How to change source port in MASQUERADE mode?

How to change source port in MASQUERADE mode?

[Richard Liu]

Hi,
I have a question about change tuple source port.
I have a nat device, and I want this device can change tuple source port
in some special conditions (not always).

I want change tuple source port in MASQUERADE module.

for example:
    Destination                Gateway                Source
    DA(Ipaddr):Port          GA:Port                SA:Port

In Masquerade modules
                                    src:GA:1000           src:SA:1000
                                    dst:DA:23               dst:DA:23

But I want to the src port be changed in some conditions like this.
                                    src:GA:50000+1000  src:SA:1000
                                    dst:DA:23               dst:DA:23

I am tracing source few days, but I still don't know which function
allocate tuple source port.
Does anyone can give me some hints, I am very appreciate.

Re: How to change source port in MASQUERADE mode?

[Henrik Nordstrom]

On Fri, 30 Sep 2005, Richard Liu wrote:

> I want change tuple source port in MASQUERADE module.

--to-ports option to MASQUERADE (or SNAT if not dynamic IP assignment).

> But I want to the src port be changed in some conditions like this.
>                                    src:GA:50000+1000  src:SA:1000
>                                    dst:DA:23               dst:DA:23

Then you simply need rules matching your conditions.

Regards
Henrik

Re: How to change source port in MASQUERADE mode?

[Richard Liu]

Henrik Nordstrom 提到:

Thanks for your mail,

But --to-port parameter cannot get tuple port result like "50000+1000"

I found a way for this situation.

in file ip_MASQUERADE.c
we can change
mr->range[0].min,
mr->range[0].max
and set
mr->range[0].flags = IP_NAT_RANGE_PROTO_SPECIFIED;
for some special purposes.

but I don't know does it have other effects to the netfilter?

> On Fri, 30 Sep 2005, Richard Liu wrote:
>
>> I want change tuple source port in MASQUERADE module.
>
>
> --to-ports option to MASQUERADE (or SNAT if not dynamic IP assignment).
>
>> But I want to the src port be changed in some conditions like this.
>> src:GA:50000+1000 src:SA:1000
>> dst:DA:23 dst:DA:23
>
>