From: Nicolas Dichtel <nicolas.dichtel@6wind•com>
To: Eric Dumazet <eric.dumazet@gmail•com>
Cc: netdev@vger•kernel.org, davem@davemloft•net
Subject: Re: [PATCH] inetpeer: ensure to set the maximum tokens the first time
Date: Thu, 27 Sep 2012 15:21:55 +0200 [thread overview]
Message-ID: <506452F3.4090409@6wind.com> (raw)
In-Reply-To: <1348750405.5093.1234.camel@edumazet-glaptop>
Le 27/09/2012 14:53, Eric Dumazet a écrit :
> On Thu, 2012-09-27 at 14:33 +0200, Nicolas Dichtel wrote:
>> When jiffies wraps around (for example, 5 minutes after the boot, see
>> INITIAL_JIFFIES) and peer has just been created, now - peer->rate_last can be
>> < XRLIM_BURST_FACTOR * timeout, so token is not set to the maximum value, thus
>> some icmp packets can be unexpectedly dropped.
>>
>> With this patch, it's still possible that last_rate and rate_tokens are 0 at the
>> same time after jiffies wraps round, but the probability is very low and the
>> only consequence is to let some ICMP packets bypass the filter.
>>
>> Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind•com>
>> ---
>> net/ipv4/inetpeer.c | 10 +++++++---
>> 1 file changed, 7 insertions(+), 3 deletions(-)
>>
>> diff --git a/net/ipv4/inetpeer.c b/net/ipv4/inetpeer.c
>> index e1e0a4e..92fec02 100644
>> --- a/net/ipv4/inetpeer.c
>> +++ b/net/ipv4/inetpeer.c
>> @@ -559,10 +559,14 @@ bool inet_peer_xrlim_allow(struct inet_peer *peer, int timeout)
>>
>> token = peer->rate_tokens;
>> now = jiffies;
>> - token += now - peer->rate_last;
>> - peer->rate_last = now;
>> - if (token > XRLIM_BURST_FACTOR * timeout)
>> + if (!peer->rate_last && !token)
>> token = XRLIM_BURST_FACTOR * timeout;
>> + else {
>> + token += now - peer->rate_last;
>> + if (token > XRLIM_BURST_FACTOR * timeout)
>> + token = XRLIM_BURST_FACTOR * timeout;
>> + }
>> + peer->rate_last = now;
>> if (token >= timeout) {
>> token -= timeout;
>> rc = true;
>
>
> I am sorry I dont understand your patch at all.
>
> Why not init rate_last to a more sensible value ?
>
> diff --git a/net/ipv4/inetpeer.c b/net/ipv4/inetpeer.c
> index e1e0a4e..25ed555 100644
> --- a/net/ipv4/inetpeer.c
> +++ b/net/ipv4/inetpeer.c
> @@ -510,7 +510,7 @@ relookup:
> secure_ipv6_id(daddr->addr.a6));
> p->metrics[RTAX_LOCK-1] = INETPEER_METRICS_NEW;
> p->rate_tokens = 0;
> - p->rate_last = 0;
> + p->rate_last = jiffies;
inet_getpeer(...,1) is called just before inet_peer_xrlim_allow().
So the result in inet_peer_xrlim_allow():
token = peer->rate_tokens; => 0
now = jiffies;
token += now - peer->rate_last; => token += jiffies - jiffies => 0
So we have no token and packet is dropped.
Am I wrong?
next prev parent reply other threads:[~2012-09-27 13:22 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-27 12:33 [PATCH] inetpeer: ensure to set the maximum tokens the first time Nicolas Dichtel
2012-09-27 12:53 ` Eric Dumazet
2012-09-27 13:21 ` Nicolas Dichtel [this message]
2012-09-27 13:30 ` Eric Dumazet
2012-09-27 13:34 ` Eric Dumazet
2012-09-27 13:39 ` Nicolas Dichtel
2012-09-27 14:11 ` [PATCH v2] inetpeer: fix token initialization Nicolas Dichtel
2012-09-27 14:18 ` Eric Dumazet
2012-09-27 23:28 ` David Miller
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