Re: [gentoo-user] Strange behaviour of dhcpcd

[Mick <michaelkintzios@gmail.com>]

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On Monday 27 Oct 2014 23:44:58 Marc Joliet wrote:
> Hi list
> 
> First off: this is a "fixed" issue, in that I don't see the behaviour
> anymore, so time is not of the essence ;) . I'm only looking for an
> explanation, or for comments from other people who experienced this.
> 
> So the issue was some really strange behaviour on the part of dhcpcd.  I
> completed a move a few weeks ago and got an internet connection last
> Wednesday (using a local cable company, that is, using a cable modem
> connected to via ethernet). I reconfigured my system to use regular DHCP
> (a relief after the PPPoE mess in the dorm), but dhcpcd could not apply
> the default route; it *obtained* one, but failed with "if_addroute:
> Invalid argument". I tried it manually, to no effect: "ip route"
> complained about invalid arguments, and I think plain "route" said "file
> exists", but I'm not sure anymore (either way, the error messages were
> less than clear).  The funny thing is, I *could* set the default route,
> just not to the one advertised via DHCP, but to the x.y.z.2+ instead of
> x.y.z.1, which even gave me access to the internet part of the time.
> 
> Now the funny thing is what fixed it:
> 
>   *commenting out the entirety of /etc/dhcpcd.conf*
> 
> Then dhcpcd ran with   default settings and could apply the default route.
> Even more bizarre is the fact that it kept working after uncommenting it
> again (and I track it with git, so I'm 100% sure I got it back to its
> original state). This leads me to believe that there was some (corrupted?)
> persistent state somewhere that got overwritten by starting dhcpcd after I
> commented out the file, but I have no clue where.
> 
> Has anyone seen this sort of behaviour before, or anything similar to it? 
> I searched for the error messages I was seeing, but couldn't find
> anything.  I was using gentoo-sources-3.15.9 (now I'm at 3.16.6) and
> dhcpcd 6.4.3 at the time, but also had the issue with dhcpcd 6.4.7, to
> which I could upgrade by using the aforementioned x.y.z.2 gateway. Perhaps
> it was a bug in the kernel? But that's just guessing.
> 
> Regards,

Since dhcpcd doesn't misbehave any more it would be difficult to check what 
was the cause of this problem.  You didn't say if the cable modem is 
functioning as a router or as in a full or half bridge mode and if there is a 
router between your PC and the modem that distributes IP addresses.  You also 
didn't say if the ISP has allocated an IP block or just a single IP address.

I have had problems with dhcpcd over the years and in particular with it using 
DUID, which my router does not like at all.  Also, for some reason it first 
checks for IPv6, then times out, and eventually it looks for IPv4 which takes 
like forever, each time I connect to my wired network.  In waiting for an IPv4 
address it may set up APIPA and then sometime later will eventually look for 
and obtain an IPv4 address from the router.

I have not found a solution to this annoying behaviour, however wirelessly the 
IP address allocation is established immediately without delays.  Go figure 
...

-- 
Regards,
Mick

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