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Date: Wed, 20 Jan 2016 14:32:05 +0800 From: zhuyj <zyjzyj2000@...il.com> To: Wengang Wang <wen.gang.wang@...cle.com>, netdev@...r.kernel.org Cc: jay.vosburgh@...onical.com Subject: Re: [PATCH] net: take care of bonding in build_skb_flow_key (v3) On 01/20/2016 02:29 PM, zhuyj wrote: > 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 <wen.gang.wang@...cle.com> >>> --- >>> 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_master_upper_dev_get_rcu is better? I am > not sure. Maybe this function netdev_master_upper_dev_get_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); >>> } >> >
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