struct msghdr in socket.h is wrong

struct msghdr in socket.h is wrong

[Sam Steingold]

cyswin/socket.h:

struct msghdr
{
	void	*	msg_name;	/* Socket name			*/
	int		msg_namelen;	/* Length of name		*/
	struct iovec *	msg_iov;	/* Data blocks			*/
	int		msg_iovlen;	/* Number of blocks		*/
	void	*	msg_accrights;	/* Per protocol magic (eg BSD file descriptor passing) */
	int		msg_accrightslen;	/* Length of rights list */
};

http://www.opengroup.org/onlinepubs/009695399/basedefs/sys/socket.h.html:

void          *msg_name        Optional address. 
socklen_t      msg_namelen     Size of address. 
struct iovec  *msg_iov         Scatter/gather array. 
int            msg_iovlen      Members in msg_iov. 
void          *msg_control     Ancillary data; see below. 
socklen_t      msg_controllen  Ancillary data buffer len. 
int            msg_flags       Flags on received message.

problems:

1. msg_flags is missing
2. msg_control is renamed msg_accrights
3. msg_controllen is renamed msg_accrightslen

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Re: struct msghdr in socket.h is wrong

[Corinna Vinschen]

On Oct 12 15:17, Sam Steingold wrote:
> cyswin/socket.h:
> 
> struct msghdr
> {
> 	void	*	msg_name;	/* Socket name			*/
> 	int		msg_namelen;	/* Length of name		*/
> 	struct iovec *	msg_iov;	/* Data blocks			*/
> 	int		msg_iovlen;	/* Number of blocks		*/
> 	void	*	msg_accrights;	/* Per protocol magic (eg BSD file descriptor passing) */
> 	int		msg_accrightslen;	/* Length of rights list */
> };

This is the so called "older" implementation of struct msghdr as defined
up to 4.2BSD.  Since it's quite useless so far and since applications
using this structure should accomodate the old implementation anyway,
I don't see a good reason to change this right now.


Corinna

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Re: struct msghdr in socket.h is wrong

[Sam Steingold]

> * Corinna Vinschen <pbevaan-pltjva@pltjva.pbz> [2005-10-12 22:42:34 +0200]:
>
> On Oct 12 15:17, Sam Steingold wrote:
>> cyswin/socket.h:
>> 
>> struct msghdr
>> {
>> 	void	*	msg_name;	/* Socket name			*/
>> 	int		msg_namelen;	/* Length of name		*/
>> 	struct iovec *	msg_iov;	/* Data blocks			*/
>> 	int		msg_iovlen;	/* Number of blocks		*/
>> 	void	*	msg_accrights;	/* Per protocol magic (eg BSD file descriptor passing) */
>> 	int		msg_accrightslen;	/* Length of rights list */
>> };
>
> This is the so called "older" implementation of struct msghdr as
> defined up to 4.2BSD.  Since it's quite useless so far and since

I am not sure I quite understand what you mean by useless.
is cygwin implementation somehow deficient?

> applications using this structure should accomodate the old
> implementation anyway, I don't see a good reason to change this right
> now.

the only reason applications have to accommodate the old implementation
is that some unixes still stick with it.
if you switch to the posix msghdr, I, for one, would not have to
accomodate the old implementation.

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Re: struct msghdr in socket.h is wrong

[Corinna Vinschen]

On Oct 15 22:23, Sam Steingold wrote:
> > * Corinna Vinschen <pbevaan-pltjva@pltjva.pbz> [2005-10-12 22:42:34 +0200]:
> >
> > On Oct 12 15:17, Sam Steingold wrote:
> >> cyswin/socket.h:
> >> 
> >> struct msghdr
> >> {
> >> 	void	*	msg_name;	/* Socket name			*/
> >> 	int		msg_namelen;	/* Length of name		*/
> >> 	struct iovec *	msg_iov;	/* Data blocks			*/
> >> 	int		msg_iovlen;	/* Number of blocks		*/
> >> 	void	*	msg_accrights;	/* Per protocol magic (eg BSD file descriptor passing) */
> >> 	int		msg_accrightslen;	/* Length of rights list */
> >> };
> >
> > This is the so called "older" implementation of struct msghdr as
> > defined up to 4.2BSD.  Since it's quite useless so far and since
> 
> I am not sure I quite understand what you mean by useless.
> is cygwin implementation somehow deficient?
> 
sendmsg and recvmsg don't utilize the msg_accrights/msg_accrightslen member.

> > applications using this structure should accomodate the old
> > implementation anyway, I don't see a good reason to change this right
> > now.
> 
> the only reason applications have to accommodate the old implementation
> is that some unixes still stick with it.

So, from a portability perspective...

> if you switch to the posix msghdr, I, for one, would not have to
> accomodate the old implementation.

