[PATCH net-next 6/6] net: use core MTU range checking in misc drivers

[PATCH net-next 6/6] net: use core MTU range checking in misc drivers

[Jarod Wilson]

firewire-net:
- set min/max_mtu
- remove fwnet_change_mtu

nes:
- set max_mtu
- clean up nes_netdev_change_mtu

xpnet:
- set min/max_mtu
- remove xpnet_dev_change_mtu

hippi:
- set min/max_mtu
- remove hippi_change_mtu

batman-adv:
- set max_mtu
- remove batadv_interface_change_mtu
- initialization is a little async, not 100% certain that max_mtu is set
  in the optimal place, don't have hardware to test with

rionet:
- set min/max_mtu
- remove rionet_change_mtu

slip:
- set min/max_mtu
- streamline sl_change_mtu

CC: netdev@vger.kernel.org
CC: Stefan Richter <stefanr@s5r6.in-berlin.de>
CC: Faisal Latif <faisal.latif@intel.com>
CC: linux-rdma@vger.kernel.org
CC: Cliff Whickman <cpw@sgi.com>
CC: Robin Holt <robinmholt@gmail.com>
CC: Jes Sorensen <jes@trained-monkey.org>
CC: Marek Lindner <mareklindner@neomailbox.ch>
CC: Simon Wunderlich <sw@simonwunderlich.de>
CC: Antonio Quartulli <a@unstable.cc>
Signed-off-by: Jarod Wilson <jarod@redhat.com>
---
 drivers/firewire/net.c              | 12 ++----------
 drivers/infiniband/hw/nes/nes.c     |  1 -
 drivers/infiniband/hw/nes/nes.h     |  4 ++--
 drivers/infiniband/hw/nes/nes_nic.c | 10 +++-------
 drivers/misc/sgi-xp/xpnet.c         | 21 ++++-----------------
 drivers/net/hippi/rrunner.c         |  1 -
 drivers/net/rionet.c                | 15 +++------------
 drivers/net/slip/slip.c             | 11 +++++------
 include/linux/hippidevice.h         |  1 -
 net/802/hippi.c                     | 14 ++------------
 net/batman-adv/soft-interface.c     | 13 +------------
 11 files changed, 22 insertions(+), 81 deletions(-)

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;
-}
-
 static const struct ethtool_ops fwnet_ethtool_ops = {
 	.get_link	= ethtool_op_get_link,
 };
@@ -1366,7 +1357,6 @@ static const struct net_device_ops fwnet_netdev_ops = {
 	.ndo_open       = fwnet_open,
 	.ndo_stop	= fwnet_stop,
 	.ndo_start_xmit = fwnet_tx,
-	.ndo_change_mtu = fwnet_change_mtu,
 };
 
 static void fwnet_init_dev(struct net_device *net)
@@ -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;
 
 	/* Set our hardware address while we're at it */
 	ha = (union fwnet_hwaddr *)net->dev_addr;
diff --git a/drivers/infiniband/hw/nes/nes.c b/drivers/infiniband/hw/nes/nes.c
index 35cbb17..2baa45a 100644
--- a/drivers/infiniband/hw/nes/nes.c
+++ b/drivers/infiniband/hw/nes/nes.c
@@ -65,7 +65,6 @@ MODULE_DESCRIPTION("NetEffect RNIC Low-level iWARP Driver");
 MODULE_LICENSE("Dual BSD/GPL");
 MODULE_VERSION(DRV_VERSION);
 
-int max_mtu = 9000;
 int interrupt_mod_interval = 0;
 
 /* Interoperability */
diff --git a/drivers/infiniband/hw/nes/nes.h b/drivers/infiniband/hw/nes/nes.h
index e7430c9..85acd08 100644
--- a/drivers/infiniband/hw/nes/nes.h
+++ b/drivers/infiniband/hw/nes/nes.h
@@ -83,6 +83,8 @@
 #define NES_FIRST_QPN           64
 #define NES_SW_CONTEXT_ALIGN    1024
 
+#define NES_MAX_MTU		9000
+
 #define NES_NIC_MAX_NICS        16
 #define NES_MAX_ARP_TABLE_SIZE  4096
 
@@ -169,8 +171,6 @@ do { \
 #include "nes_cm.h"
 #include "nes_mgt.h"
 
-extern int max_mtu;
-#define max_frame_len (max_mtu+ETH_HLEN)
 extern int interrupt_mod_interval;
 extern int nes_if_count;
 extern int mpa_version;
diff --git a/drivers/infiniband/hw/nes/nes_nic.c b/drivers/infiniband/hw/nes/nes_nic.c
index 2b27d13..7f8597d 100644
--- a/drivers/infiniband/hw/nes/nes_nic.c
+++ b/drivers/infiniband/hw/nes/nes_nic.c
@@ -981,20 +981,16 @@ static int nes_netdev_change_mtu(struct net_device *netdev, int new_mtu)
 {
 	struct nes_vnic	*nesvnic = netdev_priv(netdev);
 	struct nes_device *nesdev = nesvnic->nesdev;
-	int ret = 0;
 	u8 jumbomode = 0;
 	u32 nic_active;
 	u32 nic_active_bit;
 	u32 uc_all_active;
 	u32 mc_all_active;
 
-	if ((new_mtu < ETH_ZLEN) || (new_mtu > max_mtu))
-		return -EINVAL;
-
 	netdev->mtu = new_mtu;
 	nesvnic->max_frame_size	= new_mtu + VLAN_ETH_HLEN;
 
-	if (netdev->mtu	> 1500)	{
+	if (netdev->mtu	> ETH_DATA_LEN)	{
 		jumbomode=1;
 	}
 	nes_nic_init_timer_defaults(nesdev, jumbomode);
@@ -1020,7 +1016,7 @@ static int nes_netdev_change_mtu(struct net_device *netdev, int new_mtu)
 		nes_write_indexed(nesdev, NES_IDX_NIC_UNICAST_ALL, nic_active);
 	}
 
-	return ret;
+	return 0;
 }
 
 
@@ -1658,7 +1654,7 @@ struct net_device *nes_netdev_init(struct nes_device *nesdev,
 
 	netdev->watchdog_timeo = NES_TX_TIMEOUT;
 	netdev->irq = nesdev->pcidev->irq;
-	netdev->mtu = ETH_DATA_LEN;
+	netdev->max_mtu = NES_MAX_MTU;
 	netdev->hard_header_len = ETH_HLEN;
 	netdev->addr_len = ETH_ALEN;
 	netdev->type = ARPHRD_ETHER;
diff --git a/drivers/misc/sgi-xp/xpnet.c b/drivers/misc/sgi-xp/xpnet.c
index 557f978..0c26eaf 100644
--- a/drivers/misc/sgi-xp/xpnet.c
+++ b/drivers/misc/sgi-xp/xpnet.c
@@ -118,6 +118,8 @@ static DEFINE_SPINLOCK(xpnet_broadcast_lock);
  * now, the default is 64KB.
  */
 #define XPNET_MAX_MTU (0x800000UL - L1_CACHE_BYTES)
+/* 68 comes from min TCP+IP+MAC header */
+#define XPNET_MIN_MTU 68
 /* 32KB has been determined to be the ideal */
 #define XPNET_DEF_MTU (0x8000UL)
 
