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 __constant_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)
  70                         return false;
  71
  72                 if (ip_is_fragment(iph))
  73                         ip_proto = 0;
  74                 else
  75                         ip_proto = iph->protocol;
  76                 iph_to_flow_copy_addrs(flow, iph);
  77                 nhoff += iph->ihl * 4;
  78                 break;
  79         }
  80         case __constant_htons(ETH_P_IPV6): {
  81                 const struct ipv6hdr *iph;
  82                 struct ipv6hdr _iph;
  83 ipv6:
  84                 iph = skb_header_pointer(skb, nhoff, sizeof(_iph), &_iph);
  85                 if (!iph)
  86                         return false;
  87
  88                 ip_proto = iph->nexthdr;
  89                 flow->src = (__force __be32)ipv6_addr_hash(&iph->saddr);
  90                 flow->dst = (__force __be32)ipv6_addr_hash(&iph->daddr);
  91                 nhoff += sizeof(struct ipv6hdr);
  92                 break;
  93         }
  94         case __constant_htons(ETH_P_8021AD):
  95         case __constant_htons(ETH_P_8021Q): {
  96                 const struct vlan_hdr *vlan;
  97                 struct vlan_hdr _vlan;
  98
  99                 vlan = skb_header_pointer(skb, nhoff, sizeof(_vlan), &_vlan);
 100                 if (!vlan)
 101                         return false;
 102
 103                 proto = vlan->h_vlan_encapsulated_proto;
 104                 nhoff += sizeof(*vlan);
 105                 goto again;
 106         }
 107         case __constant_htons(ETH_P_PPP_SES): {
 108                 struct {
 109                         struct pppoe_hdr hdr;
 110                         __be16 proto;
 111                 } *hdr, _hdr;
 112                 hdr = skb_header_pointer(skb, nhoff, sizeof(_hdr), &_hdr);
 113                 if (!hdr)
 114                         return false;
 115                 proto = hdr->proto;
 116                 nhoff += PPPOE_SES_HLEN;
 117                 switch (proto) {
 118                 case __constant_htons(PPP_IP):
 119                         goto ip;
 120                 case __constant_htons(PPP_IPV6):
 121                         goto ipv6;
 122                 default:
 123                         return false;
 124                 }
 125         }
 126         default:
 127                 return false;
 128         }
 129
 130         switch (ip_proto) {
 131         case IPPROTO_GRE: {
 132                 struct gre_hdr {
 133                         __be16 flags;
 134                         __be16 proto;
 135                 } *hdr, _hdr;
 136
 137                 hdr = skb_header_pointer(skb, nhoff, sizeof(_hdr), &_hdr);
 138                 if (!hdr)
 139                         return false;
 140                 /*
 141                  * Only look inside GRE if version zero and no
 142                  * routing
 143                  */
 144                 if (!(hdr->flags & (GRE_VERSION|GRE_ROUTING))) {
 145                         proto = hdr->proto;
 146                         nhoff += 4;
 147                         if (hdr->flags & GRE_CSUM)
 148                                 nhoff += 4;
 149                         if (hdr->flags & GRE_KEY)
 150                                 nhoff += 4;
 151                         if (hdr->flags & GRE_SEQ)
 152                                 nhoff += 4;
 153                         if (proto == htons(ETH_P_TEB)) {
 154                                 const struct ethhdr *eth;
 155                                 struct ethhdr _eth;
 156
 157                                 eth = skb_header_pointer(skb, nhoff,
 158                                                          sizeof(_eth), &_eth);
 159                                 if (!eth)
 160                                         return false;
 161                                 proto = eth->h_proto;
 162                                 nhoff += sizeof(*eth);
 163                         }
 164                         goto again;
 165                 }
 166                 break;
 167         }
 168         case IPPROTO_IPIP:
 169                 proto = htons(ETH_P_IP);
 170                 goto ip;
 171         case IPPROTO_IPV6:
 172                 proto = htons(ETH_P_IPV6);
 173                 goto ipv6;
 174         default:
 175                 break;
 176         }
 177
 178         flow->ip_proto = ip_proto;
 179         flow->ports = skb_flow_get_ports(skb, nhoff, ip_proto);
 180         flow->thoff = (u16) nhoff;
 181
 182         return true;
 183 }
 184 EXPORT_SYMBOL(skb_flow_dissect);
 185
 186 static u32 hashrnd __read_mostly;
 187
 188 /*
 189  * __skb_get_rxhash: calculate a flow hash based on src/dst addresses
 190  * and src/dst port numbers.  Sets rxhash in skb to non-zero hash value
 191  * on success, zero indicates no valid hash.  Also, sets l4_rxhash in skb
 192  * if hash is a canonical 4-tuple hash over transport ports.
