Re: [Lksctp-developers] How to send ASCONF chunk with "Add IP Address Parameter" value set to 0.0.0.0

[Michael T. <Mic...@lu...>]

On Sep 18, 2009, at 9:25 PM, Bhaskar Dutta wrote:

>> From: Michael Tüxen [mailto:Mic...@lu...]
>>
>> On Sep 18, 2009, at 1:34 PM, Bhaskar Dutta wrote:
>>
>>> Hi All,
>>>
>>> Section 4.2.1 (Add IP Address) of RFC 5061 (SCTP Dynamic Address
>>> Reconfiguration) says:
>>>
>>> "  Address Parameter: TLV
>>>  If the address 0.0.0.0 or ::0 is provided, the source address of
>>> the packet MUST be added."
>>>
>>> Since sctp_bindx API doesn't provide any arguments to specify the
>>> source IP address, how can a client send an ASCONF chunk with source
>>> IP different from the INIT's source?
>>>
>>> The linux kernel upon reception of an ASCONF Chunk, uses the
>>> packet's source IP when the IP address parameter is 0.0.0.0 or ::0.
>>> But I couldn't find any analogous code when the user calls a
>>> sctp_bindx
>> The kernel can send the packets using 0.0.0.0 without explicitly  
>> being
>> asked to do so via the socket API.
>>
>> For example if the application binds to the wildcard address, the  
>> kernel
>> can setup the association single homed and then add the addresses.
>
> My application server using SCTP over SIP cannot bind to *, it can  
> bind to a specific set of addresses only. I can start with single- 
> homed all right, but how do I achieve the above then?
I guess you mean SIP/SCTP, right?
But what is the sense of explicitly binding to a set of private  
addresses the
peer never sees? Could you provide some information about the  
addressing you
are expecting to use?
>
> Thanks,
> Bhaskar
>
>
>>>
>>> I looked into function sctp_setsockopt_bindx -> sctp_bindx_add ->
>>> sctp_send_asconf_add_ip, sctp_send_asconf,  
>>> sctp_make_asconf_update_ip
>>> (net/sctp/socket.c).
>>>
>>> Am I missing something or this requires an extension in the
>>> sctp_bindx API as well as the kernel implementation?
>>>
>>> TIA.
>>>
>>> Regards,
>>> Bhaskar
>
>
>