Problem setting up nftables dnat : dport set to 0 instead of requested value (22)

Problem setting up nftables dnat : dport set to 0 instead of requested value (22)

[leroy christophe]

Hi,

I'm trying to redirect incoming tcp connections for port 222 to local 
port 22 (because I will dnat incoming connections for port 22 to another 
destination).
I've set the following ruleset, and logs shows that the port get value 0 
instead of 22.

What am I doing wrong ?

Thanks
Christophe

[ 7621.325382] IN=eth0 OUT= 
MAC=08:00:51:20:44:5b:08:00:27:fe:42:1e:08:00 SRC=172.25.231.37 
DST=172.25.231.5 LEN=60 TOS=0x00 PREC=0x00 TTL=64 ID=18010 DF PROTO=TCP 
SPT=54872 DPT=222 WINDOW=14600 RES=0x00 SYN URGP=0
[ 7621.325785] IN=eth0 OUT= 
MAC=08:00:51:20:44:5b:08:00:27:fe:42:1e:08:00 SRC=172.25.231.37 
DST=172.25.231.5 LEN=60 TOS=0x00 PREC=0x00 TTL=64 ID=18010 DF PROTO=TCP 
SPT=54872 DPT=0 WINDOW=14600 RES=0x00 SYN URGP=0

# nft list ruleset -nn
table ip filter {
         chain input {
                  type filter hook input priority 0;
                  oifname "lo" accept
                  ct state established,related accept
                  ct state new tcp dport 22 log accept
                  ip protocol icmp accept
                  udp dport { 138, 1534, 137, 17500, 67, 631, 68} drop
                  log reject with icmp type host-prohibited
         }
}
table ip nat {
         chain prerouting {
                  type nat hook prerouting priority 0;
                  tcp dport 222 counter packets 1 bytes 60 log dnat :22
         }

         chain postrouting {
                  type nat hook postrouting priority 0;
                  ip saddr 192.168.0.3 oif eth1 masquerade
         }
}

Re: Problem setting up nftables dnat : dport set to 0 instead of requested value (22)

[Pablo Neira Ayuso]

On Wed, Dec 10, 2014 at 03:39:04PM +0100, leroy christophe wrote:
> Hi,
> 
> I'm trying to redirect incoming tcp connections for port 222 to
> local port 22 (because I will dnat incoming connections for port 22
> to another destination).

Then you have to use "redirect" instead of "dnat". "redirect" will be
available since the upcoming 3.19-rc.

Cc'ing Arturo, he has worked on the redirect support.

@Arturo: Could you add documentation for your 'redirect' support to ?

http://wiki.nftables.org/wiki-nftables/index.php/Performing_Network_Address_Translation_%28NAT%29

Thanks.

Re: Problem setting up nftables dnat : dport set to 0 instead of requested value (22)

[Arturo Borrero Gonzalez]

On 10 December 2014 at 19:22, Pablo Neira Ayuso <pablo@netfilter.org> wrote:
>
> @Arturo: Could you add documentation for your 'redirect' support to ?
>

Done:

http://wiki.nftables.org/wiki-nftables/index.php/Performing_Network_Address_Translation_(NAT)#Redirect

regards.

-- 
Arturo Borrero Gonz√°lez

Re: Problem setting up nftables dnat : dport set to 0 instead of requested value (22)

[leroy christophe]

Le 10/12/2014 19:22, Pablo Neira Ayuso a écrit :
> On Wed, Dec 10, 2014 at 03:39:04PM +0100, leroy christophe wrote:
>> Hi,
>>
>> I'm trying to redirect incoming tcp connections for port 222 to
>> local port 22 (because I will dnat incoming connections for port 22
>> to another destination).
> Then you have to use "redirect" instead of "dnat". "redirect" will be
> available since the upcoming 3.19-rc.
>
> Cc'ing Arturo, he has worked on the redirect support.
>
> @Arturo: Could you add documentation for your 'redirect' support to ?
>
> http://wiki.nftables.org/wiki-nftables/index.php/Performing_Network_Address_Translation_%28NAT%29
>
> Thanks.
>
Thanks for the information.

I have now applied patches 8d13edd, 9de920e and e9105f1 on my 3.18 
kernel, so now the redirect rule is accepted, but I still get the same 
issue: dport gets value 0 instead of 22 after the redirect, see below

Is there any other patch to apply ?

