<div dir="ltr"><div dir="ltr"> </div> <div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Thu, 4 May 2023 at 14:39, Thomas Haller <<a href="mailto:thaller@redhat.com">thaller@redhat.com</a>> wrote: </div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">On Thu, 2023-05-04 at 14:33 +0200, Frédéric Martinsons wrote: > > > Le jeu. 4 mai 2023, 14:06, Thomas Haller <<a href="mailto:thaller@redhat.com" target="_blank">thaller@redhat.com</a>> a > écrit : > > Hi, > > > > On Thu, 2023-05-04 at 11:47 +0200, Frédéric Martinsons wrote: > > > Hello list, > > > > > > I would like to add some monitoring of the dhcp servers via the > > > machines which request ip addresses from it (no access to the > > > server > > > itself) > > > For the moment, we are only aware of the outage of this server > > > when > > > the lease expired. > > > > > > I first check if NM has a dbus api for that and didn't find one, > > > the > > > I use a Nagios plug-in as a standalone program > > > ( > > > <a href="https://github.com/nagios-plugins/nagios-plugins/blob/master/plugi" rel="noreferrer" target="_blank">https://github.com/nagios-plugins/nagios-plugins/blob/master/plugi</a> > > > ns > > > -root/check_dhcp.c) but it seems to not work on all cases I have > > > (strong firewalling among other). > > > > > > I don't want to use nmap or other external tools that I didn't > > > already have on the machines (I have strong constraint on the > > > size > > > available) > > > > > > Since our machines used NM to manage ethernet , I decided to look > > > at > > > the code to know how the things are handled and if a can have the > > > possibility to "ping" (just emit a DISCOVER and listen for OFFER > > > without accepting the lease). I first came up with a solution > > > that > > > involves instantiating a NMDhcpClient to use an internal dhcp > > > mechanism. It worked but I had to patch NM code to avoid messing > > > with > > > the system (I don't want to read the already accepted lease or > > > modify > > > the current lease). Moreover my binary had to link with almost > > > all NM > > > code which makes it very big. > > > > > > I finally came up with a minimal solution by mimicking what is > > > done > > > in nm-dhcp-nettools.c and talking directly to the n-dhcp4 > > > library. > > > > > > Long story short, I'm wondering if this "ping dhcp" capability is > > > a > > > feature fitted to enter as a standalone binary (or a > > > dedicated DBus > > > endpoint) in NM code ? > > > > I don't see how such functionality would fit into NetworkManager. > > But > > maybe it does, if you have a specific suggestion please make it. > > > > Instead, I would use/build a separate tool for that. If it's a > > specific > > tool for that purpose, then the API would be simple. If it's a more > > general tool (e.g. integrate it into ISC dhclient) then it is > > already > > more complicated to make the functionality general purpose and fit > > it > > into a more general tool. > > It could be generic since during my search, I found several request > for such a case (but people seems happy with the tools that are > already available like Nagios plug-in) > > > There are several DHCP client libraries and implementations. For > > example there is <a href="https://github.com/nispor/mozim" rel="noreferrer" target="_blank">https://github.com/nispor/mozim</a> > > > > I would actually use nettools' n-dhcp4 library (which you already > > investigated) and build a specialized one-purpose tool on top of > > that. > > That should be relatively straight forward, and if API is missing > > for > > making it happen, it probably can be accepted upstream. > > > > <a href="https://github.com/nettools/n-dhcp4" rel="noreferrer" target="_blank">https://github.com/nettools/n-dhcp4</a> > > > > > > Thomas > > This is exactly what I have done (thank you very much for the code in > NM which help me to achieve that), I just wanted to know if someone > here could be interdested to have that ship directly in NM but I > heard you, loud and clear. > > Thank you Thomas for the answer. Hi, maybe I just lack of imagination for how it could fit. Patch welcome, if you see a use-case :) Thomas </blockquote><div> </div><div>Ok I'll submit a merge request soon for providing such a little tool and </div><div>we will discuss the usage (and if it can remain a standalone binary or</div><div>if it should be more integrated) there.</div><div> </div></div></div>