Quoting Christian Seiler (christ...@iwakd.de):
> Hi Serge,
>
> > Thanks, nice cleanup too. One concern though - lxc_monitor_sock_name()
> > just keeps making a longer and longer path, and it's limited to 108
> > bytes. Is there any reason not to use an abstract unix sock for it?
> > The monitor-fifo doesn't have the length restriction so
> > $rundir/lxc/$lxcpath/monitor-fifo is ok for it.
>
> FWIW, the following can be used to 'circumvent' this problem:
> 1. chdir()
> 2. bind()/connect() with relative path
> 3. chdir() back
>
> Only problem: it's not thread-safe... And in contrast to openat() or the
We could just do process_lock() around the whole shebang if we had to.
But I can't think offhand of any reason why we'd ever need to go from
the socketname back to the lxcpath, so using md5sum really shouldn't
have any downsides.
> such, there's no bindat() and connectat() in Linux as far as I can tell,
> although FreeBSD is apparently discussing it...
>
> (Of course, the following would also work if you want thread safety,
> although it's a bit crazy (sketch):
>
> sock = socket(AF_UNIX, SOCK_STREAM, 0);
>
> pid = fork();
> if (pid == 0) {
> struct sockaddr_un un;
> un.sun_family = AF_UNIX;
> strcpy(un.sun_path, "monitor-fifo");
> chdir(dirname);
> r = bind(sock, (struct sockaddr *)&un,
> offsetof(struct sockaddr_un, sun_path) + 13); // or connect();
> exit(r);
> } else if (pid > 0) {
> r = waitpid(pid, ...);
> if (WIFEXITED(r))
> r = WEXITSTATUS(r);
> else
> r = -1;
> } else {
> // fork failed...
> }
>
> if (r == -1)
> // bind/connect failed
>
> r = listen(sock, ...);
>
> One doesn't even need socket passing for this, since the socket can be
socket passing I'd understand, and that could be a neat solution. But I
don't understand why the above would work. Since the pids had forked,
the fd numbered r would be meaningless to the original task, wouldn't
it? I must be missing something cool, though.
> pre-created in the parent process before the fork and the bind affects
> the entire socket, including the version of the parent's process.
>
> But as I said, might be a bit crazy. On the other hand, one could
> encapsulate this in the UNIX socket creation routines to only do this if
> the length of the path is longer than 107 bytes... I don't know, just
> throwing stuff out there.)
>
> -- Christian
------------------------------------------------------------------------------
How ServiceNow helps IT people transform IT departments:
1. Consolidate legacy IT systems to a single system of record for IT
2. Standardize and globalize service processes across IT
3. Implement zero-touch automation to replace manual, redundant tasks
http://pubads.g.doubleclick.net/gampad/clk?id=51271111&iu=/4140/ostg.clktrk
_______________________________________________
Lxc-devel mailing list
Lxc-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/lxc-devel
