netdev - Re: [PATCH net] vxlan: fix missing options_len update on RX with collect metadata

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Date:	Thu, 03 Mar 2016 09:58:00 +0100
From:	Daniel Borkmann <daniel@...earbox.net>
To:	Cong Wang <xiyou.wangcong@...il.com>
CC:	David Miller <davem@...emloft.net>, Thomas Graf <tgraf@...g.ch>,
	Pravin B Shelar <pshelar@...ira.com>, jesse@...nel.org,
	Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [PATCH net] vxlan: fix missing options_len update on RX with
 collect metadata

On 03/03/2016 02:21 AM, Cong Wang wrote:
> On Tue, Mar 1, 2016 at 5:32 PM, Daniel Borkmann <daniel@...earbox.net> wrote:
>> When signalling to metadata consumers that the metadata_dst entry
>> carries additional GBP extension data for vxlan (TUNNEL_VXLAN_OPT),
>> the dst's vxlan_metadata information is populated, but options_len
>> is left to zero. F.e. in ovs, ovs_flow_key_extract() checks for
>> options_len before extracting the data through ip_tunnel_info_opts_get().
>>
>> Geneve uses ip_tunnel_info_opts_set() helper in receive path, which
>> sets options_len internally, vxlan however uses ip_tunnel_info_opts(),
>> so when filling vxlan_metadata, we do need to update options_len.
>>
>> Fixes: 4c22279848c5 ("ip-tunnel: Use API to access tunnel metadata options.")
>> Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
>> ---
>>   drivers/net/vxlan.c | 4 +++-
>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/vxlan.c b/drivers/net/vxlan.c
>> index b601139..1c32bd1 100644
>> --- a/drivers/net/vxlan.c
>> +++ b/drivers/net/vxlan.c
>> @@ -1308,8 +1308,10 @@ static int vxlan_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
>>                  gbp = (struct vxlanhdr_gbp *)vxh;
>>                  md->gbp = ntohs(gbp->policy_id);
>>
>> -               if (tun_dst)
>> +               if (tun_dst) {
>>                          tun_dst->u.tun_info.key.tun_flags |= TUNNEL_VXLAN_OPT;
>> +                       tun_dst->u.tun_info.options_len = sizeof(*md);
>> +               }
>>
>
> Why not set it in tun_rx_dst() where it is allocated?

Nope, current convention is to only fill options_len when an actual
option was detected on RX, f.e. see ip_tunnel_info_opts_set() in
geneve. Consumers like ovs_flow_key_extract() check for options_len
and not TUNNEL_OPTIONS_PRESENT to copy it via ip_tunnel_info_opts_get()
from there.