net/core/flow_dissector.c

   1 #include <linux/skbuff.h>
   2 #include <linux/export.h>
   3 #include <linux/ip.h>
   4 #include <linux/ipv6.h>
   5 #include <linux/if_vlan.h>
   6 #include <net/ip.h>
   7 #include <net/ipv6.h>
   8 #include <linux/igmp.h>
   9 #include <linux/icmp.h>
  10 #include <linux/sctp.h>
  11 #include <linux/dccp.h>
  12 #include <linux/if_tunnel.h>
  13 #include <linux/if_pppox.h>
  14 #include <linux/ppp_defs.h>
  15 #include <net/flow_keys.h>
  16
  17 /* copy saddr & daddr, possibly using 64bit load/store
  18  * Equivalent to :      flow->src = iph->saddr;
  19  *                      flow->dst = iph->daddr;
  20  */
  21 static void iph_to_flow_copy_addrs(struct flow_keys *flow, const struct iphdr *iph)
  22 {
  23         BUILD_BUG_ON(offsetof(typeof(*flow), dst) !=
  24                      offsetof(typeof(*flow), src) + sizeof(flow->src));
  25         memcpy(&flow->src, &iph->saddr, sizeof(flow->src) + sizeof(flow->dst));
  26 }
  27
  28 bool skb_flow_dissect(const struct sk_buff *skb, struct flow_keys *flow)
  29 {
  30         int poff, nhoff = skb_network_offset(skb);
  31         u8 ip_proto;
  32         __be16 proto = skb->protocol;
  33
  34         memset(flow, 0, sizeof(*flow));
  35
  36 again:
  37         switch (proto) {
  38         case __constant_htons(ETH_P_IP): {
  39                 const struct iphdr *iph;
  40                 struct iphdr _iph;
  41 ip:
  42                 iph = skb_header_pointer(skb, nhoff, sizeof(_iph), &_iph);
  43                 if (!iph)
  44                         return false;
  45
  46                 if (ip_is_fragment(iph))
  47                         ip_proto = 0;
  48                 else
  49                         ip_proto = iph->protocol;
  50                 iph_to_flow_copy_addrs(flow, iph);
  51                 nhoff += iph->ihl * 4;
  52                 break;
  53         }
  54         case __constant_htons(ETH_P_IPV6): {
  55                 const struct ipv6hdr *iph;
  56                 struct ipv6hdr _iph;
  57 ipv6:
  58                 iph = skb_header_pointer(skb, nhoff, sizeof(_iph), &_iph);
  59                 if (!iph)
  60                         return false;
  61
  62                 ip_proto = iph->nexthdr;
  63                 flow->src = (__force __be32)ipv6_addr_hash(&iph->saddr);
  64                 flow->dst = (__force __be32)ipv6_addr_hash(&iph->daddr);
  65                 nhoff += sizeof(struct ipv6hdr);
  66                 break;
  67         }
  68         case __constant_htons(ETH_P_8021AD):
  69         case __constant_htons(ETH_P_8021Q): {
  70                 const struct vlan_hdr *vlan;
  71                 struct vlan_hdr _vlan;
  72
  73                 vlan = skb_header_pointer(skb, nhoff, sizeof(_vlan), &_vlan);
  74                 if (!vlan)
  75                         return false;
  76
  77                 proto = vlan->h_vlan_encapsulated_proto;
  78                 nhoff += sizeof(*vlan);
  79                 goto again;
  80         }
  81         case __constant_htons(ETH_P_PPP_SES): {
  82                 struct {
  83                         struct pppoe_hdr hdr;
  84                         __be16 proto;
  85                 } *hdr, _hdr;
  86                 hdr = skb_header_pointer(skb, nhoff, sizeof(_hdr), &_hdr);
  87                 if (!hdr)
  88                         return false;
  89                 proto = hdr->proto;
  90                 nhoff += PPPOE_SES_HLEN;
  91                 switch (proto) {
  92                 case __constant_htons(PPP_IP):
  93                         goto ip;
  94                 case __constant_htons(PPP_IPV6):
  95                         goto ipv6;
  96                 default:
  97                         return false;
  98                 }
  99         }
 100         default:
 101                 return false;
 102         }
 103
 104         switch (ip_proto) {
 105         case IPPROTO_GRE: {
 106                 struct gre_hdr {
 107                         __be16 flags;
 108                         __be16 proto;
 109                 } *hdr, _hdr;
 110
 111                 hdr = skb_header_pointer(skb, nhoff, sizeof(_hdr), &_hdr);
 112                 if (!hdr)
 113                         return false;
 114                 /*
 115                  * Only look inside GRE if version zero and no
 116                  * routing
 117                  */
 118                 if (!(hdr->flags & (GRE_VERSION|GRE_ROUTING))) {
 119                         proto = hdr->proto;
 120                         nhoff += 4;
 121                         if (hdr->flags & GRE_CSUM)
