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Re: [EXPERIMENTAL PATCH] 2.4 tulip jumbo frames

To: Rask Ingemann Lambertsen <rask@xxxxxxxxxx>
Subject: Re: [EXPERIMENTAL PATCH] 2.4 tulip jumbo frames
From: Ben Greear <greearb@xxxxxxxxxxxxxxx>
Date: Tue, 09 Dec 2003 09:28:23 -0800
Cc: netdev@xxxxxxxxxxx, jgarzik@xxxxxxxxx
In-reply-to: <20031209160632.D1345@xxxxxxxxxx>
Organization: Candela Technologies
References: <20031209160632.D1345@xxxxxxxxxx>
Sender: netdev-bounce@xxxxxxxxxxx
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.5) Gecko/20031007
Rask Ingemann Lambertsen wrote:
Attached is a patch which enables jumbo frames on tulip based boards. It makes it possible to set an MTU of up to 2025 bytes. However, testing
against an NE3200 board using 10base-2 shows assorted problems when going
above 2018 bytes (for frames without VLAN tags). The problems show up as
framing errors, bad CRCs and such (in both directions).

The patch is against 2.4.22-bk45.

+static int tulip_change_mtu (struct net_device *dev, int mtu)
+       if (netif_running (dev))
+               return (-EBUSY);
+       if (mtu < 0 || mtu > PKT_BUF_SZ_MAX - VLAN_ETH_HLEN - 4)
+               return (-EINVAL);

I suppose you could let them ignore the VLAN_ETH_HLEN if you
really wanted to (in case they are not running VLANs).

But, this should work fine too.


+       dev->mtu = mtu;
+       return (0);

Ben Greear <greearb@xxxxxxxxxxxxxxx>
Candela Technologies Inc

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