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/flow.h>
15#include <net/route.h>
16#include <net/xfrm.h>
17#include <net/ip.h>
18#include <net/netfilter/nf_queue.h>
19
20/* route_me_harder function, used by iptable_nat, iptable_mangle + ip_queue */
21int ip_route_me_harder(struct net *net, struct sock *sk, struct sk_buff *skb, unsigned int addr_type)
22{
23 struct net_device *dev = skb_dst_dev(skb);
24 const struct iphdr *iph = ip_hdr(skb);
25 struct rtable *rt;
26 struct flowi4 fl4 = {};
27 __be32 saddr = iph->saddr;
28 __u8 flags;
29 struct flow_keys flkeys;
30 unsigned int hh_len;
31
32 sk = sk_to_full_sk(sk);
33 flags = sk ? inet_sk_flowi_flags(sk) : 0;
34
35 if (addr_type == RTN_UNSPEC)
36 addr_type = inet_addr_type_dev_table(net, dev, addr: saddr);
37 if (addr_type == RTN_LOCAL || addr_type == RTN_UNICAST)
38 flags |= FLOWI_FLAG_ANYSRC;
39 else
40 saddr = 0;
41
42 /* some non-standard hacks like ipt_REJECT.c:send_reset() can cause
43 * packets with foreign saddr to appear on the NF_INET_LOCAL_OUT hook.
44 */
45 fl4.daddr = iph->daddr;
46 fl4.saddr = saddr;
47 fl4.flowi4_dscp = ip4h_dscp(ip4h: iph);
48 fl4.flowi4_oif = sk ? sk->sk_bound_dev_if : 0;
49 fl4.flowi4_l3mdev = l3mdev_master_ifindex(dev);
50 fl4.flowi4_mark = skb->mark;
51 fl4.flowi4_flags = flags;
52 fib4_rules_early_flow_dissect(net, skb, fl4: &fl4, flkeys: &flkeys);
53 rt = ip_route_output_key(net, flp: &fl4);
54 if (IS_ERR(ptr: rt))
55 return PTR_ERR(ptr: rt);
56
57 /* Drop old route. */
58 skb_dst_drop(skb);
59 skb_dst_set(skb, dst: &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(net, skb, fl: flowi4_to_flowi(fl4: &fl4), AF_INET) == 0) {
67 struct dst_entry *dst = skb_dst(skb);
68 /* ignore return value from skb_dstref_steal, xfrm_lookup takes
69 * care of dropping the refcnt if needed.
70 */
71 skb_dstref_steal(skb);
72 dst = xfrm_lookup(net, dst_orig: dst, fl: flowi4_to_flowi(fl4: &fl4), sk, flags: 0);
73 if (IS_ERR(ptr: dst))
74 return PTR_ERR(ptr: dst);
75 skb_dst_set(skb, dst);
76 }
77#endif
78
79 /* Change in oif may mean change in hh_len. */
80 hh_len = skb_dst_dev(skb)->hard_header_len;
81 if (skb_headroom(skb) < hh_len &&
82 pskb_expand_head(skb, HH_DATA_ALIGN(hh_len - skb_headroom(skb)),
83 ntail: 0, GFP_ATOMIC))
84 return -ENOMEM;
85
86 return 0;
87}
88EXPORT_SYMBOL(ip_route_me_harder);
89
90int nf_ip_route(struct net *net, struct dst_entry **dst, struct flowi *fl,
91 bool strict __always_unused)
92{
93 struct rtable *rt = ip_route_output_key(net, flp: &fl->u.ip4);
94 if (IS_ERR(ptr: rt))
95 return PTR_ERR(ptr: rt);
96 *dst = &rt->dst;
97 return 0;
98}
99EXPORT_SYMBOL_GPL(nf_ip_route);
100