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 */
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 fl4.flowi4_l3mdev = l3mdev_master_ifindex(dev);
49 fl4.flowi4_mark = skb->mark;
50 fl4.flowi4_flags = flags;
51 fib4_rules_early_flow_dissect(net, skb, &fl4, &flkeys);
52 rt = ip_route_output_key(net, &fl4);
53 if (IS_ERR(rt))
54 return PTR_ERR(rt);
55
56 /* Drop old route. */
57 skb_dst_drop(skb);
58 skb_dst_set(skb, &rt->dst);
59
60 if (skb_dst(skb)->error)
61 return skb_dst(skb)->error;
62
63 #ifdef CONFIG_XFRM
64 if (!(IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) &&
65 xfrm_decode_session(net, skb, flowi4_to_flowi(&fl4), AF_INET) == 0) {
66 struct dst_entry *dst = skb_dst(skb);
67 skb_dst_set(skb, NULL);
68 dst = xfrm_lookup(net, dst, flowi4_to_flowi(&fl4), sk, 0);
69 if (IS_ERR(dst))
70 return PTR_ERR(dst);
71 skb_dst_set(skb, dst);
72 }
73 #endif
74
75 /* Change in oif may mean change in hh_len. */
76 hh_len = skb_dst(skb)->dev->hard_header_len;
77 if (skb_headroom(skb) < hh_len &&
78 pskb_expand_head(skb, HH_DATA_ALIGN(hh_len - skb_headroom(skb)),
79 0, GFP_ATOMIC))
80 return -ENOMEM;
81
82 return 0;
83 }
84 EXPORT_SYMBOL(ip_route_me_harder);
85
86 int nf_ip_route(struct net *net, struct dst_entry **dst, struct flowi *fl,
87 bool strict __always_unused)
88 {
89 struct rtable *rt = ip_route_output_key(net, &fl->u.ip4);
90 if (IS_ERR(rt))
91 return PTR_ERR(rt);
92 *dst = &rt->dst;
93 return 0;
94 }
95 EXPORT_SYMBOL_GPL(nf_ip_route);
96
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