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 /**
  29  * skb_flow_get_ports - extract the upper layer ports and return them
  30  * @skb: buffer to extract the ports from
  31  * @thoff: transport header offset
  32  * @ip_proto: protocol for which to get port offset
  33  *
  34  * The function will try to retrieve the ports at offset thoff + poff where poff
  35  * is the protocol port offset returned from proto_ports_offset
  36  */
  37 __be32 skb_flow_get_ports(const struct sk_buff *skb, int thoff, u8 ip_proto)
  38 {
  39         int poff = proto_ports_offset(ip_proto);
  40
  41         if (poff >= 0) {
  42                 __be32 *ports, _ports;
  43
  44                 ports = skb_header_pointer(skb, thoff + poff,
  45                                            sizeof(_ports), &_ports);
  46                 if (ports)
  47                         return *ports;
  48         }
  49
  50         return 0;
  51 }
  52 EXPORT_SYMBOL(skb_flow_get_ports);
  53
  54 bool skb_flow_dissect(const struct sk_buff *skb, struct flow_keys *flow)
  55 {
  56         int nhoff = skb_network_offset(skb);
  57         u8 ip_proto;
  58         __be16 proto = skb->protocol;
  59
  60         memset(flow, 0, sizeof(*flow));
  61
  62 again:
  63         switch (proto) {
  64         case htons(ETH_P_IP): {
  65                 const struct iphdr *iph;
  66                 struct iphdr _iph;
  67 ip:
  68                 iph = skb_header_pointer(skb, nhoff, sizeof(_iph), &_iph);
  69                 if (!iph || iph->ihl < 5)
  70                         return false;
  71                 nhoff += iph->ihl * 4;
  72
  73                 ip_proto = iph->protocol;
  74                 if (ip_is_fragment(iph))
  75                         ip_proto = 0;
  76
  77                 iph_to_flow_copy_addrs(flow, iph);
  78                 break;
  79         }
  80         case htons(ETH_P_IPV6): {
  81                 const struct ipv6hdr *iph;
  82                 struct ipv6hdr _iph;
  83                 __be32 flow_label;
  84
  85 ipv6:
  86                 iph = skb_header_pointer(skb, nhoff, sizeof(_iph), &_iph);
  87                 if (!iph)
  88                         return false;
  89
  90                 ip_proto = iph->nexthdr;
  91                 flow->src = (__force __be32)ipv6_addr_hash(&iph->saddr);
  92                 flow->dst = (__force __be32)ipv6_addr_hash(&iph->daddr);
  93                 nhoff += sizeof(struct ipv6hdr);
  94
  95                 flow_label = ip6_flowlabel(iph);
  96                 if (flow_label) {
  97                         /* Awesome, IPv6 packet has a flow label so we can
  98                          * use that to represent the ports without any
  99                          * further dissection.
 100                          */
 101                         flow->n_proto = proto;
 102                         flow->ip_proto = ip_proto;
 103                         flow->ports = flow_label;
 104                         flow->thoff = (u16)nhoff;
 105
 106                         return true;
 107                 }
 108
 109                 break;
 110         }
 111         case htons(ETH_P_8021AD):
 112         case htons(ETH_P_8021Q): {
 113                 const struct vlan_hdr *vlan;
 114                 struct vlan_hdr _vlan;
 115
 116                 vlan = skb_header_pointer(skb, nhoff, sizeof(_vlan), &_vlan);
 117                 if (!vlan)
 118                         return false;
 119
 120                 proto = vlan->h_vlan_encapsulated_proto;
 121                 nhoff += sizeof(*vlan);
 122                 goto again;
 123         }
 124         case htons(ETH_P_PPP_SES): {
 125                 struct {
 126                         struct pppoe_hdr hdr;
 127                         __be16 proto;
 128                 } *hdr, _hdr;
 129                 hdr = skb_header_pointer(skb, nhoff, sizeof(_hdr), &_hdr);
 130                 if (!hdr)
 131                         return false;
 132                 proto = hdr->proto;
 133                 nhoff += PPPOE_SES_HLEN;
 134                 switch (proto) {
 135                 case htons(PPP_IP):
 136                         goto ip;
 137                 case htons(PPP_IPV6):
 138                         goto ipv6;
 139                 default:
 140                         return false;
 141                 }
 142         }
 143         default:
 144                 return false;
 145         }
 146
 147         switch (ip_proto) {
 148         case IPPROTO_GRE: {
 149                 struct gre_hdr {
 150                         __be16 flags;
 151                         __be16 proto;
 152                 } *hdr, _hdr;
 153
 154                 hdr = skb_header_pointer(skb, nhoff, sizeof(_hdr), &_hdr);
 155                 if (!hdr)
 156                         return false;
 157                 /*
 158                  * Only look inside GRE if version zero and no
 159                  * routing
 160                  */
