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 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        const struct sock *sk = skb_to_full_sk(skb);
  27        __u8 flags = sk ? inet_sk_flowi_flags(sk) : 0;
  28        struct net_device *dev = skb_dst(skb)->dev;
  29        unsigned int hh_len;
  30
  31        if (addr_type == RTN_UNSPEC)
  32                addr_type = inet_addr_type_dev_table(net, dev, saddr);
  33        if (addr_type == RTN_LOCAL || addr_type == RTN_UNICAST)
  34                flags |= FLOWI_FLAG_ANYSRC;
  35        else
  36                saddr = 0;
  37
  38        /* some non-standard hacks like ipt_REJECT.c:send_reset() can cause
  39         * packets with foreign saddr to appear on the NF_INET_LOCAL_OUT hook.
  40         */
  41        fl4.daddr = iph->daddr;
  42        fl4.saddr = saddr;
  43        fl4.flowi4_tos = RT_TOS(iph->tos);
  44        fl4.flowi4_oif = sk ? sk->sk_bound_dev_if : 0;
  45        if (!fl4.flowi4_oif)
  46                fl4.flowi4_oif = l3mdev_master_ifindex(dev);
  47        fl4.flowi4_mark = skb->mark;
  48        fl4.flowi4_flags = flags;
  49        rt = ip_route_output_key(net, &fl4);
  50        if (IS_ERR(rt))
  51                return PTR_ERR(rt);
  52
  53        /* Drop old route. */
  54        skb_dst_drop(skb);
  55        skb_dst_set(skb, &rt->dst);
  56
  57        if (skb_dst(skb)->error)
  58                return skb_dst(skb)->error;
  59
  60#ifdef CONFIG_XFRM
  61        if (!(IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) &&
  62            xfrm_decode_session(skb, flowi4_to_flowi(&fl4), AF_INET) == 0) {
  63                struct dst_entry *dst = skb_dst(skb);
  64                skb_dst_set(skb, NULL);
  65                dst = xfrm_lookup(net, dst, flowi4_to_flowi(&fl4), sk, 0);
  66                if (IS_ERR(dst))
  67                        return PTR_ERR(dst);
  68                skb_dst_set(skb, dst);
  69        }
  70#endif
  71
  72        /* Change in oif may mean change in hh_len. */
  73        hh_len = skb_dst(skb)->dev->hard_header_len;
  74        if (skb_headroom(skb) < hh_len &&
  75            pskb_expand_head(skb, HH_DATA_ALIGN(hh_len - skb_headroom(skb)),
  76                                0, GFP_ATOMIC))
  77                return -ENOMEM;
  78
  79        return 0;
  80}
  81EXPORT_SYMBOL(ip_route_me_harder);
  82
  83int nf_ip_route(struct net *net, struct dst_entry **dst, struct flowi *fl,
  84                bool strict __always_unused)
  85{
  86        struct rtable *rt = ip_route_output_key(net, &fl->u.ip4);
  87        if (IS_ERR(rt))
  88                return PTR_ERR(rt);
  89        *dst = &rt->dst;
  90        return 0;
  91}
  92EXPORT_SYMBOL_GPL(nf_ip_route);
  93