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// -*- Mode: Go; indent-tabs-mode: t -*-
/*
* Copyright (C) 2016-2018 Canonical Ltd
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 3 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*/
package udev
import (
"fmt"
"os/exec"
)
// udevadmTrigger runs "udevadm trigger" but ignores an non-zero exit codes.
// udevadm only started reporting errors in systemd 248 and in order to
// work correctly in LXD these errors need to be ignored. See
// https://github.com/systemd/systemd/pull/18684 for some more background
// (and https://github.com/lxc/lxd/issues/9526)
func udevadmTrigger(args ...string) error {
args = append([]string{"trigger"}, args...)
output, err := exec.Command("udevadm", args...).CombinedOutput()
// can happen when events for some of the devices or all of
// them could not be triggered, but we cannot distinguish which of
// those happened, in any case snapd invoked udevadm and tried its
// best
if exitErr, ok := err.(*exec.ExitError); ok {
// ignore "normal" exit codes but report e.g. segfaults
// that are reported as -1
if exitErr.ExitCode() > 0 {
return nil
}
}
if err != nil {
return fmt.Errorf("%s\nudev output:\n%s", err, string(output))
}
return nil
}
// reloadRules runs three commands that reload udev rule database.
//
// The commands are: udevadm control --reload-rules
//
// udevadm trigger --subsystem-nomatch=input
// udevadm settle --timeout=3
//
// and optionally trigger other subsystems as defined in the interfaces. Eg:
//
// udevadm trigger --subsystem-match=input
// udevadm trigger --property-match=ID_INPUT_JOYSTICK=1
func (b *Backend) reloadRules(subsystemTriggers []string) error {
// When running in a container observe the state of host's udev, as such
// reloading rules makes no sense, since they are ineffective.
// Similarly in preseeding, there is no point in reloading rules which
// only affect the runtime standbox.
if b.preseed || b.isContainer {
return nil
}
output, err := exec.Command("udevadm", "control", "--reload-rules").CombinedOutput()
if err != nil {
return fmt.Errorf("cannot reload udev rules: %s\nudev output:\n%s", err, string(output))
}
// By default, trigger for all events except the input subsystem since
// it can cause noticeable blocked input on, for example, classic
// desktop.
if err = udevadmTrigger("--subsystem-nomatch=input"); err != nil {
return fmt.Errorf("cannot run udev triggers: %s", err)
}
mustTriggerForInputSubsystem := false
mustTriggerForInputKeys := false
for _, subsystem := range subsystemTriggers {
if subsystem == "input/key" {
mustTriggerForInputKeys = true
} else if subsystem == "input" {
mustTriggerForInputSubsystem = true
}
// no `else` branch: we already triggered udevadm for all other
// subsystems before by running it with the `--subsystem-nomatch=input`
// option, so there's no need to do anything here.
}
if mustTriggerForInputSubsystem {
// Trigger for the whole input subsystem
if err := udevadmTrigger("--subsystem-match=input"); err != nil {
return fmt.Errorf("cannot run udev triggers for input subsystem: %s", err)
}
} else {
// More specific triggers, to avoid blocking keyboards and mice
if mustTriggerForInputKeys {
// If one of the interfaces said it uses the input
// subsystem for input keys, then trigger the keys
// events in a way that is specific to input keys
// to not block other inputs.
if err = udevadmTrigger("--property-match=ID_INPUT_KEY=1", "--property-match=ID_INPUT_KEYBOARD!=1"); err != nil {
return fmt.Errorf("cannot run udev triggers for keys: %s", err)
}
}
// FIXME: if not already triggered, trigger the joystick property if it
// wasn't already since we are not able to detect interfaces that are
// removed and set subsystemTriggers correctly. When we can, remove
// this. Allows joysticks to be removed from the device cgroup on
// interface disconnect.
if err := udevadmTrigger("--property-match=ID_INPUT_JOYSTICK=1"); err != nil {
return fmt.Errorf("cannot run udev triggers for joysticks: %s", err)
}
}
// give our triggered events a chance to be handled before exiting.
// Ignore errors since we don't want to error on still pending events.
_ = exec.Command("udevadm", "settle", "--timeout=10").Run()
return nil
}
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