@@ -330,22 +332,6 @@ xpnet_dev_stop(struct net_device *dev)
 	return 0;
 }
 
-static int
-xpnet_dev_change_mtu(struct net_device *dev, int new_mtu)
-{
-	/* 68 comes from min TCP+IP+MAC header */
-	if ((new_mtu < 68) || (new_mtu > XPNET_MAX_MTU)) {
-		dev_err(xpnet, "ifconfig %s mtu %d failed; value must be "
-			"between 68 and %ld\n", dev->name, new_mtu,
-			XPNET_MAX_MTU);
-		return -EINVAL;
-	}
-
-	dev->mtu = new_mtu;
-	dev_dbg(xpnet, "ifconfig %s mtu set to %d\n", dev->name, new_mtu);
-	return 0;
-}
-
 /*
  * Notification that the other end has received the message and
  * DMA'd the skb information.  At this point, they are done with
@@ -519,7 +505,6 @@ static const struct net_device_ops xpnet_netdev_ops = {
 	.ndo_open		= xpnet_dev_open,
 	.ndo_stop		= xpnet_dev_stop,
 	.ndo_start_xmit		= xpnet_dev_hard_start_xmit,
-	.ndo_change_mtu		= xpnet_dev_change_mtu,
 	.ndo_tx_timeout		= xpnet_dev_tx_timeout,
 	.ndo_set_mac_address 	= eth_mac_addr,
 	.ndo_validate_addr	= eth_validate_addr,
@@ -555,6 +540,8 @@ xpnet_init(void)
 
 	xpnet_device->netdev_ops = &xpnet_netdev_ops;
 	xpnet_device->mtu = XPNET_DEF_MTU;
+	xpnet_device->min_mtu = XPNET_MIN_MTU;
+	xpnet_device->max_mtu = XPNET_MAX_MTU;
 
 	/*
 	 * Multicast assumes the LSB of the first octet is set for multicast
diff --git a/drivers/net/hippi/rrunner.c b/drivers/net/hippi/rrunner.c
index 95c0b45..f5a9728 100644
--- a/drivers/net/hippi/rrunner.c
+++ b/drivers/net/hippi/rrunner.c
@@ -68,7 +68,6 @@ static const struct net_device_ops rr_netdev_ops = {
 	.ndo_stop		= rr_close,
 	.ndo_do_ioctl		= rr_ioctl,
 	.ndo_start_xmit		= rr_start_xmit,
-	.ndo_change_mtu		= hippi_change_mtu,
 	.ndo_set_mac_address	= hippi_mac_addr,
 };
 
diff --git a/drivers/net/rionet.c b/drivers/net/rionet.c
index a31f461..300bb14 100644
--- a/drivers/net/rionet.c
+++ b/drivers/net/rionet.c
@@ -466,17 +466,6 @@ static void rionet_set_msglevel(struct net_device *ndev, u32 value)
 	rnet->msg_enable = value;
 }
 
-static int rionet_change_mtu(struct net_device *ndev, int new_mtu)
-{
-	if ((new_mtu < 68) || (new_mtu > RIONET_MAX_MTU)) {
-		printk(KERN_ERR "%s: Invalid MTU size %d\n",
-		       ndev->name, new_mtu);
-		return -EINVAL;
-	}
-	ndev->mtu = new_mtu;
-	return 0;
-}
-
 static const struct ethtool_ops rionet_ethtool_ops = {
 	.get_drvinfo = rionet_get_drvinfo,
 	.get_msglevel = rionet_get_msglevel,
@@ -488,7 +477,6 @@ static const struct net_device_ops rionet_netdev_ops = {
 	.ndo_open		= rionet_open,
 	.ndo_stop		= rionet_close,
 	.ndo_start_xmit		= rionet_start_xmit,
-	.ndo_change_mtu		= rionet_change_mtu,
 	.ndo_validate_addr	= eth_validate_addr,
 	.ndo_set_mac_address	= eth_mac_addr,
 };
@@ -525,6 +513,9 @@ static int rionet_setup_netdev(struct rio_mport *mport, struct net_device *ndev)
 
 	ndev->netdev_ops = &rionet_netdev_ops;
 	ndev->mtu = RIONET_MAX_MTU;
+	/* MTU range: 68 - 4082 */
+	ndev->min_mtu = ETH_MIN_MTU;
+	ndev->max_mtu = RIONET_MAX_MTU;
 	ndev->features = NETIF_F_LLTX;
 	SET_NETDEV_DEV(ndev, &mport->dev);
 	ndev->ethtool_ops = &rionet_ethtool_ops;
diff --git a/drivers/net/slip/slip.c b/drivers/net/slip/slip.c
index 9ed6d1c..7e933d8 100644
--- a/drivers/net/slip/slip.c
+++ b/drivers/net/slip/slip.c
@@ -561,12 +561,7 @@ static int sl_change_mtu(struct net_device *dev, int new_mtu)
 {
 	struct slip *sl = netdev_priv(dev);
 
-	if (new_mtu < 68 || new_mtu > 65534)
-		return -EINVAL;
-
-	if (new_mtu != dev->mtu)
-		return sl_realloc_bufs(sl, new_mtu);
-	return 0;
+	return sl_realloc_bufs(sl, new_mtu);
 }
 
 /* Netdevice get statistics request */
@@ -663,6 +658,10 @@ static void sl_setup(struct net_device *dev)
 	dev->addr_len		= 0;
 	dev->tx_queue_len	= 10;
 
+	/* MTU range: 68 - 65534 */
+	dev->min_mtu = 68;
+	dev->max_mtu = 65534;
+
 	/* New-style flags. */
 	dev->flags		= IFF_NOARP|IFF_POINTOPOINT|IFF_MULTICAST;
 }
diff --git a/include/linux/hippidevice.h b/include/linux/hippidevice.h
index 8ec23fb..402f99e 100644
--- a/include/linux/hippidevice.h
+++ b/include/linux/hippidevice.h
@@ -32,7 +32,6 @@ struct hippi_cb {
 };
 
 __be16 hippi_type_trans(struct sk_buff *skb, struct net_device *dev);
-int hippi_change_mtu(struct net_device *dev, int new_mtu);
 int hippi_mac_addr(struct net_device *dev, void *p);
 int hippi_neigh_setup_dev(struct net_device *dev, struct neigh_parms *p);
 struct net_device *alloc_hippi_dev(int sizeof_priv);
diff --git a/net/802/hippi.c b/net/802/hippi.c
index ade1a52..5e4427b 100644
--- a/net/802/hippi.c
+++ b/net/802/hippi.c
@@ -116,18 +116,6 @@ __be16 hippi_type_trans(struct sk_buff *skb, struct net_device *dev)
 
 EXPORT_SYMBOL(hippi_type_trans);
 
-int hippi_change_mtu(struct net_device *dev, int new_mtu)
-{
-	/*
-	 * HIPPI's got these nice large MTUs.
-	 */
-	if ((new_mtu < 68) || (new_mtu > 65280))
-		return -EINVAL;
-	dev->mtu = new_mtu;
-	return 0;
-}
-EXPORT_SYMBOL(hippi_change_mtu);
-
 /*
  * For HIPPI we will actually use the lower 4 bytes of the hardware
  * address as the I-FIELD rather than the actual hardware address.
@@ -174,6 +162,8 @@ static void hippi_setup(struct net_device *dev)
 	dev->type		= ARPHRD_HIPPI;
 	dev->hard_header_len 	= HIPPI_HLEN;
 	dev->mtu		= 65280;
+	dev->min_mtu		= 68;
+	dev->max_mtu		= 65280;
 	dev->addr_len		= HIPPI_ALEN;
 	dev->tx_queue_len	= 25 /* 5 */;
 	memset(dev->broadcast, 0xFF, HIPPI_ALEN);
diff --git a/net/batman-adv/soft-interface.c b/net/batman-adv/soft-interface.c
index 49e16b6..112679d 100644
--- a/net/batman-adv/soft-interface.c
+++ b/net/batman-adv/soft-interface.c
@@ -158,17 +158,6 @@ static int batadv_interface_set_mac_addr(struct net_device *dev, void *p)
 	return 0;
 }
 
