Default command-line option values depend on other command-line options (ref `detectPublicIPv4`)

[rpardini]

Default command-line option values depend on other command-line options (ref detectPublicIPv4)

The main issue here is that when running Smee directly in the host network, I'd like to avoid specifying any IP addresses at all, while being able to specify ports.

The way this is implemented (in flags.go) doesn't allow us to default DHCP/ipxe script to the listened-to ports.

TFTP listen port vs DHCP value

• if tftp-addr is unset, it will auto-detect IP and default to port 69. https://github.com/tinkerbell/smee/blob/main/cmd/smee/flag.go#L90
• dhcp-tftp-ip behaves the same; thus auto-detected-IP + :69 https://github.com/tinkerbell/smee/blob/main/cmd/smee/flag.go#L120
• if tftp-addr is set to eg 0.0.0.0:10669 (to avoid specifying IP address), then one is forced to specify IP address in dhcp-tftp-ip just to specify the port

HTTP port

still working on this part, but principle is the same; I couldn't make sense of the :80, :8080 and ` (defaulting to 80) defaults used involvinghttp-addrtodhcp-http-ipxe-binary-url,dhcp-http-ipxe-script-url`

[rpardini]

I'm unsure there's provisions for handling this in https://github.com/peterbourgon/ff ...

[rpardini]

Solution tested & works perfectly. Thanks!