BFD socket bind error upon reboot

[J. Kendzorra]

Hi,

upon a reboot of a system running BFD I recently noticed BFD breaking
with error "Cannot assign requested address" once the system came back.
Restarting the BFD protocol in question solved the problem.
Hence, apparently the system's network wasn't fully up and running at
the time bird started; according to systemd documentation
(https://www.freedesktop.org/wiki/Software/systemd/NetworkTarget/), one
possible fix is to change bird.service from
After=network.target
to
After=network-online.target
Wants=network-online.target
Alternatively, IP_FREEBIND on the BFD tx socket would allow binding to
an IP address that does not (yet) exist which seems more elegant since
it doesn't need to take into account that different systems may define
"online" differently.
I'm wondering whether there's something I'm missing as to why
IP_FREEBIND shouldn't be used?

Thanks,
J.