net/ipv4/netfilter.c

   1 #include <linux/config.h>
   2
   3 #ifdef CONFIG_NETFILTER
   4
   5 /* IPv4 specific functions of netfilter core */
   6 #include <linux/kernel.h>
   7 #include <linux/netfilter.h>
   8
   9 #include <linux/tcp.h>
  10 #include <linux/udp.h>
  11 #include <linux/icmp.h>
  12 #include <net/route.h>
  13 #include <linux/ip.h>
  14
  15 /* route_me_harder function, used by iptable_nat, iptable_mangle + ip_queue */
  16 int ip_route_me_harder(struct sk_buff **pskb)
  17 {
  18         struct iphdr *iph = (*pskb)->nh.iph;
  19         struct rtable *rt;
  20         struct flowi fl = {};
  21         struct dst_entry *odst;
  22         unsigned int hh_len;
  23
  24         /* some non-standard hacks like ipt_REJECT.c:send_reset() can cause
  25          * packets with foreign saddr to appear on the NF_IP_LOCAL_OUT hook.
  26          */
  27         if (inet_addr_type(iph->saddr) == RTN_LOCAL) {
  28                 fl.nl_u.ip4_u.daddr = iph->daddr;
  29                 fl.nl_u.ip4_u.saddr = iph->saddr;
  30                 fl.nl_u.ip4_u.tos = RT_TOS(iph->tos);
  31                 fl.oif = (*pskb)->sk ? (*pskb)->sk->sk_bound_dev_if : 0;
  32 #ifdef CONFIG_IP_ROUTE_FWMARK
  33                 fl.nl_u.ip4_u.fwmark = (*pskb)->nfmark;
  34 #endif
  35                 fl.proto = iph->protocol;
  36                 if (ip_route_output_key(&rt, &fl) != 0)
  37                         return -1;
  38
  39                 /* Drop old route. */
  40                 dst_release((*pskb)->dst);
  41                 (*pskb)->dst = &rt->u.dst;
  42         } else {
  43                 /* non-local src, find valid iif to satisfy
  44                  * rp-filter when calling ip_route_input. */
  45                 fl.nl_u.ip4_u.daddr = iph->saddr;
  46                 if (ip_route_output_key(&rt, &fl) != 0)
  47                         return -1;
  48
  49                 odst = (*pskb)->dst;
  50                 if (ip_route_input(*pskb, iph->daddr, iph->saddr,
  51                                    RT_TOS(iph->tos), rt->u.dst.dev) != 0) {
  52                         dst_release(&rt->u.dst);
  53                         return -1;
  54                 }
  55                 dst_release(&rt->u.dst);
  56                 dst_release(odst);
  57         }
  58
  59         if ((*pskb)->dst->error)
  60                 return -1;
  61
  62         /* Change in oif may mean change in hh_len. */
  63         hh_len = (*pskb)->dst->dev->hard_header_len;
  64         if (skb_headroom(*pskb) < hh_len) {
  65                 struct sk_buff *nskb;
  66
  67                 nskb = skb_realloc_headroom(*pskb, hh_len);
  68                 if (!nskb)
  69                         return -1;
  70                 if ((*pskb)->sk)
  71                         skb_set_owner_w(nskb, (*pskb)->sk);
  72                 kfree_skb(*pskb);
  73                 *pskb = nskb;
  74         }
  75
  76         return 0;
  77 }
  78 EXPORT_SYMBOL(ip_route_me_harder);
  79 #endif /* CONFIG_NETFILTER */