Commit 2a7851bf authored by Florian Westphal's avatar Florian Westphal Committed by Pablo Neira Ayuso

netfilter: add nf_ipv6_ops hook to fix xt_addrtype with IPv6

Quoting https://bugzilla.netfilter.org/show_bug.cgi?id=812:

[ ip6tables -m addrtype ]
When I tried to use in the nat/PREROUTING it messes up the
routing cache even if the rule didn't matched at all.
[..]
If I remove the --limit-iface-in from the non-working scenario, so just
use the -m addrtype --dst-type LOCAL it works!

This happens when LOCAL type matching is requested with --limit-iface-in,
and the default ipv6 route is via the interface the packet we test
arrived on.

Because xt_addrtype uses ip6_route_output, the ipv6 routing implementation
creates an unwanted cached entry, and the packet won't make it to the
real/expected destination.

Silently ignoring --limit-iface-in makes the routing work but it breaks
rule matching (--dst-type LOCAL with limit-iface-in is supposed to only
match if the dst address is configured on the incoming interface;
without --limit-iface-in it will match if the address is reachable
via lo).

The test should call ipv6_chk_addr() instead.  However, this would add
a link-time dependency on ipv6.

There are two possible solutions:

1) Revert the commit that moved ipt_addrtype to xt_addrtype,
   and put ipv6 specific code into ip6t_addrtype.
2) add new "nf_ipv6_ops" struct to register pointers to ipv6 functions.

