When arp is off on a device, and ioctl(SIOCGARP) is queried,
a buggy answer is given with MAC address of the device, instead
of the mac address of the destination/gateway.
We filter out NUD_NOARP neighbours for /proc/net/arp,
we must do the same for SIOCGARP ioctl.
Tested:
lpaa23:~# ./arp 10.246.7.190
MAC=00:01:e8:22:cb:1d // correct answer
lpaa23:~# ip link set dev eth0 arp off
lpaa23:~# cat /proc/net/arp # check arp table is now 'empty'
IP address HW type Flags HW address Mask Device
lpaa23:~# ./arp 10.246.7.190
MAC=00:1a:11:c3:0d:7f // buggy answer before patch (this is eth0 mac)
After patch :
lpaa23:~# ip link set dev eth0 arp off
lpaa23:~# ./arp 10.246.7.190
ioctl(SIOCGARP) failed: No such device or address
Signed-off-by: Eric Dumazet <[email protected]>
Reported-by: Vytautas Valancius <[email protected]>
Cc: Willem de Bruijn <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
Eric Dumazet
11c91ef98f