bug#26099: [PATCH] services: Add inetd-service-type.

[Ludovic Courtès]

Hi Thomas,

Thomas Danckaert <address@hidden> skribis:

> this patch adds an inetd-service.  The service is configured using a list of 
> <inetd-entry> records, which correspond to lines in the inetd.conf file 
> (documented in the inetutils info manual).  The following example will start 
> inetd with the built-in “echo” service, and with an smtp service, which uses 
> ssh to tunnel smtp traffic to a server “smtp-server” behind a gateway 
> “hostname”:
>
> (service inetd-service-type
>                            (list
>                             (inetd-entry
>                              (name "echo")
>                              (socket-type 'stream)
>                              (protocol "tcp")
>                              (wait? #t)
>                              (user "root")) ; no program and arguments fields 
> required for inetd's "internal" services such as echo
>                             (inetd-entry
>                              (node "127.0.0.1")
>                              (name "smtp")
>                              (socket-type 'stream)
>                              (protocol "tcp")
>                              (wait? #f)
>                              (user "root")
>                              (program (file-append openssh "/bin/ssh"))
>                              (arguments "-q -T -i /path/to/key -W 
> smtp-server:25 address@hidden"))))

Very nice!

> The configuration doesn't include an “escape hatch” option where the user can 
> specify an arbitrary inetd.conf, but I think the current configuration method 
> captures all possibilities, and inetd's configuration format is unlikely to 
> change radically?  Or perhaps the (inetd-config-file) procedure can be 
> exported, so users can either use the procedure with a list of 
> <inetd-entry>'s, or directly pass a (mixed-text-file) or any other file-like.

As you write, I think an escape hatch isn’t needed in this case.
<inetd-entry> is expressive enough and inetd.conf isn’t going to change
overnight.

> Obviously documentation is still missing, but I wanted to wait for a first 
> round of comments before writing the docs.  Let me know if I should already 
> include them anyway.

Sure.  :-)  Make sure to include an example like the one above (but wrap
lines to 80 chars).

Some very minor cosmetic comments:

> From 85b01d04d8b140ed3a1960b1678cc133367b916b Mon Sep 17 00:00:00 2001
> From: Thomas Danckaert <address@hidden>
> Date: Tue, 14 Mar 2017 18:12:34 +0100
> Subject: [PATCH] services: Add inetd-service-type.
>
> * gnu/services/networking.scm (<inetd-entry>): New record type.
> (inetd-config-file, inetd-shepherd-service): New procedures.
> (inetd-service-type): New variable.

[...]

> +(define-record-type* <inetd-entry> inetd-entry make-inetd-entry
> +  inetd-entry?
> +  (node inetd-entry-node (default #f))   ;string or #f
> +  (name inetd-entry-name)                ;string, from /etc/services
> +  (socket-type inetd-entry-socket-type)  ;stream | dgram | raw | rdm | 
> seqpacket
> +  (protocol inetd-entry-protocol)        ;string, from /etc/protocols 
> ("tcp", "udp", ...)
> +  (wait? inetd-entry-wait? (default #t)) ;Boolean
> +  (user inetd-entry-user)                ;string
> +  (program inetd-entry-program           ;string or file-like
> +           (default "internal"))
> +  (arguments inetd-entry-arguments       ;string
> +           (default "internal")))

It would be nice to add a ‘package’ field that would default to
‘inetutils’, so that users can choose which package or variant inetd is
taken from.

> +(define (inetd-config-file service-list)
> +  (apply mixed-text-file "inetd.conf"
> +         (fold-right ; The order of address lines in inetd.conf matters.
> +          (lambda (s prev)

Please avoid one-letter identifier.  If it makes lines too long, you can
always move the ‘lambda’ to an internal ‘define’ above.

Also I have a slight preference for “services” rather than
“service-list”.  :-)

> +            (append
> +             (list
> +              (let* ((node (inetd-entry-node s))
> +                     (name (inetd-entry-name s))
> +                     (socket
> +                      (if node (string-append node ":" name) name))
> +                     (type
> +                      (match (inetd-entry-socket-type s)
> +                        ((or 'stream 'dgram 'raw 'rdm 'seqpacket)
> +                         (symbol->string (inetd-entry-socket-type s)))))
> +                     (protocol (inetd-entry-protocol s))
> +                     (wait (if (inetd-entry-wait? s) "wait" "nowait"))
> +                     (user (inetd-entry-user s))
> +                     (program (inetd-entry-program s))
> +                     (args (inetd-entry-arguments s)))
> +                #~(string-join
> +                   (list #$@(list socket type protocol wait user program 
> args))
> +                   " "))
> +              "\n") prev)) '() service-list)))

I think you could just use (map entry->inetd.conf-line service-list),
where ‘entry->inetd.conf-line’ is the lambda above, no?

> +(define-public inetd-service-type
> +  (service-type
> +   (name 'inetd)
> +   (extensions
> +    (list (service-extension shepherd-root-service-type 
> inetd-shepherd-service)))))

I think you also need to add ‘extend’ and ‘compose’ such that other
services (say, OpenSSH) can add inetd entries via service extensions.

Thank you!

Ludo’.