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 14:29:40 +0800 Message-ID: <569F2954.9080103@gmail.com> References: <1453267933-25381-1-git-send-email-wen.gang.wang@oracle.com> <569F2806.70608@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Cc: jay.vosburgh@canonical.com To: Wengang Wang , netdev@vger.kernel.org Return-path: Received: from mail-pa0-f52.google.com ([209.85.220.52]:36775 "EHLO mail-pa0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750840AbcATG3N (ORCPT ); Wed, 20 Jan 2016 01:29:13 -0500 Received: by mail-pa0-f52.google.com with SMTP id yy13so372092416pab.3 for ; Tue, 19 Jan 2016 22:29:13 -0800 (PST) In-Reply-To: <569F2806.70608@gmail.com> Sender: netdev-owner@vger.kernel.org List-ID: On 01/20/2016 02:24 PM, zhuyj wrote: > 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 fragment >> 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 >> actually >> tries to update is the slave (skb->dev), not the master. Thus since no >> PMTU change happens on master, the fragment size for later packets >> doesn't >> change so all later fragments/packets are dropped too. >> >> The fix is letting build_skb_flow_key() take care of the transition of >> device index from bonding slave to the master. That makes the 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 >> *fl4, const struct sk_buff *skb, >> const struct sock *sk) >> { >> const struct iphdr *iph = ip_hdr(skb); >> - int oif = skb->dev->ifindex; >> + struct net_device *master = NULL; >> u8 tos = RT_TOS(iph->tos); >> u8 prot = iph->protocol; >> u32 mark = skb->mark; >> + int oif; >> + >> + if (skb->dev->flags & IFF_SLAVE) { >> + rtnl_lock(); >> + master = netdev_master_upper_dev_get(skb->dev); >> + rtnl_unlock(); > update_pmtu is called very frequently. Is it appropriate to use > rtnl_lock here? > That is, rtnl_lock is called frequently. Maybe other functions have > little chance to call rtnl_lock. Maybe this function netdev_upper_get_next_dev_rcu is better? I am not sure. > > Best Regards! > Zhu Yanjun >> + } >> + if (master) >> + oif = master->ifindex; >> + else >> + oif = skb->dev->ifindex; >> __build_flow_key(fl4, sk, iph, oif, tos, prot, mark, 0); >> } >