 193  */
 194 void __skb_get_rxhash(struct sk_buff *skb)
 195 {
 196         struct flow_keys keys;
 197         u32 hash;
 198
 199         if (!skb_flow_dissect(skb, &keys))
 200                 return;
 201
 202         if (keys.ports)
 203                 skb->l4_rxhash = 1;
 204
 205         /* get a consistent hash (same value on both flow directions) */
 206         if (((__force u32)keys.dst < (__force u32)keys.src) ||
 207             (((__force u32)keys.dst == (__force u32)keys.src) &&
 208              ((__force u16)keys.port16[1] < (__force u16)keys.port16[0]))) {
 209                 swap(keys.dst, keys.src);
 210                 swap(keys.port16[0], keys.port16[1]);
 211         }
 212
 213         hash = jhash_3words((__force u32)keys.dst,
 214                             (__force u32)keys.src,
 215                             (__force u32)keys.ports, hashrnd);
 216         if (!hash)
 217                 hash = 1;
 218
 219         skb->rxhash = hash;
 220 }
 221 EXPORT_SYMBOL(__skb_get_rxhash);
 222
 223 /*
 224  * Returns a Tx hash based on the given packet descriptor a Tx queues' number
 225  * to be used as a distribution range.
 226  */
 227 u16 __skb_tx_hash(const struct net_device *dev, const struct sk_buff *skb,
 228                   unsigned int num_tx_queues)
 229 {
 230         u32 hash;
 231         u16 qoffset = 0;
 232         u16 qcount = num_tx_queues;
 233
 234         if (skb_rx_queue_recorded(skb)) {
 235                 hash = skb_get_rx_queue(skb);
 236                 while (unlikely(hash >= num_tx_queues))
 237                         hash -= num_tx_queues;
 238                 return hash;
 239         }
 240
 241         if (dev->num_tc) {
 242                 u8 tc = netdev_get_prio_tc_map(dev, skb->priority);
 243                 qoffset = dev->tc_to_txq[tc].offset;
 244                 qcount = dev->tc_to_txq[tc].count;
 245         }
 246
 247         if (skb->sk && skb->sk->sk_hash)
 248                 hash = skb->sk->sk_hash;
 249         else
 250                 hash = (__force u16) skb->protocol;
 251         hash = jhash_1word(hash, hashrnd);
 252
 253         return (u16) (((u64) hash * qcount) >> 32) + qoffset;
 254 }
 255 EXPORT_SYMBOL(__skb_tx_hash);
 256
 257 /* __skb_get_poff() returns the offset to the payload as far as it could
 258  * be dissected. The main user is currently BPF, so that we can dynamically
 259  * truncate packets without needing to push actual payload to the user
 260  * space and can analyze headers only, instead.
 261  */
 262 u32 __skb_get_poff(const struct sk_buff *skb)
 263 {
 264         struct flow_keys keys;
 265         u32 poff = 0;
 266
 267         if (!skb_flow_dissect(skb, &keys))
 268                 return 0;
 269
 270         poff += keys.thoff;
 271         switch (keys.ip_proto) {
 272         case IPPROTO_TCP: {
 273                 const struct tcphdr *tcph;
 274                 struct tcphdr _tcph;
 275
 276                 tcph = skb_header_pointer(skb, poff, sizeof(_tcph), &_tcph);
 277                 if (!tcph)
 278                         return poff;
 279
 280                 poff += max_t(u32, sizeof(struct tcphdr), tcph->doff * 4);
 281                 break;
 282         }
 283         case IPPROTO_UDP:
 284         case IPPROTO_UDPLITE:
 285                 poff += sizeof(struct udphdr);
 286                 break;
 287         /* For the rest, we do not really care about header
 288          * extensions at this point for now.
