Kernel TLS

[Jeffrey Walton]

On Fri, Nov 29, 2019 at 2:48 PM Valentin Vidić
<vvidic at valentin-vidic.from.hr> wrote:
>
> On Fri, Nov 29, 2019 at 02:36:10PM -0500, Jeffrey Walton wrote:
> > I'm trying to run through the example at
> > https://www.kernel.org/doc/html/latest/networking/tls.html#kernel-tls
> > .
> >
> > I'm working on Fedora 31 x86_64 (fully patched). Running my program results in:
> >
> >     $ ./ktls
> >     setsockopt failed, 2, No such file or directory
> >
> > I observed:
> >
> >     $ cat /proc/sys/net/ipv4/tcp_available_ulp
> >     $
> >
> > Is there a way to enable ULP at boot? Or is this a kernel config
> > option? Or maybe I am doing something else wrong?
>
> strace gives me:
>
> ...
> socket(AF_INET, SOCK_STREAM, IPPROTO_IP) = 3
> setsockopt(3, SOL_TCP, TCP_ULP, [7564404], 4) = -1 ENOENT (No such file or directory)
> fstat(1, {st_mode=S_IFCHR|0620, st_rdev=makedev(0x88, 0x2), ...}) = 0
> brk(NULL)                               = 0x55d76b14e000
> brk(0x55d76b16f000)                     = 0x55d76b16f000
> write(1, "setsockopt failed, 2, No such fi"..., 48setsockopt failed, 2, No such file or directory
> ) = 48
> exit_group(1)                           = ?
> +++ exited with 1 +++
>
> $ grep TLS /boot/config-4.19.0-6-amd64
> CONFIG_HAVE_COPY_THREAD_TLS=y
> # CONFIG_TLS is not set
> # CONFIG_VIDEO_IVTV_DEPRECATED_IOCTLS is not set
>
> So you probably need to rebuild the kernel with CONFIG_TLS to get this working.

Thanks Valentin.

Here's what I am seeing:

    $ grep TLS /boot/config-5.3.12-300.fc31.x86_64
    CONFIG_HAVE_COPY_THREAD_TLS=y
    CONFIG_TLS=m
    ...

I believe the 'm' means a loadable module. But:

    $ insmod tls
    insmod: ERROR: could not load module tls: No such file or directory

Jeff