 122                                 nhoff += 4;
 123                         if (hdr->flags & GRE_KEY)
 124                                 nhoff += 4;
 125                         if (hdr->flags & GRE_SEQ)
 126                                 nhoff += 4;
 127                         if (proto == htons(ETH_P_TEB)) {
 128                                 const struct ethhdr *eth;
 129                                 struct ethhdr _eth;
 130
 131                                 eth = skb_header_pointer(skb, nhoff,
 132                                                          sizeof(_eth), &_eth);
 133                                 if (!eth)
 134                                         return false;
 135                                 proto = eth->h_proto;
 136                                 nhoff += sizeof(*eth);
 137                         }
 138                         goto again;
 139                 }
 140                 break;
 141         }
 142         case IPPROTO_IPIP:
 143                 proto = htons(ETH_P_IP);
 144                 goto ip;
 145         case IPPROTO_IPV6:
 146                 proto = htons(ETH_P_IPV6);
 147                 goto ipv6;
 148         default:
 149                 break;
 150         }
 151
 152         flow->ip_proto = ip_proto;
 153         poff = proto_ports_offset(ip_proto);
 154         if (poff >= 0) {
 155                 __be32 *ports, _ports;
 156
 157                 nhoff += poff;
 158                 ports = skb_header_pointer(skb, nhoff, sizeof(_ports), &_ports);
 159                 if (ports)
 160                         flow->ports = *ports;
 161         }
 162
 163         flow->thoff = (u16) nhoff;
 164
 165         return true;
 166 }
 167 EXPORT_SYMBOL(skb_flow_dissect);
 168
 169 static u32 hashrnd __read_mostly;
 170
 171 /*
 172  * __skb_get_rxhash: calculate a flow hash based on src/dst addresses
 173  * and src/dst port numbers.  Sets rxhash in skb to non-zero hash value
 174  * on success, zero indicates no valid hash.  Also, sets l4_rxhash in skb
 175  * if hash is a canonical 4-tuple hash over transport ports.
 176  */
 177 void __skb_get_rxhash(struct sk_buff *skb)
 178 {
 179         struct flow_keys keys;
 180         u32 hash;
 181
 182         if (!skb_flow_dissect(skb, &keys))
 183                 return;
 184
 185         if (keys.ports)
 186                 skb->l4_rxhash = 1;
 187
 188         /* get a consistent hash (same value on both flow directions) */
 189         if (((__force u32)keys.dst < (__force u32)keys.src) ||
 190             (((__force u32)keys.dst == (__force u32)keys.src) &&
 191              ((__force u16)keys.port16[1] < (__force u16)keys.port16[0]))) {
 192                 swap(keys.dst, keys.src);
 193                 swap(keys.port16[0], keys.port16[1]);
 194         }
 195
 196         hash = jhash_3words((__force u32)keys.dst,
 197                             (__force u32)keys.src,
 198                             (__force u32)keys.ports, hashrnd);
 199         if (!hash)
 200                 hash = 1;
 201
 202         skb->rxhash = hash;
 203 }
 204 EXPORT_SYMBOL(__skb_get_rxhash);
 205
 206 /*
 207  * Returns a Tx hash based on the given packet descriptor a Tx queues' number
 208  * to be used as a distribution range.
 209  */
 210 u16 __skb_tx_hash(const struct net_device *dev, const struct sk_buff *skb,
 211                   unsigned int num_tx_queues)
 212 {
 213         u32 hash;
 214         u16 qoffset = 0;
 215         u16 qcount = num_tx_queues;
 216
 217         if (skb_rx_queue_recorded(skb)) {
 218                 hash = skb_get_rx_queue(skb);
 219                 while (unlikely(hash >= num_tx_queues))
 220                         hash -= num_tx_queues;
 221                 return hash;
 222         }
 223
 224         if (dev->num_tc) {
 225                 u8 tc = netdev_get_prio_tc_map(dev, skb->priority);
 226                 qoffset = dev->tc_to_txq[tc].offset;
 227                 qcount = dev->tc_to_txq[tc].count;
 228         }
 229
 230         if (skb->sk && skb->sk->sk_hash)
 231                 hash = skb->sk->sk_hash;
 232         else
 233                 hash = (__force u16) skb->protocol;
 234         hash = jhash_1word(hash, hashrnd);
 235
 236         return (u16) (((u64) hash * qcount) >> 32) + qoffset;
 237 }
 238 EXPORT_SYMBOL(__skb_tx_hash);
 239
 240 /* __skb_get_poff() returns the offset to the payload as far as it could
 241  * be dissected. The main user is currently BPF, so that we can dynamically
 242  * truncate packets without needing to push actual payload to the user
 243  * space and can analyze headers only, instead.
