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