-static int batadv_interface_change_mtu(struct net_device *dev, int new_mtu)
-{
-	/* check ranges */
-	if ((new_mtu < 68) || (new_mtu > batadv_hardif_min_mtu(dev)))
-		return -EINVAL;
-
-	dev->mtu = new_mtu;
-
-	return 0;
-}
-
 /**
  * batadv_interface_set_rx_mode - set the rx mode of a device
  * @dev: registered network device to modify
@@ -920,7 +909,6 @@ static const struct net_device_ops batadv_netdev_ops = {
 	.ndo_vlan_rx_add_vid = batadv_interface_add_vid,
 	.ndo_vlan_rx_kill_vid = batadv_interface_kill_vid,
 	.ndo_set_mac_address = batadv_interface_set_mac_addr,
-	.ndo_change_mtu = batadv_interface_change_mtu,
 	.ndo_set_rx_mode = batadv_interface_set_rx_mode,
 	.ndo_start_xmit = batadv_interface_tx,
 	.ndo_validate_addr = eth_validate_addr,
@@ -987,6 +975,7 @@ struct net_device *batadv_softif_create(struct net *net, const char *name)
 	dev_net_set(soft_iface, net);
 
 	soft_iface->rtnl_link_ops = &batadv_link_ops;
+	soft_iface->max_mtu = batadv_hardif_min_mtu(soft_iface);
 
 	ret = register_netdevice(soft_iface);
 	if (ret < 0) {
-- 
2.10.0

Re: [PATCH net-next 6/6] net: use core MTU range checking in misc drivers

[Robin Holt]

On Tue, Oct 18, 2016 at 9:33 PM, Jarod Wilson <jarod@redhat.com> wrote:
> CC: netdev@vger.kernel.org
> CC: Stefan Richter <stefanr@s5r6.in-berlin.de>
> CC: Faisal Latif <faisal.latif@intel.com>
> CC: linux-rdma@vger.kernel.org
> CC: Cliff Whickman <cpw@sgi.com>

Acked-by: Robin Holt <robinmholt@gmail.com>

> CC: Jes Sorensen <jes@trained-monkey.org>
> CC: Marek Lindner <mareklindner@neomailbox.ch>
> CC: Simon Wunderlich <sw@simonwunderlich.de>
> CC: Antonio Quartulli <a@unstable.cc>
> Signed-off-by: Jarod Wilson <jarod@redhat.com>

Re: [PATCH net-next 6/6] net: use core MTU range checking in misc drivers

[Sabrina Dubroca]

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.

>  static const struct ethtool_ops fwnet_ethtool_ops = {
>  	.get_link	= ethtool_op_get_link,
>  };
> @@ -1366,7 +1357,6 @@ static const struct net_device_ops fwnet_netdev_ops = {
>  	.ndo_open       = fwnet_open,
>  	.ndo_stop	= fwnet_stop,
>  	.ndo_start_xmit = fwnet_tx,
> -	.ndo_change_mtu = fwnet_change_mtu,
>  };
>  
>  static void fwnet_init_dev(struct net_device *net)
> @@ -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?

-- 
Sabrina

Re: [PATCH net-next 6/6] net: use core MTU range checking in misc drivers

[Stefan Richter]

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.

> >  static const struct ethtool_ops fwnet_ethtool_ops = {
> >  	.get_link	= ethtool_op_get_link,
> >  };
> > @@ -1366,7 +1357,6 @@ static const struct net_device_ops fwnet_netdev_ops = {
> >  	.ndo_open       = fwnet_open,
> >  	.ndo_stop	= fwnet_stop,
> >  	.ndo_start_xmit = fwnet_tx,
> > -	.ndo_change_mtu = fwnet_change_mtu,
> >  };
> >  
> >  static void fwnet_init_dev(struct net_device *net)
> > @@ -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.

PS:
If the IP packet plus encapsulation header fits into IEEE 1394 packet
payload, it is transported without link fragmentation.  If it does not
fit, link fragmentation occurs (which reduces bandwidth a bit and
consumes additional buffering resources at the transmitter and the
receiver).

Broadcast and multicast packets are transmitted via IEEE 1394 asynchronous
stream packets at a low bus speed (because our code does not attempt to
find the maximum speed and size that is supported by all potential
listeners).  This limits the payload to 512 bytes.

Unicast packets are transmitted via IEEE 1394 asynchronous write request
packets at optimum speed.  In most cases, this means that 2048 bytes
payload is possible, in some cases 4096 bytes.  Many CardBus FireWire
cards support only 1024 bytes payload of these packets though.
Furthermore, some low-speed long-haul cablings may cap the bus speed and
thereby the payload size to 1024 or 512 bytes, but this is uncommon in
practice.
-- 
Stefan Richter
-======----- =-=- =-=--
http://arcgraph.de/sr/

Re: [PATCH net-next 6/6] net: use core MTU range checking in misc drivers

[Jarod Wilson]

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.

> > >  static const struct ethtool_ops fwnet_ethtool_ops = {
> > >  	.get_link	= ethtool_op_get_link,
> > >  };
> > > @@ -1366,7 +1357,6 @@ static const struct net_device_ops fwnet_netdev_ops = {
> > >  	.ndo_open       = fwnet_open,
> > >  	.ndo_stop	= fwnet_stop,
> > >  	.ndo_start_xmit = fwnet_tx,
> > > -	.ndo_change_mtu = fwnet_change_mtu,
> > >  };
> > >  
> > >  static void fwnet_init_dev(struct net_device *net)
> > > @@ -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?

> PS:
> If the IP packet plus encapsulation header fits into IEEE 1394 packet
> payload, it is transported without link fragmentation.  If it does not
> fit, link fragmentation occurs (which reduces bandwidth a bit and
> consumes additional buffering resources at the transmitter and the
> receiver).
> 
> Broadcast and multicast packets are transmitted via IEEE 1394 asynchronous
> stream packets at a low bus speed (because our code does not attempt to
> find the maximum speed and size that is supported by all potential
> listeners).  This limits the payload to 512 bytes.
> 
> Unicast packets are transmitted via IEEE 1394 asynchronous write request
> packets at optimum speed.  In most cases, this means that 2048 bytes
> payload is possible, in some cases 4096 bytes.  Many CardBus FireWire
> cards support only 1024 bytes payload of these packets though.
> Furthermore, some low-speed long-haul cablings may cap the bus speed and
> thereby the payload size to 1024 or 512 bytes, but this is uncommon in
> practice.

Thorough as always, Stefan! :)

-- 
Jarod Wilson
jarod@redhat.com

Re: [PATCH net-next 6/6] net: use core MTU range checking in misc drivers

[Stefan Richter]

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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Re: [PATCH net-next 6/6] net: use core MTU range checking in misc drivers

[Stefan Richter]

On Oct 22 Stefan Richter wrote:
> 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:
[...]
> > > > > @@ -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).

Besides, card->max_receive is about what the card can receive (at the IEEE
1394 link layer), not about what the card can send.
-- 
Stefan Richter
-======----- =-=- =-==-
http://arcgraph.de/sr/

[PATCH net-next v2 7/9] net: use core MTU range checking in misc drivers

[Jarod Wilson]

firewire-net:
- set min/max_mtu
- remove fwnet_change_mtu

nes:
- set max_mtu
- clean up nes_netdev_change_mtu

xpnet:
- set min/max_mtu
- remove xpnet_dev_change_mtu

hippi:
- set min/max_mtu
- remove hippi_change_mtu

batman-adv:
- set max_mtu
- remove batadv_interface_change_mtu
- initialization is a little async, not 100% certain that max_mtu is set
  in the optimal place, don't have hardware to test with

rionet:
- set min/max_mtu
- remove rionet_change_mtu

slip:
- set min/max_mtu
- streamline sl_change_mtu

um/net_kern:
- remove pointless ndo_change_mtu

hsi/clients/ssi_protocol:
- use core MTU range checking
- remove now redundant ssip_pn_set_mtu

ipoib:
- set a default max MTU value
- Note: ipoib's actual max MTU can vary, depending on if the device is in
  connected mode or not, so we'll just set the max_mtu value to the max
  possible, and let the ndo_change_mtu function continue to validate any new
  MTU change requests with checks for CM or not. Note that ipoib has no
  min_mtu set, and thus, the network core's mtu > 0 check is the only lower
  bounds here.

