2007-09-11 14:42:58

by Ed Swierk

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Subject: [PATCH] Configurable tap interface MTU

This patch makes it possible to change the MTU on a tap interface.
Increasing the MTU beyond the 1500-byte default is useful for
applications that interoperate with Ethernet devices supporting jumbo
frames.

The patch caps the MTU somewhat arbitrarily at 16000 bytes. This is
slightly lower than the value used by the e1000 driver, so it seems
like a safe upper limit.

Signed-off-by: Ed Swierk <[email protected]>

---

Attachments:
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 tap-change-mtu.patch (931.00 B)
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2007-09-11 17:21:31

by Rick Jones

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Subject: Re: [PATCH] Configurable tap interface MTU

Ed Swierk wrote:
> This patch makes it possible to change the MTU on a tap interface.
> Increasing the MTU beyond the 1500-byte default is useful for
> applications that interoperate with Ethernet devices supporting jumbo
> frames.
>
> The patch caps the MTU somewhat arbitrarily at 16000 bytes. This is
> slightly lower than the value used by the e1000 driver, so it seems
> like a safe upper limit.

FWIW the OFED 1.2 bits take the MTU of IPoIB up to 65520 bytes :)

rick jones

2007-09-12 03:30:15

by Herbert Xu

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Subject: Re: [PATCH] Configurable tap interface MTU

Ed Swierk <[email protected]> wrote:
>
> The patch caps the MTU somewhat arbitrarily at 16000 bytes. This is
> slightly lower than the value used by the e1000 driver, so it seems
> like a safe upper limit.

Please make it 65535 without an Ethernet header and 65521
with an Ethernet header.

Cheers,
--
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <[email protected]>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt

2007-09-12 16:54:48

by Ed Swierk

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Subject: Re: [PATCH] Configurable tap interface MTU

On 9/11/07, Herbert Xu <[email protected]> wrote:
> Please make it 65535 without an Ethernet header and 65521
> with an Ethernet header.

Here is a revised patch that allows MTUs up to 65535 for tap
interfaces and up to 65521 for tun interfaces.

(If I set the MTU to 65521 on a tun interface, ping complains "message
too long" when I send a 65521-byte packet; 65520 works okay, though.)

--Ed

Attachments:
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 tap-change-mtu.patch (1.16 kB)
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2007-09-16 19:22:58

by David Miller

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Subject: Re: [PATCH] Configurable tap interface MTU

From: "Ed Swierk" <[email protected]>
Date: Wed, 12 Sep 2007 09:54:35 -0700

> On 9/11/07, Herbert Xu <[email protected]> wrote:
> > Please make it 65535 without an Ethernet header and 65521
> > with an Ethernet header.
>
> Here is a revised patch that allows MTUs up to 65535 for tap
> interfaces and up to 65521 for tun interfaces.
>
> (If I set the MTU to 65521 on a tun interface, ping complains "message
> too long" when I send a 65521-byte packet; 65520 works okay, though.)

Applied to net-2.6.24

Please provide a proper Signed-off-by: line and a full
changelog with every patch submission and revision in
the future.

Thanks.