netdev - RE: [PATCH net 1/2] net/mlx4_en: Change min MTU size to ETH_MIN

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <f8df9ad96b3d4b65ad73251e1e96386d@AcuMS.aculab.com>
Date:   Tue, 4 Dec 2018 17:17:18 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Eric Dumazet' <eric.dumazet@...il.com>,
        'Tariq Toukan' <tariqt@...lanox.com>,
        "David S. Miller" <davem@...emloft.net>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Eran Ben Elisha <eranbe@...lanox.com>
Subject: RE: [PATCH net 1/2] net/mlx4_en: Change min MTU size to ETH_MIN_MTU

From: Eric Dumazet
> Sent: 04 December 2018 17:04
> 
> On 12/04/2018 08:59 AM, David Laight wrote:
> > From: Tariq Toukan
> >> Sent: 02 December 2018 12:35
> >> From: Eran Ben Elisha <eranbe@...lanox.com>
> >>
> >> NIC driver minimal MTU size shall be set to ETH_MIN_MTU, as defined in
> >> the RFC791 and in the network stack. Remove old mlx4_en only define for
> >> it, which was set to wrong value.
> > ...
> >>
> >> -	/* MTU range: 46 - hw-specific max */
> >> -	dev->min_mtu = MLX4_EN_MIN_MTU;
> >> +	/* MTU range: 68 - hw-specific max */
> >> +	dev->min_mtu = ETH_MIN_MTU;
> >>  	dev->max_mtu = priv->max_mtu;
> >
> > Where does 68 come from?
> 
> Min IPv4 MTU per RFC791

Which has nothing to do with an ethernet driver.
Indeed, IIRC, it is the smallest maximum frame size that IPv4
can work over.

	David

-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)