On 31.08.2010 12:04, 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.
I don't have any plans to remove the implied connect support from the socket
layer
or other protocols, only from TCP.
> 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.
>
(I won't be sorry to see the complexity go, but I'm not sure I have all the
implications in mind as
yet...)
The only implication would be a FreeBSD-only application (since nobody else ever
supported it) that depends on the TCP implied connect. While not impossible it
is unlikely for such an application to exist.
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.
--
Andre
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