Re: [Lksctp-developers] sctp_get_no_strms not work, getsockopt error: Invalid argument

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On Oct 21, 2012, at 2:39 PM, Michael Tuexen <Mic...@lu...> wrote:

> On Oct 21, 2012, at 8:00 PM, Neil Horman wrote:
> 
>> On Sun, Oct 21, 2012 at 12:38:50PM +0200, Michael Tuexen wrote:
>>> On Oct 21, 2012, at 10:16 AM, Zhu Bicen wrote:
>>> 
>>>> Thanks Michael. 
>>>> It looks issue in UNP code, or portability problem.
>>>> 
>>>> I found the option SCTP_GET_PEER_ADDR_INFO can work(get the valid asssociation id)
>>>> but not SCTP_PEER_ADDR_PARAMS. and later i can use the association id to get the number of out streams.
>>> In FreeBSD both work. I don't see a reason why SCTP_PEER_ADDR_PARAMS shouldn't support it.
>> For what its worth it apparers that sctp_getsockopt_peer_addr_params presumes
>> that spp_assoc_id is a passed in value, which it will use to look up information
>> about the requested peer address.  I.e. it expects that you first call
>> sctp_get_peer_addr_info to retrieve the needed association id.  Nominally if you
>> pass in a zero for your assoc id, you will get a EINVAL return from
>> SCTP_PEER_ADDR_PARAMS, as it will not match the association id returned by the
>> address lookup.  The exception to that rule is if you are using a SOCK_STREAM
>> socket, in which case, only one transport is available to the socket, which is
>> what will be returned.  The function will not howver copy in the association id
>> to the sctp_paddrparams structure, as it assume the user has already filled that
>> field out.  This seems (by my reading) to be in line with whats expected in
>> section 8.1.12 of RFC 6458, although, at least in the case of stream sockets,
>> that it certainly wouldn't hurt to fill in the association id like we do with
>> PEER_ADDR_INFO.
>> 
>> Thoughts?
> For one-to-one style sockets the assoc id is not relevant. For one-to-many
> style sockets we try the socket and the assoc_id first to find the
> association. If that does not work, we try to find the association
> based on the socket and the address provided. We do this for
> SCTP_GET_PEER_ADDR_INFO and SCTP_PEER_ADDR_PARAMS. (We means FreeBSD...).
> I agree, this behavior is not stated explicitly in the socket API RFC,
> but I think both should behave the same for consistency.
> So it might be a solution if Linux can do the same. Haven't tested what
> Solaris does. Then we could file an error on the socket API RFC to
> make things clear.
> 

I agree that we could do a lookup for a GET operation, but a set operation needs to specify associd if it is needed.  I just checked the spec and it is totally silent on the matter.  On the other hand, description for SCTP_GET_PEER_ADDR_INFO is very clear as to what should happen and even mentions that the call can be used as a mapping from address to associd.   The more I think about it, the more I think that we need only 1 way to do it.  Seems that the wrong option was chosen by the library implementation in this case.

