Re: iproute2: hide devices starting with period by default

[Andy Gospodarek <andy@greyhouse.net>]

On Thu, Feb 23, 2017 at 11:50:28AM -0800, stephen hemminger wrote:
> Some use cases create Linux networking devices which are not intended for use
> by normal networking. This is an enhancement to ip command to hide network
> devices starting with period (like files in normal directory).  Interfaces whose
> name start with "." are not shown by default, and the -a (or -all) flag must
> be used to show these devices.
> 
> Example:
> $ ip -brief link show
> lo               UNKNOWN        00:00:00:00:00:00 <LOOPBACK,UP,LOWER_UP>
> eth0             UP             00:25:90:86:b3:6b <BROADCAST,MULTICAST,UP,LOWER_UP>
> eth1             DOWN           00:25:90:86:b3:6a <NO-CARRIER,BROADCAST,MULTICAST,UP>
> $ ip -all -brief link show
> lo               UNKNOWN        00:00:00:00:00:00 <LOOPBACK,UP,LOWER_UP>
> eth0             UP             00:25:90:86:b3:6b <BROADCAST,MULTICAST,UP,LOWER_UP>
> eth1             DOWN           00:25:90:86:b3:6a <NO-CARRIER,BROADCAST,MULTICAST,UP>
> .eth2            DOWN           00:1b:21:a0:e7:06 <BROADCAST,MULTICAST>

I've run across a time when there was a perceived need for this with an
out of tree driver that created a netdev that was never used.  I was
never a big fan of the attempt to hide it.  It seemed like the better
answer would be to try and fix the driver that is creating and
registering this unnecessary netdev so it no longer appears and that was
what we did.  

As an admin I'd be pretty frustrated if I somehow had a network issue
that I could not properly debug due to a hidden network interface.  If
there was an extra flag that was needed to a tool like iproute2 to show
the hidden device, soon admin's hands would just type 'ip -all link
show' each time to get the full picture.  

If the concensus is that we DO want to hide devices I've seen David
Ahern's set and it is much more complete than this.  It is probably the
better approach to not leave too many loose ends.

> Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
> ---
>  include/utils.h |  1 +
>  ip/ip.c         |  5 ++++-
>  ip/ipaddress.c  | 31 ++++++++++++++++++++++++-------
>  man/man8/ip.8   |  5 +++++
>  4 files changed, 34 insertions(+), 8 deletions(-)
> 
> diff --git a/include/utils.h b/include/utils.h
> index 22369e0b4e03..50712d27f112 100644
> --- a/include/utils.h
> +++ b/include/utils.h
> @@ -16,6 +16,7 @@ extern int human_readable;
>  extern int use_iec;
>  extern int show_stats;
>  extern int show_details;
> +extern int show_all;
>  extern int show_raw;
>  extern int resolve_hosts;
>  extern int oneline;
> diff --git a/ip/ip.c b/ip/ip.c
> index 07050b07592a..ed637b065b58 100644
> --- a/ip/ip.c
> +++ b/ip/ip.c
> @@ -30,6 +30,7 @@ int human_readable;
>  int use_iec;
>  int show_stats;
>  int show_details;
> +int show_all;
>  int resolve_hosts;
>  int oneline;
>  int brief;
> @@ -54,7 +55,7 @@ static void usage(void)
>  "                   netns | l2tp | fou | macsec | tcp_metrics | token | netconf | ila |\n"
>  "                   vrf }\n"
>  "       OPTIONS := { -V[ersion] | -s[tatistics] | -d[etails] | -r[esolve] |\n"
> -"                    -h[uman-readable] | -iec |\n"
> +"                    -h[uman-readable] | -iec | -all |\n"
>  "                    -f[amily] { inet | inet6 | ipx | dnet | mpls | bridge | link } |\n"
>  "                    -4 | -6 | -I | -D | -B | -0 |\n"
>  "                    -l[oops] { maximum-addr-flush-attempts } | -br[ief] |\n"
> @@ -231,6 +232,8 @@ int main(int argc, char **argv)
>  			++show_stats;
>  		} else if (matches(opt, "-details") == 0) {
>  			++show_details;
> +		} else if (matches(opt, "-all") == 0) {
> +			++show_all;
>  		} else if (matches(opt, "-resolve") == 0) {
>  			++resolve_hosts;
>  		} else if (matches(opt, "-oneline") == 0) {
> diff --git a/ip/ipaddress.c b/ip/ipaddress.c
> index 400ebb4de563..029aae100549 100644
> --- a/ip/ipaddress.c
> +++ b/ip/ipaddress.c
> @@ -660,6 +660,7 @@ int print_linkinfo_brief(const struct sockaddr_nl *who,
>  	struct ifinfomsg *ifi = NLMSG_DATA(n);
>  	struct rtattr *tb[IFLA_MAX+1];
>  	int len = n->nlmsg_len;
> +	const char *ifname;
>  	char *name;
>  	char buf[32] = { 0, };
>  	unsigned int m_flag = 0;
> @@ -677,14 +678,22 @@ int print_linkinfo_brief(const struct sockaddr_nl *who,
>  		return -1;
>  
>  	parse_rtattr(tb, IFLA_MAX, IFLA_RTA(ifi), len);
> -	if (tb[IFLA_IFNAME] == NULL)
> -		fprintf(stderr, "BUG: device with ifindex %d has nil ifname\n", ifi->ifi_index);
> +	if (tb[IFLA_IFNAME])
> +		ifname = rta_getattr_str(tb[IFLA_IFNAME]);
> +	else {
> +		fprintf(stderr, "BUG: device with ifindex %d has nil ifname\n",
> +			ifi->ifi_index);
> +		ifname = "<nil>";
> +	}
>  
>  	if (filter.label &&
>  	    (!filter.family || filter.family == AF_PACKET) &&
>  	    fnmatch(filter.label, RTA_DATA(tb[IFLA_IFNAME]), 0))
>  		return -1;
>  
> +	if (!filter.ifindex && *ifname == '.' && !show_all)
> +		return 0;
> +
>  	if (tb[IFLA_GROUP]) {
>  		int group = *(int *)RTA_DATA(tb[IFLA_GROUP]);
>  
> @@ -758,6 +767,7 @@ int print_linkinfo(const struct sockaddr_nl *who,
>  	struct ifinfomsg *ifi = NLMSG_DATA(n);
>  	struct rtattr *tb[IFLA_MAX+1];
>  	int len = n->nlmsg_len;
> +	const char *ifname;
>  	unsigned int m_flag = 0;
>  
>  	if (n->nlmsg_type != RTM_NEWLINK && n->nlmsg_type != RTM_DELLINK)
> @@ -773,12 +783,20 @@ int print_linkinfo(const struct sockaddr_nl *who,
>  		return 0;
>  
>  	parse_rtattr(tb, IFLA_MAX, IFLA_RTA(ifi), len);
> -	if (tb[IFLA_IFNAME] == NULL)
> -		fprintf(stderr, "BUG: device with ifindex %d has nil ifname\n", ifi->ifi_index);
> +	if (tb[IFLA_IFNAME])
> +		ifname = rta_getattr_str(tb[IFLA_IFNAME]);
> +	else {
> +		fprintf(stderr, "BUG: device with ifindex %d has nil ifname\n",
> +			ifi->ifi_index);
> +		ifname = "<nil>";
> +	}
>  
>  	if (filter.label &&
>  	    (!filter.family || filter.family == AF_PACKET) &&
> -	    fnmatch(filter.label, RTA_DATA(tb[IFLA_IFNAME]), 0))
> +	    fnmatch(filter.label, ifname, 0))
> +		return 0;
> +
> +	if (!filter.ifindex && *ifname == '.' && !show_all)
>  		return 0;
>  
>  	if (tb[IFLA_GROUP]) {
> @@ -806,8 +824,7 @@ int print_linkinfo(const struct sockaddr_nl *who,
>  		fprintf(fp, "Deleted ");
>  
>  	fprintf(fp, "%d: ", ifi->ifi_index);
> -	color_fprintf(fp, COLOR_IFNAME, "%s",
> -		      tb[IFLA_IFNAME] ? rta_getattr_str(tb[IFLA_IFNAME]) : "<nil>");
> +	color_fprintf(fp, COLOR_IFNAME, "%s", ifname);
>  
>  	if (tb[IFLA_LINK]) {
>  		SPRINT_BUF(b1);
> diff --git a/man/man8/ip.8 b/man/man8/ip.8
> index 8ecb1996da92..813dbec2a6f2 100644
> --- a/man/man8/ip.8
> +++ b/man/man8/ip.8
> @@ -31,6 +31,7 @@ ip \- show / manipulate routing, devices, policy routing and tunnels
>  \fB\-h\fR[\fIuman-readable\fR] |
>  \fB\-s\fR[\fItatistics\fR] |
>  \fB\-d\fR[\fIetails\fR] |
> +\fB\-a\fR[\fll\fR] |
>  \fB\-r\fR[\fIesolve\fR] |
>  \fB\-iec\fR |
>  \fB\-f\fR[\fIamily\fR] {
> @@ -84,6 +85,10 @@ As a rule, the information is statistics or some time values.
>  Output more detailed information.
>  
>  .TP
> +.BR "\-a" , " \-all"
> +Show all devices, do not ignore entries starting with period.
> +
> +.TP
>  .BR "\-l" , " \-loops " <COUNT>
>  Specify maximum number of loops the 'ip address flush' logic
>  will attempt before giving up. The default is 10.