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(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