From mboxrd@z Thu Jan 1 00:00:00 1970 From: zhuyj Subject: Re: [PATCH] net: take care of bonding in build_skb_flow_key (v3) Date: Wed, 20 Jan 2016 17:56:40 +0800 Message-ID: <569F59D8.2060200@gmail.com> References: <1453267933-25381-1-git-send-email-wen.gang.wang@oracle.com> <569F2806.70608@gmail.com> <569F397B.7010808@oracle.com> <569F3D19.8020307@gmail.com> <569F579F.1060708@oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: jay.vosburgh@canonical.com To: Wengang Wang , netdev@vger.kernel.org Return-path: Received: from mail-pa0-f45.google.com ([209.85.220.45]:33551 "EHLO mail-pa0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751218AbcATJ4M (ORCPT ); Wed, 20 Jan 2016 04:56:12 -0500 Received: by mail-pa0-f45.google.com with SMTP id cy9so2331595pac.0 for ; Wed, 20 Jan 2016 01:56:12 -0800 (PST) In-Reply-To: <569F579F.1060708@oracle.com> Sender: netdev-owner@vger.kernel.org List-ID: On 01/20/2016 05:47 PM, Wengang Wang wrote: > > > =E5=9C=A8 2016=E5=B9=B401=E6=9C=8820=E6=97=A5 15:54, zhuyj =E5=86=99=E9= =81=93: >> On 01/20/2016 03:38 PM, Wengang Wang wrote: >>> >>> >>> =E5=9C=A8 2016=E5=B9=B401=E6=9C=8820=E6=97=A5 14:24, zhuyj =E5=86=99= =E9=81=93: >>>> On 01/20/2016 01:32 PM, Wengang Wang wrote: >>>>> In a bonding setting, we determines fragment size according to MT= U=20 >>>>> and >>>>> PMTU associated to the bonding master. If the slave finds the=20 >>>>> fragment >>>>> size is too big, it drops the fragment and calls ip_rt_update_pmt= u(), >>>>> passing _skb_ and _pmtu_, trying to update the path MTU. >>>>> Problem is that the target device that function ip_rt_update_pmtu= =20 >>>>> actually >>>>> tries to update is the slave (skb->dev), not the master. Thus=20 >>>>> since no >>>>> PMTU change happens on master, the fragment size for later packet= s=20 >>>>> doesn't >>>>> change so all later fragments/packets are dropped too. >>>>> >>>>> The fix is letting build_skb_flow_key() take care of the=20 >>>>> transition of >>>>> device index from bonding slave to the master. That makes the=20 >>>>> master become >>>>> the target device that ip_rt_update_pmtu tries to update PMTU to. >>>>> >>>>> Signed-off-by: Wengang Wang >>>>> --- >>>>> net/ipv4/route.c | 13 ++++++++++++- >>>>> 1 file changed, 12 insertions(+), 1 deletion(-) >>>>> >>>>> diff --git a/net/ipv4/route.c b/net/ipv4/route.c >>>>> index 85f184e..c59fb0d 100644 >>>>> --- a/net/ipv4/route.c >>>>> +++ b/net/ipv4/route.c >>>>> @@ -523,10 +523,21 @@ static void build_skb_flow_key(struct flowi= 4=20 >>>>> *fl4, const struct sk_buff *skb, >>>>> const struct sock *sk) >>>>> { >>>>> const struct iphdr *iph =3D ip_hdr(skb); >>>>> - int oif =3D skb->dev->ifindex; >>>>> + struct net_device *master =3D NULL; >>>>> u8 tos =3D RT_TOS(iph->tos); >>>>> u8 prot =3D iph->protocol; >>>>> u32 mark =3D skb->mark; >>>>> + int oif; >>>>> + >>>>> + if (skb->dev->flags & IFF_SLAVE) { >>>>> + rtnl_lock(); >>>>> + master =3D netdev_master_upper_dev_get(skb->dev); >>>>> + rtnl_unlock(); >>>> update_pmtu is called very frequently. Is it appropriate to use=20 >>>> rtnl_lock here? >>> By "very frequently", how frequently it is expected? And what=20 >>> situation can cause that? >>> For my case, the update_pmtu is called only once. >> ip_tunnel_xmit >> > Can you please explain with more details? dev_queue_xmit->ipip_tunnel_xmit->ip_tunnel_xmit->tnl_update_pmtu->=20 skb_dst(skb)->ops->update_pmtu > > thanks, > wengang > > >> Zhu Yanjun >> >>> >>> thanks, >>> wengang >>> >>>> That is, rtnl_lock is called frequently. Maybe other functions hav= e=20 >>>> little chance to call rtnl_lock. >>>> >>>> Best Regards! >>>> Zhu Yanjun >>>>> + } >>>>> + if (master) >>>>> + oif =3D master->ifindex; >>>>> + else >>>>> + oif =3D skb->dev->ifindex; >>>>> __build_flow_key(fl4, sk, iph, oif, tos, prot, mark, 0); >>>>> } >>>> >>> >> >