From: Stefan Richter <stefanr-MtYdepGKPcBMYopoZt5u/LNAH6kLmebB@public.gmane.org>
To: Jarod Wilson <jarod-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: Sabrina Dubroca <sd-y1jBWg8GRStKuXlAQpz2QA@public.gmane.org>,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
Faisal Latif
<faisal.latif-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>,
linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
Cliff Whickman <cpw-sJ/iWh9BUns@public.gmane.org>,
Robin Holt <robinmholt-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
Jes Sorensen
<jes-dtAfj9ClZIwnoBwkMbRkTB2eb7JE58TQ@public.gmane.org>,
Marek Lindner
<mareklindner-rVWd3aGhH2z5bpWLKbzFeg@public.gmane.org>,
Simon Wunderlich
<sw-2YrNx6rUIHYiY0qSoAWiAoQuADTiUCJX@public.gmane.org>,
Antonio Quartulli <a@unstable.cc>
Subject: Re: [PATCH net-next 6/6] net: use core MTU range checking in misc drivers
Date: Sat, 22 Oct 2016 11:36:07 +0200 [thread overview]
Message-ID: <20161022113607.55832988@kant> (raw)
In-Reply-To: <20161020031641.GJ18569-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
On Oct 19 Jarod Wilson wrote:
> On Thu, Oct 20, 2016 at 12:38:46AM +0200, Stefan Richter wrote:
> > On Oct 19 Sabrina Dubroca wrote:
> > > 2016-10-18, 22:33:33 -0400, Jarod Wilson wrote:
> > > [...]
> > > > diff --git a/drivers/firewire/net.c b/drivers/firewire/net.c
> > > > index 309311b..b5f125c 100644
> > > > --- a/drivers/firewire/net.c
> > > > +++ b/drivers/firewire/net.c
> > > > @@ -1349,15 +1349,6 @@ static netdev_tx_t fwnet_tx(struct sk_buff *skb, struct net_device *net)
> > > > return NETDEV_TX_OK;
> > > > }
> > > >
> > > > -static int fwnet_change_mtu(struct net_device *net, int new_mtu)
> > > > -{
> > > > - if (new_mtu < 68)
> > > > - return -EINVAL;
> > > > -
> > > > - net->mtu = new_mtu;
> > > > - return 0;
> > > > -}
> > > > -
> > >
> > > This doesn't do any upper bound checking.
> >
> > I need to check more closely, but I think the RFC 2734 encapsulation spec
> > and our implementation do not impose a particular upper limit. Though I
> > guess it's bad to let userland set arbitrarily large values here.
>
> In which case, that would suggest using IP_MAX_MTU (65535) here.
Probably. I (or somebody) need to check the spec and the code once more.
[...]
> > > > @@ -1481,6 +1471,8 @@ static int fwnet_probe(struct fw_unit *unit,
> > > > max_mtu = (1 << (card->max_receive + 1))
> > > > - sizeof(struct rfc2734_header) - IEEE1394_GASP_HDR_SIZE;
> > > > net->mtu = min(1500U, max_mtu);
> > > > + net->min_mtu = ETH_MIN_MTU;
> > > > + net->max_mtu = net->mtu;
> > >
> > > But that will now prevent increasing the MTU above the initial value?
> >
> > Indeed, therefore NAK.
>
> However, there's an explicit calculation for 'max_mtu' right there that I
> glazed right over. It would seem perhaps *that* should be used for
> net->max_mtu here, no?
No. This 'max_mtu' here is not the absolute maximum. It is only an
initial MTU which has the property that link fragmentation is not
going to happen (if all other peers will at least as capable as this
node).
