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Prevent attempting to firmware update while another in progress #48

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Prevent attempting to firmware update while another in progress #48

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11 changes: 10 additions & 1 deletion lib/ssh_subsystem_fwup.ex
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Original file line number Diff line number Diff line change
Expand Up @@ -96,7 +96,8 @@ defmodule SSHSubsystemFwup do
@impl :ssh_client_channel
def handle_msg({:ssh_channel_up, channel_id, cm}, state) do
with {:ok, options} <- precheck(state.options[:precheck_callback], state.options),
:ok <- check_devpath(options[:devpath]) do
:ok <- check_devpath(options[:devpath]),
:ok <- check_fwup_not_running() do
Logger.debug("ssh_subsystem_fwup: starting fwup")
fwup = FwupPort.open_port(options)
{:ok, %{state | id: channel_id, cm: cm, fwup: fwup}}
Expand Down Expand Up @@ -210,6 +211,14 @@ defmodule SSHSubsystemFwup do
end
end

defp check_fwup_not_running() do
if Enum.any?(Port.list(), &("#{Port.info(&1)[:name]}" =~ ~r/fwup/)) do
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Ok, this is clever enough that I feel compelled to think if there's another way. But, I can definitely see how this works and prevents two instances of fwup running.

Fwiw, the best other idea I have at the moment would be for fwup to create a lock file based on the output when it runs.

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Ya, I had the same thought, researched a bit, then decided to just start with the easiest

We could also just wrap this port process in a singleton genserver or something as well which would control fwup processes. I'm open to whatever.

It seems like checking for a running fwup port process is going to be just as effective as checking for a file on disk. The file seems like more risk to me in case the fwup process crashes without cleaning it up and thinks look to still be running (but I might guess you know the C way to get around that 😂)

{:error, "update already in progress"}
else
:ok
end
end

defp precheck(nil, options), do: {:ok, options}

defp precheck({m, f, a}, options) do
Expand Down
18 changes: 17 additions & 1 deletion test/ssh_subsystem_fwup_test.exs
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Expand Up @@ -23,7 +23,7 @@ defmodule SSHSubsystemFwupTest do
def start_sshd(options) do
{:ok, ref} =
:ssh.daemon(@port, [
{:max_sessions, 1},
{:max_sessions, options[:max_sessions] || 1},
{:user_passwords, [{'user', 'password'}]},
{:system_dir, 'test/fixtures'},
{:subsystems, [SSHSubsystemFwup.subsystem_spec(options)]}
Expand Down Expand Up @@ -285,4 +285,20 @@ defmodule SSHSubsystemFwupTest do
# Check that the update was applied
assert match?(<<"Hello, world!", _::binary()>>, File.read!(options[:devpath]))
end

test "does not allow more than one update at a time", context do
options = default_options(context.test) |> Keyword.put(:max_sessions, 2)
File.touch!(options[:devpath])
start_sshd(options)

large_fw = Fwup.create_firmware(message: :binary.copy("a", 24 * 1024 * 1024))
fw_contents = Fwup.create_firmware()

{:ok, t} = Task.start(fn -> do_ssh(large_fw) end)
{output, exit_status} = do_ssh(fw_contents)

assert exit_status != 0
assert output =~ "Error: update already in progress"
Process.exit(t, :kill)
end
end