I won't change it now.  I'll change it at one point when there's some
functionality.

Hint: Applications using only the first four members of this structure
will be binary compatible...


Corinna

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Re: struct msghdr in socket.h is wrong

[Corinna Vinschen]

On Oct 17 10:44, Corinna Vinschen wrote:
> On Oct 15 22:23, Sam Steingold wrote:
> > > * Corinna Vinschen [2005-10-12 22:42:34 +0200]:
> > > On Oct 12 15:17, Sam Steingold wrote:
> > >> cyswin/socket.h:
> > >> 
> > >> struct msghdr
> > >> {
> > >> 	void	*	msg_name;	/* Socket name			*/
> > >> 	int		msg_namelen;	/* Length of name		*/
> > >> 	struct iovec *	msg_iov;	/* Data blocks			*/
> > >> 	int		msg_iovlen;	/* Number of blocks		*/
> > >> 	void	*	msg_accrights;	/* Per protocol magic (eg BSD file descriptor passing) */
> > >> 	int		msg_accrightslen;	/* Length of rights list */
> > >> };
> > >
> > > This is the so called "older" implementation of struct msghdr as
> > > defined up to 4.2BSD.  Since it's quite useless so far and since
> > 
> > I am not sure I quite understand what you mean by useless.
> > is cygwin implementation somehow deficient?
> > 
> sendmsg and recvmsg don't utilize the msg_accrights/msg_accrightslen member.
> 
> > > applications using this structure should accomodate the old
> > > implementation anyway, I don't see a good reason to change this right
> > > now.
> > 
> > the only reason applications have to accommodate the old implementation
> > is that some unixes still stick with it.
> 
> So, from a portability perspective...
> 
> > if you switch to the posix msghdr, I, for one, would not have to
> > accomodate the old implementation.
> 
> I won't change it now.  I'll change it at one point when there's some
> functionality.

Never mind, I've changed it in CVS.  Note that msg_control, msg_controllen
and msg_flags members are still without function.  However, msg_controllen
and msg_flags are both set to 0 on return from recvmsg.  The CMSG_FIRSTHDR
macro is meant to handle this gracefully, so please try the next Cygwin
snapshot and report back.  Keep in mind that for testing this correctly,
you have to install at least /usr/include/cygwin/socket.h and
/usr/lib/libcygwin.a additionally to the DLL.


Corinna

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Corinna Vinschen                  Please, send mails regarding Cygwin to
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Re: struct msghdr in socket.h is wrong

[Sam Steingold]

> * Corinna Vinschen <pbevaan-pltjva@pltjva.pbz> [2005-10-17 23:34:52 +0200]:
>
> Never mind, I've changed it in CVS.  Note that msg_control,
> msg_controllen and msg_flags members are still without function.

that's OK, as long as they are there.

while you are at it, two more networking functions appear AWOL:
http://www.opengroup.org/onlinepubs/007904975/functions/getaddrinfo.html
http://www.opengroup.org/onlinepubs/007904975/functions/getnameinfo.html

thanks!

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Re: struct msghdr in socket.h is wrong

[Corinna Vinschen]

On Oct 21 16:18, Sam Steingold wrote:
> > * Corinna Vinschen <pbevaan-pltjva@pltjva.pbz> [2005-10-17 23:34:52 +0200]:
> >
> > Never mind, I've changed it in CVS.  Note that msg_control,
> > msg_controllen and msg_flags members are still without function.
> 
> that's OK, as long as they are there.
> 
> while you are at it, two more networking functions appear AWOL:
> http://www.opengroup.org/onlinepubs/007904975/functions/getaddrinfo.html
> http://www.opengroup.org/onlinepubs/007904975/functions/getnameinfo.html

No, not yet.


Corinna

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Re: struct msghdr in socket.h is wrong

[Corinna Vinschen]

On Oct 22 11:07, Corinna Vinschen wrote:
> On Oct 21 16:18, Sam Steingold wrote:
> > > * Corinna Vinschen <pbevaan-pltjva@pltjva.pbz> [2005-10-17 23:34:52 +0200]:
> > >
> > > Never mind, I've changed it in CVS.  Note that msg_control,
> > > msg_controllen and msg_flags members are still without function.
> > 
> > that's OK, as long as they are there.
> > 
> > while you are at it, two more networking functions appear AWOL:
> > http://www.opengroup.org/onlinepubs/007904975/functions/getaddrinfo.html
> > http://www.opengroup.org/onlinepubs/007904975/functions/getnameinfo.html
> 
> No, not yet.

Btw., you have a Cygwin assignment in place, AFAIR.

http://cygwin.com/acronyms/#SHTDI
http://cygwin.com/acronyms/#PTC


Corinna

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