netdev - Endless "ip route show" if 255.255.255.255 route exists

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Date:   Wed, 4 Dec 2019 16:22:54 +0100 (CET)
From:   Sven-Haegar Koch <haegar@...net.de>
To:     netdev@...r.kernel.org
Subject: Endless "ip route show" if 255.255.255.255 route exists

Moin,

I see a strange problem on kernel 5.4.0, also exists in 5.3.9, but not 
in 4.19. For now only tried with the Debian binary kernels.

root@...gar-test:~# uname -a
Linux haegar-test 5.4.0-trunk-amd64 #1 SMP Debian 5.4-1~exp1 
(2019-11-26) x86_64 GNU/Linux
root@...gar-test:~# ip -V
ip utility, iproute2-ss191125
(debian 5.4.0-1)


Routing table before test:

root@...gar-test:~# ip ro sh | head -n 10
default via 10.140.184.1 dev ens18
10.140.184.0/24 dev ens18 proto kernel scope link src 10.140.184.244


Adding 255.255.255.255/32 route:

root@...gar-test:~# ip ro add 255.255.255.255/32 dev ens18


Then trying to show the routing table:

root@...gar-test:~# ip ro sh | head -n 10
default via 10.140.184.1 dev ens18
10.140.184.0/24 dev ens18 proto kernel scope link src 10.140.184.244
255.255.255.255 dev ens18 scope link
default via 10.140.184.1 dev ens18
10.140.184.0/24 dev ens18 proto kernel scope link src 10.140.184.244
255.255.255.255 dev ens18 scope link
default via 10.140.184.1 dev ens18
10.140.184.0/24 dev ens18 proto kernel scope link src 10.140.184.244
255.255.255.255 dev ens18 scope link
default via 10.140.184.1 dev ens18 

(Repeats endless without the "head" limit)


The output of "route -n" is correct.

root@...gar-test:~# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use 
Iface
0.0.0.0         10.140.184.1    0.0.0.0         UG    0      0        0 
ens18
10.140.184.0    0.0.0.0         255.255.255.0   U     0      0        0 
ens18
255.255.255.255 0.0.0.0         255.255.255.255 UH    0      0        0 
ens18

c'ya
sven-haegar

-- 
Three may keep a secret, if two of them are dead.
- Ben F.