2 * IPv4 specific functions of netfilter core
4 * Rusty Russell (C) 2000 -- This code is GPL.
5 * Patrick McHardy (C) 2006-2012
7 #include <linux/kernel.h>
8 #include <linux/netfilter.h>
9 #include <linux/netfilter_ipv4.h>
11 #include <linux/skbuff.h>
12 #include <linux/gfp.h>
13 #include <linux/export.h>
14 #include <net/route.h>
17 #include <net/netfilter/nf_queue.h>
19 /* route_me_harder function, used by iptable_nat, iptable_mangle + ip_queue */
20 int ip_route_me_harder(struct net *net, struct sk_buff *skb, unsigned int addr_type)
22 const struct iphdr *iph = ip_hdr(skb);
24 struct flowi4 fl4 = {};
25 __be32 saddr = iph->saddr;
26 const struct sock *sk = skb_to_full_sk(skb);
27 __u8 flags = sk ? inet_sk_flowi_flags(sk) : 0;
28 struct net_device *dev = skb_dst(skb)->dev;
31 if (addr_type == RTN_UNSPEC)
32 addr_type = inet_addr_type_dev_table(net, dev, saddr);
33 if (addr_type == RTN_LOCAL || addr_type == RTN_UNICAST)
34 flags |= FLOWI_FLAG_ANYSRC;
38 /* some non-standard hacks like ipt_REJECT.c:send_reset() can cause
39 * packets with foreign saddr to appear on the NF_INET_LOCAL_OUT hook.
41 fl4.daddr = iph->daddr;
43 fl4.flowi4_tos = RT_TOS(iph->tos);
44 fl4.flowi4_oif = sk ? sk->sk_bound_dev_if : 0;
46 fl4.flowi4_oif = l3mdev_master_ifindex(dev);
47 fl4.flowi4_mark = skb->mark;
48 fl4.flowi4_flags = flags;
49 rt = ip_route_output_key(net, &fl4);
55 skb_dst_set(skb, &rt->dst);
57 if (skb_dst(skb)->error)
58 return skb_dst(skb)->error;
61 if (!(IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED) &&
62 xfrm_decode_session(skb, flowi4_to_flowi(&fl4), AF_INET) == 0) {
63 struct dst_entry *dst = skb_dst(skb);
64 skb_dst_set(skb, NULL);
65 dst = xfrm_lookup(net, dst, flowi4_to_flowi(&fl4), sk, 0);
68 skb_dst_set(skb, dst);
72 /* Change in oif may mean change in hh_len. */
73 hh_len = skb_dst(skb)->dev->hard_header_len;
74 if (skb_headroom(skb) < hh_len &&
75 pskb_expand_head(skb, HH_DATA_ALIGN(hh_len - skb_headroom(skb)),
81 EXPORT_SYMBOL(ip_route_me_harder);
83 int nf_ip_reroute(struct sk_buff *skb, const struct nf_queue_entry *entry)
85 const struct ip_rt_info *rt_info = nf_queue_entry_reroute(entry);
87 if (entry->state.hook == NF_INET_LOCAL_OUT) {
88 const struct iphdr *iph = ip_hdr(skb);
90 if (!(iph->tos == rt_info->tos &&
91 skb->mark == rt_info->mark &&
92 iph->daddr == rt_info->daddr &&
93 iph->saddr == rt_info->saddr))
94 return ip_route_me_harder(entry->state.net, skb,
99 EXPORT_SYMBOL_GPL(nf_ip_reroute);
101 __sum16 nf_ip_checksum(struct sk_buff *skb, unsigned int hook,
102 unsigned int dataoff, u_int8_t protocol)
104 const struct iphdr *iph = ip_hdr(skb);
107 switch (skb->ip_summed) {
108 case CHECKSUM_COMPLETE:
109 if (hook != NF_INET_PRE_ROUTING && hook != NF_INET_LOCAL_IN)
111 if ((protocol == 0 && !csum_fold(skb->csum)) ||
112 !csum_tcpudp_magic(iph->saddr, iph->daddr,
113 skb->len - dataoff, protocol,
115 skb->ip_summed = CHECKSUM_UNNECESSARY;
123 skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr,
126 csum = __skb_checksum_complete(skb);
130 EXPORT_SYMBOL(nf_ip_checksum);
132 __sum16 nf_ip_checksum_partial(struct sk_buff *skb, unsigned int hook,
133 unsigned int dataoff, unsigned int len,
136 const struct iphdr *iph = ip_hdr(skb);
139 switch (skb->ip_summed) {
140 case CHECKSUM_COMPLETE:
141 if (len == skb->len - dataoff)
142 return nf_ip_checksum(skb, hook, dataoff, protocol);
145 skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr, protocol,
146 skb->len - dataoff, 0);
147 skb->ip_summed = CHECKSUM_NONE;
148 return __skb_checksum_complete_head(skb, dataoff + len);
152 EXPORT_SYMBOL_GPL(nf_ip_checksum_partial);
154 int nf_ip_route(struct net *net, struct dst_entry **dst, struct flowi *fl,
155 bool strict __always_unused)
157 struct rtable *rt = ip_route_output_key(net, &fl->u.ip4);
163 EXPORT_SYMBOL_GPL(nf_ip_route);