 161                 if (!(hdr->flags & (GRE_VERSION|GRE_ROUTING))) {
 162                         proto = hdr->proto;
 163                         nhoff += 4;
 164                         if (hdr->flags & GRE_CSUM)
 165                                 nhoff += 4;
 166                         if (hdr->flags & GRE_KEY)
 167                                 nhoff += 4;
 168                         if (hdr->flags & GRE_SEQ)
 169                                 nhoff += 4;
 170                         if (proto == htons(ETH_P_TEB)) {
 171                                 const struct ethhdr *eth;
 172                                 struct ethhdr _eth;
 173
 174                                 eth = skb_header_pointer(skb, nhoff,
 175                                                          sizeof(_eth), &_eth);
 176                                 if (!eth)
 177                                         return false;
 178                                 proto = eth->h_proto;
 179                                 nhoff += sizeof(*eth);
 180                         }
 181                         goto again;
 182                 }
 183                 break;
 184         }
 185         case IPPROTO_IPIP:
 186                 proto = htons(ETH_P_IP);
 187                 goto ip;
 188         case IPPROTO_IPV6:
 189                 proto = htons(ETH_P_IPV6);
 190                 goto ipv6;
 191         default:
 192                 break;
 193         }
 194
 195         flow->n_proto = proto;
 196         flow->ip_proto = ip_proto;
 197         flow->ports = skb_flow_get_ports(skb, nhoff, ip_proto);
 198         flow->thoff = (u16) nhoff;
 199
 200         return true;
 201 }
 202 EXPORT_SYMBOL(skb_flow_dissect);
 203
 204 static u32 hashrnd __read_mostly;
 205 static __always_inline void __flow_hash_secret_init(void)
 206 {
 207         net_get_random_once(&hashrnd, sizeof(hashrnd));
 208 }
 209
 210 static __always_inline u32 __flow_hash_3words(u32 a, u32 b, u32 c)
 211 {
 212         __flow_hash_secret_init();
 213         return jhash_3words(a, b, c, hashrnd);
 214 }
 215
 216 static inline u32 __flow_hash_from_keys(struct flow_keys *keys)
 217 {
 218         u32 hash;
 219
 220         /* get a consistent hash (same value on both flow directions) */
 221         if (((__force u32)keys->dst < (__force u32)keys->src) ||
 222             (((__force u32)keys->dst == (__force u32)keys->src) &&
 223              ((__force u16)keys->port16[1] < (__force u16)keys->port16[0]))) {
 224                 swap(keys->dst, keys->src);
 225                 swap(keys->port16[0], keys->port16[1]);
 226         }
 227
 228         hash = __flow_hash_3words((__force u32)keys->dst,
 229                                   (__force u32)keys->src,
 230                                   (__force u32)keys->ports);
 231         if (!hash)
 232                 hash = 1;
 233
 234         return hash;
 235 }
 236
 237 u32 flow_hash_from_keys(struct flow_keys *keys)
 238 {
 239         return __flow_hash_from_keys(keys);
 240 }
 241 EXPORT_SYMBOL(flow_hash_from_keys);
 242
 243 /*
 244  * __skb_get_hash: calculate a flow hash based on src/dst addresses
 245  * and src/dst port numbers.  Sets hash in skb to non-zero hash value
 246  * on success, zero indicates no valid hash.  Also, sets l4_hash in skb
 247  * if hash is a canonical 4-tuple hash over transport ports.
 248  */
 249 void __skb_get_hash(struct sk_buff *skb)
 250 {
 251         struct flow_keys keys;
 252
 253         if (!skb_flow_dissect(skb, &keys))
 254                 return;
 255
 256         if (keys.ports)
 257                 skb->l4_hash = 1;
 258
 259         skb->sw_hash = 1;
 260
 261         skb->hash = __flow_hash_from_keys(&keys);
 262 }
 263 EXPORT_SYMBOL(__skb_get_hash);
 264
 265 /*
 266  * Returns a Tx hash based on the given packet descriptor a Tx queues' number
 267  * to be used as a distribution range.
 268  */
 269 u16 __skb_tx_hash(const struct net_device *dev, struct sk_buff *skb,
 270                   unsigned int num_tx_queues)
 271 {
 272         u32 hash;
 273         u16 qoffset = 0;
 274         u16 qcount = num_tx_queues;
 275
 276         if (skb_rx_queue_recorded(skb)) {
 277                 hash = skb_get_rx_queue(skb);
 278                 while (unlikely(hash >= num_tx_queues))
 279                         hash -= num_tx_queues;
 280                 return hash;
 281         }
 282
 283         if (dev->num_tc) {
 284                 u8 tc = netdev_get_prio_tc_map(dev, skb->priority);
 285                 qoffset = dev->tc_to_txq[tc].offset;
 286                 qcount = dev->tc_to_txq[tc].count;
 287         }
 288
 289         return (u16) (((u64)skb_get_hash(skb) * qcount) >> 32) + qoffset;
 290 }
 291 EXPORT_SYMBOL(__skb_tx_hash);
 292
 293 /* __skb_get_poff() returns the offset to the payload as far as it could
 294  * be dissected. The main user is currently BPF, so that we can dynamically
 295  * truncate packets without needing to push actual payload to the user
 296  * space and can analyze headers only, instead.
