netdev - Re: Fw: [Bug 209427] New: Incorrect timestamp cause packet to be dropped

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Message-ID: <alpine.LFD.2.23.451.2009302010190.4321@ja.home.ssi.bg>
Date:   Wed, 30 Sep 2020 20:17:02 +0300 (EEST)
From:   Julian Anastasov <ja@....bg>
To:     Eric Dumazet <eric.dumazet@...il.com>
cc:     Stephen Hemminger <stephen@...workplumber.org>,
        netdev@...r.kernel.org,
        "lvs-devel@...r.kernel.org" <lvs-devel@...r.kernel.org>,
        abt-admin@...l.ru
Subject: Re: Fw: [Bug 209427] New: Incorrect timestamp cause packet to be
 dropped


	Hello,

On Wed, 30 Sep 2020, Eric Dumazet wrote:

> On 9/29/20 7:35 PM, Stephen Hemminger wrote:
> > 
> > 
> > then I noticed that in some cases skb->tstamp is equal to real ts whereas in
> > the regular cases where a packet pass through it's time since kernel boot. This
> > doesn't make any sense for me as this condition is satisfied constantly
> > 
> > net/sched/sch_fq.c:439
> > static bool fq_packet_beyond_horizon(const struct sk_buff *skb,
> >                                     const struct fq_sched_data *q)
> > {
> >         return unlikely((s64)skb->tstamp > (s64)(q->ktime_cache + q->horizon));
> > }
> > 
> > Any ideas on what it can be?
> > 
> Thanks for the detailed report !
> 
> I suspect ipvs or bridge code needs something similar to the fixes done in 
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=de20900fbe1c4fd36de25a7a5a43223254ecf0d0
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=41d1c8839e5f8cb781cc635f12791decee8271b7
> 
> The reason for that is that skb->tstamp can get a timestamp in input path,
> with a base which is not CLOCK_MONOTONIC, unfortunately.
> 
> Whenever a packet is forwarded, its tstamp must be cleared.
> 
> Can you try :
> 
> diff --git a/net/netfilter/ipvs/ip_vs_xmit.c b/net/netfilter/ipvs/ip_vs_xmit.c
> index b00866d777fe0e9ed8018087ebc664c56f29b5c9..11e8ccdae358a89067046efa62ed40308b9e06f9 100644
> --- a/net/netfilter/ipvs/ip_vs_xmit.c
> +++ b/net/netfilter/ipvs/ip_vs_xmit.c
> @@ -952,6 +952,8 @@ ip_vs_prepare_tunneled_skb(struct sk_buff *skb, int skb_af,
>  
>         ip_vs_drop_early_demux_sk(skb);
>  
> +       skb->tstamp = 0;
> +

	Should be after all skb_forward_csum() calls in ip_vs_xmit.c

>         if (skb_headroom(skb) < max_headroom || skb_cloned(skb)) {
>                 new_skb = skb_realloc_headroom(skb, max_headroom);
>                 if (!new_skb)

Regards

--
Julian Anastasov <ja@....bg>