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Re: [PATCH] Increase snd/rcv buffers in pppoe

To: Andi Kleen <ak@xxxxxxx>
Subject: Re: [PATCH] Increase snd/rcv buffers in pppoe
From: "David S. Miller" <davem@xxxxxxxxxx>
Date: Mon, 23 Feb 2004 13:32:33 -0800
Cc: yoshfuji@xxxxxxxxxxxxxx, ak@xxxxxx, netdev@xxxxxxxxxxx
In-reply-to: <20040225211526.74478066.ak@suse.de>
References: <20040223105359.GA91938@colin2.muc.de> <20040223.200101.39143636.yoshfuji@linux-ipv6.org> <20040223111659.GB10681@colin2.muc.de> <20040223.203843.04073965.yoshfuji@linux-ipv6.org> <20040223102613.33838132.davem@redhat.com> <20040225211526.74478066.ak@suse.de>
Sender: netdev-bounce@xxxxxxxxxxx
On Wed, 25 Feb 2004 21:15:26 +0100
Andi Kleen <ak@xxxxxxx> wrote:

[ mostrows removed from CC:, he bounces and this is no longer a pppoe discussion
  anymore :) ]

> On Mon, 23 Feb 2004 10:26:13 -0800
> "David S. Miller" <davem@xxxxxxxxxx> wrote:
> 
> > 1) IPV4 icmp sents sk_sndbuf of it's sockets to "2 * SK_WMEM_MAX", that's 
> > not
> >    what it really wants.  What it really wants is enough space to hold
> >    ~2 full sized IPV4 packets, roughly 2 * 64K + struct sk_buff overhead
> >    and thus that is what it should be using there.
> 
> Just sk_buff overhead for what MTU? 576? (would be a bit extreme)
> And in theory it could be one byte packets too.

Two full sized ICMP echo responses (64K) of data plus 2 struct sk_buff, for 
example.

> > 2) IPV6 icmp does the same as ipv4, except this value is even more wrong 
> > there
> >    especially considering jumbograms.  With current code, sending a 
> > jumbogram
> >    ipv6 icmp packet would simply fail, and I wonder if anyone has even tried
> >    this.
> 
> Isn't even ICMPv6 limited to the minimum guaranteed MTU (1000 something) like 
> ICMPv4 is to
> 576 bytes?

What about ECHO?  I can't send an ICMPv6 jumbo sized ECHO and expect a fully 
quoted response
back?

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