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 */
ip_route_me_harder(struct net * net,struct sock * sk,struct sk_buff * skb,unsigned int addr_type)20 int 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 }
85 EXPORT_SYMBOL(ip_route_me_harder);
86 
nf_ip_route(struct net * net,struct dst_entry ** dst,struct flowi * fl,bool strict __always_unused)87 int 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 }
96 EXPORT_SYMBOL_GPL(nf_ip_route);
97