From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Dumazet <eric.dumazet@gmail.com>
Subject: Re: [RFC PATCH] sock: add SO_RCVQUEUE_SIZE getsockopt
Date: Mon, 13 Mar 2017 18:31:27 -0700
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To: Josh Hunt <johunt@akamai.com>
Cc: David Miller <davem@davemloft.net>, edumazet@google.com, arnd@arndb.de, soheil@google.com, willemb@google.com, pabeni@redhat.com, linux-arch@vger.kernel.org, netdev@vger.kernel.org

On Mon, 2017-03-13 at 18:34 -0500, Josh Hunt wrote:

> In this particular case they really do want to know total # of bytes in 
> the receive queue, not the data bytes they can consume from an 
> application pov. The kernel currently only exposes this value through 
> netlink or /proc/net/udp from what I saw.
> 
> I believe Eric's suggestion in his previous mail was to export all of 
> these meminfo metrics via a single socket option call similar to how its 
> done in netlink. We could then use that for both call sites.
> 
> I agree that it would be useful to also have the data you and Eric are 
> suggesting exposed somewhere, the total # of skb->len bytes sitting in 
> the receive queue. I could add that as a second socket option.

Please note that UDP stack does not maintain a per socket sum(skb->len)

Implementing this in a system call would require to lock the receive
queue (blocking BH) and iterating over a potential huge skb list.

Or add a new socket field and add/sub every skb->len of packets
added/removed to/from receive queue.

So I would prefer to not provide this information, this looks quite a
bloat.