[PATCH v2] net: netfilter: Fix ipv6 rp_filter dropping vrf packets by mistake

[PATCH v2] net: netfilter: Fix ipv6 rp_filter dropping vrf packets by mistake

[linmiaohe]

From: Miaohe Lin <linmiaohe@huawei.com>

When firewall is enabled with rp_filter, vrf ipv6 packets
will be dropped because in device is vrf but out device
is an enslaved device. So rt->rt6i_idev->dev != dev and
maybe return false in func rpfilter_lookup_reverse6.

Here is the out message when I ping the peer:
ip vrf exec vrf1 ping 2013::2 -c 1
1 packets transmitted, 0 received, 100% packet loss, time 0ms

The drop info in /var/log/message:
Apr 24 14:59:45 localhost kernel: [81316.158259] rpfilter_DROP: IN=vrf1
OUT= MAC=52:54:00:9e:dd:c1:52:54:00:4f:81:38:86:dd
SRC=2013:0000:0000:0000:0000:0000:0000:0002
DST=2013:0000:0000:0000:0000:0000:0000:0001 LEN=104 TC=0 HOPLIMIT=64
FLOWLBL=1032942 PROTO=ICMPv6 TYPE=129 CODE=0 ID=14943 SEQ=1

Signed-off-by: linmiaohe <linmiaohe@huawei.com>
---
 net/ipv6/netfilter/ip6t_rpfilter.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/net/ipv6/netfilter/ip6t_rpfilter.c b/net/ipv6/netfilter/ip6t_rpfilter.c
index c3c6b09acdc4..cf1070ab1252 100644
--- a/net/ipv6/netfilter/ip6t_rpfilter.c
+++ b/net/ipv6/netfilter/ip6t_rpfilter.c
@@ -73,6 +73,12 @@ static bool rpfilter_lookup_reverse6(struct net *net, const struct sk_buff *skb,
 		goto out;
 	}

+	if (netif_is_l3_master(dev)) {
+		dev = dev_get_by_index_rcu(dev_net(dev), IP6CB(skb)->iif);
+		if (!dev)
+			goto out;
+	}
+
 	if (rt->rt6i_idev->dev == dev || (flags & XT_RPFILTER_LOOSE))
 		ret = true;
  out:
-- 
2.19.1

Re: [PATCH v2] net: netfilter: Fix ipv6 rp_filter dropping vrf packets by mistake

[David Ahern]

On 4/24/19 3:12 AM, linmiaohe wrote:
> From: Miaohe Lin <linmiaohe@huawei.com>
> 
> When firewall is enabled with rp_filter, vrf ipv6 packets
> will be dropped because in device is vrf but out device
> is an enslaved device. So rt->rt6i_idev->dev != dev and
> maybe return false in func rpfilter_lookup_reverse6.
> 
> Here is the out message when I ping the peer:
> ip vrf exec vrf1 ping 2013::2 -c 1
> 1 packets transmitted, 0 received, 100% packet loss, time 0ms
> 
> The drop info in /var/log/message:
> Apr 24 14:59:45 localhost kernel: [81316.158259] rpfilter_DROP: IN=vrf1
> OUT= MAC=52:54:00:9e:dd:c1:52:54:00:4f:81:38:86:dd
> SRC=2013:0000:0000:0000:0000:0000:0000:0002
> DST=2013:0000:0000:0000:0000:0000:0000:0001 LEN=104 TC=0 HOPLIMIT=64
> FLOWLBL=1032942 PROTO=ICMPv6 TYPE=129 CODE=0 ID=14943 SEQ=1
> 
> Signed-off-by: linmiaohe <linmiaohe@huawei.com>
> ---
>  net/ipv6/netfilter/ip6t_rpfilter.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/net/ipv6/netfilter/ip6t_rpfilter.c b/net/ipv6/netfilter/ip6t_rpfilter.c
> index c3c6b09acdc4..cf1070ab1252 100644
> --- a/net/ipv6/netfilter/ip6t_rpfilter.c
> +++ b/net/ipv6/netfilter/ip6t_rpfilter.c
> @@ -73,6 +73,12 @@ static bool rpfilter_lookup_reverse6(struct net *net, const struct sk_buff *skb,
>  		goto out;
>  	}
> 
> +	if (netif_is_l3_master(dev)) {
> +		dev = dev_get_by_index_rcu(dev_net(dev), IP6CB(skb)->iif);
> +		if (!dev)
> +			goto out;
> +	}
> +
>  	if (rt->rt6i_idev->dev == dev || (flags & XT_RPFILTER_LOOSE))
>  		ret = true;
>   out:
> 

What about the case where XT_RPFILTER_LOOSE is set? flowi6_oif needs to
be set to the dev->ifindex if dev is an l3 master.