mptlan:
- use net core MTU range checking
- remove now redundant mpt_lan_change_mtu

fddi:
- min_mtu = 21, max_mtu = 4470
- remove now redundant fddi_change_mtu (including export)

fjes:
- min_mtu = 8192, max_mtu = 65536
- The max_mtu value is actually one over IP_MAX_MTU here, but the idea is to
  get past the core net MTU range checks so fjes_change_mtu can validate a
  new MTU against what it supports (see fjes_support_mtu in fjes_hw.c)

hsr:
- min_mtu = 0 (calls ether_setup, max_mtu is 1500)

f_phonet:
- min_mtu = 6, max_mtu = 65541

u_ether:
- min_mtu = 14, max_mtu = 15412

phonet/pep-gprs:
- min_mtu = 576, max_mtu = 65530
- remove redundant gprs_set_mtu

CC: netdev@vger.kernel.org
CC: linux-rdma@vger.kernel.org
CC: Stefan Richter <stefanr@s5r6.in-berlin.de>
CC: Faisal Latif <faisal.latif@intel.com>
CC: linux-rdma@vger.kernel.org
CC: Cliff Whickman <cpw@sgi.com>
CC: Robin Holt <robinmholt@gmail.com>
CC: Jes Sorensen <jes@trained-monkey.org>
CC: Marek Lindner <mareklindner@neomailbox.ch>
CC: Simon Wunderlich <sw@simonwunderlich.de>
CC: Antonio Quartulli <a@unstable.cc>
CC: Sathya Prakash <sathya.prakash@broadcom.com>
CC: Chaitra P B <chaitra.basappa@broadcom.com>
CC: Suganath Prabu Subramani <suganath-prabu.subramani@broadcom.com>
CC: MPT-FusionLinux.pdl@broadcom.com
CC: Sebastian Reichel <sre@kernel.org>
CC: Felipe Balbi <balbi@kernel.org>
CC: Arvid Brodin <arvid.brodin@alten.se>
CC: Remi Denis-Courmont <courmisch@gmail.com>
Signed-off-by: Jarod Wilson <jarod@redhat.com>
---
 arch/um/drivers/net_kern.c                |  8 --------
 drivers/firewire/net.c                    | 18 ++++--------------
 drivers/hsi/clients/ssi_protocol.c        | 14 ++++----------
 drivers/infiniband/hw/nes/nes.c           |  1 -
 drivers/infiniband/hw/nes/nes.h           |  4 ++--
 drivers/infiniband/hw/nes/nes_nic.c       | 10 +++-------
 drivers/infiniband/ulp/ipoib/ipoib_main.c |  1 +
 drivers/message/fusion/mptlan.c           | 15 ++++-----------
 drivers/misc/sgi-xp/xpnet.c               | 21 ++++-----------------
 drivers/net/fddi/skfp/skfddi.c            |  1 -
 drivers/net/fjes/fjes_main.c              |  2 ++
 drivers/net/hippi/rrunner.c               |  1 -
 drivers/net/rionet.c                      | 15 +++------------
 drivers/net/slip/slip.c                   | 11 +++++------
 drivers/usb/gadget/function/f_phonet.c    | 11 ++---------
 drivers/usb/gadget/function/u_ether.c     | 14 ++++----------
 include/linux/fddidevice.h                |  1 -
 include/linux/hippidevice.h               |  1 -
 net/802/fddi.c                            | 11 ++---------
 net/802/hippi.c                           | 14 ++------------
 net/batman-adv/soft-interface.c           | 13 +------------
 net/hsr/hsr_device.c                      |  1 +
 net/phonet/pep-gprs.c                     | 12 ++----------
 23 files changed, 46 insertions(+), 154 deletions(-)

diff --git a/arch/um/drivers/net_kern.c b/arch/um/drivers/net_kern.c
index 2cd5b68..1669240 100644
--- a/arch/um/drivers/net_kern.c
+++ b/arch/um/drivers/net_kern.c
@@ -256,13 +256,6 @@ static void uml_net_tx_timeout(struct net_device *dev)
 	netif_wake_queue(dev);
 }
 
-static int uml_net_change_mtu(struct net_device *dev, int new_mtu)
-{
-	dev->mtu = new_mtu;
-
-	return 0;
-}
-
 #ifdef CONFIG_NET_POLL_CONTROLLER
 static void uml_net_poll_controller(struct net_device *dev)
 {
@@ -374,7 +367,6 @@ static const struct net_device_ops uml_netdev_ops = {
 	.ndo_set_rx_mode	= uml_net_set_multicast_list,
 	.ndo_tx_timeout 	= uml_net_tx_timeout,
 	.ndo_set_mac_address	= eth_mac_addr,
-	.ndo_change_mtu 	= uml_net_change_mtu,
 	.ndo_validate_addr	= eth_validate_addr,
 #ifdef CONFIG_NET_POLL_CONTROLLER
 	.ndo_poll_controller = uml_net_poll_controller,
diff --git a/drivers/firewire/net.c b/drivers/firewire/net.c
index 309311b..8430222 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;
-}
-
 static const struct ethtool_ops fwnet_ethtool_ops = {
 	.get_link	= ethtool_op_get_link,
 };
@@ -1366,7 +1357,6 @@ static const struct net_device_ops fwnet_netdev_ops = {
 	.ndo_open       = fwnet_open,
 	.ndo_stop	= fwnet_stop,
 	.ndo_start_xmit = fwnet_tx,
-	.ndo_change_mtu = fwnet_change_mtu,
 };
 
 static void fwnet_init_dev(struct net_device *net)
@@ -1435,7 +1425,6 @@ static int fwnet_probe(struct fw_unit *unit,
 	struct net_device *net;
 	bool allocated_netdev = false;
 	struct fwnet_device *dev;
-	unsigned max_mtu;
 	int ret;
 	union fwnet_hwaddr *ha;
 
@@ -1478,9 +1467,10 @@ static int fwnet_probe(struct fw_unit *unit,
 	 * Use the RFC 2734 default 1500 octets or the maximum payload
 	 * as initial MTU
 	 */
-	max_mtu = (1 << (card->max_receive + 1))
-		  - sizeof(struct rfc2734_header) - IEEE1394_GASP_HDR_SIZE;
-	net->mtu = min(1500U, max_mtu);
+	net->max_mtu = (1 << (card->max_receive + 1))
+		       - sizeof(struct rfc2734_header) - IEEE1394_GASP_HDR_SIZE;
+	net->mtu = min(1500U, net->max_mtu);
+	net->min_mtu = ETH_MIN_MTU;
 
 	/* Set our hardware address while we're at it */
 	ha = (union fwnet_hwaddr *)net->dev_addr;
diff --git a/drivers/hsi/clients/ssi_protocol.c b/drivers/hsi/clients/ssi_protocol.c
index 6031cd1..7ef8196 100644
--- a/drivers/hsi/clients/ssi_protocol.c
+++ b/drivers/hsi/clients/ssi_protocol.c
@@ -960,15 +960,6 @@ static int ssip_pn_stop(struct net_device *dev)
 	return 0;
 }
 
-static int ssip_pn_set_mtu(struct net_device *dev, int new_mtu)
-{
-	if (new_mtu > SSIP_MAX_MTU || new_mtu < PHONET_MIN_MTU)
-		return -EINVAL;
-	dev->mtu = new_mtu;
-
-	return 0;
-}
-
 static void ssip_xmit_work(struct work_struct *work)
 {
 	struct ssi_protocol *ssi =
@@ -1060,7 +1051,6 @@ static const struct net_device_ops ssip_pn_ops = {
 	.ndo_open	= ssip_pn_open,
 	.ndo_stop	= ssip_pn_stop,
 	.ndo_start_xmit	= ssip_pn_xmit,
-	.ndo_change_mtu	= ssip_pn_set_mtu,
 };
 
 static void ssip_pn_setup(struct net_device *dev)
@@ -1136,6 +1126,10 @@ static int ssi_protocol_probe(struct device *dev)
 		goto out1;
 	}
 