--
Stefan Richter
-======----- =-=- =-==-
http://arcgraph.de/sr/
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next prev parent reply other threads:[~2016-10-22 9:36 UTC|newest]
Thread overview: 69+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-19 2:33 [PATCH net-next 0/6] net: use core MTU range checking everywhere Jarod Wilson
2016-10-19 2:33 ` [PATCH net-next 1/6] net: use core MTU range checking in USB NIC drivers Jarod Wilson
2016-10-19 2:33 ` [PATCH net-next 2/6] net: use core MTU range checking in wireless drivers Jarod Wilson
2016-10-19 7:38 ` Johannes Berg
2016-10-19 14:27 ` Jarod Wilson
2016-10-19 14:28 ` Johannes Berg
2016-10-19 2:33 ` [PATCH net-next 3/6] net: use core MTU range checking in WAN drivers Jarod Wilson
2016-10-21 12:04 ` Krzysztof Hałasa
2016-10-19 2:33 ` [PATCH net-next 4/6] net: use core MTU range checking in core net infra Jarod Wilson
2016-10-19 12:17 ` Jiri Benc
2016-10-19 14:51 ` Jarod Wilson
2016-10-19 13:55 ` Sabrina Dubroca
2016-10-19 14:40 ` Jarod Wilson
2016-10-19 15:28 ` Sabrina Dubroca
2016-10-19 15:46 ` Jarod Wilson
2016-10-19 2:33 ` [PATCH net-next 5/6] net: use core MTU range checking in virt drivers Jarod Wilson
2016-10-19 13:06 ` Aaron Conole
2016-10-19 13:59 ` Michael S. Tsirkin
2016-10-19 14:03 ` Michael S. Tsirkin
2016-10-19 14:17 ` Jarod Wilson
2016-10-19 14:15 ` Jarod Wilson
2016-10-19 14:07 ` Haiyang Zhang via Virtualization
2016-10-19 14:23 ` Jarod Wilson
2016-10-19 22:21 ` Shrikrishna Khare
2016-10-19 2:33 ` [PATCH net-next 6/6] net: use core MTU range checking in misc drivers Jarod Wilson
2016-10-19 14:37 ` Robin Holt
2016-10-19 16:05 ` Sabrina Dubroca
2016-10-19 22:38 ` Stefan Richter
2016-10-20 3:16 ` Jarod Wilson
[not found] ` <20161020031641.GJ18569-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2016-10-22 9:36 ` Stefan Richter [this message]
2016-10-22 18:51 ` Stefan Richter
2016-10-19 19:10 ` [PATCH net-next 0/6] net: use core MTU range checking everywhere David Miller
2016-10-19 19:29 ` Jarod Wilson
2016-10-20 17:55 ` [PATCH net-next v2 0/9] " Jarod Wilson
2016-10-20 17:55 ` [PATCH net-next v2 1/9] ethernet: use net core MTU range checking in more drivers Jarod Wilson
2016-10-20 17:55 ` [PATCH net-next v2 2/9] net: use core MTU range checking in USB NIC drivers Jarod Wilson
2016-10-20 17:55 ` [PATCH net-next v2 3/9] net: use core MTU range checking in wireless drivers Jarod Wilson
2016-10-20 18:22 ` Johannes Berg
2016-10-20 18:38 ` David Miller
2016-10-20 17:55 ` [PATCH net-next v2 4/9] net: use core MTU range checking in WAN drivers Jarod Wilson
2016-10-20 17:55 ` [PATCH net-next v2 5/9] net: use core MTU range checking in core net infra Jarod Wilson
2016-10-20 17:55 ` [PATCH net-next v2 6/9] net: use core MTU range checking in virt drivers Jarod Wilson
2016-10-20 18:05 ` Haiyang Zhang
2016-10-20 20:12 ` Kershner, David A
2016-10-20 20:23 ` Michael S. Tsirkin
2016-10-21 2:37 ` Jarod Wilson
2016-10-21 3:36 ` Michael S. Tsirkin
2016-10-21 13:24 ` Aaron Conole
2016-10-21 10:09 ` Wei Liu
2016-10-20 17:55 ` [PATCH net-next v2 7/9] net: use core MTU range checking in misc drivers Jarod Wilson
2016-10-21 6:52 ` Rémi Denis-Courmont
2016-10-21 16:22 ` Sebastian Reichel
[not found] ` <20161020175524.6184-8-jarod-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2016-10-22 7:17 ` [net-next,v2,7/9] " Sven Eckelmann
2016-10-22 19:16 ` [PATCH net-next v2 7/9] " Stefan Richter
2016-10-22 19:27 ` Stefan Richter
2016-10-23 1:18 ` Jarod Wilson
2016-10-23 14:29 ` [PATCH net-next 1/2] firewire: net: fix maximum possible MTU Stefan Richter
2016-10-23 14:30 ` [PATCH net-next 2/2] firewire: net: set initial MTU = 1500 unconditionally, fix IPv6 on some CardBus cards Stefan Richter
2016-10-24 1:50 ` Jarod Wilson
2016-10-24 12:26 ` [PATCH net-next 2/2 v2] " Stefan Richter
2016-10-25 3:05 ` Jarod Wilson
2016-10-26 21:29 ` [PATCH net-next 2/2] " David Miller
2016-10-29 20:16 ` [PATCH net-next] firewire: net: really fix maximum possible MTU Stefan Richter
2016-10-30 3:01 ` David Miller
2016-10-24 1:50 ` [PATCH net-next 1/2] firewire: net: " Jarod Wilson
2016-10-26 21:29 ` David Miller
2016-10-20 17:55 ` [PATCH net-next v2 8/9] s390/net: use net core MTU range checking Jarod Wilson
2016-10-20 17:55 ` [PATCH net-next v2 9/9] ipv4/6: use core net " Jarod Wilson
2016-10-20 18:53 ` [PATCH net-next v2 0/9] net: use core MTU range checking everywhere David Miller
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