Christophe


[  932.304106] redir IN=eth0 OUT= 
MAC=08:00:51:20:44:5b:08:00:27:fe:42:1e:08:00 SRC=172.25.231.37 
DST=172.25.231.5 LEN=60 TOS=0x00 PREC=0x00 TTL=64 ID=22863 DF PROTO=TCP 
SPT=55116 DPT=222 WINDOW=14600 RES=0x00 SYN URGP=0
[  932.304523] rejected IN=eth0 OUT= 
MAC=08:00:51:20:44:5b:08:00:27:fe:42:1e:08:00 SRC=172.25.231.37 
DST=172.25.231.5 LEN=60 TOS=0x00 PREC=0x00 TTL=64 ID=22863 DF PROTO=TCP 
SPT=55116 DPT=0 WINDOW=14600 RES=0x00 SYN URGP=0


# nft list ruleset -nn
table ip filter {
         chain input {
                  type filter hook input priority 0;
                  oifname "lo" accept
                  ct state established,related accept
                  ct state new tcp dport 22 log prefix "ssh " accept
                  ip protocol icmp accept
                  udp dport { 631, 137, 68, 67, 1534, 17500, 138} drop
                  log prefix "rejected " reject with icmp type 
host-prohibited
         }
}
table ip nat {
         chain prerouting {
                  type nat hook prerouting priority 0;
                  tcp dport 222 counter packets 1 bytes 60 log prefix 
"redir " redirect :22
         }

         chain postrouting {
                  type nat hook postrouting priority 0;
                  ip saddr 192.168.0.3 oif eth1 masquerade
         }
}

Re: Problem setting up nftables dnat : dport set to 0 instead of requested value (22)

[leroy christophe]

Le 11/12/2014 14:12, leroy christophe a écrit :
>
> Le 10/12/2014 19:22, Pablo Neira Ayuso a écrit :
>> On Wed, Dec 10, 2014 at 03:39:04PM +0100, leroy christophe wrote:
>>> Hi,
>>>
>>> I'm trying to redirect incoming tcp connections for port 222 to
>>> local port 22 (because I will dnat incoming connections for port 22
>>> to another destination).
>> Then you have to use "redirect" instead of "dnat". "redirect" will be
>> available since the upcoming 3.19-rc.
>>
>> Cc'ing Arturo, he has worked on the redirect support.
>>
>> @Arturo: Could you add documentation for your 'redirect' support to ?
>>
>> http://wiki.nftables.org/wiki-nftables/index.php/Performing_Network_Address_Translation_%28NAT%29 
>>
>>
>> Thanks.
>>
> Thanks for the information.
>
> I have now applied patches 8d13edd, 9de920e and e9105f1 on my 3.18 
> kernel, so now the redirect rule is accepted, but I still get the same 
> issue: dport gets value 0 instead of 22 after the redirect, see below
>
> Is there any other patch to apply ?
>
> Christophe
>
Issue identified. I'll write another mail to explain it.

Christophe
>
> [  932.304106] redir IN=eth0 OUT= 
> MAC=08:00:51:20:44:5b:08:00:27:fe:42:1e:08:00 SRC=172.25.231.37 
> DST=172.25.231.5 LEN=60 TOS=0x00 PREC=0x00 TTL=64 ID=22863 DF 
> PROTO=TCP SPT=55116 DPT=222 WINDOW=14600 RES=0x00 SYN URGP=0
> [  932.304523] rejected IN=eth0 OUT= 
> MAC=08:00:51:20:44:5b:08:00:27:fe:42:1e:08:00 SRC=172.25.231.37 
> DST=172.25.231.5 LEN=60 TOS=0x00 PREC=0x00 TTL=64 ID=22863 DF 
> PROTO=TCP SPT=55116 DPT=0 WINDOW=14600 RES=0x00 SYN URGP=0
>

bug : nft_redirect port byteorder issue

[leroy christophe]

Hi,

table ip nat {
         chain prerouting {
                  type nat hook prerouting priority 0;
                  tcp dport 222 redirect :22
         }
         chain postrouting {
                  type nat hook postrouting priority 0;
         }
}

With the above rules, data[priv->sreg_proto_min].data[0] has value 
0x160000 instead of 0x16 on powerpc (Big Endian byte order)

Due to this, mr.range[0].min.all gets assigned value 0 instead of 22.

Below patch fixes it, but it is maybe not the proper way to fix it, so I 
let it up to you.

Christophe

diff --git a/net/ipv4/netfilter/nft_redir_ipv4.c 
b/net/ipv4/netfilter/nft_redir_ipv4.c
index 643c596..554bb32 100644
--- a/net/ipv4/netfilter/nft_redir_ipv4.c
+++ b/net/ipv4/netfilter/nft_redir_ipv4.c
@@ -28,9 +28,9 @@ static void nft_redir_ipv4_eval(const struct nft_expr 
*expr,
  	memset(&mr, 0, sizeof(mr));
  	if (priv->sreg_proto_min) {
  		mr.range[0].min.all = (__force __be16)
-					data[priv->sreg_proto_min].data[0];
+					*(__be16*)&data[priv->sreg_proto_min].data[0];
  		mr.range[0].max.all = (__force __be16)
-					data[priv->sreg_proto_max].data[0];
+					*(__be16*)&data[priv->sreg_proto_max].data[0];
  		mr.range[0].flags |= NF_NAT_RANGE_PROTO_SPECIFIED;
  	}