wrong family for IP addresses given by sctp library

wrong family for IP addresses given by sctp library

[Boiteux Frederic]

          Hello,

I'm trying to use SCTP on Linux machines with 'old' kernels (Debian 5, 2.6.26 kernel and Debian 7, 3.2 kernel). I've setup a program which can handles IPv4 and IPv6 addresses, and for that, I use a socket with AF_INET6 family, then I bind it to IPv4 or v6 addresses with sctp_bindx() (its manual page says this call can handle both v4 and v6 adresses if the socket is an IPv6 one).
It seems to work well, but I have a strange behavior : on a test platform with only IPv4 addresses, when I get messages or notifications (using sctp_recvmsg()), the addresses given in it (IP address of the sender, or confirmation/fail of some peer addresses) are always from the IPv6 family !
For example, for received messages, the « from » socket address returned by sctp_recvmsg() has always a sa_family field to AF_INET6, even if the address is in fact an IPv4 address ! Using getnameinfo() with NI_NUMERICHOST option, I  can get the ascii representation of the address, a 4 dotted address, and then I have to fix the address to use it with its real family (as I expected to receive).
It seems to be directly related to the AF_INET6 family of the socket, but I don't know if it' s a known problem, possibly fixed since then in latest linux-sctip library, or probably a programmatic error from me.

  Have you ever heard for such problem ? What is your feeling about ?

	With regards,
                      Fred.

Re: wrong family for IP addresses given by sctp library

[Ivan Skytte Jørgensen]

On Wednesday 03 December 2014 11:50:31 Boiteux Frederic wrote:
> 
> I'm trying to use SCTP on Linux machines with 'old' kernels (Debian 5, 2.6.26 kernel and Debian 7, 3.2 kernel). I've setup a program which can handles IPv4 and IPv6 addresses, and for that, I use a socket with AF_INET6 family, then I bind it to IPv4 or v6 addresses with sctp_bindx() (its manual page says this call can handle both v4 and v6 adresses if the socket is an IPv6 one).
> It seems to work well, but I have a strange behavior : on a test platform with only IPv4 addresses, when I get messages or notifications (using sctp_recvmsg()), the addresses given in it (IP address of the sender, or confirmation/fail of some peer addresses) are always from the IPv6 family !

Isn't the returned address simply a IPv6-mapped IPv4 address (::ffff:1.2.3.4) ? You can test it with IN6_IS_ADDR_V4MAPPED.


/isj

Re: wrong family for IP addresses given by sctp library

[Michael Tuexen]

On 03 Dec 2014, at 11:50, Boiteux Frederic <fboiteux@prosodie.com> wrote:

>          Hello,
> 
> I'm trying to use SCTP on Linux machines with 'old' kernels (Debian 5, 2.6.26 kernel and Debian 7, 3.2 kernel). I've setup a program which can handles IPv4 and IPv6 addresses, and for that, I use a socket with AF_INET6 family, then I bind it to IPv4 or v6 addresses with sctp_bindx() (its manual page says this call can handle both v4 and v6 adresses if the socket is an IPv6 one).
> It seems to work well, but I have a strange behavior : on a test platform with only IPv4 addresses, when I get messages or notifications (using sctp_recvmsg()), the addresses given in it (IP address of the sender, or confirmation/fail of some peer addresses) are always from the IPv6 family !
Is it possible that the address are mapped V4 addresses?

Best regards
Michael
> For example, for received messages, the « from » socket address returned by sctp_recvmsg() has always a sa_family field to AF_INET6, even if the address is in fact an IPv4 address ! Using getnameinfo() with NI_NUMERICHOST option, I  can get the ascii representation of the address, a 4 dotted address, and then I have to fix the address to use it with its real family (as I expected to receive).
> It seems to be directly related to the AF_INET6 family of the socket, but I don't know if it' s a known problem, possibly fixed since then in latest linux-sctip library, or probably a programmatic error from me.
> 
>  Have you ever heard for such problem ? What is your feeling about ?
> 
> 	With regards,
>                      Fred.
> 
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Re: wrong family for IP addresses given by sctp library

[Daniel Borkmann]

On 12/03/2014 12:25 PM, Michael Tuexen wrote:
> On 03 Dec 2014, at 11:50, Boiteux Frederic <fboiteux@prosodie.com> wrote:
>
>>           Hello,
>>
>> I'm trying to use SCTP on Linux machines with 'old' kernels (Debian 5, 2.6.26 kernel and Debian 7, 3.2 kernel). I've setup a program which can handles IPv4 and IPv6 addresses, and for that, I use a socket with AF_INET6 family, then I bind it to IPv4 or v6 addresses with sctp_bindx() (its manual page says this call can handle both v4 and v6 adresses if the socket is an IPv6 one).
>> It seems to work well, but I have a strange behavior : on a test platform with only IPv4 addresses, when I get messages or notifications (using sctp_recvmsg()), the addresses given in it (IP address of the sender, or confirmation/fail of some peer addresses) are always from the IPv6 family !
> Is it possible that the address are mapped V4 addresses?

