From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wengang Wang Subject: Re: [PATCH] net: take care of bonding in build_skb_flow_key (v3) Date: Wed, 20 Jan 2016 17:47:11 +0800 Message-ID: <569F579F.1060708@oracle.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> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: jay.vosburgh@canonical.com To: zhuyj , netdev@vger.kernel.org Return-path: Received: from userp1040.oracle.com ([156.151.31.81]:17181 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758387AbcATJnx (ORCPT ); Wed, 20 Jan 2016 04:43:53 -0500 In-Reply-To: <569F3D19.8020307@gmail.com> Sender: netdev-owner@vger.kernel.org List-ID: =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 MTU= and >>>> PMTU associated to the bonding master. If the slave finds the frag= ment >>>> size is too big, it drops the fragment and calls ip_rt_update_pmtu= (), >>>> 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 sinc= e no >>>> PMTU change happens on master, the fragment size for later packets= =20 >>>> doesn't >>>> change so all later fragments/packets are dropped too. >>>> >>>> The fix is letting build_skb_flow_key() take care of the transitio= n 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 flowi4= =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? thanks, wengang > Zhu Yanjun > >> >> thanks, >> wengang >> >>> That is, rtnl_lock is called frequently. Maybe other functions have= =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); >>>> } >>> >> >