On Wed, Aug 23, 2023 at 1:06 AM Roland Mainz via Cygwin <cygwin@cygwin.com> wrote: > > On Tue, Aug 22, 2023 at 4:52 PM Lavrentiev, Anton (NIH/NLM/NCBI) [C] > via Cygwin <cygwin@cygwin.com> wrote: > > > FIFOs which don't make *any* sense > > > ... FWIW, a remote NFS fileystem. > > > > I got an impression that the OP is trying to deploy something (maybe the > > entire Cygwin) onto an > > NFS share. So the named FIFO "file" is also created in there. > > I agree with that impression. This is basically what large sites > (universities etc) do with UNIX and Linux: The machines mount an > user's ${HOMR} directory via automounter over NFS, and users are > discouraged (e.g. grumpy admin visiting you in person, blocking all > escape routes... =:-) ) from using the machine's local filesystems (in > Cygwin's case that includes "C:"!). > > In that case people want to use |mkfifo()|/|mkfifoat()| and/or > /usr/bin/mkfifo in their home directory, and don't expect that it does > not work. > > But that is what happens on Cygwin 3.4.8 right now, if someone tries > to do a |mkfifo()| on a NFS home directory (tested with MS NFSv3 and > CITI NFSv4 clients): > |mkfifo()| succeeds, but the resulting inode is *NOT* a FIFO as requested > > Example (/cygdrive/h/ is my home directory shared from my Linux machine): > ---- snip ---- > roland_mainz@winkrakra1 /cygdrive/h/work/cygwin_mkfifo_on_nfs > $ uname -a > CYGWIN_NT-10.0-19045 winkrakra1 3.4.8-1.x86_64 2023-08-17 17:02 UTC > x86_64 Cygwin > > roland_mainz@winkrakra1 /cygdrive/h/work/cygwin_mkfifo_on_nfs > $ mount > C:/cygwin64/bin on /usr/bin type ntfs (binary,auto) > C:/cygwin64/lib on /usr/lib type ntfs (binary,auto) > C:/cygwin64 on / type ntfs (binary,auto) > C: on /cygdrive/c type ntfs (binary,posix=0,user,noumount,auto) > H: on /cygdrive/h type nfs (binary,posix=0,user,noumount,auto) > > roland_mainz@winkrakra1 /cygdrive/h/work/cygwin_mkfifo_on_nfs > $ ls -l > total 1 > -rw-rw-rw- 1 Unix_User+0 Unix_Group+0 330 Aug 22 23:58 cygwin_mkfifo_on_nfs.c > > roland_mainz@winkrakra1 /cygdrive/h/work/cygwin_mkfifo_on_nfs > $ cat -n cygwin_mkfifo_on_nfs.c > 1 #include <stdlib.h> > 2 #include <stdio.h> > 3 #include <stdio.h> > 4 #include <errno.h> > 5 #include <sys/types.h> > 6 #include <sys/stat.h> > 7 > 8 int main(int ac, char *av[]) > 9 { > 10 (void)puts("# start"); > 11 > 12 if > (mkfifo("/cygdrive/h/work/cygwin_mkfifo_on_nfs/myfifo.fifo", 0) != 0) > 13 perror("mkfifo failed"); > 14 (void)puts("# done."); > 15 return EXIT_SUCCESS; > 16 } > 17 > > roland_mainz@winkrakra1 /cygdrive/h/work/cygwin_mkfifo_on_nfs > $ gcc -g cygwin_mkfifo_on_nfs.c > > roland_mainz@winkrakra1 /cygdrive/h/work/cygwin_mkfifo_on_nfs > $ ./a > # start > # done. > > roland_mainz@winkrakra1 /cygdrive/h/work/cygwin_mkfifo_on_nfs > $ ls -l > total 68 > -rwxr-xr-x 1 Unix_User+0 Unix_Group+0 66951 Aug 23 00:12 a.exe > -rw-rw-rw- 1 Unix_User+0 Unix_Group+0 330 Aug 22 23:58 > cygwin_mkfifo_on_nfs.c > lrwxrwxrwx 1 Unix_User+0 Unix_Group+0 11 Aug 23 00:12 myfifo.fifo > -> ':\0:c4:1000' > > roland_mainz@winkrakra1 /cygdrive/h/work/cygwin_mkfifo_on_nfs > $ cat <myfifo.fifo > -bash: myfifo.fifo: No such file or directory > ---- snip ---- > > Note that Cygwin does not interpret the file |myfifo.fifo| as FIFO, > instead it comes back as a symlink "myfifo.fifo -> ':\0:c4:1000'". > > AFAIK there are (at least) these two options to fix the problems: > 1. Check whether the filesystem for the fifos path is NFS > (cgywin.dll's |fs.fs_is_nfs()|), and if it is a symlink check if it > starts with ':\0:c4:' (assuming "c4" is the prefix for inodes created > with |mkfifo()|). If this condition is |true|, then cygwin |stat()|, > |open()| etc. should treat this inode as FIFO. > 2. Check whether the filesystem for the fifos path is NFS > (cgywin.dll's |fs.fs_is_nfs()|), and then just refuse |mkfifo()| with > |ENOSYS| (not implemented) > > Better algorithm for [1] might be to check whether the inode is a > symlink, and then do a |fs.fs_is_nfs()| on the symlinks |pathname|, > assuming this is more performant.
We would like to see option 1 implemented, maybe as an option in the CYGWIN environment variable (CYGWIN=nfs_emulate_dev_special_files_as_symlink ?) Thanks, Martin -- Problem reports: https://cygwin.com/problems.html FAQ: https://cygwin.com/faq/ Documentation: https://cygwin.com/docs.html Unsubscribe info: https://cygwin.com/ml/#unsubscribe-simple