+	/* MTU range: 6 - 65535 */
+	ssi->netdev->min_mtu = PHONET_MIN_MTU;
+	ssi->netdev->max_mtu = SSIP_MAX_MTU;
+
 	SET_NETDEV_DEV(ssi->netdev, dev);
 	netif_carrier_off(ssi->netdev);
 	err = register_netdev(ssi->netdev);
diff --git a/drivers/infiniband/hw/nes/nes.c b/drivers/infiniband/hw/nes/nes.c
index 35cbb17..2baa45a 100644
--- a/drivers/infiniband/hw/nes/nes.c
+++ b/drivers/infiniband/hw/nes/nes.c
@@ -65,7 +65,6 @@ MODULE_DESCRIPTION("NetEffect RNIC Low-level iWARP Driver");
 MODULE_LICENSE("Dual BSD/GPL");
 MODULE_VERSION(DRV_VERSION);
 
-int max_mtu = 9000;
 int interrupt_mod_interval = 0;
 
 /* Interoperability */
diff --git a/drivers/infiniband/hw/nes/nes.h b/drivers/infiniband/hw/nes/nes.h
index e7430c9..85acd08 100644
--- a/drivers/infiniband/hw/nes/nes.h
+++ b/drivers/infiniband/hw/nes/nes.h
@@ -83,6 +83,8 @@
 #define NES_FIRST_QPN           64
 #define NES_SW_CONTEXT_ALIGN    1024
 
+#define NES_MAX_MTU		9000
+
 #define NES_NIC_MAX_NICS        16
 #define NES_MAX_ARP_TABLE_SIZE  4096
 
@@ -169,8 +171,6 @@ do { \
 #include "nes_cm.h"
 #include "nes_mgt.h"
 
-extern int max_mtu;
-#define max_frame_len (max_mtu+ETH_HLEN)
 extern int interrupt_mod_interval;
 extern int nes_if_count;
 extern int mpa_version;
diff --git a/drivers/infiniband/hw/nes/nes_nic.c b/drivers/infiniband/hw/nes/nes_nic.c
index 2b27d13..7f8597d 100644
--- a/drivers/infiniband/hw/nes/nes_nic.c
+++ b/drivers/infiniband/hw/nes/nes_nic.c
@@ -981,20 +981,16 @@ static int nes_netdev_change_mtu(struct net_device *netdev, int new_mtu)
 {
 	struct nes_vnic	*nesvnic = netdev_priv(netdev);
 	struct nes_device *nesdev = nesvnic->nesdev;
-	int ret = 0;
 	u8 jumbomode = 0;
 	u32 nic_active;
 	u32 nic_active_bit;
 	u32 uc_all_active;
 	u32 mc_all_active;
 
-	if ((new_mtu < ETH_ZLEN) || (new_mtu > max_mtu))
-		return -EINVAL;
-
 	netdev->mtu = new_mtu;
 	nesvnic->max_frame_size	= new_mtu + VLAN_ETH_HLEN;
 
-	if (netdev->mtu	> 1500)	{
+	if (netdev->mtu	> ETH_DATA_LEN)	{
 		jumbomode=1;
 	}
 	nes_nic_init_timer_defaults(nesdev, jumbomode);
@@ -1020,7 +1016,7 @@ static int nes_netdev_change_mtu(struct net_device *netdev, int new_mtu)
 		nes_write_indexed(nesdev, NES_IDX_NIC_UNICAST_ALL, nic_active);
 	}
 
-	return ret;
+	return 0;
 }
 
 
@@ -1658,7 +1654,7 @@ struct net_device *nes_netdev_init(struct nes_device *nesdev,
 
 	netdev->watchdog_timeo = NES_TX_TIMEOUT;
 	netdev->irq = nesdev->pcidev->irq;
-	netdev->mtu = ETH_DATA_LEN;
+	netdev->max_mtu = NES_MAX_MTU;
 	netdev->hard_header_len = ETH_HLEN;
 	netdev->addr_len = ETH_ALEN;
 	netdev->type = ARPHRD_ETHER;
diff --git a/drivers/infiniband/ulp/ipoib/ipoib_main.c b/drivers/infiniband/ulp/ipoib/ipoib_main.c
index cc05921..ae5d7cd 100644
--- a/drivers/infiniband/ulp/ipoib/ipoib_main.c
+++ b/drivers/infiniband/ulp/ipoib/ipoib_main.c
@@ -2017,6 +2017,7 @@ static struct net_device *ipoib_add_port(const char *format,
 	/* MTU will be reset when mcast join happens */
 	priv->dev->mtu  = IPOIB_UD_MTU(priv->max_ib_mtu);
 	priv->mcast_mtu  = priv->admin_mtu = priv->dev->mtu;
+	priv->dev->max_mtu = IPOIB_CM_MTU;
 
 	priv->dev->neigh_priv_len = sizeof(struct ipoib_neigh);
 
diff --git a/drivers/message/fusion/mptlan.c b/drivers/message/fusion/mptlan.c
index 6955c9e..55dd71b 100644
--- a/drivers/message/fusion/mptlan.c
+++ b/drivers/message/fusion/mptlan.c
@@ -549,16 +549,6 @@ mpt_lan_close(struct net_device *dev)
 }
 
 /*=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=*/
-static int
-mpt_lan_change_mtu(struct net_device *dev, int new_mtu)
-{
-	if ((new_mtu < MPT_LAN_MIN_MTU) || (new_mtu > MPT_LAN_MAX_MTU))
-		return -EINVAL;
-	dev->mtu = new_mtu;
-	return 0;
-}
-
-/*=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=*/
 /* Tx timeout handler. */
 static void
 mpt_lan_tx_timeout(struct net_device *dev)
@@ -1304,7 +1294,6 @@ static const struct net_device_ops mpt_netdev_ops = {
 	.ndo_open       = mpt_lan_open,
 	.ndo_stop       = mpt_lan_close,
 	.ndo_start_xmit = mpt_lan_sdu_send,
-	.ndo_change_mtu = mpt_lan_change_mtu,
 	.ndo_tx_timeout = mpt_lan_tx_timeout,
 };
 
@@ -1375,6 +1364,10 @@ mpt_register_lan_device (MPT_ADAPTER *mpt_dev, int pnum)
 	dev->netdev_ops = &mpt_netdev_ops;
 	dev->watchdog_timeo = MPT_LAN_TX_TIMEOUT;
 
+	/* MTU range: 96 - 65280 */
+	dev->min_mtu = MPT_LAN_MIN_MTU;
+	dev->max_mtu = MPT_LAN_MAX_MTU;
+
 	dlprintk((KERN_INFO MYNAM ": Finished registering dev "
 		"and setting initial values\n"));
 
diff --git a/drivers/misc/sgi-xp/xpnet.c b/drivers/misc/sgi-xp/xpnet.c
index 557f978..0c26eaf 100644
--- a/drivers/misc/sgi-xp/xpnet.c
+++ b/drivers/misc/sgi-xp/xpnet.c
@@ -118,6 +118,8 @@ static DEFINE_SPINLOCK(xpnet_broadcast_lock);
  * now, the default is 64KB.
  */
 #define XPNET_MAX_MTU (0x800000UL - L1_CACHE_BYTES)
+/* 68 comes from min TCP+IP+MAC header */
+#define XPNET_MIN_MTU 68
 /* 32KB has been determined to be the ideal */
 #define XPNET_DEF_MTU (0x8000UL)
 
