netdev - Re: [PATCH iproute2] ss: Tell user about -EOPNOTSUPP for SOCK

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Date:	Mon, 16 May 2016 20:24:03 -0600
From:	David Ahern <dsa@...ulusnetworks.com>
To:	Lorenzo Colitti <lorenzo@...gle.com>,
	Stephen Hemminger <stephen@...workplumber.org>
Cc:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH iproute2] ss: Tell user about -EOPNOTSUPP for SOCK_DESTROY

On 5/16/16 8:04 PM, Lorenzo Colitti wrote:
> Given that the filter can specify a number of sockets, some of which
> can and some of which can't be closed, and that whether a given socket
> can be closed is only known at the time we attempt to close it, there
> is a choice between two bad outcomes:
>
> 1. Users try to use "ss -K" with a kernel that doesn't support it, and
> get confused about why it does nothing and doesn't print an error
> message.
> 2. Users use "ss -K" with a kernel that does support it, and get
> irritated by seeing one error message per TCP_TIME_WAIT socket, UDP
> socket, etc.

As I mentioned we can print the unsupported once or per socket matched 
and with the socket params. e.g.,

+               } else if (errno == EOPNOTSUPP) {
+                       printf("Operation not supported for:\n");
+                       inet_show_sock(h, diag_arg->f, diag_arg->protocol);

Actively suppressing all error messages is just wrong. I get the 
flooding issue so I'm fine with just printing it once.