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/* IPv4 specific functions of netfilter core */
#include <linux/kernel.h>
#include <linux/netfilter.h>
#include <linux/netfilter_ipv4.h>
#include <linux/ip.h>
#include <net/route.h>
#include <net/xfrm.h>
#include <net/ip.h>
/* route_me_harder function, used by iptable_nat, iptable_mangle + ip_queue */
int ip_route_me_harder(struct sk_buff **pskb, unsigned addr_type)
{
const struct iphdr *iph = ip_hdr(*pskb);
struct rtable *rt;
struct flowi fl = {};
struct dst_entry *odst;
unsigned int hh_len;
unsigned int type;
type = inet_addr_type(iph->saddr);
if (addr_type == RTN_UNSPEC)
addr_type = type;
/* some non-standard hacks like ipt_REJECT.c:send_reset() can cause
* packets with foreign saddr to appear on the NF_IP_LOCAL_OUT hook.
*/
if (addr_type == RTN_LOCAL) {
fl.nl_u.ip4_u.daddr = iph->daddr;
if (type == RTN_LOCAL)
fl.nl_u.ip4_u.saddr = iph->saddr;
fl.nl_u.ip4_u.tos = RT_TOS(iph->tos);
fl.oif = (*pskb)->sk ? (*pskb)->sk->sk_bound_dev_if : 0;
fl.mark = (*pskb)->mark;
if (ip_route_output_key(&rt, &fl) != 0)
return -1;
/* Drop old route. */
dst_release((*pskb)->dst);
(*pskb)->dst = &rt->u.dst;
} else {
/* non-local src, find valid iif to satisfy
* rp-filter when calling ip_route_input. */
fl.nl_u.ip4_u.daddr = iph->saddr;
if (ip_route_output_key(&rt, &fl) != 0)
return -1;
odst = (*pskb)->dst;
if (ip_route_input(*pskb, iph->daddr, iph->saddr,
RT_TOS(iph->tos), rt->u.dst.dev) != 0) {
dst_release(&rt->u.dst);
return -1;
}
dst_release(&rt->u.dst);
dst_release(odst);
}
if ((*pskb)->dst->error)
return -1;
#ifdef CONFIG_XFRM
if (!(IPCB(*pskb)->flags & IPSKB_XFRM_TRANSFORMED) &&
xfrm_decode_session(*pskb, &fl, AF_INET) == 0)
if (xfrm_lookup(&(*pskb)->dst, &fl, (*pskb)->sk, 0))
return -1;
#endif
/* Change in oif may mean change in hh_len. */
hh_len = (*pskb)->dst->dev->hard_header_len;
if (skb_headroom(*pskb) < hh_len) {
struct sk_buff *nskb;
nskb = skb_realloc_headroom(*pskb, hh_len);
if (!nskb)
return -1;
if ((*pskb)->sk)
skb_set_owner_w(nskb, (*pskb)->sk);
kfree_skb(*pskb);
*pskb = nskb;
}
return 0;
}
EXPORT_SYMBOL(ip_route_me_harder);
#ifdef CONFIG_XFRM
int ip_xfrm_me_harder(struct sk_buff **pskb)
{
struct flowi fl;
unsigned int hh_len;
struct dst_entry *dst;
if (IPCB(*pskb)->flags & IPSKB_XFRM_TRANSFORMED)
return 0;
if (xfrm_decode_session(*pskb, &fl, AF_INET) < 0)
return -1;
dst = (*pskb)->dst;
if (dst->xfrm)
dst = ((struct xfrm_dst *)dst)->route;
dst_hold(dst);
if (xfrm_lookup(&dst, &fl, (*pskb)->sk, 0) < 0)
return -1;
dst_release((*pskb)->dst);
(*pskb)->dst = dst;
/* Change in oif may mean change in hh_len. */
hh_len = (*pskb)->dst->dev->hard_header_len;
if (skb_headroom(*pskb) < hh_len) {
struct sk_buff *nskb;
nskb = skb_realloc_headroom(*pskb, hh_len);
if (!nskb)
return -1;
if ((*pskb)->sk)
skb_set_owner_w(nskb, (*pskb)->sk);
kfree_skb(*pskb);
*pskb = nskb;
}
return 0;
}
EXPORT_SYMBOL(ip_xfrm_me_harder);
#endif
void (*ip_nat_decode_session)(struct sk_buff *, struct flowi *);
EXPORT_SYMBOL(ip_nat_decode_session);
/*
* Extra routing may needed on local out, as the QUEUE target never
* returns control to the table.
*/
struct ip_rt_info {
__be32 daddr;
__be32 saddr;
u_int8_t tos;
};
static void nf_ip_saveroute(const struct sk_buff *skb, struct nf_info *info)
{
struct ip_rt_info *rt_info = nf_info_reroute(info);
if (info->hook == NF_IP_LOCAL_OUT) {
const struct iphdr *iph = ip_hdr(skb);
rt_info->tos = iph->tos;
rt_info->daddr = iph->daddr;
rt_info->saddr = iph->saddr;
}
}
static int nf_ip_reroute(struct sk_buff **pskb, const struct nf_info *info)
{
const struct ip_rt_info *rt_info = nf_info_reroute(info);
if (info->hook == NF_IP_LOCAL_OUT) {
const struct iphdr *iph = ip_hdr(*pskb);
if (!(iph->tos == rt_info->tos
&& iph->daddr == rt_info->daddr
&& iph->saddr == rt_info->saddr))
return ip_route_me_harder(pskb, RTN_UNSPEC);
}
return 0;
}
__sum16 nf_ip_checksum(struct sk_buff *skb, unsigned int hook,
unsigned int dataoff, u_int8_t protocol)
{
const struct iphdr *iph = ip_hdr(skb);
__sum16 csum = 0;
switch (skb->ip_summed) {
case CHECKSUM_COMPLETE:
if (hook != NF_IP_PRE_ROUTING && hook != NF_IP_LOCAL_IN)
break;
if ((protocol == 0 && !csum_fold(skb->csum)) ||
!csum_tcpudp_magic(iph->saddr, iph->daddr,
skb->len - dataoff, protocol,
skb->csum)) {
skb->ip_summed = CHECKSUM_UNNECESSARY;
break;
}
/* fall through */
case CHECKSUM_NONE:
if (protocol == 0)
skb->csum = 0;
else
skb->csum = csum_tcpudp_nofold(iph->saddr, iph->daddr,
skb->len - dataoff,
protocol, 0);
csum = __skb_checksum_complete(skb);
}
return csum;
}
EXPORT_SYMBOL(nf_ip_checksum);
static struct nf_afinfo nf_ip_afinfo = {
.family = AF_INET,
.checksum = nf_ip_checksum,
.saveroute = nf_ip_saveroute,
.reroute = nf_ip_reroute,
.route_key_size = sizeof(struct ip_rt_info),
};
static int ipv4_netfilter_init(void)
{
return nf_register_afinfo(&nf_ip_afinfo);
}
static void ipv4_netfilter_fini(void)
{
nf_unregister_afinfo(&nf_ip_afinfo);
}
module_init(ipv4_netfilter_init);
module_exit(ipv4_netfilter_fini);
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