netdev - Re: [PATCH net-next 2/2] bonding: use l4 hash if available

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Message-ID: <1442361832.4116.21.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Tue, 15 Sep 2015 17:03:52 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Tom Herbert <tom@...bertland.com>
Cc:	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	Mahesh Bandewar <maheshb@...gle.com>
Subject: Re: [PATCH net-next 2/2] bonding: use l4 hash if available

On Tue, 2015-09-15 at 16:45 -0700, Tom Herbert wrote:
> > +       if (bond->params.xmit_policy == BOND_XMIT_POLICY_ENCAP34 &&
> > +           skb->l4_hash)
> > +                       return skb->hash;
> > +
> >         if (bond->params.xmit_policy == BOND_XMIT_POLICY_LAYER2 ||
> >             !bond_flow_dissect(bond, skb, &flow))
> >                 return bond_eth_hash(skb);
> >
> >
> Ugh, bond_flow_dissect is yet another instance of customized flow
> dissection! We should really clean this up. I suggest that in cases
> were we want L4 hash a call to skb_get_hash should suffice. We can
> create skb_get_l3hash when caller explicitly wants an L3 hash-- this
> would return skb->hash if it's valid and skb->l4_hash is not set, else
> call flow dissector with FLOW_DISSECTOR_F_STOP_AT_L3 and then do the
> normal hash over flow keys (don't save result in skb->hash in this
> case).

This code predates all the change you did recently ;)

BTW, the simple xor weakness is showing up after
our change favoring even ports at connect() time, for a bonding device
with 2 or 4 slaves.

(commit 07f4c90062f8fc7c8c26f8f95324cbe8fa3145a5
"tcp/dccp: try to not exhaust ip_local_port_range in connect()")




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