 289          */
 290         case IPPROTO_ICMP:
 291                 poff += sizeof(struct icmphdr);
 292                 break;
 293         case IPPROTO_ICMPV6:
 294                 poff += sizeof(struct icmp6hdr);
 295                 break;
 296         case IPPROTO_IGMP:
 297                 poff += sizeof(struct igmphdr);
 298                 break;
 299         case IPPROTO_DCCP:
 300                 poff += sizeof(struct dccp_hdr);
 301                 break;
 302         case IPPROTO_SCTP:
 303                 poff += sizeof(struct sctphdr);
 304                 break;
 305         }
 306
 307         return poff;
 308 }
 309
 310 static inline u16 dev_cap_txqueue(struct net_device *dev, u16 queue_index)
 311 {
 312         if (unlikely(queue_index >= dev->real_num_tx_queues)) {
 313                 net_warn_ratelimited("%s selects TX queue %d, but real number of TX queues is %d\n",
 314                                      dev->name, queue_index,
 315                                      dev->real_num_tx_queues);
 316                 return 0;
 317         }
 318         return queue_index;
 319 }
 320
 321 static inline int get_xps_queue(struct net_device *dev, struct sk_buff *skb)
 322 {
 323 #ifdef CONFIG_XPS
 324         struct xps_dev_maps *dev_maps;
 325         struct xps_map *map;
 326         int queue_index = -1;
 327
 328         rcu_read_lock();
 329         dev_maps = rcu_dereference(dev->xps_maps);
 330         if (dev_maps) {
 331                 map = rcu_dereference(
 332                     dev_maps->cpu_map[raw_smp_processor_id()]);
 333                 if (map) {
 334                         if (map->len == 1)
 335                                 queue_index = map->queues[0];
 336                         else {
 337                                 u32 hash;
 338                                 if (skb->sk && skb->sk->sk_hash)
 339                                         hash = skb->sk->sk_hash;
 340                                 else
 341                                         hash = (__force u16) skb->protocol ^
 342                                             skb->rxhash;
 343                                 hash = jhash_1word(hash, hashrnd);
 344                                 queue_index = map->queues[
 345                                     ((u64)hash * map->len) >> 32];
 346                         }
 347                         if (unlikely(queue_index >= dev->real_num_tx_queues))
 348                                 queue_index = -1;
 349                 }
 350         }
 351         rcu_read_unlock();
 352
 353         return queue_index;
 354 #else
 355         return -1;
 356 #endif
 357 }
 358
 359 u16 __netdev_pick_tx(struct net_device *dev, struct sk_buff *skb)
 360 {
 361         struct sock *sk = skb->sk;
 362         int queue_index = sk_tx_queue_get(sk);
 363
 364         if (queue_index < 0 || skb->ooo_okay ||
 365             queue_index >= dev->real_num_tx_queues) {
 366                 int new_index = get_xps_queue(dev, skb);
 367                 if (new_index < 0)
 368                         new_index = skb_tx_hash(dev, skb);
 369
 370                 if (queue_index != new_index && sk &&
 371                     rcu_access_pointer(sk->sk_dst_cache))
 372                         sk_tx_queue_set(sk, new_index);
 373
 374                 queue_index = new_index;
 375         }
 376
 377         return queue_index;
 378 }
 379 EXPORT_SYMBOL(__netdev_pick_tx);
 380
 381 struct netdev_queue *netdev_pick_tx(struct net_device *dev,
 382                                     struct sk_buff *skb)
 383 {
 384         int queue_index = 0;
 385
 386         if (dev->real_num_tx_queues != 1) {
 387                 const struct net_device_ops *ops = dev->netdev_ops;
 388                 if (ops->ndo_select_queue)
 389                         queue_index = ops->ndo_select_queue(dev, skb);
 390                 else
 391                         queue_index = __netdev_pick_tx(dev, skb);
 392                 queue_index = dev_cap_txqueue(dev, queue_index);
 393         }
 394
 395         skb_set_queue_mapping(skb, queue_index);
 396         return netdev_get_tx_queue(dev, queue_index);
 397 }
 398
 399 static int __init initialize_hashrnd(void)
 400 {
 401         get_random_bytes(&hashrnd, sizeof(hashrnd));
 402         return 0;
 403 }
 404
 405 late_initcall_sync(initialize_hashrnd);