1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * IPv4 specific functions of netfilter core 4 * 5 * Rusty Russell (C) 2000 6 * Patrick McHardy (C) 2006-2012 7 */ 8 #include <linux/kernel.h> 9 #include <linux/netfilter.h> 10 #include <linux/netfilter_ipv4.h> 11 #include <linux/ip.h> 12 #include <linux/skbuff.h> 13 #include <linux/gfp.h> 14 #include <linux/export.h> 15 #include <net/flow.h> 16 #include <net/route.h> 17 #include <net/xfrm.h> 18 #include <net/ip.h> 19 #include <net/netfilter/nf_queue.h> 20 21 /* route_me_harder function, used by iptable_nat, iptable_mangle + ip_queue */ 22 int ip_route_me_harder(struct net *net, struct sock *sk, struct sk_buff *skb, unsigned int addr_type) 23 { 24 struct net_device *dev = skb_dst_dev(skb); 25 const struct iphdr *iph = ip_hdr(skb); 26 struct rtable *rt; 27 struct flowi4 fl4 = {}; 28 __be32 saddr = iph->saddr; 29 __u8 flags; 30 struct flow_keys flkeys; 31 unsigned int hh_len; 32 33 sk = sk_to_full_sk(sk); 34 flags = sk ? inet_sk_flowi_flags(sk) : 0; 35 36 if (addr_type == RTN_UNSPEC) 37 addr_type = inet_addr_type_dev_table(net, dev, saddr); 38 if (addr_type == RTN_LOCAL || addr_type == RTN_UNICAST) 39 flags |= FLOWI_FLAG_ANYSRC; 40 else 41 saddr = 0; 42 43 /* some non-standard hacks like ipt_REJECT.c:send_reset() can cause 44 * packets with foreign saddr to appear on the NF_INET_LOCAL_OUT hook. 45 */ 46 fl4.daddr = iph->daddr; 47 fl4.saddr = saddr; 48 fl4.flowi4_dscp = ip4h_dscp(iph); 49 fl4.flowi4_oif = sk ? sk->sk_bound_dev_if : 0; 50 fl4.flowi4_l3mdev = l3mdev_master_ifindex(dev); 51 fl4.flowi4_mark = skb->mark; 52 fl4.flowi4_flags = flags; 53 fib4_rules_early_flow_dissect(net, skb, &fl4, &flkeys); 54 rt = ip_route_output_key(net, &fl4); 55 if (IS_ERR(rt)) 56 return PTR_ERR(rt); 57 58 /* Drop old route. */ 59 skb_dst_drop(skb); 60 skb_dst_set(skb, &rt->dst); 61 62 if (skb_dst(skb)->error) 63 return skb_dst(skb)->error; 64 65 #ifdef CONFIG_XFRM 66 if (!(IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) && 67 xfrm_decode_session(net, skb, flowi4_to_flowi(&fl4), AF_INET) == 0) { 68 struct dst_entry *dst = skb_dst(skb); 69 /* ignore return value from skb_dstref_steal, xfrm_lookup takes 70 * care of dropping the refcnt if needed. 71 */ 72 skb_dstref_steal(skb); 73 dst = xfrm_lookup(net, dst, flowi4_to_flowi(&fl4), sk, 0); 74 if (IS_ERR(dst)) 75 return PTR_ERR(dst); 76 skb_dst_set(skb, dst); 77 } 78 #endif 79 80 /* Change in oif may mean change in hh_len. */ 81 hh_len = skb_dst_dev(skb)->hard_header_len; 82 if (skb_headroom(skb) < hh_len && 83 pskb_expand_head(skb, HH_DATA_ALIGN(hh_len - skb_headroom(skb)), 84 0, GFP_ATOMIC)) 85 return -ENOMEM; 86 87 return 0; 88 } 89 EXPORT_SYMBOL(ip_route_me_harder); 90 91 int nf_ip_route(struct net *net, struct dst_entry **dst, struct flowi *fl, 92 bool strict __always_unused) 93 { 94 struct rtable *rt = ip_route_output_key(net, &fl->u.ip4); 95 if (IS_ERR(rt)) 96 return PTR_ERR(rt); 97 *dst = &rt->dst; 98 return 0; 99 } 100 EXPORT_SYMBOL_GPL(nf_ip_route); 101