Removal of deprecated implied connect for TCP

[Randall Stewart]

All:

One thing to note.. when you can do an implied connection setup, the
3-way hand shake has the potential to carry data (don't know if tcp  
does in FreeBSD)
on the third leg of the 3-way handshake.

This is one of the reasons SCTP uses this.. since we often will
carry data an the third and even possibly the 4th leg of the handshake  
(we
have one extra leg).

Taking this feature out of TCP will make it so we will be like all other
o/s's and the socket semantic will prevent you from doing data on the  
third leg..

----SYN---->
<----SYN-ACK---
----ACK--->

instead of

----SYN-->
<---SYN-ACk--
---ACK+DATA-->


In the past I have mentioned in classes I teach that TCP is capable of  
this but the O/S's
of the world do not allow this later behavior..

Just thoughts and ramblings ;-)

R


On Sep 10, 2010, at 2:51 PM, Karim Fodil-Lemelin wrote:

> On 31/08/2010 5:32 PM, Robert Watson wrote:
>>
>> On Tue, 31 Aug 2010, Andre Oppermann wrote:
>>
>>>> I'm not entirely comfortable with this change, and would like a  
>>>> chance to cogitate on it a bit more. While I'm not aware of any  
>>>> applications depending on the semantic for TCP, I know that we do  
>>>> use it for UNIX domain sockets.
>>>
>>> I don't have any plans to remove the implied connect support from  
>>> the socket layer or other protocols, only from TCP.
>>
>> Right -- the implicit question is: why should TCP be the only  
>> stream protocol in our stack *not* to support implied connection,  
>> when we plan to continue to support it for all other protocols?
>>
>>> For deprecating this part of the TCP API there is no documentation  
>>> to the implied connect in tcp(4).  In sendto(2) it doesn't  
>>> differentiate between protocols and simply says: "... sendto() and  
>>> sendmsg() may be used at any time."  For MSG_EOF it says that is  
>>> only supported for SOCK_STREAM sockets in the PF_INET protocol  
>>> family. These sentences have to be corrected.
>>
>> In general, deprecating is taken to mean providing significant and  
>> explicit advance warning of removal -- for example, updating the  
>> 8.x man page to point out that the feature is deprecated and it  
>> will not appear in future releases of FreeBSD.
>>
>> Robert
>>
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> Hi,
>
> For what its worth, we at Xiphos (now XipLink), are still using  
> sendto and T/TCP and is one of the reasons we've chosen FreeBSD more  
> then 10 years ago!
>
> Best regards,
>
> Karim.
> _______________________________________________
> freebsd-net at freebsd.org mailing list
> http://lists.freebsd.org/mailman/listinfo/freebsd-net
> To unsubscribe, send any mail to "freebsd-net-unsubscribe at freebsd.org"
>

------------------------------
Randall Stewart
803-317-4952 (cell)