Date: Mon, 8 Aug 2022 23:21:35 +0100 From: Roy Marples <roy@marples.name> To: Hiroki Sato <hrs@FreeBSD.org> Cc: freebsd-net@freebsd.org Subject: Re: Import dhcpcd(8) into FreeBSD base Message-ID: <74a1d9c2-6eab-b685-e71e-7d69a6fe6a9f@marples.name> In-Reply-To: <20220809.054039.722614217650843004.hrs@FreeBSD.org> References: <e401671f-6a67-49ed-bc41-e8fbb9de27cb@www.fastmail.com> <20220807.232337.383956020917382126.hrs@FreeBSD.org> <4516f415-939e-6374-45ce-df19a2ac65cb@marples.name> <20220809.054039.722614217650843004.hrs@FreeBSD.org>
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On 08/08/2022 21:40, Hiroki Sato wrote: > Roy Marples <roy@marples.name> wrote > in <4516f415-939e-6374-45ce-df19a2ac65cb@marples.name>: > > ro> On 07/08/2022 15:23, Hiroki Sato wrote: > ro> > 1) Import dhcpcd and make it invoked via Other Configuration flag > ro> > in RA for DHCPv6. This means that the rtsold daemon remains a > ro> > consumer of RA messages, and the default value of the -O option is > ro> > set to run dhcpcd. > ro> > ro> I don't think this is a viable option as there is no easy way to > ro> transition from Other to Managed (or the other way around) from the > ro> dhcpcd commandline or signals. > > The rtsold daemon just invokes a corresponding helper script when > receiving RAs with these flags. A transition from O to M or vice > versa is supposed to be handled by them. I think it is possible to > stop the running dhcpcd and/or restart it with another configuration > via the scripts. Is there a critical problem with it? I do not > insist that it is the best way since it is not a graceful transition, > but I still believe it should work for most DHCPv6-enabled networks. > > ro> Also, please consider than dhcpcd supports DNSSL and RDNSS options > ro> from RA messages whereas FreeBSD rtsold/kernel RA do not (please > ro> correct me if I'm wrong). > > The FreeBSD rtsold has supported them for >10 years. Resolvconf, one > of your projects, was imported at the same time to solve the problem > of multiple information source for /etc/resolv.conf. > > ro> Sure it works fine for the one interface wired system - which > ro> admitedly is the most popular setup. But when more than one interface > ro> comes into play or you have plugable interfaces it then becomes more > ro> complicated and will consume more resources having many more daemon > ro> runing to allow capsicum and makes dhcpcd just as predictable as > ro> dhclient on a multi-homed system (ie it's not predictable). > ro> > ro> I modified wpa_supplicant upstream to support the -M directive (I > ro> don't know if FreeBSD compiles wpa_supplicant with CONFIG_MATCH_IFACE > ro> defined) to allow plugable interfaces just for this reason. > > I agree that running processes for each interface independently is > sub-optimal. However, I think it is a separate topic from whether > importing a DHCPv6 client into the base system or not. More > specifically, the following three are orthogonal: > > 1. Use dhcpcd or not as a replacement of dhclient and rtsold. > > This leads to a never-ending discussion. Some people like the > existing ones because they have worked well and do not want to > change. > > 2. Adopt a single process managing the multiple interfaces on the > system or use per-interface processes. > > Changing this requires a lot of work and breaks the existing > configurations. A side node of the design and behavior of the > current rc.d/netif is as follows: > > - The current rc.d/netif (and other network-related rc.d scripts > such as rc.d/wpa_supplicant) are based on the per-interface > model. The rc.d/netif script is invoked asynchronously while it > also runs at boot time sequentially. This asynchronous > invocation is specific to FreeBSD, and not seen in other BSDs > (correct me if I am wrong). > > - The devd(8) daemon is the main process receiving events of the > interfaces such as arrival/departure/link-state changes, and > invokes a process upon an event if necessary. > > - The rtsold(8) daemon is the main process receiving RAs in > userland and invokes a process upon an event if necessary. > Currently, it handles O/M flags and RDNSS/DNSSL options. > > 3. Add an implementation of the DHCPv6 client-side functionality or > not. > > I believe no one objects for adding one because we have no > implementation in the base system. Some people like another one, > such as ISC dhclient or WIDE dhcp6. > > My opinion is: 1) "no need", 2) "keep the current model for a while", > and 3) "go for it". I tend to prefer WIDE dhcp6 because I have used > it for >15 years with accumulated local patchset, but I do not stick > to it as long as there is a good working implementation supporting > IA_NA and IA_PD, and someone actively maintains it. WIDE dhcp6 works > well, but it has a lot of rough edges (and fixed locally by many > people, as bz@ pointed out). > > As mentioned in my previous email, avoiding POLA violations is the top > priority. Regardless of which implementation we import, I still > believe keeping the current per-interface model is the least > intrusive for the existing configurations. > > So we need a consensus about how to get started with the integration. > An idea in my mind is: 1) import dhcpcd (or whatever supports > per-interface mode), 2) add a per-interface helper script for it, and > 3) set rtsold_enable="YES" effectively by default for all > RA-accepting interfaces so that people do not need to manually > configure it at least on an IPv6 network with M/O bit enabled. This > should be enough for IA_NA. More complicated configurations can be > supported incrementally. > > And I hope this discussion focuses on how to integrate DHCPv6 > functionality, not changing the current rc.d/netif drastically or > replacing the existing components unrelated to DHCPv6 such as > dhclient or rtsold. If the import involves an immediate change of > the current model due to the nature of the implementation, I cannot > entirely agree with it. > > Technical discussions about improving the current model are always > welcome. I am also interested in them because I have recognized the > downsides since I am one of the contributors who have added > substantial changes to network.subr over the years. However, > thinking about the import and the improvement of boot-time > configuration together does not make good sense to me to judge the > reasonableness of the import. I agree with all of this. I would only ask that there is the ability to just enable dhcpcd as a generic service in rc.conf as dhcpcd_enabled=YES so that people can play with it as intended and not affect any existing configuration. Roy
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