From: Florian Westphal <fw@strlen.de>
To: Du Fan <fengyuleidian0615@gmail.com>
Cc: Florian Westphal <fw@strlen.de>, Thomas Graf <tgraf@suug.ch>,
"Michael S. Tsirkin" <mst@redhat.com>,
Jesse Gross <jesse@nicira.com>, Flavio Leitner <fbl@redhat.com>,
"davem@davemloft.net" <davem@davemloft.net>,
pshelar@nicira.com, netdev <netdev@vger.kernel.org>,
"dev@openvswitch.org" <dev@openvswitch.org>,
"Du, Fan" <fan.du@intel.com>
Subject: Re: [Discussion] About over-MTU-sized skb in virtualized env
Date: Wed, 3 Dec 2014 11:50:46 +0100 [thread overview]
Message-ID: <20141203105046.GE16959@breakpoint.cc> (raw)
In-Reply-To: <547EB029.5010102@gmail.com>
Du Fan <fengyuleidian0615@gmail.com> wrote:
> Sorry for resend this mail, because my company email is rejected by netdev.
>
>
> Hi Florian
>
> 214 static int ip_finish_output_gso(struct sk_buff *skb)
> 215 {
> 216 netdev_features_t features;
> 217 struct sk_buff *segs;
> 218 int ret = 0;
> 219
> 220 /* common case: locally created skb or seglen is <= mtu */
> 221 if (((IPCB(skb)->flags & IPSKB_FORWARDED) == 0) ||
> 222 skb_gso_network_seglen(skb) <= ip_skb_dst_mtu(skb))
> 223 return ip_finish_output2(skb);
>
> Could you please state _concrete_ reason why locally created skb
> length is ＿always＿ fitting into MTU size? or why we needs this
> checking.
We don't "need" this checking. Its just to avoid skb_gso_network_seglen()
computation for the common (local-out) case.
Locally generated GSO packet is not supposed to exceed dst_mtu, as that
is the PMTU discovery start point in absence of lower/learned value.
next prev parent reply other threads:[~2014-12-03 10:51 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-12-03 6:39 [Discussion] About over-MTU-sized skb in virtualized env Du Fan
2014-12-03 10:50 ` Florian Westphal [this message]
-- strict thread matches above, loose matches on Subject: below --
2014-12-03 5:40 Du, Fan
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