When using filter-mirror like the example below where the interface
'ndev0' does not exist on the host, QEMU crashes into segmentation
fault.
$ qemu-system-x86_64 -S -machine pc -netdev user,id=ndev0 -object filter-mirror,id=test-object,netdev=ndev0
This happens because the function filter_mirror_setup() does not check
if the device actually exists and still keep on processing calling
qemu_chr_find(). This patch fixes this issue.
Signed-off-by: Eduardo Otubo <otubo@redhat.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>