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Date:      Thu, 8 Nov 2012 15:32:59 -0800
From:      Adrian Chadd <adrian@freebsd.org>
To:        Andre Oppermann <andre@freebsd.org>
Cc:        pyunyh@gmail.com, FreeBSD Net <freebsd-net@freebsd.org>, Pyun YongHyeon <yongari@freebsd.org>
Subject:   Re: svn commit: r242739 - stable/9/sys/dev/ti
Message-ID:  <CAJ-Vmo=QuP1s=ppnp2u%2BVpuJRbncaHLwi_0ku5=dr9%2BReYp79w@mail.gmail.com>
In-Reply-To: <509BC2E2.4030907@freebsd.org>
References:  <201211080206.qA826RiN054539@svn.freebsd.org> <CAJ-VmomEOPGbLwmOmL0EdenZA7QKbV5P-hAYsTRcwLao2LbAqg@mail.gmail.com> <20121108023858.GA3127@michelle.cdnetworks.com> <CAJ-Vmoma1DJRT8_ezdEpVYrZXak%2B2B4mBHAPxhoUKr0nUrO6YQ@mail.gmail.com> <509BC2E2.4030907@freebsd.org>

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On 8 November 2012 06:34, Andre Oppermann <andre@freebsd.org> wrote:

> TCP/UDP doesn't (want to) generate any fragments at all and tries
> to avoid it at almost all cost.  We want to send very large packets
> and have the NIC fragment/segment it (TSO/UDP frag offload).

What about if it's a router and the frames don't have DF set?

Not that it should happen often, however..

>
>> We could create a device or interface flag that indicates whether the
>> driver can handle multiple mbufs chained via m_nextpkt through
>> if_transmit(), and then teach one or two drivers that particular
>> logic.
>
>
> Agreed.  I think that's the way to go.  It must be very well specified
> in semantics though.  Otherwise it's just too easy to leak mbuf all
> over the place.

I mentioned this to Robert Watson today at the FreeBSD vendor summit
and he said much the same thing about testing and assertions.



Adrian


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