@@ -330,22 +332,6 @@ xpnet_dev_stop(struct net_device *dev)
 	return 0;
 }
 
-static int
-xpnet_dev_change_mtu(struct net_device *dev, int new_mtu)
-{
-	/* 68 comes from min TCP+IP+MAC header */
-	if ((new_mtu < 68) || (new_mtu > XPNET_MAX_MTU)) {
-		dev_err(xpnet, "ifconfig %s mtu %d failed; value must be "
-			"between 68 and %ld\n", dev->name, new_mtu,
-			XPNET_MAX_MTU);
-		return -EINVAL;
-	}
-
-	dev->mtu = new_mtu;
-	dev_dbg(xpnet, "ifconfig %s mtu set to %d\n", dev->name, new_mtu);
-	return 0;
-}
-
 /*
  * Notification that the other end has received the message and
  * DMA'd the skb information.  At this point, they are done with
@@ -519,7 +505,6 @@ static const struct net_device_ops xpnet_netdev_ops = {
 	.ndo_open		= xpnet_dev_open,
 	.ndo_stop		= xpnet_dev_stop,
 	.ndo_start_xmit		= xpnet_dev_hard_start_xmit,
-	.ndo_change_mtu		= xpnet_dev_change_mtu,
 	.ndo_tx_timeout		= xpnet_dev_tx_timeout,
 	.ndo_set_mac_address 	= eth_mac_addr,
 	.ndo_validate_addr	= eth_validate_addr,
@@ -555,6 +540,8 @@ xpnet_init(void)
 
 	xpnet_device->netdev_ops = &xpnet_netdev_ops;
 	xpnet_device->mtu = XPNET_DEF_MTU;
+	xpnet_device->min_mtu = XPNET_MIN_MTU;
+	xpnet_device->max_mtu = XPNET_MAX_MTU;
 
 	/*
 	 * Multicast assumes the LSB of the first octet is set for multicast
diff --git a/drivers/net/fddi/skfp/skfddi.c b/drivers/net/fddi/skfp/skfddi.c
index 51acc6d..3a63918 100644
--- a/drivers/net/fddi/skfp/skfddi.c
+++ b/drivers/net/fddi/skfp/skfddi.c
@@ -166,7 +166,6 @@ static const struct net_device_ops skfp_netdev_ops = {
 	.ndo_stop		= skfp_close,
 	.ndo_start_xmit		= skfp_send_pkt,
 	.ndo_get_stats		= skfp_ctl_get_stats,
-	.ndo_change_mtu		= fddi_change_mtu,
 	.ndo_set_rx_mode	= skfp_ctl_set_multicast_list,
 	.ndo_set_mac_address	= skfp_ctl_set_mac_address,
 	.ndo_do_ioctl		= skfp_ioctl,
diff --git a/drivers/net/fjes/fjes_main.c b/drivers/net/fjes/fjes_main.c
index f36eb4a..b77e4ecf 100644
--- a/drivers/net/fjes/fjes_main.c
+++ b/drivers/net/fjes/fjes_main.c
@@ -1316,6 +1316,8 @@ static void fjes_netdev_setup(struct net_device *netdev)
 	netdev->netdev_ops = &fjes_netdev_ops;
 	fjes_set_ethtool_ops(netdev);
 	netdev->mtu = fjes_support_mtu[3];
+	netdev->min_mtu = fjes_support_mtu[0];
+	netdev->max_mtu = fjes_support_mtu[3];
 	netdev->flags |= IFF_BROADCAST;
 	netdev->features |= NETIF_F_HW_CSUM | NETIF_F_HW_VLAN_CTAG_FILTER;
 }
diff --git a/drivers/net/hippi/rrunner.c b/drivers/net/hippi/rrunner.c
index 95c0b45..f5a9728 100644
--- a/drivers/net/hippi/rrunner.c
+++ b/drivers/net/hippi/rrunner.c
@@ -68,7 +68,6 @@ static const struct net_device_ops rr_netdev_ops = {
 	.ndo_stop		= rr_close,
 	.ndo_do_ioctl		= rr_ioctl,
 	.ndo_start_xmit		= rr_start_xmit,
-	.ndo_change_mtu		= hippi_change_mtu,
 	.ndo_set_mac_address	= hippi_mac_addr,
 };
 
diff --git a/drivers/net/rionet.c b/drivers/net/rionet.c
index a31f461..300bb14 100644
--- a/drivers/net/rionet.c
+++ b/drivers/net/rionet.c
@@ -466,17 +466,6 @@ static void rionet_set_msglevel(struct net_device *ndev, u32 value)
 	rnet->msg_enable = value;
 }
 
-static int rionet_change_mtu(struct net_device *ndev, int new_mtu)
-{
-	if ((new_mtu < 68) || (new_mtu > RIONET_MAX_MTU)) {
-		printk(KERN_ERR "%s: Invalid MTU size %d\n",
-		       ndev->name, new_mtu);
-		return -EINVAL;
-	}
-	ndev->mtu = new_mtu;
-	return 0;
-}
-
 static const struct ethtool_ops rionet_ethtool_ops = {
 	.get_drvinfo = rionet_get_drvinfo,
 	.get_msglevel = rionet_get_msglevel,
@@ -488,7 +477,6 @@ static const struct net_device_ops rionet_netdev_ops = {
 	.ndo_open		= rionet_open,
 	.ndo_stop		= rionet_close,
 	.ndo_start_xmit		= rionet_start_xmit,
-	.ndo_change_mtu		= rionet_change_mtu,
 	.ndo_validate_addr	= eth_validate_addr,
 	.ndo_set_mac_address	= eth_mac_addr,
 };
@@ -525,6 +513,9 @@ static int rionet_setup_netdev(struct rio_mport *mport, struct net_device *ndev)
 
 	ndev->netdev_ops = &rionet_netdev_ops;
 	ndev->mtu = RIONET_MAX_MTU;
+	/* MTU range: 68 - 4082 */
+	ndev->min_mtu = ETH_MIN_MTU;
+	ndev->max_mtu = RIONET_MAX_MTU;
 	ndev->features = NETIF_F_LLTX;
 	SET_NETDEV_DEV(ndev, &mport->dev);
 	ndev->ethtool_ops = &rionet_ethtool_ops;
diff --git a/drivers/net/slip/slip.c b/drivers/net/slip/slip.c
index 9ed6d1c..7e933d8 100644
--- a/drivers/net/slip/slip.c
+++ b/drivers/net/slip/slip.c
@@ -561,12 +561,7 @@ static int sl_change_mtu(struct net_device *dev, int new_mtu)
 {
 	struct slip *sl = netdev_priv(dev);
 
-	if (new_mtu < 68 || new_mtu > 65534)
-		return -EINVAL;
-
-	if (new_mtu != dev->mtu)
-		return sl_realloc_bufs(sl, new_mtu);
-	return 0;
+	return sl_realloc_bufs(sl, new_mtu);
 }
 
 /* Netdevice get statistics request */
@@ -663,6 +658,10 @@ static void sl_setup(struct net_device *dev)
 	dev->addr_len		= 0;
 	dev->tx_queue_len	= 10;
 
+	/* MTU range: 68 - 65534 */
+	dev->min_mtu = 68;
+	dev->max_mtu = 65534;
+
 	/* New-style flags. */
 	dev->flags		= IFF_NOARP|IFF_POINTOPOINT|IFF_MULTICAST;
 }
diff --git a/drivers/usb/gadget/function/f_phonet.c b/drivers/usb/gadget/function/f_phonet.c
index 0473d61..b4058f0 100644
--- a/drivers/usb/gadget/function/f_phonet.c
+++ b/drivers/usb/gadget/function/f_phonet.c
@@ -261,19 +261,10 @@ static int pn_net_xmit(struct sk_buff *skb, struct net_device *dev)
 	return NETDEV_TX_OK;
 }
 
