[PATCH net] netfilter: remove the nh_scope test in rpfilter_lookup_reverse of ipt_rpfilter

[PATCH net] netfilter: remove the nh_scope test in rpfilter_lookup_reverse of ipt_rpfilter

[Xin Long]

--accept-local  option works for res.type == RTN_LOCAL, which should be from
the local table, but there, the fib_info's nh->nh_scope = RT_SCOPE_NOWHERE
( > RT_SCOPE_HOST). in fib_create_info().

	if (cfg->fc_scope == RT_SCOPE_HOST) {
		struct fib_nh *nh = fi->fib_nh;

		/* Local address is added. */
		if (nhs != 1 || nh->nh_gw)
			goto err_inval;
		nh->nh_scope = RT_SCOPE_NOWHERE;   <===
		nh->nh_dev = dev_get_by_index(net, fi->fib_nh->nh_oif);
		err = -ENODEV;
		if (!nh->nh_dev)
			goto failure;

but in our rpfilter_lookup_reverse():

	if (dev_match || flags & XT_RPFILTER_LOOSE)
		return FIB_RES_NH(res).nh_scope <= RT_SCOPE_HOST;

if nh->nh_scope > RT_SCOPE_HOST, it will fail. --accept-local option will never
be passed.

it seems the test is bogus and can be removed to fix this issue.

	if (dev_match || flags & XT_RPFILTER_LOOSE)
		return FIB_RES_NH(res).nh_scope <= RT_SCOPE_HOST;

ipv6 does not have this issue.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
---
 net/ipv4/netfilter/ipt_rpfilter.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/net/ipv4/netfilter/ipt_rpfilter.c b/net/ipv4/netfilter/ipt_rpfilter.c
index 8618fd1..11c5662 100644
--- a/net/ipv4/netfilter/ipt_rpfilter.c
+++ b/net/ipv4/netfilter/ipt_rpfilter.c
@@ -61,8 +61,6 @@ static bool rpfilter_lookup_reverse(struct flowi4 *fl4,
 	if (FIB_RES_DEV(res) == dev)
 		dev_match = true;
 #endif
-	if (dev_match || flags & XT_RPFILTER_LOOSE)
-		return FIB_RES_NH(res).nh_scope <= RT_SCOPE_HOST;
 	return dev_match;
 }
 
-- 
2.1.0

Re: [PATCH net] netfilter: remove the nh_scope test in rpfilter_lookup_reverse of ipt_rpfilter

[Florian Westphal]

Xin Long <lucien.xin@gmail.com> wrote:
> it seems the test is bogus and can be removed to fix this issue.
> 
> 	if (dev_match || flags & XT_RPFILTER_LOOSE)
> 		return FIB_RES_NH(res).nh_scope <= RT_SCOPE_HOST;
> 
> ipv6 does not have this issue.

netfilter patches should be sent to netfilter-devel@vger.kernel.org

>  #endif
> -	if (dev_match || flags & XT_RPFILTER_LOOSE)
> -		return FIB_RES_NH(res).nh_scope <= RT_SCOPE_HOST;
>  	return dev_match;
>  }

This breaks --loose option, no?

Thats why I earlier suggested to change this to

> -	if (dev_match || flags & XT_RPFILTER_LOOSE)
> -		return FIB_RES_NH(res).nh_scope <= RT_SCOPE_HOST;
+	return dev_match || flags & XT_RPFILTER_LOOSE;