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

From: "David S. Miller" <[email-masked]>
Date: Mon, 23 Feb 2004 13:32:33 -0800

On Wed, 25 Feb 2004 21:15:26 +0100
Andi Kleen <[email-masked]> 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" <[email-masked]> 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?