Removal of deprecated implied connect for TCP

[Michael Tüxen]

On Aug 31, 2010, at 12:04 PM, Robert Watson wrote:

> 
> On Sun, 29 Aug 2010, Andre Oppermann wrote:
> 
>> When T/TCP RFC1644 support was introduced in r6283 by wollman 15 years ago the semantics of sendto(2) with regard to TCP sockets were changed.
>> 
>> It became possible directly do a sendto(2) call with the target address in the *to argument instead of doing a connect(2) first and subsequent write(2) or send(2) calls as the standard TCP API specifies.  Optionally MSG_EOR could be specified to close the connection again right again after the data has been sent out.
>> 
>> This is totally non-portable and no other OS (Linux, NetBSD, OpenBSD, Solaris, HP-UX) ever supported this functionality for TCP sockets. FreeBSD was the only OS to ever ship this.
>> 
>> T/TCP was ill-defined and had major security issues and never gained any support. It has been defunct in FreeBSD and most code has been removed about 6 years ago.  The sendto(2) extended functionality is one of the last parts that persisted and remained around living a zombie life.
>> 
>> I want to remove it now because it is totally non-portable, has no known users and complicates the TCP send path.  The patch is attached.
>> 
>> If you have any objections speak up now.
> 
> 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. Since it's a documented API, if we are going to remove it, then we need to go through a deprecation process, not least by marking it as a deprecated API in 8.x before having it vanish in 9.0.
sendto() is also used for SCTP SOCK_STREAMS and SOCK_SEQPACKET sockets...

Best regards
Michael
> 
> (I won't be sorry to see the complexity go, but I'm not sure I have all the implications in mind as yet...)
> 
> Robert
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