netdev - Re: [PATCH net-next v2] ipv6: ioam: Support for Queue depth data field

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <Ychq4ggTdpVG24Zp@shredder>
Date:   Sun, 26 Dec 2021 15:15:14 +0200
From:   Ido Schimmel <idosch@...sch.org>
To:     Justin Iurman <justin.iurman@...ege.be>
Cc:     netdev@...r.kernel.org, davem@...emloft.net, kuba@...nel.org,
        dsahern@...nel.org, yoshfuji@...ux-ipv6.org
Subject: Re: [PATCH net-next v2] ipv6: ioam: Support for Queue depth data
 field

On Sun, Dec 26, 2021 at 01:59:08PM +0100, Justin Iurman wrote:
> On Dec 26, 2021, at 1:40 PM, Ido Schimmel idosch@...sch.org wrote:
> > On Sun, Dec 26, 2021 at 12:47:51PM +0100, Justin Iurman wrote:
> >> On Dec 24, 2021, at 6:53 PM, Ido Schimmel idosch@...sch.org wrote:
> >> > Why 'qlen' is used and not 'backlog'? From the paragraph you quoted it
> >> > seems that queue depth needs to take into account the size of the
> >> > enqueued packets, not only their number.
> >> 
> >> The quoted paragraph contains the following sentence:
> >> 
> >>    "The queue depth is expressed as the current amount of memory
> >>     buffers used by the queue"
> >> 
> >> So my understanding is that we need their number, not their size.
> > 
> > It also says "a packet could consume one or more memory buffers,
> > depending on its size". If, for example, you define tc-red limit as 1M,
> > then it makes a lot of difference if the 1,000 packets you have in the
> > queue are 9,000 bytes in size or 64 bytes.
> 
> Agree. We probably could use 'backlog' instead, regarding this
> statement:
> 
>   "It should be noted that the semantics of some of the node data fields
>    that are defined below, such as the queue depth and buffer occupancy,
>    are implementation specific.  This approach is intended to allow IOAM
>    nodes with various different architectures."
> 
> It would indeed make more sense, based on your example. However, the
> limit (32 bits) could be reached faster using 'backlog' rather than
> 'qlen'. But I guess this tradeoff is the price to pay to be as close
> as possible to the spec.

At least in Linux 'backlog' is 32 bits so we are OK :)
We don't have such big buffers in hardware and I'm not sure what
insights an operator will get from a queue depth larger than 4GB...

I just got an OOO auto-reply from my colleague so I'm not sure I will be
able to share his input before next week. Anyway, reporting 'backlog'
makes sense to me, FWIW.