netdev - [PATCH iproute2-next] ip: don't use program name to select command

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Date:   Mon, 11 Jan 2021 20:05:45 +0100
From:   Matteo Croce <mcroce@...ux.microsoft.com>
To:     netdev@...r.kernel.org
Cc:     Stephen Hemminger <stephen@...workplumber.org>,
        David Ahern <dsahern@...il.com>
Subject: [PATCH iproute2-next] ip: don't use program name to select command

From: Matteo Croce <mcroce@...rosoft.com>

ip has an ancient behaviour of looking at its program name to determine
the command to run. If the name is longer than 2 characters, the first two
letters are stripped and the others are interpreted as the command name:

    $ ln -s /sbin/ip iproute
    $ ln -s /sbin/ip ipa
    $ ./iproute
    default via 192.168.55.1 dev wlp0s20f3 proto dhcp metric 600
    192.168.55.0/24 dev wlp0s20f3 proto kernel scope link src 192.168.55.26 metric 600
    192.168.122.0/24 dev virbr0 proto kernel scope link src 192.168.122.1 linkdown
    $ ./ipa show dev lo
    1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
        link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
        inet 127.0.0.1/8 scope host lo
           valid_lft forever preferred_lft forever

This creates problems when the ip binary is renamed. For example, Yocto
renames it to 'ip.iproute2' when also the busybox implementation is
present, giving the following error:

    $ ip.iproute2
    Object ".iproute2" is unknown, try "ip help".

Since noone is using it, remove this undocumented feature.

Signed-off-by: Matteo Croce <mcroce@...rosoft.com>
---
 ip/ip.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/ip/ip.c b/ip/ip.c
index 40d2998a..9b772307 100644
--- a/ip/ip.c
+++ b/ip/ip.c
@@ -311,9 +311,6 @@ int main(int argc, char **argv)
 
 	rtnl_set_strict_dump(&rth);
 
-	if (strlen(basename) > 2)
-		return do_cmd(basename+2, argc, argv);
-
 	if (argc > 1)
 		return do_cmd(argv[1], argc-1, argv+1);
 
-- 
2.29.2