netdev - Re: [PATCH] netconsole: Append kernel version to message

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Message-ID: <ZKU1Sy7dk8yESm4d@gmail.com>
Date: Wed, 5 Jul 2023 02:18:03 -0700
From: Breno Leitao <leitao@...ian.org>
To: Stephen Hemminger <stephen@...workplumber.org>
Cc: "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	sergey.senozhatsky@...il.com, pmladek@...e.com, tj@...nel.org,
	Dave Jones <davej@...emonkey.org.uk>,
	"open list:NETWORKING DRIVERS" <netdev@...r.kernel.org>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] netconsole: Append kernel version to message

On Tue, Jul 04, 2023 at 08:58:00AM -0700, Stephen Hemminger wrote:
> > > This should be runtime configured like other netconsole options.
> > > Not enabled at compile time.  
> > 
> > Do you mean I should add a new option to netconsole line? This is the
> > current line format today:
> > 
> > 	[+][src-port]@[src-ip]/[<dev>],[tgt-port]@<tgt-ip>/[tgt-macaddr]
> > 
> > If that is the case, I suppose I want to add something at the beginning
> > of format, that specify that uname should be sent. What about something
> > as?
> > 
> > 	[u][+][src-port]@[src-ip]/[<dev>],[tgt-port]@<tgt-ip>/[tgt-macaddr]
> > 
> > Thanks!
> 
> Keep it as simple as possible.
> What ever program is reading udp socket knows where it is coming from.

Right, the server knows from where the package is coming, so, the source
address is known at receive time, and that is good. I want to do the
same with uname.

> The uname is really not needed.

The uname is useful if the receiver side is looking (grepping) for
specific messages (warnings, oops, etc) affecting specific kernel
versions. If the uname is not available, the receiver needs to read boot
message and keep a map for source IP to kernel version. This is far from
ideal at a hyperscale level.

Things get worse when you have VMs using different kernels, and both
host and guests are sending traffic to the same receiver. In this case, you
have two different kernels versions mapped to the same IP.

Thanks!