 244  */
 245 u32 __skb_get_poff(const struct sk_buff *skb)
 246 {
 247         struct flow_keys keys;
 248         u32 poff = 0;
 249
 250         if (!skb_flow_dissect(skb, &keys))
 251                 return 0;
 252
 253         poff += keys.thoff;
 254         switch (keys.ip_proto) {
 255         case IPPROTO_TCP: {
 256                 const struct tcphdr *tcph;
 257                 struct tcphdr _tcph;
 258
 259                 tcph = skb_header_pointer(skb, poff, sizeof(_tcph), &_tcph);
 260                 if (!tcph)
 261                         return poff;
 262
 263                 poff += max_t(u32, sizeof(struct tcphdr), tcph->doff * 4);
 264                 break;
 265         }
 266         case IPPROTO_UDP:
 267         case IPPROTO_UDPLITE:
 268                 poff += sizeof(struct udphdr);
 269                 break;
 270         /* For the rest, we do not really care about header
 271          * extensions at this point for now.
 272          */
 273         case IPPROTO_ICMP:
 274                 poff += sizeof(struct icmphdr);
 275                 break;
 276         case IPPROTO_ICMPV6:
 277                 poff += sizeof(struct icmp6hdr);
 278                 break;
 279         case IPPROTO_IGMP:
 280                 poff += sizeof(struct igmphdr);
 281                 break;
 282         case IPPROTO_DCCP:
 283                 poff += sizeof(struct dccp_hdr);
 284                 break;
 285         case IPPROTO_SCTP:
 286                 poff += sizeof(struct sctphdr);
 287                 break;
 288         }
 289
 290         return poff;
 291 }
 292
 293 static inline u16 dev_cap_txqueue(struct net_device *dev, u16 queue_index)
 294 {
 295         if (unlikely(queue_index >= dev->real_num_tx_queues)) {
 296                 net_warn_ratelimited("%s selects TX queue %d, but real number of TX queues is %d\n",
 297                                      dev->name, queue_index,
 298                                      dev->real_num_tx_queues);
 299                 return 0;
 300         }
 301         return queue_index;
 302 }
 303
 304 static inline int get_xps_queue(struct net_device *dev, struct sk_buff *skb)
 305 {
 306 #ifdef CONFIG_XPS
 307         struct xps_dev_maps *dev_maps;
 308         struct xps_map *map;
 309         int queue_index = -1;
 310
 311         rcu_read_lock();
 312         dev_maps = rcu_dereference(dev->xps_maps);
 313         if (dev_maps) {
 314                 map = rcu_dereference(
 315                     dev_maps->cpu_map[raw_smp_processor_id()]);
 316                 if (map) {
 317                         if (map->len == 1)
 318                                 queue_index = map->queues[0];
 319                         else {
 320                                 u32 hash;
 321                                 if (skb->sk && skb->sk->sk_hash)
 322                                         hash = skb->sk->sk_hash;
 323                                 else
 324                                         hash = (__force u16) skb->protocol ^
 325                                             skb->rxhash;
 326                                 hash = jhash_1word(hash, hashrnd);
 327                                 queue_index = map->queues[
 328                                     ((u64)hash * map->len) >> 32];
 329                         }
 330                         if (unlikely(queue_index >= dev->real_num_tx_queues))
 331                                 queue_index = -1;
 332                 }
 333         }
 334         rcu_read_unlock();
 335
 336         return queue_index;
 337 #else
 338         return -1;
 339 #endif
 340 }
 341
 342 u16 __netdev_pick_tx(struct net_device *dev, struct sk_buff *skb)
 343 {
 344         struct sock *sk = skb->sk;
 345         int queue_index = sk_tx_queue_get(sk);
 346
 347         if (queue_index < 0 || skb->ooo_okay ||
 348             queue_index >= dev->real_num_tx_queues) {
 349                 int new_index = get_xps_queue(dev, skb);
 350                 if (new_index < 0)
 351                         new_index = skb_tx_hash(dev, skb);
 352
 353                 if (queue_index != new_index && sk &&
 354                     rcu_access_pointer(sk->sk_dst_cache))
 355                         sk_tx_queue_set(sk, new_index);
 356
 357                 queue_index = new_index;
 358         }
 359
 360         return queue_index;
 361 }
 362 EXPORT_SYMBOL(__netdev_pick_tx);
 363
 364 struct netdev_queue *netdev_pick_tx(struct net_device *dev,
 365                                     struct sk_buff *skb)
 366 {
 367         int queue_index = 0;
 368
 369         if (dev->real_num_tx_queues != 1) {
 370                 const struct net_device_ops *ops = dev->netdev_ops;
 371                 if (ops->ndo_select_queue)
 372                         queue_index = ops->ndo_select_queue(dev, skb);
 373                 else
 374                         queue_index = __netdev_pick_tx(dev, skb);
 375                 queue_index = dev_cap_txqueue(dev, queue_index);
 376         }
 377
 378         skb_set_queue_mapping(skb, queue_index);
 379         return netdev_get_tx_queue(dev, queue_index);
 380 }
 381
 382 static int __init initialize_hashrnd(void)
 383 {
 384         get_random_bytes(&hashrnd, sizeof(hashrnd));
 385         return 0;
 386 }
 387
 388 late_initcall_sync(initialize_hashrnd);