Re: [Samba] SMB3 Unix Extensions - creating special files

[Paulo Alcantara <pc@manguebit.org>]

Paulo Alcantara <pc@manguebit.org> writes:

> Ralph Boehme <slow@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@fed:~# mount.cifs //192.168.124.1/test /mnt/1 -o username=testuser,password=foo-123,unix
> root@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@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'.

Looks like a regression caused by

        6c06be908ca1 ("cifs: Check if server supports reparse points before using them")

By mounting the share again with 'unix,symlink=native,nonativesocket'
and getting rid of this check in cifs_symlink()

	if (le32_to_cpu(pTcon->fsAttrInfo.Attributes) & FILE_SUPPORTS_REPARSE_POINTS)

I was able to create symlink and socket:

root@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)
total 0
brwxrwxrwx 1 root fsgqa 3, 4 Jul 31 14:51 blk
crwxrwxrwx 1 root fsgqa 2, 1 Jul 31 14:51 chr
prwxrwxrwx 1 root fsgqa    0 Jul 31 14:51 fifo
lrwxrwxrwx 1 root fsgqa    2 Jul 31 14:51 l0 -> f0
srwxrwxrwx 1 root fsgqa    0 Jul 31 14:51 sock