netdev - Re: [PATCH iproute2 net-next 0/3] ss: Allow selection of columns to be displayed

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Message-ID: <7ffc00c8-bdf6-5c75-564e-2663494bda5d@gmail.com>
Date:   Tue, 30 Oct 2018 10:34:45 -0600
From:   David Ahern <dsahern@...il.com>
To:     Stefano Brivio <sbrivio@...hat.com>
Cc:     "Yoann P." <yoann.p.public@...il.com>,
        Stephen Hemminger <stephen@...workplumber.org>,
        netdev@...r.kernel.org
Subject: Re: [PATCH iproute2 net-next 0/3] ss: Allow selection of columns to
 be displayed

On 10/30/18 9:05 AM, Stefano Brivio wrote:
> Now that we have an abstraction for columns, it's relatively easy to
> selectively display only some of them, and Yoann has a use case for it.
> 
> Patch 1/3 fixes a rendering issue that shows up only when display of
> arbitrary columns is disabled. Patch 2/3 implements the relevant option,
> and patch 3/3 makes the output more readable when some columns are
> disabled.
> 
>

I like the intent, and I have prototyped something similar for 'ip'.

A more flexible approach is to use format strings to allow users to
customize the output order and whitespace as well. So for ss and your
column list (winging it here):

    netid          = %N
    state          = %S
    recv Q         = %Qr
    send Q         = %Qs
    local address  = %Al
    lport port     = %Pl
    remote address = %Ar
    remote port    = %Pr
    process data   = %p
    ...

then a format string could be: "%S  %Qr %Qs  %Al:%Pl %Ar:%Pr  %p\n"

or for csv output: "%S,%Qr,%Qs,%Al,%Pl,%Ar,%Pr,%p\n"

I have not had time to look into an implementation for ip. Conceptually
- and scanning the kernel's vsprintf code - it does not look that
difficult, just time consuming on the frontend with the initial setup.