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 tcp_flag_word(th2) |= flags & (TCP_FLAG_FIN | TCP_FLAG_PSH); 272 273 out_check_final: 274 flush = len < mss; 275 flush |= (__force int)(flags & (TCP_FLAG_URG | TCP_FLAG_PSH | 276 TCP_FLAG_RST | TCP_FLAG_SYN | 277 TCP_FLAG_FIN)); 278 279 if (p && (!NAPI_GRO_CB(skb)->same_flow || flush)) 280 pp = head; 281 282 out: 283 NAPI_GRO_CB(skb)->flush |= (flush != 0); 284 285 return pp; 286 } 287 288 int tcp_gro_complete(struct sk_buff *skb) 289 { 290 struct tcphdr *th = tcp_hdr(skb); 291 292 skb->csum_start = (unsigned char *)th - skb->head; 293 skb->csum_offset = offsetof(struct tcphdr, check); 294 skb->ip_summed = CHECKSUM_PARTIAL; 295 296 skb_shinfo(skb)->gso_segs = NAPI_GRO_CB(skb)->count; 297 298 if (th->cwr) 299 skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN; 300 301 return 0; 302 } 303 EXPORT_SYMBOL(tcp_gro_complete); 304 305 static struct sk_buff **tcp4_gro_receive(struct sk_buff **head, struct sk_buff *skb) 306 { 307 /* Don't bother verifying checksum if we're going to flush anyway. */ 308 if (!NAPI_GRO_CB(skb)->flush && 309 skb_gro_checksum_validate(skb, IPPROTO_TCP, 310 inet_gro_compute_pseudo)) { 311 NAPI_GRO_CB(skb)->flush = 1; 312 return NULL; 313 } 314 315 return tcp_gro_receive(head, skb); 316 } 317 318 static int tcp4_gro_complete(struct sk_buff *skb, int thoff) 319 { 320 const struct iphdr *iph = ip_hdr(skb); 321 struct tcphdr *th = tcp_hdr(skb); 322 323 th->check = ~tcp_v4_check(skb->len - thoff, iph->saddr, 324 iph->daddr, 0); 325 skb_shinfo(skb)->gso_type |= SKB_GSO_TCPV4; 326 327 if (NAPI_GRO_CB(skb)->is_atomic) 328 skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_FIXEDID; 329 330 return tcp_gro_complete(skb); 331 } 332 333 static const struct net_offload tcpv4_offload = { 334 .callbacks = { 335 .gso_segment = tcp4_gso_segment, 336 .gro_receive = tcp4_gro_receive, 337 .gro_complete = tcp4_gro_complete, 338 }, 339 }; 340 341 int __init tcpv4_offload_init(void) 342 { 343 return inet_add_offload(&tcpv4_offload, IPPROTO_TCP); 344 } 345