net/ipv4/netfilter.c

   1 /* IPv4 specific functions of netfilter core */
   2
   3 #include <linux/config.h>
   4 #ifdef CONFIG_NETFILTER
   5
   6 #include <linux/kernel.h>
   7 #include <linux/netfilter.h>
   8 #include <linux/netfilter_ipv4.h>
   9
  10 #include <linux/tcp.h>
  11 #include <linux/udp.h>
  12 #include <linux/icmp.h>
  13 #include <net/route.h>
  14 #include <linux/ip.h>
  15
  16 /* route_me_harder function, used by iptable_nat, iptable_mangle + ip_queue */
  17 int ip_route_me_harder(struct sk_buff **pskb)
  18 {
  19         struct iphdr *iph = (*pskb)->nh.iph;
  20         struct rtable *rt;
  21         struct flowi fl = {};
  22         struct dst_entry *odst;
  23         unsigned int hh_len;
  24
  25         /* some non-standard hacks like ipt_REJECT.c:send_reset() can cause
  26          * packets with foreign saddr to appear on the NF_IP_LOCAL_OUT hook.
  27          */
  28         if (inet_addr_type(iph->saddr) == RTN_LOCAL) {
  29                 fl.nl_u.ip4_u.daddr = iph->daddr;
  30                 fl.nl_u.ip4_u.saddr = iph->saddr;
  31                 fl.nl_u.ip4_u.tos = RT_TOS(iph->tos);
  32                 fl.oif = (*pskb)->sk ? (*pskb)->sk->sk_bound_dev_if : 0;
  33 #ifdef CONFIG_IP_ROUTE_FWMARK
  34                 fl.nl_u.ip4_u.fwmark = (*pskb)->nfmark;
  35 #endif
  36                 fl.proto = iph->protocol;
  37                 if (ip_route_output_key(&rt, &fl) != 0)
  38                         return -1;
  39
  40                 /* Drop old route. */
  41                 dst_release((*pskb)->dst);
  42                 (*pskb)->dst = &rt->u.dst;
  43         } else {
  44                 /* non-local src, find valid iif to satisfy
  45                  * rp-filter when calling ip_route_input. */
  46                 fl.nl_u.ip4_u.daddr = iph->saddr;
  47                 if (ip_route_output_key(&rt, &fl) != 0)
  48                         return -1;
  49
  50                 odst = (*pskb)->dst;
  51                 if (ip_route_input(*pskb, iph->daddr, iph->saddr,
  52                                    RT_TOS(iph->tos), rt->u.dst.dev) != 0) {
  53                         dst_release(&rt->u.dst);
  54                         return -1;
  55                 }
  56                 dst_release(&rt->u.dst);
  57                 dst_release(odst);
  58         }
  59
  60         if ((*pskb)->dst->error)
  61                 return -1;
  62
  63         /* Change in oif may mean change in hh_len. */
  64         hh_len = (*pskb)->dst->dev->hard_header_len;
  65         if (skb_headroom(*pskb) < hh_len) {
  66                 struct sk_buff *nskb;
  67
  68                 nskb = skb_realloc_headroom(*pskb, hh_len);
  69                 if (!nskb)
  70                         return -1;
  71                 if ((*pskb)->sk)
  72                         skb_set_owner_w(nskb, (*pskb)->sk);
  73                 kfree_skb(*pskb);
  74                 *pskb = nskb;
  75         }
  76
  77         return 0;
  78 }
  79 EXPORT_SYMBOL(ip_route_me_harder);
  80
  81 /*
  82  * Extra routing may needed on local out, as the QUEUE target never
  83  * returns control to the table.
  84  */
  85
  86 struct ip_rt_info {
  87         u_int32_t daddr;
  88         u_int32_t saddr;
  89         u_int8_t tos;
  90 };
  91
  92 static void queue_save(const struct sk_buff *skb, struct nf_info *info)
  93 {
  94         struct ip_rt_info *rt_info = nf_info_reroute(info);
  95
  96         if (info->hook == NF_IP_LOCAL_OUT) {
  97                 const struct iphdr *iph = skb->nh.iph;
  98
  99                 rt_info->tos = iph->tos;
 100                 rt_info->daddr = iph->daddr;
 101                 rt_info->saddr = iph->saddr;
 102         }
 103 }
 104
 105 static int queue_reroute(struct sk_buff **pskb, const struct nf_info *info)
 106 {
 107         const struct ip_rt_info *rt_info = nf_info_reroute(info);
 108
 109         if (info->hook == NF_IP_LOCAL_OUT) {
 110                 struct iphdr *iph = (*pskb)->nh.iph;
 111
 112                 if (!(iph->tos == rt_info->tos
 113                       && iph->daddr == rt_info->daddr
 114                       && iph->saddr == rt_info->saddr))
 115                         return ip_route_me_harder(pskb);
 116         }
 117         return 0;
 118 }
 119
 120 static struct nf_queue_rerouter ip_reroute = {
 121         .rer_size       = sizeof(struct ip_rt_info),
 122         .save           = queue_save,
 123         .reroute        = queue_reroute,
 124 };
 125
 126 static int init(void)
 127 {
 128         return nf_register_queue_rerouter(PF_INET, &ip_reroute);
 129 }
 130
 131 static void fini(void)
 132 {
 133         nf_unregister_queue_rerouter(PF_INET);
 134 }
 135
 136 module_init(init);
 137 module_exit(fini);
 138
 139 #endif /* CONFIG_NETFILTER */