tftp: add external_ip setting

[aparcar]

Just as with the external (path) setting, it's helpful for the DUT to know from which IP the server offers firmware.

Description

Checklist

• Documentation for the feature
• Tests for the feature

• The arguments and description in doc/configuration.rst have been updated

• Add a section on how to use the feature to doc/usage.rst

• Add a section on how to use the feature to doc/development.rst

• PR has been tested

• Man pages have been regenerated

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 55.8%. Comparing base (d6d20d7) to head (e73d676).
Report is 19 commits behind head on master.

✅ All tests successful. No failed tests found.

Additional details and impacted files

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  Coverage    55.7%   55.8%           
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  Files         170     170           
  Lines       13393   13395    +2     
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+ Hits         7473    7475    +2     
  Misses       5920    5920           

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3.11	55.8% <100.0%> (+<0.1%)	⬆️
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[aparcar]

I'm running this already in my lab setup and it seems to work just fine.

[aparcar]

Here is an example how to use it https://github.com/aparcar/openwrt-tests/blob/main/strategies/tftpstrategy.py#L65

[Bastian-Krause]

Why can't the DUT simply use the host attribute instead?

[aparcar]

Using a proxied setup, the host value is something like hostname-foobar, which doesn't help the tftp DUT at all. The specified IP is instead handed over via a setenv call in a custom strategy

[aparcar]

@Bastian-Krause any further comments? My code looks like this right now and works just fine

elif status == Status.uboot:
            self.transition(Status.off)
            self.target.activate(self.tftp)
            self.target.activate(self.console)

            staged_file = self.tftp.stage(self.target.env.config.get_image_path("root"))
            tftp_server_ip = self.target.get_resource(
                RemoteTFTPProvider, wait_avail=False
            ).external_ip

            self.power.cycle()
            # interrupt uboot

            self.uboot.init_commands = (
                f"setenv bootfile {staged_file}",
            ) + self.uboot.init_commands

            if tftp_server_ip:
                tftp_dut_ip = ipaddress.ip_address(tftp_server_ip) + 1
                self.uboot.init_commands = (
                    f"setenv serverip {tftp_server_ip}",
                    f"setenv ipaddr {tftp_dut_ip}",
                ) + self.uboot.init_commands

            self.target.activate(self.uboot)