First of all, do not reply to mails sent in private on a public list, it's
impolite and will expose my email address to more spam.
Second, man 4 pppoe says:
MTU/MSS ISSUES
Problems can arise on machines with private IPs connecting to the Inter-
net via a machine running both Network Address Translation (NAT) and
pppoe. Standard Ethernet uses a Maximum Transmission Unit (MTU) of 1500
bytes, whereas PPPoE mechanisms need a further 8 bytes of overhead.
This
leaves a maximum MTU of 1492. pppoe sets the MTU on its interface to
1492 as a matter of course. However, machines connecting on a private
LAN will still have their MTUs set to 1500, causing conflict.
While pppoe(8) has an internal option, ``mssfixup'', which is enabled by
default and takes care of this, pppoe users have to rely on other meth-
ods. Using a packet filter, the Maximum Segment Size (MSS) can be set
(clamped) to the required value. The following rule in pf.conf(5) would
set the MSS to 1440:
match on pppoe0 scrub (max-mss 1440)
Although in theory the maximum MSS over a PPPoE interface is 1452 bytes,
1440 appears to be a safer bet. Note that setting the MSS this way can
have undesirable effects, such as interfering with the OS detection fea-
tures of pf(4).
which is definitely not "the same as man 8 pppoe".
> -----Original Message-----
> From: owner-m...@openbsd.org [mailto:owner-m...@openbsd.org] On Behalf Of
Matt
> Schwartz
> Sent: Wednesday, July 14, 2010 10:42 PM
> To: misc@openbsd.org
> Subject: Re: kernel pppoe performance problems
>
> Hi. I don't see that option available for kernel pppoe. I see it for a
> userland version. man 4 pppoe shows the same as man 8 pppoe.
>
>
>
> On Jul 14, 2010, at 1:25 PM, Mitja MuE>eniD
> <mi...@muzenic.net> wrote:
>
> > Sounds like you didn't clamp the MSS, see man 4 pppoe towards the end.
It's
> > not a performance problem, but a misconfiguration one.
> >
> >> -----Original Message-----
> >> From: owner-m...@openbsd.org [mailto:owner-m...@openbsd.org] On Behalf
Of
> > Matt
> >> S
> >> Sent: Wednesday, July 14, 2010 10:16 PM
> >> To: misc@openbsd.org
> >> Subject: kernel pppoe performance problems
> >>
> >> Hello All,
> >>
> >> I want to try to use pppoe with kernel ppp in an attempt to improve
> >> performance. So, I have a pppoe0 device configured and connection
> >> established properly. The box that runs kernel pppoe is obviously my
> >> gateway machine. If I am on the gateway machine, performance is decent.
> > If
> >> I am on one of my other boxes, performance really drops to the point of
> >> dialup. I made certain to rm -f /etc/mygate as one wiki suggested but
it
> >> had no effect. If I use userland pppoe, I don't have this problem so I
> >> think that both my NIC cards are okay. The nic card connected to my DSL
> >> modem is bge0 and the nic for my home network is em0. My home network
is
> >> 10.40.60.0/24. I know I have NAT correctly configured because I can
ping
> >> google.com from one of the other boxes. Do you have any hints as to how
I
> >> can troubleshoot this further? Below is my configuration for the
> >> hostname.pppoe0 :
> >>
> >> inet 0.0.0.0 255.255.255.255 NONE pppoedev bge0 authproto pap authname
> >> "<myauthname>" authkey "<myauthkey>" up
> >> dest 0.0.0.1
> >> !/sbin/route add default 0.0.0.1
> >>
> >>
> >> Thank you,
> >> Matt