 297  */
 298 u32 __skb_get_poff(const struct sk_buff *skb)
 299 {
 300         struct flow_keys keys;
 301         u32 poff = 0;
 302
 303         if (!skb_flow_dissect(skb, &keys))
 304                 return 0;
 305
 306         poff += keys.thoff;
 307         switch (keys.ip_proto) {
 308         case IPPROTO_TCP: {
 309                 const struct tcphdr *tcph;
 310                 struct tcphdr _tcph;
 311
 312                 tcph = skb_header_pointer(skb, poff, sizeof(_tcph), &_tcph);
 313                 if (!tcph)
 314                         return poff;
 315
 316                 poff += max_t(u32, sizeof(struct tcphdr), tcph->doff * 4);
 317                 break;
 318         }
 319         case IPPROTO_UDP:
 320         case IPPROTO_UDPLITE:
 321                 poff += sizeof(struct udphdr);
 322                 break;
 323         /* For the rest, we do not really care about header
 324          * extensions at this point for now.
 325          */
 326         case IPPROTO_ICMP:
 327                 poff += sizeof(struct icmphdr);
 328                 break;
 329         case IPPROTO_ICMPV6:
 330                 poff += sizeof(struct icmp6hdr);
 331                 break;
 332         case IPPROTO_IGMP:
 333                 poff += sizeof(struct igmphdr);
 334                 break;
 335         case IPPROTO_DCCP:
 336                 poff += sizeof(struct dccp_hdr);
 337                 break;
 338         case IPPROTO_SCTP:
 339                 poff += sizeof(struct sctphdr);
 340                 break;
 341         }
 342
 343         return poff;
 344 }
 345
 346 static inline int get_xps_queue(struct net_device *dev, struct sk_buff *skb)
 347 {
 348 #ifdef CONFIG_XPS
 349         struct xps_dev_maps *dev_maps;
 350         struct xps_map *map;
 351         int queue_index = -1;
 352
 353         rcu_read_lock();
 354         dev_maps = rcu_dereference(dev->xps_maps);
 355         if (dev_maps) {
 356                 map = rcu_dereference(
 357                     dev_maps->cpu_map[raw_smp_processor_id()]);
 358                 if (map) {
 359                         if (map->len == 1)
 360                                 queue_index = map->queues[0];
 361                         else
 362                                 queue_index = map->queues[
 363                                     ((u64)skb_get_hash(skb) * map->len) >> 32];
 364
 365                         if (unlikely(queue_index >= dev->real_num_tx_queues))
 366                                 queue_index = -1;
 367                 }
 368         }
 369         rcu_read_unlock();
 370
 371         return queue_index;
 372 #else
 373         return -1;
 374 #endif
 375 }
 376
 377 static u16 __netdev_pick_tx(struct net_device *dev, struct sk_buff *skb)
 378 {
 379         struct sock *sk = skb->sk;
 380         int queue_index = sk_tx_queue_get(sk);
 381
 382         if (queue_index < 0 || skb->ooo_okay ||
 383             queue_index >= dev->real_num_tx_queues) {
 384                 int new_index = get_xps_queue(dev, skb);
 385                 if (new_index < 0)
 386                         new_index = skb_tx_hash(dev, skb);
 387
 388                 if (queue_index != new_index && sk &&
 389                     rcu_access_pointer(sk->sk_dst_cache))
 390                         sk_tx_queue_set(sk, new_index);
 391
 392                 queue_index = new_index;
 393         }
 394
 395         return queue_index;
 396 }
 397
 398 struct netdev_queue *netdev_pick_tx(struct net_device *dev,
 399                                     struct sk_buff *skb,
 400                                     void *accel_priv)
 401 {
 402         int queue_index = 0;
 403
 404         if (dev->real_num_tx_queues != 1) {
 405                 const struct net_device_ops *ops = dev->netdev_ops;
 406                 if (ops->ndo_select_queue)
 407                         queue_index = ops->ndo_select_queue(dev, skb, accel_priv,
 408                                                             __netdev_pick_tx);
 409                 else
 410                         queue_index = __netdev_pick_tx(dev, skb);
 411
 412                 if (!accel_priv)
 413                         queue_index = netdev_cap_txqueue(dev, queue_index);
 414         }
 415
 416         skb_set_queue_mapping(skb, queue_index);
 417         return netdev_get_tx_queue(dev, queue_index);
 418 }