netdev - Re: RX/dropped counter values for tagged packets

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Message-ID: <CAOQZsUjbx9fHtjexmpfGCETRjVJU7QOBJcng6ndT1nFaZKmf5w@mail.gmail.com>
Date:	Sun, 31 Mar 2013 20:17:39 -0700
From:	Ani Sinha <linuxdev@...rban.org>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Ani Sinha <ani@...stanetworks.com>, netdev@...r.kernel.org
Subject: Re: RX/dropped counter values for tagged packets

On Sun, Mar 31, 2013 at 8:09 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> On Sun, 2013-03-31 at 18:24 -0700, Ani Sinha wrote:
>
>> So in "another_round", if pt_prev is null at the end of the function
>> (not sure if this can actually happen in reality, but from the code it
>> looks like a possibility), the dropped counts will get incremented.
>>
>
> If packets are dropped, we increment rx_dropped.
>
> Nothing special with vlan, its the same with non tagged packets.
>
> So far so good.
>

Correct. Now if you combine the two cases, we increment the rx count
for tagged packets in  vlan_do_receive() and then in "another_round",
if pt_prev is null, we also increment the rx_dropped.

Now I have no issue with that _except_ it seems that when we report
the counter values in /proc, we do so in a way that for a tagged
packet, it seems that there might be a case where we combine the two
numbers so that the same packet results in a single increment of
receive and dropped counters at the same time (see my very first
email).

Hence my confusion.
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