[systemd-devel] [PATCH 1/3] core: Add LISTEN_NAMES environment variable

Krzysztof Opasiak k.opasiak at samsung.com
Tue May 19 01:44:49 PDT 2015

On 05/18/2015 09:45 PM, Lennart Poettering wrote:
> On Mon, 18.05.15 17:55, Zbigniew Jędrzejewski-Szmek (zbyszek at in.waw.pl) wrote:
>> On Mon, May 18, 2015 at 06:01:10PM +0200, Lennart Poettering wrote:
>>> Being able to attach a name to the fds is hence really useful. logind
>>> could use this to attach the session identifier to the fds, and would
>>> hence be able to safely map the fds back to their sessions after
>>> coming back from a restart...
>> Yeah, that makes sense. But currently there's no proposal how to specify
>> those identifiers. Would be nice discuss both sides of the proposal at
>> the same time.
>> sd_pid_notify_with_fds() would probably have to be extended to be
>> sd_pid_notify_with_fds2(pid_t pid, int unset_environment, const char
>> *state, const int *fds, const char* const *names, unsigned n_fds)
> Hmm, nah. I think we can avoid adding a new call. Instead we should
> explicitly allow non-unique names, and then simply pass the name to
> use in a normal sd_notify_with_fds() text field, so that it is applied
> to all fds pushed the same way. If you want to send multiple fds with
> different ids, then one would do this with multiple
> sd_pid_notify_with_fds() invocations.
> Example:
>          sd_pid_notify_with_fds(0, false, "FDSTORE=1\nFDNAME=foobar", (int[]) { STDIN_FILENO, STDOUT_FILENO }, 2);
> This would push stdin and stdout of the client into PID 1 and label
> both of them "foobar". On next invocation the process would then see:
>          LISTEN_FDS=2
>          LISTEN_NAMES=foobar:foobar
>> And what about socket units: we could automatically generate identifiers
>> like blah.socket-1, foo.socket-1, foo.socket-2 to allow sockets from multiple
>> socket files be distinguished. In principle this could be made configurable
>> through a new option, but I don't think it's worth the trouble.
> I'd add a new option for this:
>          FileDescriptorName=waldi
> would apply to all fds declared with a .socket unit. If you want to
> apply distinct names to multiple fds, you should define them in two
> seperate .socket units.
> Hope that makes sense?

Make sens for me. I now see your point of view more clearly.
I will update my patches according to your remarks and idea described here.

Thank you for the review and clarification,
Krzysztof Opasiak
Samsung R&D Institute Poland
Samsung Electronics

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