While the former might seem preferable, Pablo pointed out that there
are more xt modules with link-time dependeny issues regarding ipv6,
so lets go for 2).
Signed-off-by: default avatarFlorian Westphal <fw@strlen.de>
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
parent 497574c7
......@@ -17,6 +17,22 @@ extern __sum16 nf_ip6_checksum(struct sk_buff *skb, unsigned int hook,
extern int ipv6_netfilter_init(void);
extern void ipv6_netfilter_fini(void);
/*
* Hook functions for ipv6 to allow xt_* modules to be built-in even
* if IPv6 is a module.
*/
struct nf_ipv6_ops {
int (*chk_addr)(struct net *net, const struct in6_addr *addr,
const struct net_device *dev, int strict);
};
extern const struct nf_ipv6_ops __rcu *nf_ipv6_ops;
static inline const struct nf_ipv6_ops *nf_get_ipv6_ops(void)
{
return rcu_dereference(nf_ipv6_ops);
}
#else /* CONFIG_NETFILTER */
static inline int ipv6_netfilter_init(void) { return 0; }
static inline void ipv6_netfilter_fini(void) { return; }
......
......@@ -65,7 +65,7 @@ extern int addrconf_set_dstaddr(struct net *net,
extern int ipv6_chk_addr(struct net *net,
const struct in6_addr *addr,
struct net_device *dev,
const struct net_device *dev,
int strict);
#if defined(CONFIG_IPV6_MIP6) || defined(CONFIG_IPV6_MIP6_MODULE)
......
......@@ -1487,7 +1487,7 @@ static int ipv6_count_addresses(struct inet6_dev *idev)
}
int ipv6_chk_addr(struct net *net, const struct in6_addr *addr,
struct net_device *dev, int strict)
const struct net_device *dev, int strict)
{
struct inet6_ifaddr *ifp;
unsigned int hash = inet6_addr_hash(addr);
......
......@@ -10,6 +10,7 @@
#include <linux/netfilter.h>
#include <linux/netfilter_ipv6.h>
#include <linux/export.h>
#include <net/addrconf.h>
#include <net/dst.h>
#include <net/ipv6.h>
#include <net/ip6_route.h>
......@@ -186,6 +187,10 @@ static __sum16 nf_ip6_checksum_partial(struct sk_buff *skb, unsigned int hook,
return csum;
};
static const struct nf_ipv6_ops ipv6ops = {
.chk_addr = ipv6_chk_addr,
};
static const struct nf_afinfo nf_ip6_afinfo = {
.family = AF_INET6,
.checksum = nf_ip6_checksum,
......@@ -198,6 +203,7 @@ static const struct nf_afinfo nf_ip6_afinfo = {
int __init ipv6_netfilter_init(void)
{
RCU_INIT_POINTER(nf_ipv6_ops, &ipv6ops);
return nf_register_afinfo(&nf_ip6_afinfo);
}
......@@ -206,5 +212,6 @@ int __init ipv6_netfilter_init(void)
*/
void ipv6_netfilter_fini(void)
{
RCU_INIT_POINTER(nf_ipv6_ops, NULL);
nf_unregister_afinfo(&nf_ip6_afinfo);
}
......@@ -30,6 +30,8 @@ static DEFINE_MUTEX(afinfo_mutex);
const struct nf_afinfo __rcu *nf_afinfo[NFPROTO_NUMPROTO] __read_mostly;
EXPORT_SYMBOL(nf_afinfo);
const struct nf_ipv6_ops __rcu *nf_ipv6_ops __read_mostly;
EXPORT_SYMBOL_GPL(nf_ipv6_ops);
int nf_register_afinfo(const struct nf_afinfo *afinfo)
{
......
......@@ -22,6 +22,7 @@
#include <net/ip6_fib.h>
#endif
#include <linux/netfilter_ipv6.h>
#include <linux/netfilter/xt_addrtype.h>
#include <linux/netfilter/x_tables.h>
......@@ -33,12 +34,12 @@ MODULE_ALIAS("ip6t_addrtype");
#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
static u32 match_lookup_rt6(struct net *net, const struct net_device *dev,
const struct in6_addr *addr)
const struct in6_addr *addr, u16 mask)
{
const struct nf_afinfo *afinfo;
struct flowi6 flow;
struct rt6_info *rt;
u32 ret;
u32 ret = 0;
int route_err;
memset(&flow, 0, sizeof(flow));
......@@ -49,12 +50,19 @@ static u32 match_lookup_rt6(struct net *net, const struct net_device *dev,
rcu_read_lock();
afinfo = nf_get_afinfo(NFPROTO_IPV6);
if (afinfo != NULL)
if (afinfo != NULL) {
const struct nf_ipv6_ops *v6ops;
if (dev && (mask & XT_ADDRTYPE_LOCAL)) {
v6ops = nf_get_ipv6_ops();
if (v6ops && v6ops->chk_addr(net, addr, dev, true))
ret = XT_ADDRTYPE_LOCAL;
}
route_err = afinfo->route(net, (struct dst_entry **)&rt,
flowi6_to_flowi(&flow), !!dev);
else
flowi6_to_flowi(&flow), false);
} else {
route_err = 1;
}
rcu_read_unlock();
if (route_err)
......@@ -62,15 +70,12 @@ static u32 match_lookup_rt6(struct net *net, const struct net_device *dev,
if (rt->rt6i_flags & RTF_REJECT)
ret = XT_ADDRTYPE_UNREACHABLE;
else
ret = 0;
if (rt->rt6i_flags & RTF_LOCAL)
if (dev == NULL && rt->rt6i_flags & RTF_LOCAL)
ret |= XT_ADDRTYPE_LOCAL;
if (rt->rt6i_flags & RTF_ANYCAST)
ret |= XT_ADDRTYPE_ANYCAST;
dst_release(&rt->dst);
return ret;
}
......@@ -90,7 +95,7 @@ static bool match_type6(struct net *net, const struct net_device *dev,
if ((XT_ADDRTYPE_LOCAL | XT_ADDRTYPE_ANYCAST |
XT_ADDRTYPE_UNREACHABLE) & mask)
return !!(mask & match_lookup_rt6(net, dev, addr));
return !!(mask & match_lookup_rt6(net, dev, addr, mask));
return true;
}
......
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