Hmm, Frederic, could you try with a current kernel? We've had fixes
in the past such as ...

commit 299ee123e19889d511092347f5fc14db0f10e3a6
Author: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Date:   Wed Jul 30 12:40:53 2014 -0600

     sctp: Fixup v4mapped behaviour to comply with Sock API

> Best regards
> Michael
>> For example, for received messages, the « from » socket address returned by sctp_recvmsg() has always a sa_family field to AF_INET6, even if the address is in fact an IPv4 address ! Using getnameinfo() with NI_NUMERICHOST option, I  can get the ascii representation of the address, a 4 dotted address, and then I have to fix the address to use it with its real family (as I expected to receive).
>> It seems to be directly related to the AF_INET6 family of the socket, but I don't know if it' s a known problem, possibly fixed since then in latest linux-sctip library, or probably a programmatic error from me.
>>
>>   Have you ever heard for such problem ? What is your feeling about ?
>>
>> 	With regards,
>>                       Fred.
>>
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>> the body of a message to majordomo@vger.kernel.org
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>>
>
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RE: wrong family for IP addresses given by sctp library

[Boiteux Frederic]

	Hello Ivan, Michael, Daniel,

> Isn't the returned address simply a IPv6-mapped IPv4 address (::ffff:1.2.3.4) ? You can test it with IN6_IS_ADDR_V4MAPPED.

Yes, it is (I've verified with the provided macro) ! I'll use this macro to detect and update provided addresses, thanks !


Daniel, I'll try to test it on a recent kernel, but it will take some time to set up... thanks for the commit's reference !

	Regards,
		Fred.

Re: wrong family for IP addresses given by sctp library

[Michael Tuexen]

On 03 Dec 2014, at 14:27, Boiteux Frederic <fboiteux@prosodie.com> wrote:

> 	Hello Ivan, Michael, Daniel,
> 
>> Isn't the returned address simply a IPv6-mapped IPv4 address (::ffff:1.2.3.4) ? You can test it with IN6_IS_ADDR_V4MAPPED.
> 
> Yes, it is (I've verified with the provided macro) ! I'll use this macro to detect and update provided addresses, thanks !
Not sure if LKSCTP supports it, but you can use
https://tools.ietf.org/html/rfc6458#section-8.1.15
to control if the addresses should be provided as IPv4 addresses or mapped IPv6 ones.

Best regards
Michael
> 
> 
> Daniel, I'll try to test it on a recent kernel, but it will take some time to set up... thanks for the commit's reference !
> 
> 	Regards,
> 		Fred.
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Re: wrong family for IP addresses given by sctp library

[Vlad Yasevich]

On 12/03/2014 10:30 AM, Michael Tuexen wrote:
> On 03 Dec 2014, at 14:27, Boiteux Frederic <fboiteux@prosodie.com> wrote:
> 
>> 	Hello Ivan, Michael, Daniel,
>>
>>> Isn't the returned address simply a IPv6-mapped IPv4 address (::ffff:1.2.3.4) ? You can test it with IN6_IS_ADDR_V4MAPPED.
>>
>> Yes, it is (I've verified with the provided macro) ! I'll use this macro to detect and update provided addresses, thanks !
> Not sure if LKSCTP supports it, but you can use
> https://tools.ietf.org/html/rfc6458#section-8.1.15
> to control if the addresses should be provided as IPv4 addresses or mapped IPv6 ones.

Yes it's supported, but there was an issue that was recently fixed.

-vlad

> 
> Best regards
> Michael
>>
>>
>> Daniel, I'll try to test it on a recent kernel, but it will take some time to set up... thanks for the commit's reference !
>>
>> 	Regards,
>> 		Fred.
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>>
> 
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RE: wrong family for IP addresses given by sctp library

[Boiteux Frederic]

>> Isn't the returned address simply a IPv6-mapped IPv4 address (::ffff:1.2.3.4) ? You can test it with IN6_IS_ADDR_V4MAPPED.

> Yes, it is (I've verified with the provided macro) ! I'll use this macro to detect and update provided addresses, thanks !

Testing more carefully, no it actually seems NOT to be IPv4-mapped addresses !

I test it like this :

static struct sockaddr *fix_adr(struct sockaddr *addr)
{
    if (addr->sa_family != AF_INET6) {
        log_info("not an IPv6 address, nothing to do\n");
        return addr;
    }

  struct sockaddr_in6 *addr6 = (struct sockaddr_in6 *) &addr;
    if (! IN6_IS_ADDR_V4MAPPED(&(addr6->sin6_addr))) {
        log_warn("@IP v6 '%s' is NOT an IPv4-mapped address !",
                   addr_ntoa(addr));
    }

  // convert it to ipv4 addr...
...
}

I get messages like :
@IP v6 '10.7.11.132' is NOT an IPv4-mapped address!

(the addr_ntoa() function uses getnameinfo(..., NI_NUMERICHOST) to retrieve ascii notation from given sockaddr address).

  I'm not fluent with IPv6 addressing, so I don't know what to check...

	Fred.