_validate(skb, IPPROTO_TCP,
300                                       inet_gro_compute_pseudo)) {
301                 NAPI_GRO_CB(skb)->flush = 1;
302                 return NULL;
303         }
304 
305         return tcp_gro_receive(head, skb);
306 }
307 
308 static int tcp4_gro_complete(struct sk_buff *skb, int thoff)
309 {
310         const struct iphdr *iph = ip_hdr(skb);
311         struct tcphdr *th = tcp_hdr(skb);
312 
313         th->check = ~tcp_v4_check(skb->len - thoff, iph->saddr,
314                                   iph->daddr, 0);
315         skb_shinfo(skb)->gso_type |= SKB_GSO_TCPV4;
316 
317         return tcp_gro_complete(skb);
318 }
319 
320 static const struct net_offload tcpv4_offload = {
321         .callbacks = {
322                 .gso_segment    =       tcp4_gso_segment,
323                 .gro_receive    =       tcp4_gro_receive,
324                 .gro_complete   =       tcp4_gro_complete,
325         },
326 };
327 
328 int __init tcpv4_offload_init(void)
329 {
330         return inet_add_offload(&tcpv4_offload, IPPROTO_TCP);
331 }
332 

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