LXR linux/net/ipv4/netfilter.c

   1/*
   2 * IPv4 specific functions of netfilter core
   3 *
   4 * Rusty Russell (C) 2000 -- This code is GPL.
   5 * Patrick McHardy (C) 2006-2012
   6 */
   7#include <linux/kernel.h>
   8#include <linux/netfilter.h>
   9#include <linux/netfilter_ipv4.h>
  10#include <linux/ip.h>
  11#include <linux/skbuff.h>
  12#include <linux/gfp.h>
  13#include <linux/export.h>
  14#include <net/route.h>
  15#include <net/xfrm.h>
  16#include <net/ip.h>
  17#include <net/netfilter/nf_queue.h>
  18
  19/* route_me_harder function, used by iptable_nat, iptable_mangle + ip_queue */
  20int ip_route_me_harder(struct net *net, struct sock *sk, struct sk_buff *skb, unsigned int addr_type)
  21{
  22        const struct iphdr *iph = ip_hdr(skb);
  23        struct rtable *rt;
  24        struct flowi4 fl4 = {};
  25        __be32 saddr = iph->saddr;
  26        __u8 flags;
  27        struct net_device *dev = skb_dst(skb)->dev;
  28        struct flow_keys flkeys;
  29        unsigned int hh_len;
  30
  31        sk = sk_to_full_sk(sk);
  32        flags = sk ? inet_sk_flowi_flags(sk) : 0;
  33
  34        if (addr_type == RTN_UNSPEC)
  35                addr_type = inet_addr_type_dev_table(net, dev, saddr);
  36        if (addr_type == RTN_LOCAL || addr_type == RTN_UNICAST)
  37                flags |= FLOWI_FLAG_ANYSRC;
  38        else
  39                saddr = 0;
  40
  41        /* some non-standard hacks like ipt_REJECT.c:send_reset() can cause
  42         * packets with foreign saddr to appear on the NF_INET_LOCAL_OUT hook.
  43         */
  44        fl4.daddr = iph->daddr;
  45        fl4.saddr = saddr;
  46        fl4.flowi4_tos = RT_TOS(iph->tos);
  47        fl4.flowi4_oif = sk ? sk->sk_bound_dev_if : 0;
  48        if (!fl4.flowi4_oif)
  49                fl4.flowi4_oif = l3mdev_master_ifindex(dev);
  50        fl4.flowi4_mark = skb->mark;
  51        fl4.flowi4_flags = flags;
  52        fib4_rules_early_flow_dissect(net, skb, &fl4, &flkeys);
  53        rt = ip_route_output_key(net, &fl4);
  54        if (IS_ERR(rt))
  55                return PTR_ERR(rt);
  56
  57        /* Drop old route. */
  58        skb_dst_drop(skb);
  59        skb_dst_set(skb, &rt->dst);
  60
  61        if (skb_dst(skb)->error)
  62                return skb_dst(skb)->error;
  63
  64#ifdef CONFIG_XFRM
  65        if (!(IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) &&
  66            xfrm_decode_session(skb, flowi4_to_flowi(&fl4), AF_INET) == 0) {
  67                struct dst_entry *dst = skb_dst(skb);
  68                skb_dst_set(skb, NULL);
  69                dst = xfrm_lookup(net, dst, flowi4_to_flowi(&fl4), sk, 0);
  70                if (IS_ERR(dst))
  71                        return PTR_ERR(dst);
  72                skb_dst_set(skb, dst);
  73        }
  74#endif
  75
  76        /* Change in oif may mean change in hh_len. */
  77        hh_len = skb_dst(skb)->dev->hard_header_len;
  78        if (skb_headroom(skb) < hh_len &&
  79            pskb_expand_head(skb, HH_DATA_ALIGN(hh_len - skb_headroom(skb)),
  80                                0, GFP_ATOMIC))
  81                return -ENOMEM;
  82
  83        return 0;
  84}
  85EXPORT_SYMBOL(ip_route_me_harder);
  86
  87int nf_ip_route(struct net *net, struct dst_entry **dst, struct flowi *fl,
  88                bool strict __always_unused)
  89{
  90        struct rtable *rt = ip_route_output_key(net, &fl->u.ip4);
  91        if (IS_ERR(rt))
  92                return PTR_ERR(rt);
  93        *dst = &rt->dst;
  94        return 0;
  95}
  96EXPORT_SYMBOL_GPL(nf_ip_route);
  97