And looking at the IPv4 version I do not see how it could be correct
either. Have you tested it?

Re: [PATCH v2] net: netfilter: Fix ipv6 rp_filter dropping vrf packets by mistake

[linmiaohe]

On 2019/4/24 23:24, David Ahern wrote:
> On 4/24/19 3:12 AM, linmiaohe wrote:
>> From: Miaohe Lin <linmiaohe@huawei.com>
>>
>> When firewall is enabled with rp_filter, vrf ipv6 packets
>> will be dropped because in device is vrf but out device
>> is an enslaved device. So rt->rt6i_idev->dev != dev and
>> maybe return false in func rpfilter_lookup_reverse6.
>>
>> Here is the out message when I ping the peer:
>> ip vrf exec vrf1 ping 2013::2 -c 1
>> 1 packets transmitted, 0 received, 100% packet loss, time 0ms
>>
>> The drop info in /var/log/message:
>> Apr 24 14:59:45 localhost kernel: [81316.158259] rpfilter_DROP: IN=vrf1
>> OUT= MAC=52:54:00:9e:dd:c1:52:54:00:4f:81:38:86:dd
>> SRC=2013:0000:0000:0000:0000:0000:0000:0002
>> DST=2013:0000:0000:0000:0000:0000:0000:0001 LEN=104 TC=0 HOPLIMIT=64
>> FLOWLBL=1032942 PROTO=ICMPv6 TYPE=129 CODE=0 ID=14943 SEQ=1
>>
>> Signed-off-by: linmiaohe <linmiaohe@huawei.com>
>> ---
>>  net/ipv6/netfilter/ip6t_rpfilter.c | 6 ++++++
>>  1 file changed, 6 insertions(+)
>>
>> diff --git a/net/ipv6/netfilter/ip6t_rpfilter.c b/net/ipv6/netfilter/ip6t_rpfilter.c
>> index c3c6b09acdc4..cf1070ab1252 100644
>> --- a/net/ipv6/netfilter/ip6t_rpfilter.c
>> +++ b/net/ipv6/netfilter/ip6t_rpfilter.c
>> @@ -73,6 +73,12 @@ static bool rpfilter_lookup_reverse6(struct net *net, const struct sk_buff *skb,
>>  		goto out;
>>  	}
>>
>> +	if (netif_is_l3_master(dev)) {
>> +		dev = dev_get_by_index_rcu(dev_net(dev), IP6CB(skb)->iif);
>> +		if (!dev)
>> +			goto out;
>> +	}
>> +
>>  	if (rt->rt6i_idev->dev == dev || (flags & XT_RPFILTER_LOOSE))
>>  		ret = true;
>>   out:
>>
> 
> What about the case where XT_RPFILTER_LOOSE is set? flowi6_oif needs to
> be set to the dev->ifindex if dev is an l3 master.
> 

Thanks, you are right. I miss the case when XT_RPFILTER_LOOSE is set. flowi6_oif
needs to be set to the device ifindex if dev is an l3 master or l3 slave which
looks like this in function rpfilter_lookup_reverse6:

} else if ((flags & XT_RPFILTER_LOOSE) == 0) {
	fl6.flowi6_oif = dev->ifindex;
} else if (netif_is_l3_master(dev) || netif_is_l3_slave(dev))
	fl6.flowi6_oif = dev->ifindex;

> And looking at the IPv4 version I do not see how it could be correct
> either. Have you tested it?
> 
> .
> 

I thought rp_filter is ok with ipv4 version because it works in my enviroment. But
I forgot rp_filter func in my enviroment is provided by sysctl rather than iptables
rpfilter. So I tested again and found we need to fix ipv4 version too.

Thanks for your remind, I will fix all of these and send a patch v2 soon.
Thanks.