-static int pn_net_mtu(struct net_device *dev, int new_mtu)
-{
-	if ((new_mtu < PHONET_MIN_MTU) || (new_mtu > PHONET_MAX_MTU))
-		return -EINVAL;
-	dev->mtu = new_mtu;
-	return 0;
-}
-
 static const struct net_device_ops pn_netdev_ops = {
 	.ndo_open	= pn_net_open,
 	.ndo_stop	= pn_net_close,
 	.ndo_start_xmit	= pn_net_xmit,
-	.ndo_change_mtu	= pn_net_mtu,
 };
 
 static void pn_net_setup(struct net_device *dev)
@@ -282,6 +273,8 @@ static void pn_net_setup(struct net_device *dev)
 	dev->type		= ARPHRD_PHONET;
 	dev->flags		= IFF_POINTOPOINT | IFF_NOARP;
 	dev->mtu		= PHONET_DEV_MTU;
+	dev->min_mtu		= PHONET_MIN_MTU;
+	dev->max_mtu		= PHONET_MAX_MTU;
 	dev->hard_header_len	= 1;
 	dev->dev_addr[0]	= PN_MEDIA_USB;
 	dev->addr_len		= 1;
diff --git a/drivers/usb/gadget/function/u_ether.c b/drivers/usb/gadget/function/u_ether.c
index 9c8c9ed..39a6df1 100644
--- a/drivers/usb/gadget/function/u_ether.c
+++ b/drivers/usb/gadget/function/u_ether.c
@@ -142,15 +142,6 @@ static inline int qlen(struct usb_gadget *gadget, unsigned qmult)
 
 /* NETWORK DRIVER HOOKUP (to the layer above this driver) */
 
-static int ueth_change_mtu(struct net_device *net, int new_mtu)
-{
-	if (new_mtu <= ETH_HLEN || new_mtu > GETHER_MAX_ETH_FRAME_LEN)
-		return -ERANGE;
-	net->mtu = new_mtu;
-
-	return 0;
-}
-
 static void eth_get_drvinfo(struct net_device *net, struct ethtool_drvinfo *p)
 {
 	struct eth_dev *dev = netdev_priv(net);
@@ -736,7 +727,6 @@ static const struct net_device_ops eth_netdev_ops = {
 	.ndo_open		= eth_open,
 	.ndo_stop		= eth_stop,
 	.ndo_start_xmit		= eth_start_xmit,
-	.ndo_change_mtu		= ueth_change_mtu,
 	.ndo_set_mac_address 	= eth_mac_addr,
 	.ndo_validate_addr	= eth_validate_addr,
 };
@@ -799,6 +789,10 @@ struct eth_dev *gether_setup_name(struct usb_gadget *g,
 
 	net->ethtool_ops = &ops;
 
+	/* MTU range: 14 - 15412 */
+	net->min_mtu = ETH_HLEN;
+	net->max_mtu = GETHER_MAX_ETH_FRAME_LEN;
+
 	dev->gadget = g;
 	SET_NETDEV_DEV(net, &g->dev);
 	SET_NETDEV_DEVTYPE(net, &gadget_type);
diff --git a/include/linux/fddidevice.h b/include/linux/fddidevice.h
index 9a79f01..32c22cf 100644
--- a/include/linux/fddidevice.h
+++ b/include/linux/fddidevice.h
@@ -26,7 +26,6 @@
 
 #ifdef __KERNEL__
 __be16 fddi_type_trans(struct sk_buff *skb, struct net_device *dev);
-int fddi_change_mtu(struct net_device *dev, int new_mtu);
 struct net_device *alloc_fddidev(int sizeof_priv);
 #endif
 
diff --git a/include/linux/hippidevice.h b/include/linux/hippidevice.h
index 8ec23fb..402f99e 100644
--- a/include/linux/hippidevice.h
+++ b/include/linux/hippidevice.h
@@ -32,7 +32,6 @@ struct hippi_cb {
 };
 
 __be16 hippi_type_trans(struct sk_buff *skb, struct net_device *dev);
-int hippi_change_mtu(struct net_device *dev, int new_mtu);
 int hippi_mac_addr(struct net_device *dev, void *p);
 int hippi_neigh_setup_dev(struct net_device *dev, struct neigh_parms *p);
 struct net_device *alloc_hippi_dev(int sizeof_priv);
diff --git a/net/802/fddi.c b/net/802/fddi.c
index 7d3a0af..6356623 100644
--- a/net/802/fddi.c
+++ b/net/802/fddi.c
@@ -141,15 +141,6 @@ __be16 fddi_type_trans(struct sk_buff *skb, struct net_device *dev)
 
 EXPORT_SYMBOL(fddi_type_trans);
 
-int fddi_change_mtu(struct net_device *dev, int new_mtu)
-{
-	if ((new_mtu < FDDI_K_SNAP_HLEN) || (new_mtu > FDDI_K_SNAP_DLEN))
-		return -EINVAL;
-	dev->mtu = new_mtu;
-	return 0;
-}
-EXPORT_SYMBOL(fddi_change_mtu);
-
 static const struct header_ops fddi_header_ops = {
 	.create		= fddi_header,
 };
@@ -161,6 +152,8 @@ static void fddi_setup(struct net_device *dev)
 	dev->type		= ARPHRD_FDDI;
 	dev->hard_header_len	= FDDI_K_SNAP_HLEN+3;	/* Assume 802.2 SNAP hdr len + 3 pad bytes */
 	dev->mtu		= FDDI_K_SNAP_DLEN;	/* Assume max payload of 802.2 SNAP frame */
+	dev->min_mtu		= FDDI_K_SNAP_HLEN;
+	dev->max_mtu		= FDDI_K_SNAP_DLEN;
 	dev->addr_len		= FDDI_K_ALEN;
 	dev->tx_queue_len	= 100;			/* Long queues on FDDI */
 	dev->flags		= IFF_BROADCAST | IFF_MULTICAST;
diff --git a/net/802/hippi.c b/net/802/hippi.c
index ade1a52..5e4427b 100644
--- a/net/802/hippi.c
+++ b/net/802/hippi.c
@@ -116,18 +116,6 @@ __be16 hippi_type_trans(struct sk_buff *skb, struct net_device *dev)
 
 EXPORT_SYMBOL(hippi_type_trans);
 
-int hippi_change_mtu(struct net_device *dev, int new_mtu)
-{
-	/*
-	 * HIPPI's got these nice large MTUs.
-	 */
-	if ((new_mtu < 68) || (new_mtu > 65280))
-		return -EINVAL;
-	dev->mtu = new_mtu;
-	return 0;
-}
-EXPORT_SYMBOL(hippi_change_mtu);
-
 /*
  * For HIPPI we will actually use the lower 4 bytes of the hardware
  * address as the I-FIELD rather than the actual hardware address.
@@ -174,6 +162,8 @@ static void hippi_setup(struct net_device *dev)
 	dev->type		= ARPHRD_HIPPI;
 	dev->hard_header_len 	= HIPPI_HLEN;
 	dev->mtu		= 65280;
+	dev->min_mtu		= 68;
+	dev->max_mtu		= 65280;
 	dev->addr_len		= HIPPI_ALEN;
 	dev->tx_queue_len	= 25 /* 5 */;
 	memset(dev->broadcast, 0xFF, HIPPI_ALEN);
diff --git a/net/batman-adv/soft-interface.c b/net/batman-adv/soft-interface.c
index 49e16b6..112679d 100644
--- a/net/batman-adv/soft-interface.c
+++ b/net/batman-adv/soft-interface.c
@@ -158,17 +158,6 @@ static int batadv_interface_set_mac_addr(struct net_device *dev, void *p)
 	return 0;
 }
 
