Date: Tue, 31 Aug 2010 15:25:15 +0200 From: Andre Oppermann <andre@freebsd.org> To: =?ISO-8859-1?Q?Michael_T=FCxen?= <Michael.Tuexen@lurchi.franken.de> Cc: freebsd-net@freebsd.org, Robert Watson <rwatson@freebsd.org> Subject: Re: Removal of deprecated implied connect for TCP Message-ID: <4C7D02BB.40300@freebsd.org> In-Reply-To: <7B42D7FB-B782-4EE9-8813-BF7D3ED3274B@lurchi.franken.de> References: <4C7A7B25.9040300@freebsd.org> <alpine.BSF.2.00.1008311102220.22661@fledge.watson.org> <7B42D7FB-B782-4EE9-8813-BF7D3ED3274B@lurchi.franken.de>
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On 31.08.2010 15:01, Michael Tüxen wrote: > 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... sendto() will not be touched or modified. It's just that on a TCP socket the tcp protocol will not perform an implied connect anymore. The only thing that changes is TCP dropping a deprecated and experimental extension and behaving like every other UNIXy OS. sendto() will continue to work for UDP, SCTP and Domain sockets and whoever else currently supports it, except TCP. -- Andre
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