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netfilter: add nf_ipv6_ops hook to fix xt_addrtype with IPv6

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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: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Florian Westphal
2013-05-17 03:56:10 +00:00
committed by Pablo Neira Ayuso
parent 497574c72c
commit 2a7851bffb
6 changed files with 44 additions and 14 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
net/netfilter/core.c
View File

@@ -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)
{

29
net/netfilter/xt_addrtype.c
View File

@@ -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)
route_err = afinfo->route(net, (struct dst_entry **)&rt,
flowi6_to_flowi(&flow), !!dev);
else
route_err = 1;
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), 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;
}