From: Ken Brown <kbrown@cornell.edu>
To: cygwin-developers@cygwin.com
Subject: Re: fstat and similar methods in fhandler_socket_local and fhandler_socket_unix
Date: Wed, 24 Feb 2021 10:32:23 -0500 [thread overview]
Message-ID: <db1bab02-ec13-8925-5932-9ed03ebc544d@cornell.edu> (raw)
In-Reply-To: <YDYXCyk595abgkHI@calimero.vinschen.de>
On 2/24/2021 4:06 AM, Corinna Vinschen via Cygwin-developers wrote:
> On Feb 22 15:01, Ken Brown via Cygwin-developers wrote:
>> OK, I've got patches ready to go for fstat, fstatvfs, fchmod, fchown, facl,
>> and link. I have to test them, and then I'll send them to cygwin-patches.
>> In the case of link, I think the only way an fhandler_socket's link method
>> can be called is through link(2) being called on a socket file. So the
>> following should do the job:
>>
>> diff --git a/winsup/cygwin/fhandler.h b/winsup/cygwin/fhandler.h
>> index 21e1df172..f4aa12956 100644
>> --- a/winsup/cygwin/fhandler.h
>> +++ b/winsup/cygwin/fhandler.h
>> @@ -611,7 +611,6 @@ class fhandler_socket: public fhandler_base
>> int __reg1 fchmod (mode_t newmode);
>> int __reg2 fchown (uid_t newuid, gid_t newgid);
>> int __reg3 facl (int, int, struct acl *);
>> - int __reg2 link (const char *);
>> off_t lseek (off_t, int)
>> {
>> set_errno (ESPIPE);
>> diff --git a/winsup/cygwin/fhandler_socket.cc b/winsup/cygwin/fhandler_socket.cc
>> index f22412650..08870cc6b 100644
>> --- a/winsup/cygwin/fhandler_socket.cc
>> +++ b/winsup/cygwin/fhandler_socket.cc
>> @@ -357,9 +357,3 @@ fhandler_socket::facl (int cmd, int nentries, aclent_t *aclbufp)
>> set_errno (EOPNOTSUPP);
>> return -1;
>> }
>> -
>> -int
>> -fhandler_socket::link (const char *newpath)
>> -{
>> - return fhandler_base::link (newpath);
>> -}
>
> Hmm. What about linkat (AT_EMPTY_PATH, socket, ...)?
>
> This could be called for inet sockets as well as unnamed or abstract
> unix sockets, in theory...
Thanks, I missed that case. So we do need fhandler_socket::link. The only
question in my mind is what errno it should set. I just tried the following:
$ cat socket_linkat.c
#define _GNU_SOURCE
#include <sys/socket.h>
#include <sys/un.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#define NEW_PATH "/tmp/newpath"
int
main ()
{
struct sockaddr_un addr;
int fd;
if (unlink (NEW_PATH) == -1 && errno != ENOENT)
{
perror ("unlink");
exit (1);
}
fd = socket (AF_UNIX, SOCK_STREAM, 0);
if (fd == -1)
{
perror ("socket");
exit (1);
}
if (linkat (fd, "", AT_FDCWD, NEW_PATH, AT_EMPTY_PATH) == -1)
perror ("linkat");
}
On Linux I get
linkat: Invalid cross-device link
So I think fhandler_socket::link should fail with EXDEV. Probably it should
continue to call fhandler_base::link, and the latter should fail with EXDEV
instead of EPERM. Or is there some case where EPERM is more appropriate?
Ken
next prev parent reply other threads:[~2021-02-24 15:32 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-20 23:32 Ken Brown
2021-02-20 23:51 ` Ken Brown
2021-02-21 18:04 ` Ken Brown
2021-02-22 9:44 ` Corinna Vinschen
2021-02-22 20:01 ` Ken Brown
2021-02-24 9:06 ` Corinna Vinschen
2021-02-24 15:32 ` Ken Brown [this message]
2021-02-24 17:06 ` Corinna Vinschen
2021-02-24 17:27 ` Ken Brown
2021-02-25 13:18 ` Ken Brown
2021-02-25 17:03 ` Corinna Vinschen
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