ffx not detecting emulator

[fctorial]

I'm unable to list the running emulator with `ffx target list`. I'm also getting an error when running any command other than shell builtins (cd, pwd):

$ ls
/boot/bin/sh: 2: Cannot create child process: -1 (ZX_ERR_INTERNAL): failed to resolve fuchsia-pkg://fuchsia.com/ls#bin/ls: -25

I'm using this build config:

    fx set core.qemu-x64 --ccache --auto-dir

This is the full log:

https://gist.github.com/fctorial/0feb073d8e94a1253da292e3641db9ef

This error message doesn't appear when running via `fx qemu`.

[Shai Barack]

Do you have `fx serve` running? This is the process that will serve packages to your emulator that include tools such as ls.

What guide are you following? Maybe we could clarify the instructions. 

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[Brett Wilson]

Hi!

I had a similar problem recently. Check the workaround in https://bugs.fuchsia.dev/p/fuchsia/issues/detail?id=66905 (comment 5) to see if it helps.

Brett

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[fctorial]

@Shai

`fx serve` command gets stuck at 'Discovery...' phase. I was following this guide:

https://fuchsia.dev/fuchsia-src/development/tools/ffx/getting-started

I didn't know it was needed for 'ls' utility.

Do I need to launch the emulator first or the update-server? (Same results in both cases)

@Brett

I'm seeing same results with this option.

`fx shell` and `fx list-devices` commands are also unable to connect to the emulator. 

[Shai Barack]

I usually start `fx serve` before `fx qemu`, not sure if it matters.

I couldn't repro the issue that you or Brett are reporting.

You can get on the bug that Brett linked to and see if you could find help there. 🤞

[Geevarghese V K]

@fctorial. Are you getting any error after running just "fx shell" after running Emulator

[Sagar Tiwari]

$ fx shell
ERROR: Cannot find a device.

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[Geevarghese V K]

Can you use -N and retry?  fx set core.qemu-x64 -N --ccache --auto-dir  

[fctorial]

fx uses mdns to detect targets. Avahi daemon must be running on linux hosts for it to work. 

`fx serve` still doesn't work. It fails to register itself to the target as a package source:

    $ amberctl add_src -n devhost -f http://[fe80::e49a:deff:fe74:a9fb%25ethp0003]:8083/config.json

    2021/01/06 07:01:14 error adding source: failed to GET file: Get "http://[fe80::e49a:deff:fe74:a9fb%25ethp0003]:8083/config.json": dial tcp [fe80::e49a:deff:fe74:a9fb%ethp0003]:8083: errno(110)

[fctorial]

Setting up avahi and opening firewall to everything fixes this issue. Fuchsia devtools include this ufw configuration:

    dryer sudo ufw allow proto udp from fe80::/10 to any port 33331:33340 comment 'Fuchsia Netboot Protocol'

    dryer sudo ufw allow proto tcp from fe80::/10 to any port 8083 comment 'Fuchsia Package Server'

    dryer sudo ufw allow proto udp from fe80::/10 port 33340 comment 'Fuchsia Netboot TFTP Source Port'

    dryer sudo ufw allow proto udp from fe80::/10 port 5353 comment 'Fuchsia MDNS'

Can anyone translate these rules into simple language so that I could properly setup firewall on my system?

Also, emu command doesn't warn about firewall configuration if `ufw` command isn't available. Shall I submit a PR for it?

Thanks. 

[fctorial]

I tried these rules but they don't work:

TCP: 8083

UDP: 33331-33340, 33340, 5353

[John Wittrock]

You seem on the correct path with firewall configuration. I think MDNS is the thing you likely have to get working for device discovery to work. I don't know the specifics of how your firewall setup works, but our ufw configuration relies on the fact that Fuchsia devices will generally set up a Link-Local IPv6 address to communicate with the host (that link-local address is the fe80 address you see in our ufw configuration). 

This raises two questions:

- Does your firewall configuration require an interface to be specified on which to set rules?

- Can you set rules based on source IP address for incoming traffic?

The firewall rules we set up with `ufw` are (for example) "allow UDP traffic on any network interface from link-local IPs beginning with fe80 to ports 33331-33340 for the Fuchsia Netboot Protocol"

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[fctorial]

Correction. Above firewall config fixes the issue.

[John Wittrock]

Great, thanks for the update. Can you get through the rest of the flow with `fx serve` and `ls` now?

[fctorial]

Yes