-static int batadv_interface_change_mtu(struct net_device *dev, int new_mtu)
-{
-	/* check ranges */
-	if ((new_mtu < 68) || (new_mtu > batadv_hardif_min_mtu(dev)))
-		return -EINVAL;
-
-	dev->mtu = new_mtu;
-
-	return 0;
-}
-
 /**
  * batadv_interface_set_rx_mode - set the rx mode of a device
  * @dev: registered network device to modify
@@ -920,7 +909,6 @@ static const struct net_device_ops batadv_netdev_ops = {
 	.ndo_vlan_rx_add_vid = batadv_interface_add_vid,
 	.ndo_vlan_rx_kill_vid = batadv_interface_kill_vid,
 	.ndo_set_mac_address = batadv_interface_set_mac_addr,
-	.ndo_change_mtu = batadv_interface_change_mtu,
 	.ndo_set_rx_mode = batadv_interface_set_rx_mode,
 	.ndo_start_xmit = batadv_interface_tx,
 	.ndo_validate_addr = eth_validate_addr,
@@ -987,6 +975,7 @@ struct net_device *batadv_softif_create(struct net *net, const char *name)
 	dev_net_set(soft_iface, net);
 
 	soft_iface->rtnl_link_ops = &batadv_link_ops;
+	soft_iface->max_mtu = batadv_hardif_min_mtu(soft_iface);
 
 	ret = register_netdevice(soft_iface);
 	if (ret < 0) {
diff --git a/net/hsr/hsr_device.c b/net/hsr/hsr_device.c
index 16737cd..fc65b14 100644
--- a/net/hsr/hsr_device.c
+++ b/net/hsr/hsr_device.c
@@ -398,6 +398,7 @@ void hsr_dev_setup(struct net_device *dev)
 	random_ether_addr(dev->dev_addr);
 
 	ether_setup(dev);
+	dev->min_mtu = 0;
 	dev->header_ops = &hsr_header_ops;
 	dev->netdev_ops = &hsr_device_ops;
 	SET_NETDEV_DEVTYPE(dev, &hsr_type);
diff --git a/net/phonet/pep-gprs.c b/net/phonet/pep-gprs.c
index fa8237f..21c28b5 100644
--- a/net/phonet/pep-gprs.c
+++ b/net/phonet/pep-gprs.c
@@ -217,20 +217,10 @@ static netdev_tx_t gprs_xmit(struct sk_buff *skb, struct net_device *dev)
 	return NETDEV_TX_OK;
 }
 
-static int gprs_set_mtu(struct net_device *dev, int new_mtu)
-{
-	if ((new_mtu < 576) || (new_mtu > (PHONET_MAX_MTU - 11)))
-		return -EINVAL;
-
-	dev->mtu = new_mtu;
-	return 0;
-}
-
 static const struct net_device_ops gprs_netdev_ops = {
 	.ndo_open	= gprs_open,
 	.ndo_stop	= gprs_close,
 	.ndo_start_xmit	= gprs_xmit,
-	.ndo_change_mtu	= gprs_set_mtu,
 };
 
 static void gprs_setup(struct net_device *dev)
@@ -239,6 +229,8 @@ static void gprs_setup(struct net_device *dev)
 	dev->type		= ARPHRD_PHONET_PIPE;
 	dev->flags		= IFF_POINTOPOINT | IFF_NOARP;
 	dev->mtu		= GPRS_DEFAULT_MTU;
+	dev->min_mtu		= 576;
+	dev->max_mtu		= (PHONET_MAX_MTU - 11);
 	dev->hard_header_len	= 0;
 	dev->addr_len		= 0;
 	dev->tx_queue_len	= 10;
-- 
2.10.0

Re: [PATCH net-next v2 7/9] net: use core MTU range checking in misc drivers

[Rémi Denis-Courmont]

Acked-by: Rémi Denis-Courmont <courmisch@gmail.com>

-- 
Rémi Denis-Courmont
http://www.remlab.net/CV.pdf

Re: [PATCH net-next v2 7/9] net: use core MTU range checking in misc drivers

[Sebastian Reichel]

[-- Attachment #1: Type: text/plain, Size: 228 bytes --]

Hi,

On Thu, Oct 20, 2016 at 01:55:22PM -0400, Jarod Wilson wrote:
> hsi/clients/ssi_protocol:
> - use core MTU range checking
> - remove now redundant ssip_pn_set_mtu

Acked-By: Sebastian Reichel <sre@kernel.org>

-- Sebastian

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Re: [net-next,v2,7/9] net: use core MTU range checking in misc drivers

[Sven Eckelmann]

[-- Attachment #1: Type: text/plain, Size: 2230 bytes --]

On Donnerstag, 20. Oktober 2016 13:55:22 CEST Jarod Wilson wrote:
[...]
> batman-adv:
> - set max_mtu
> - remove batadv_interface_change_mtu
> - initialization is a little async, not 100% certain that max_mtu is set
>   in the optimal place, don't have hardware to test with

batman-adv is creating a virtual interface - so there are no
hardware requirements (ok, ethernet compatible hardware - even
when only virtual/emulated).

[...]
> diff --git a/net/batman-adv/soft-interface.c b/net/batman-adv/soft-interface.c
> index 49e16b6..112679d 100644
> --- a/net/batman-adv/soft-interface.c
> +++ b/net/batman-adv/soft-interface.c
> @@ -158,17 +158,6 @@ static int batadv_interface_set_mac_addr(struct net_device *dev, void *p)
>  	return 0;
>  }
>  
> -static int batadv_interface_change_mtu(struct net_device *dev, int new_mtu)
> -{
> -	/* check ranges */
> -	if ((new_mtu < 68) || (new_mtu > batadv_hardif_min_mtu(dev)))
> -		return -EINVAL;
> -
> -	dev->mtu = new_mtu;
> -
> -	return 0;
> -}
> -
>  /**
>   * batadv_interface_set_rx_mode - set the rx mode of a device
>   * @dev: registered network device to modify
> @@ -920,7 +909,6 @@ static const struct net_device_ops batadv_netdev_ops = {
>  	.ndo_vlan_rx_add_vid = batadv_interface_add_vid,
>  	.ndo_vlan_rx_kill_vid = batadv_interface_kill_vid,
>  	.ndo_set_mac_address = batadv_interface_set_mac_addr,
> -	.ndo_change_mtu = batadv_interface_change_mtu,
>  	.ndo_set_rx_mode = batadv_interface_set_rx_mode,
>  	.ndo_start_xmit = batadv_interface_tx,
>  	.ndo_validate_addr = eth_validate_addr,
> @@ -987,6 +975,7 @@ struct net_device *batadv_softif_create(struct net *net, const char *name)
>  	dev_net_set(soft_iface, net);
>  
>  	soft_iface->rtnl_link_ops = &batadv_link_ops;
> +	soft_iface->max_mtu = batadv_hardif_min_mtu(soft_iface);
>  
>  	ret = register_netdevice(soft_iface);
>  	if (ret < 0) {

This looks bogus to me. You are now setting max_mtu during initialization of
the virtual interface. But at this time no slave interfaces were added to the
master batman-adv interface. So the batadv_hardif_min_mtu will not return the
correct value here. Especially if you don't have fragmentation enabled.

So this change looks like a bug to me

Kind regards,
	Sven

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Re: [PATCH net-next v2 7/9] net: use core MTU range checking in misc drivers

[Stefan Richter]

On Oct 20 Jarod Wilson wrote:
> firewire-net:
> - set min/max_mtu
> - remove fwnet_change_mtu
[...]
> --- a/drivers/firewire/net.c
> +++ b/drivers/firewire/net.c
[...]
> @@ -1478,9 +1467,10 @@ static int fwnet_probe(struct fw_unit *unit,
>  	 * Use the RFC 2734 default 1500 octets or the maximum payload
>  	 * as initial MTU
>  	 */
> -	max_mtu = (1 << (card->max_receive + 1))
> -		  - sizeof(struct rfc2734_header) - IEEE1394_GASP_HDR_SIZE;
> -	net->mtu = min(1500U, max_mtu);
> +	net->max_mtu = (1 << (card->max_receive + 1))
> +		       - sizeof(struct rfc2734_header) - IEEE1394_GASP_HDR_SIZE;
> +	net->mtu = min(1500U, net->max_mtu);
> +	net->min_mtu = ETH_MIN_MTU;
>  
>  	/* Set our hardware address while we're at it */
>  	ha = (union fwnet_hwaddr *)net->dev_addr;

Please preserve the current behavior, i.e. do not enforce any particular
upper bound.  (Especially none based on the local link layer controller's
max_receive parameter.)

BTW, after having read RFC 2734, RFC 3146, and the code, I am convinced
that net->mtu should be initialized to 1500, not less.  But such a change
should be done in a separate patch.
-- 
Stefan Richter
-======----- =-=- =-==-
http://arcgraph.de/sr/