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 <linux/if_tunnel.h>
   8 #include <linux/if_pppox.h>
   9 #include <linux/ppp_defs.h>
  10 #include <net/flow_keys.h>
  11
  12 /* copy saddr & daddr, possibly using 64bit load/store
  13  * Equivalent to :      flow->src = iph->saddr;
  14  *                      flow->dst = iph->daddr;
  15  */
  16 static void iph_to_flow_copy_addrs(struct flow_keys *flow, const struct iphdr *iph)
  17 {
  18         BUILD_BUG_ON(offsetof(typeof(*flow), dst) !=
  19                      offsetof(typeof(*flow), src) + sizeof(flow->src));
  20         memcpy(&flow->src, &iph->saddr, sizeof(flow->src) + sizeof(flow->dst));
  21 }
  22
  23 bool skb_flow_dissect(const struct sk_buff *skb, struct flow_keys *flow)
  24 {
  25         int poff, nhoff = skb_network_offset(skb);
  26         u8 ip_proto;
  27         __be16 proto = skb->protocol;
  28
  29         memset(flow, 0, sizeof(*flow));
  30
  31 again:
  32         switch (proto) {
  33         case __constant_htons(ETH_P_IP): {
  34                 const struct iphdr *iph;
  35                 struct iphdr _iph;
  36 ip:
  37                 iph = skb_header_pointer(skb, nhoff, sizeof(_iph), &_iph);
  38                 if (!iph)
  39                         return false;
  40
  41                 if (ip_is_fragment(iph))
  42                         ip_proto = 0;
  43                 else
  44                         ip_proto = iph->protocol;
  45                 iph_to_flow_copy_addrs(flow, iph);
  46                 nhoff += iph->ihl * 4;
  47                 break;
  48         }
  49         case __constant_htons(ETH_P_IPV6): {
  50                 const struct ipv6hdr *iph;
  51                 struct ipv6hdr _iph;
  52 ipv6:
  53                 iph = skb_header_pointer(skb, nhoff, sizeof(_iph), &_iph);
  54                 if (!iph)
  55                         return false;
  56
  57                 ip_proto = iph->nexthdr;
  58                 flow->src = iph->saddr.s6_addr32[3];
  59                 flow->dst = iph->daddr.s6_addr32[3];
  60                 nhoff += sizeof(struct ipv6hdr);
  61                 break;
  62         }
  63         case __constant_htons(ETH_P_8021Q): {
  64                 const struct vlan_hdr *vlan;
  65                 struct vlan_hdr _vlan;
  66
  67                 vlan = skb_header_pointer(skb, nhoff, sizeof(_vlan), &_vlan);
  68                 if (!vlan)
  69                         return false;
  70
  71                 proto = vlan->h_vlan_encapsulated_proto;
  72                 nhoff += sizeof(*vlan);
  73                 goto again;
  74         }
  75         case __constant_htons(ETH_P_PPP_SES): {
  76                 struct {
  77                         struct pppoe_hdr hdr;
  78                         __be16 proto;
  79                 } *hdr, _hdr;
  80                 hdr = skb_header_pointer(skb, nhoff, sizeof(_hdr), &_hdr);
  81                 if (!hdr)
  82                         return false;
  83                 proto = hdr->proto;
  84                 nhoff += PPPOE_SES_HLEN;
  85                 switch (proto) {
  86                 case __constant_htons(PPP_IP):
  87                         goto ip;
  88                 case __constant_htons(PPP_IPV6):
  89                         goto ipv6;
  90                 default:
  91                         return false;
  92                 }
  93         }
  94         default:
  95                 return false;
  96         }
  97
  98         switch (ip_proto) {
  99         case IPPROTO_GRE: {
 100                 struct gre_hdr {
 101                         __be16 flags;
 102                         __be16 proto;
 103                 } *hdr, _hdr;
 104
 105                 hdr = skb_header_pointer(skb, nhoff, sizeof(_hdr), &_hdr);
 106                 if (!hdr)
 107                         return false;
 108                 /*
 109                  * Only look inside GRE if version zero and no
 110                  * routing
 111                  */
 112                 if (!(hdr->flags & (GRE_VERSION|GRE_ROUTING))) {
 113                         proto = hdr->proto;
 114                         nhoff += 4;
 115                         if (hdr->flags & GRE_CSUM)
 116                                 nhoff += 4;
 117                         if (hdr->flags & GRE_KEY)
 118                                 nhoff += 4;
 119                         if (hdr->flags & GRE_SEQ)
 120                                 nhoff += 4;
 121                         goto again;
 122                 }
 123                 break;
 124         }
 125         case IPPROTO_IPIP:
 126                 goto again;
 127         default:
 128                 break;
 129         }
 130
 131         flow->ip_proto = ip_proto;
 132         poff = proto_ports_offset(ip_proto);
 133         if (poff >= 0) {
 134                 __be32 *ports, _ports;
 135
 136                 nhoff += poff;
 137                 ports = skb_header_pointer(skb, nhoff, sizeof(_ports), &_ports);
 138                 if (ports)
 139                         flow->ports = *ports;
 140         }
 141
 142         return true;
 143 }
 144 EXPORT_SYMBOL(skb_flow_dissect);