-vlad

> Best regards
> Michael
>> Neil
>> 
>>>> 
>>>> Thanks!
>>>> 
>>>> I got following info from Sockets API Extensions for Stream Control Transmission Protocol (SCTP) draft-ietf-tsvwg-sctpsocket-09.txt:
>>> Just a hint: The ID version is very old, so use RFC 6458 instead.
>>> 
>>> Best regards
>>> Michael
>>>> 
>>>> 7.2.2 Peer Address Information (SCTP_GET_PEER_ADDR_INFO)
>>>> Applications can retrieve information about a specific peer address
>>>> of an association, including its reachability state, congestion
>>>> window, and retransmission timer values. This information is
>>>> read-only. The following structure is used to access this
>>>> information:
>>>> struct sctp_paddrinfo {
>>>> sctp_assoc_t spinfo_assoc_id;
>>>> struct sockaddr_storage spinfo_address;
>>>> int32_t spinfo_state;
>>>> uint32_t spinfo_cwnd;
>>>> uint32_t spinfo_srtt;
>>>> uint32_t spinfo_rto;
>>>> uint32_t spinfo_mtu;
>>>> };
>>>> 
>>>> On Sun, Oct 21, 2012 at 3:42 PM, Michael Tuexen <Mic...@lu...> wrote:
>>>> On Oct 21, 2012, at 8:09 AM, Zhu Bicen wrote:
>>>> 
>>>>> Thanks Neil so much.
>>>>> 
>>>>> I find the returned association id is ZERO.
>>>>> Following info also found on Unix Network Programming Volume 1 3rd edition:
>>>>> The function(sctp_address_to_associd) returns the association ID to the
>>>>> caller. Note that if the call fails, the earlier clearing of the structure
>>>>> will assure our caller of getting a 0 as the returned association ID. *An
>>>>> association ID of 0 is not **allowed and is used to indicate no association
>>>>> by the SCTP implementation as well.*i
>>>>> 
>>>>> The implementation of sctp_address_to_associd is like below, the input
>>>>> argument i also checked
>>>>> the sa, and salen is valid, the sctp_opt_info also return success.
>>>>> the client data(sent by sctp_sendmsg) has been received by this server
>>>>> program. Then the socket has been worked, but why it's has an invalid
>>>>> association id, Which situation can lead to this(a zero association id)?
>>>>> 
>>>>> 
>>>>> 
>>>>> sctp_assoc_t
>>>>> sctp_address_to_associd(int sock_fd, struct sockaddr *sa, socklen_t salen)
>>>>> {
>>>>>  struct sctp_paddrparams sp;
>>>>>  int siz;
>>>>> 
>>>>>  siz = sizeof(struct sctp_paddrparams);
>>>>>  bzero(&sp,siz);
>>>>>  memcpy(&sp.spp_address,sa,salen);
>>>>>  int ret = sctp_opt_info(sock_fd,0,
>>>>>              SCTP_PEER_ADDR_PARAMS, &sp, &siz);
>>>>>  if (ret != 0){
>>>>>    printf("sctp_opt_info fatal, ret = %d\n", ret);
>>>>>    exit(1);
>>>>>  }
>>>>>  return(sp.spp_assoc_id);
>>>>> }
>>>> Could it be that Linux does not look up the association by address
>>>> if the association is not found by assoc_id when processing the
>>>> getsockopt() of SCTP_PEER_ADDR_PARAMS? At least FreeBSD does this
>>>> and the UNP code was written using FreeBSD...
>>>> 
>>>> Best regards
>>>> Michael
>>>>> 
>>>>> Thanks!
>>>>> 
>>>>> 
>>>>> On Sun, Oct 21, 2012 at 10:22 AM, Neil Horman <nh...@tu...> wrote:
>>>>> 
>>>>>> On Sat, Oct 20, 2012 at 11:24:05PM +0800, Zhu Bicen wrote:
>>>>>>> Hello, all,
>>>>>>> 
>>>>>>> There is a problem when trying the first SCTP example(10.2 SCTP
>>>>>>> One-to-Many-Style Streaming Echo Server sctpserv01.c ) on Unix Network
>>>>>>> Programming.
>>>>>>> 
>>>>>>> The issue is the the call to sctp_get_no_strms fail due to getsockopt
>>>>>>> error: Invalid argument.
>>>>>>> 
>>>>>>> I tried this also on Debian 6, and CentOs 6.3, both have the same issue.
>>>>>>> the sctp related toos and lib all installed by apt-get, i didn't build
>>>>>>> these manually.
>>>>>>> 
>>>>>>> Linux debian 2.6.32-5-686 #1 SMP Sun Sep 23 09:49:36 UTC 2012 i686
>>>>>> GNU/Linux
>>>>>>> 
>>>>>>> Has anyone met this issue before?
>>>>>>> 
>>>>>>> Thanks!
>>>>>>> 
>>>>>> Theres only 2 reasons that calling that socket options returns EINVAL, if
>>>>>> you
>>>>>> don't pass in at least sizeof(struct sctp_status) bytes of data, or if your
>>>>>> association id is invalid.  Since its pretty clear your passing in enough
>>>>>> of a
>>>>>> buffer, I imagine the sctp_address_to_associd is returning an association
>>>>>> id
>>>>>> thats invalid.  What does your implementation of that function look like?
>>>>>> 
>>>>>> Also, a nit, you probably don't want to pass IPPROTO_SCTP as your socket
>>>>>> level
>>>>>> arugment.  SOL_SCTP is the right define to pass.  Both are defined to be
>>>>>> the
>>>>>> same value in linux, so its not a big deal, but you probably want to use
>>>>>> the
>>>>>> latter value to make your code portable.
>>>>>> 
>>>>>> Neil
>>>>>> 
>>>>>>> 
>>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> --
>>>>> Best Regards
>>>>> Bicen Zhu
>>>>> ------------------------------------------------------------------------------
>>>>> Everyone hates slow websites. So do we.
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>>>>> 
>>>> 
>>>> 
>>>> 
>>>> 
>>>> -- 
>>>> Best Regards
>>>> Bicen Zhu
>>> 
>>> 
>> 
> 
> 
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