samba - Jul 2025 - SMB3 Unix Extensions - creating special files

Ralph Boehme <slow at samba.org> writes:
> ...adding linux-cifs and Steve to the loop....
>
> Looks to be a client issue: the client is checking for existence of the 
> targets, the server returns ENOENT and then that's it. There no attempt
> to create either a symlink nor the fifo as reparse points.
>
> @Steve: any idea of what could be going wrong? Iirc this is supposed to 
> be working in the client.
With Linux v6.16 and samba master (f1a828016921):

root at fed:~# mount.cifs //192.168.124.1/test /mnt/1 -o
username=testuser,password=foo-123,unix
root at fed:~# mount -t cifs
//192.168.124.1/test on /mnt/1 type cifs
(rw,relatime,vers=3.1.1,cache=strict,upcall_target=app,username=testuser,uid=0,noforceuid,gid=0,noforcegid,addr=192.168.124.1,file_mode=0755,dir_mode=0755,soft,posix,posixpaths,serverino,reparse=nfs,nativesocket,symlink=unix,rsize=4194304,wsize=4194304,bsize=1048576,retrans=1,echo_interval=60,actimeo=1,closetimeo=1)
root at fed:~# (cd /mnt/1; rm -rf *; mknod chr c 2 1; mknod blk b 3 4; mknod
fifo p; ln -s f0 l0; python -c "import socket as s; sock =
s.socket(s.AF_UNIX); sock.bind('sock')"; ls -lh)
ln: failed to create symbolic link 'l0': Operation not supported
total 0
brwxrwxrwx 1 root fsgqa 3, 4 Jul 31 14:31 blk
crwxrwxrwx 1 root fsgqa 2, 1 Jul 31 14:31 chr
prwxrwxrwx 1 root fsgqa    0 Jul 31 14:31 fifo
-rwxrwxrwx 1 root fsgqa    0 Jul 31 14:31 sock

I see a regression when attempting to create symlinks and sockets.  Note
the 'nativesocket' and 'symlink=unix' options, which are
definitely
wrong for SMB3.1.1 POSIX mounts.  It should have 'symlink=native' and
'nonativesocket'.

Thanks for spotting this. I can confirm that I see different behaviour 
with different kernels:

6.13.0 - mkfifo and ln-s work as expected.
6.14.0 - mkfifo works, ln-s gives 'operation not supported'.
 >=6.15.7 - both give 'operation not supported'.

Which implies possibly more than one regression?

Thanks,

Matthew


On 31/07/2025 18:37, Paulo Alcantara wrote:
> [You don't often get email from pc at manguebit.org. Learn why this is
important at https://aka.ms/LearnAboutSenderIdentification ]
> 
> Ralph Boehme <slow at samba.org> writes:
> 
>> ...adding linux-cifs and Steve to the loop....
>>
>> Looks to be a client issue: the client is checking for existence of the
>> targets, the server returns ENOENT and then that's it. There no
attempt
>> to create either a symlink nor the fifo as reparse points.
>>
>> @Steve: any idea of what could be going wrong? Iirc this is supposed to
>> be working in the client.
> 
> With Linux v6.16 and samba master (f1a828016921):
> 
> root at fed:~# mount.cifs //192.168.124.1/test /mnt/1 -o
username=testuser,password=foo-123,unix
> root at fed:~# mount -t cifs
> //192.168.124.1/test on /mnt/1 type cifs
(rw,relatime,vers=3.1.1,cache=strict,upcall_target=app,username=testuser,uid=0,noforceuid,gid=0,noforcegid,addr=192.168.124.1,file_mode=0755,dir_mode=0755,soft,posix,posixpaths,serverino,reparse=nfs,nativesocket,symlink=unix,rsize=4194304,wsize=4194304,bsize=1048576,retrans=1,echo_interval=60,actimeo=1,closetimeo=1)
> root at fed:~# (cd /mnt/1; rm -rf *; mknod chr c 2 1; mknod blk b 3 4;
mknod fifo p; ln -s f0 l0; python -c "import socket as s; sock =
s.socket(s.AF_UNIX); sock.bind('sock')"; ls -lh)
> ln: failed to create symbolic link 'l0': Operation not supported
> total 0
> brwxrwxrwx 1 root fsgqa 3, 4 Jul 31 14:31 blk
> crwxrwxrwx 1 root fsgqa 2, 1 Jul 31 14:31 chr
> prwxrwxrwx 1 root fsgqa    0 Jul 31 14:31 fifo
> -rwxrwxrwx 1 root fsgqa    0 Jul 31 14:31 sock
> 
> I see a regression when attempting to create symlinks and sockets.  Note
> the 'nativesocket' and 'symlink=unix' options, which are
definitely
> wrong for SMB3.1.1 POSIX mounts.  It should have 'symlink=native'
and
> 'nonativesocket'.
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On 7/31/25 7:37 PM, Paulo Alcantara wrote:
> I see a regression when attempting to create symlinks and sockets.  Note
> the 'nativesocket' and 'symlink=unix' options, which are
definitely
> wrong for SMB3.1.1 POSIX mounts.  It should have 'symlink=native'
and
> 'nonativesocket'.
ahh, sorry, but I was kind of expecting that. There are just too many 
options.

-slow
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