netdev - Re: [PATCH] Fix ss Netid column and Local/Peer

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Date:   Mon, 29 Oct 2018 19:20:36 +0100
From:   Stefano Brivio <sbrivio@...hat.com>
To:     "Yoann P." <yoann.p.public@...il.com>
Cc:     netdev@...r.kernel.org,
        Stephen Hemminger <stephen@...workplumber.org>
Subject: Re: [PATCH] Fix ss Netid column and Local/Peer_Address

Hi Yohann,

On Fri, 26 Oct 2018 22:53:32 +0200
"Yoann P." <yoann.p.public@...il.com> wrote:

> When using ss -Hutn4 or -utn3, Netid and State columns are sometime merged, it 
> can be confusing when trying to pipe into awk or column.

Thanks for fixing this. A few comments though:

> @@ -144,9 +144,9 @@ static struct column columns[] = {
>         { ALIGN_LEFT,   "State",                " ",    0, 0, 0 },
>         { ALIGN_LEFT,   "Recv-Q",               " ",    0, 0, 0 },
>         { ALIGN_LEFT,   "Send-Q",               " ",    0, 0, 0 },
> -       { ALIGN_RIGHT,  "Local Address:",       " ",    0, 0, 0 },
> +       { ALIGN_RIGHT,  "Local_Address:",       " ",    0, 0, 0 },
>         { ALIGN_LEFT,   "Port",                 "",     0, 0, 0 },
> -       { ALIGN_RIGHT,  "Peer Address:",        " ",    0, 0, 0 },
> +       { ALIGN_RIGHT,  "Peer_Address:",        " ",    0, 0, 0 },

This is needed only if you pipe the output to column(1), I don't think
it's a bug, because printing the header when you pass the output to
column(1) makes little sense -- one should use -H then.

By the way, why do you use column(1), when ss already prints output in
columns? Any other issue you are working around?

>         { ALIGN_LEFT,   "Port",                 "",     0, 0, 0 },
>         { ALIGN_LEFT,   "",                     "",     0, 0, 0 },
>  };
> @@ -1334,7 +1334,7 @@ static void sock_state_print(struct sockstat *s)
>                 out("`- %s", sctp_sstate_name[s->state]);
>         } else {
>                 field_set(COL_NETID);
> -               out("%s", sock_name);
> +               out("%-6s", sock_name);

I could reproduce this issue with a 70-columns terminal and the options
you gave.

Anyway, I don't think this is the right way to fix it: this will waste
one to two columns in case we have three letters for the Netid
specifier, and won't work the day we get six-letters names. In general,
it looks like a bad idea to reintroduce hardcoded width counts.

The actual issue seems to be that in some cases the left delimiter for
the State column is not printed, and I think you should fix that
instead. I'll look into this within a couple of days and give you some
more specific hints in case you still need them by then.

-- 
Stefano