kernel-ark/net/ipv4/netfilter.c
Patrick McHardy ee68cea2c2 [NETFILTER]: Fix xfrm lookup after SNAT
To find out if a packet needs to be handled by IPsec after SNAT, packets
are currently rerouted in POST_ROUTING and a new xfrm lookup is done. This
breaks SNAT of non-unicast packets to non-local addresses because the
packet is routed as incoming packet and no neighbour entry is bound to the
dst_entry. In general, it seems to be a bad idea to replace the dst_entry
after the packet was already sent to the output routine because its state
might not match what's expected.

This patch changes the xfrm lookup in POST_ROUTING to re-use the original
dst_entry without routing the packet again. This means no policy routing
can be used for transport mode transforms (which keep the original route)
when packets are SNATed to match the policy, but it looks like the best
we can do for now.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
2006-02-15 01:34:23 -08:00

182 lines
4.2 KiB
C

/* 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)
{
struct iphdr *iph = (*pskb)->nh.iph;
struct rtable *rt;
struct flowi fl = {};
struct dst_entry *odst;
unsigned int hh_len;
/* 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 (inet_addr_type(iph->saddr) == RTN_LOCAL) {
fl.nl_u.ip4_u.daddr = iph->daddr;
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;
#ifdef CONFIG_IP_ROUTE_FWMARK
fl.nl_u.ip4_u.fwmark = (*pskb)->nfmark;
#endif
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 {
u_int32_t daddr;
u_int32_t saddr;
u_int8_t tos;
};
static void queue_save(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 = skb->nh.iph;
rt_info->tos = iph->tos;
rt_info->daddr = iph->daddr;
rt_info->saddr = iph->saddr;
}
}
static int queue_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) {
struct iphdr *iph = (*pskb)->nh.iph;
if (!(iph->tos == rt_info->tos
&& iph->daddr == rt_info->daddr
&& iph->saddr == rt_info->saddr))
return ip_route_me_harder(pskb);
}
return 0;
}
static struct nf_queue_rerouter ip_reroute = {
.rer_size = sizeof(struct ip_rt_info),
.save = queue_save,
.reroute = queue_reroute,
};
static int init(void)
{
return nf_register_queue_rerouter(PF_INET, &ip_reroute);
}
static void fini(void)
{
nf_unregister_queue_rerouter(PF_INET);
}
module_init(init);
module_exit(fini);