linux-kernel - Re: [PATCH] geneve: fix max

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Date:	Mon, 27 Jun 2016 09:10:56 -0700
From:	Jesse Gross <jesse@...nel.org>
To:	严海双 <yanhaishuang@...s.chinamobile.com>
Cc:	zhuyj <zyjzyj2000@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Pravin B Shelar <pshelar@...ira.com>,
	Tom Herbert <tom@...bertland.com>,
	netdev <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] geneve: fix max_mtu setting

On Sun, Jun 26, 2016 at 6:13 PM, 严海双 <yanhaishuang@...s.chinamobile.com> wrote:
>
>> On Jun 26, 2016, at 8:35 PM, zhuyj <zyjzyj2000@...il.com> wrote:
>>
>> +       if (geneve->remote.sa.sa_family == AF_INET)
>> +               max_mtu -= sizeof(struct iphdr);
>> +       else
>> +               max_mtu -= sizeof(struct ipv6hdr);
>>
>> Sorry, if sa_family is not AF_NET, it is AF_INET6?
>>
>> There is a lot of macros in include/linux/socket.h.
>>
>> Zhu Yanjun
>>
>
> There are only two enumerations AF_INET and AF_INET6 have been assigned in geneve_newlink:

There's actually a third possibility: AF_UNSPEC, which is the default
if neither remote type is specified. This is used by lightweight
tunnels and should be able to work with either IPv4/v6. For the
purposes of the MTU calculation this means that the IPv4 header size
should be used to avoid disallowing potentially valid configurations.