netdev - RE: [net-next 03/12] i40e: Handle a single mss packet with more than 8 frags

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Date:	Mon, 17 Nov 2014 14:15:40 +0000
From:	David Laight <David.Laight@...LAB.COM>
To:	'Eric Dumazet' <eric.dumazet@...il.com>,
	Jeff Kirsher <jeffrey.t.kirsher@...el.com>
CC:	"davem@...emloft.net" <davem@...emloft.net>,
	Serey Kong <serey.kong@...el.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"nhorman@...hat.com" <nhorman@...hat.com>,
	"sassmann@...hat.com" <sassmann@...hat.com>,
	"jogreene@...hat.com" <jogreene@...hat.com>,
	"Shannon Nelson" <shannon.nelson@...el.com>
Subject: RE: [net-next 03/12] i40e: Handle a single mss packet with more
 than 8 frags

From: Eric Dumazet
> > This handles the case where a single packet with more than 8 data
> > descriptors triggers a Malicious Driver Detect event in the device.

Whose bright idea was that?

> > @@ -2129,10 +2129,16 @@ static void i40e_tx_map(struct i40e_ring *tx_ring, struct sk_buff *skb,
> >  			 I40E_TX_FLAGS_VLAN_SHIFT;
> >  	}
> >
> > -	if (tx_flags & (I40E_TX_FLAGS_TSO | I40E_TX_FLAGS_FSO))
> > +	if (tx_flags & (I40E_TX_FLAGS_TSO | I40E_TX_FLAGS_FSO)) {
> >  		gso_segs = skb_shinfo(skb)->gso_segs;
> > -	else
> > +	} else {
> >  		gso_segs = 1;
> > +		if (skb_shinfo(skb)->nr_frags >= I40E_MAX_BUFFER_TXD)
> > +			skb_linearize(skb);
> 
> What exactly happens if skb_linearize() fails ?

Didn't someone write a function that significantly reduces the
number of fragments without actually requiring a single linear block?

	David