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/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, 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(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, &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(net, skb, flowi4_to_flowi(&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, flowi4_to_flowi(&fl4), sk, 0);
73		if (IS_ERR(dst))
74			return PTR_ERR(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				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, &fl->u.ip4);
94	if (IS_ERR(rt))
95		return PTR_ERR(rt);
96	*dst = &rt->dst;
97	return 0;
98}
99EXPORT_SYMBOL_GPL(nf_ip_route);