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/if_tunnel.h>
   9 #include <linux/if_pppox.h>
  10 #include <linux/ppp_defs.h>
  11 #include <net/flow_keys.h>
  12
  13 /* copy saddr & daddr, possibly using 64bit load/store
  14  * Equivalent to :      flow->src = iph->saddr;
  15  *                      flow->dst = iph->daddr;
  16  */
  17 static void iph_to_flow_copy_addrs(struct flow_keys *flow, const struct iphdr *iph)
  18 {
  19         BUILD_BUG_ON(offsetof(typeof(*flow), dst) !=
  20                      offsetof(typeof(*flow), src) + sizeof(flow->src));
  21         memcpy(&flow->src, &iph->saddr, sizeof(flow->src) + sizeof(flow->dst));
  22 }
  23
  24 bool skb_flow_dissect(const struct sk_buff *skb, struct flow_keys *flow)
  25 {
  26         int poff, nhoff = skb_network_offset(skb);
  27         u8 ip_proto;
  28         __be16 proto = skb->protocol;
  29
  30         memset(flow, 0, sizeof(*flow));
  31
  32 again:
  33         switch (proto) {
  34         case __constant_htons(ETH_P_IP): {
  35                 const struct iphdr *iph;
  36                 struct iphdr _iph;
  37 ip:
  38                 iph = skb_header_pointer(skb, nhoff, sizeof(_iph), &_iph);
  39                 if (!iph)
  40                         return false;
  41
  42                 if (ip_is_fragment(iph))
  43                         ip_proto = 0;
  44                 else
  45                         ip_proto = iph->protocol;
  46                 iph_to_flow_copy_addrs(flow, iph);
  47                 nhoff += iph->ihl * 4;
  48                 break;
  49         }
  50         case __constant_htons(ETH_P_IPV6): {
  51                 const struct ipv6hdr *iph;
  52                 struct ipv6hdr _iph;
  53 ipv6:
  54                 iph = skb_header_pointer(skb, nhoff, sizeof(_iph), &_iph);
  55                 if (!iph)
  56                         return false;
  57
  58                 ip_proto = iph->nexthdr;
  59                 flow->src = (__force __be32)ipv6_addr_hash(&iph->saddr);
  60                 flow->dst = (__force __be32)ipv6_addr_hash(&iph->daddr);
  61                 nhoff += sizeof(struct ipv6hdr);
  62                 break;
  63         }
  64         case __constant_htons(ETH_P_8021Q): {
  65                 const struct vlan_hdr *vlan;
  66                 struct vlan_hdr _vlan;
  67
  68                 vlan = skb_header_pointer(skb, nhoff, sizeof(_vlan), &_vlan);
  69                 if (!vlan)
  70                         return false;
  71
  72                 proto = vlan->h_vlan_encapsulated_proto;
  73                 nhoff += sizeof(*vlan);
  74                 goto again;
  75         }
  76         case __constant_htons(ETH_P_PPP_SES): {
  77                 struct {
  78                         struct pppoe_hdr hdr;
  79                         __be16 proto;
  80                 } *hdr, _hdr;
  81                 hdr = skb_header_pointer(skb, nhoff, sizeof(_hdr), &_hdr);
  82                 if (!hdr)
  83                         return false;
  84                 proto = hdr->proto;
  85                 nhoff += PPPOE_SES_HLEN;
  86                 switch (proto) {
  87                 case __constant_htons(PPP_IP):
  88                         goto ip;
  89                 case __constant_htons(PPP_IPV6):
  90                         goto ipv6;
  91                 default:
  92                         return false;
  93                 }
  94         }
  95         default:
  96                 return false;
  97         }
  98
  99         switch (ip_proto) {
 100         case IPPROTO_GRE: {
 101                 struct gre_hdr {
 102                         __be16 flags;
 103                         __be16 proto;
 104                 } *hdr, _hdr;
 105
 106                 hdr = skb_header_pointer(skb, nhoff, sizeof(_hdr), &_hdr);
 107                 if (!hdr)
 108                         return false;
 109                 /*
 110                  * Only look inside GRE if version zero and no
 111                  * routing
 112                  */
 113                 if (!(hdr->flags & (GRE_VERSION|GRE_ROUTING))) {
 114                         proto = hdr->proto;
 115                         nhoff += 4;
 116                         if (hdr->flags & GRE_CSUM)
 117                                 nhoff += 4;
 118                         if (hdr->flags & GRE_KEY)
 119                                 nhoff += 4;
 120                         if (hdr->flags & GRE_SEQ)
 121                                 nhoff += 4;
 122                         goto again;
 123                 }
 124                 break;
 125         }
 126         case IPPROTO_IPIP:
 127                 goto again;
 128         default:
 129                 break;
 130         }
 131
 132         flow->ip_proto = ip_proto;
 133         poff = proto_ports_offset(ip_proto);
 134         if (poff >= 0) {
 135                 __be32 *ports, _ports;
 136
 137                 nhoff += poff;
 138                 ports = skb_header_pointer(skb, nhoff, sizeof(_ports), &_ports);
 139                 if (ports)
 140                         flow->ports = *ports;
 141         }
 142
 143         return true;
 144 }
 145 EXPORT_SYMBOL(skb_flow_dissect);