github.com/david-imola/snapd@v0.0.0-20210611180407-2de8ddeece6d/overlord/configstate/configcore/handlers.go (about)

     1  // -*- Mode: Go; indent-tabs-mode: t -*-
     2  
     3  /*
     4   * Copyright (C) 2020 Canonical Ltd
     5   *
     6   * This program is free software: you can redistribute it and/or modify
     7   * it under the terms of the GNU General Public License version 3 as
     8   * published by the Free Software Foundation.
     9   *
    10   * This program is distributed in the hope that it will be useful,
    11   * but WITHOUT ANY WARRANTY; without even the implied warranty of
    12   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    13   * GNU General Public License for more details.
    14   *
    15   * You should have received a copy of the GNU General Public License
    16   * along with this program.  If not, see <http://www.gnu.org/licenses/>.
    17   *
    18   */
    19  
    20  package configcore
    21  
    22  import (
    23  	"fmt"
    24  
    25  	"github.com/snapcore/snapd/overlord/configstate/config"
    26  	"github.com/snapcore/snapd/sysconfig"
    27  )
    28  
    29  type configHandler interface {
    30  	validate(config.ConfGetter) error
    31  	handle(config.ConfGetter, *fsOnlyContext) error
    32  	needsState() bool
    33  	flags() flags
    34  }
    35  
    36  // flags carries extra flags that influence how the handler is called.
    37  type flags struct {
    38  	// coreOnlyConfig tells Run/FilesystemOnlyApply to apply the config on core
    39  	// systems only.
    40  	coreOnlyConfig bool
    41  	// validatedOnlyStateConfig tells that the config requires only validation,
    42  	// its options are applied dynamically elsewhere.
    43  	validatedOnlyStateConfig bool
    44  	// earlyConfigFilter expresses whether the handler supports
    45  	// any early configuration options (that can and must be
    46  	// set before even seeding is finished).
    47  	// If set the function should copy such options from values
    48  	// to early.
    49  	earlyConfigFilter filterFunc
    50  }
    51  
    52  type fsOnlyHandler struct {
    53  	validateFunc func(config.ConfGetter) error
    54  	handleFunc   func(config.ConfGetter, *fsOnlyContext) error
    55  	configFlags  flags
    56  }
    57  
    58  var handlers []configHandler
    59  
    60  func init() {
    61  	// Most of these handlers are no-op on classic.
    62  	// TODO: consider allowing some of these on classic too?
    63  	// consider erroring on core-only options on classic?
    64  
    65  	coreOnly := &flags{coreOnlyConfig: true}
    66  
    67  	// watchdog.{runtime-timeout,shutdown-timeout}
    68  	addFSOnlyHandler(validateWatchdogOptions, handleWatchdogConfiguration, coreOnly)
    69  
    70  	// Export experimental.* flags to a place easily accessible from snapd helpers.
    71  	addFSOnlyHandler(validateExperimentalSettings, doExportExperimentalFlags, &flags{earlyConfigFilter: earlyExperimentalSettingsFilter})
    72  
    73  	// network.disable-ipv6
    74  	addFSOnlyHandler(validateNetworkSettings, handleNetworkConfiguration, coreOnly)
    75  
    76  	// service.*.disable
    77  	addFSOnlyHandler(nil, handleServiceDisableConfiguration, coreOnly)
    78  
    79  	// system.power-key-action
    80  	addFSOnlyHandler(nil, handlePowerButtonConfiguration, coreOnly)
    81  
    82  	// pi-config.*
    83  	addFSOnlyHandler(nil, handlePiConfiguration, coreOnly)
    84  
    85  	// system.disable-backlight-service
    86  	addFSOnlyHandler(validateBacklightServiceSettings, handleBacklightServiceConfiguration, coreOnly)
    87  
    88  	// swap.size
    89  	addFSOnlyHandler(validateSystemSwapConfiguration, handlesystemSwapConfiguration, coreOnly)
    90  
    91  	// system.kernel.printk.console-loglevel
    92  	addFSOnlyHandler(validateSysctlOptions, handleSysctlConfiguration, coreOnly)
    93  
    94  	// journal.persistent
    95  	addFSOnlyHandler(validateJournalSettings, handleJournalConfiguration, coreOnly)
    96  
    97  	// system.timezone
    98  	addFSOnlyHandler(validateTimezoneSettings, handleTimezoneConfiguration, coreOnly)
    99  
   100  	sysconfig.ApplyFilesystemOnlyDefaultsImpl = func(rootDir string, defaults map[string]interface{}, options *sysconfig.FilesystemOnlyApplyOptions) error {
   101  		return filesystemOnlyApply(rootDir, defaults, options)
   102  	}
   103  }
   104  
   105  // addFSOnlyHandler registers functions to validate and handle a subset of
   106  // system config options that do not require to manipulate state but only
   107  // the file system.
   108  func addFSOnlyHandler(validate func(config.ConfGetter) error, handle func(config.ConfGetter, *fsOnlyContext) error, flags *flags) {
   109  	if handle == nil {
   110  		panic("cannot have nil handle with fsOnlyHandler")
   111  	}
   112  	h := &fsOnlyHandler{
   113  		validateFunc: validate,
   114  		handleFunc:   handle,
   115  	}
   116  	if flags != nil {
   117  		h.configFlags = *flags
   118  	}
   119  	handlers = append(handlers, h)
   120  }
   121  
   122  func (h *fsOnlyHandler) needsState() bool {
   123  	return false
   124  }
   125  
   126  func (h *fsOnlyHandler) flags() flags {
   127  	return h.configFlags
   128  }
   129  
   130  func (h *fsOnlyHandler) validate(cfg config.ConfGetter) error {
   131  	if h.validateFunc != nil {
   132  		return h.validateFunc(cfg)
   133  	}
   134  	return nil
   135  }
   136  
   137  func (h *fsOnlyHandler) handle(cfg config.ConfGetter, opts *fsOnlyContext) error {
   138  	// handleFunc is guaranteed to be non-nil by addFSOnlyHandler
   139  	return h.handleFunc(cfg, opts)
   140  }
   141  
   142  // filesystemOnlyApply applies filesystem modifications under rootDir, according to the
   143  // cfg configuration. This is a subset of core config options that is important
   144  // early during boot, before all the configuration is applied as part of
   145  // normal execution of configure hook.
   146  // Exposed for use via sysconfig.ApplyFilesystemOnlyDefaults.
   147  func filesystemOnlyApply(rootDir string, values map[string]interface{}, opts *sysconfig.FilesystemOnlyApplyOptions) error {
   148  	if rootDir == "" {
   149  		return fmt.Errorf("internal error: root directory for configcore.FilesystemOnlyApply() not set")
   150  	}
   151  
   152  	if opts == nil {
   153  		opts = &sysconfig.FilesystemOnlyApplyOptions{}
   154  	}
   155  
   156  	cfg := plainCoreConfig(values)
   157  
   158  	ctx := &fsOnlyContext{
   159  		RootDir: rootDir,
   160  	}
   161  	for _, h := range handlers {
   162  		if h.needsState() {
   163  			continue
   164  		}
   165  		if err := h.validate(cfg); err != nil {
   166  			return err
   167  		}
   168  	}
   169  
   170  	for _, h := range handlers {
   171  		if h.needsState() {
   172  			continue
   173  		}
   174  		if h.flags().coreOnlyConfig && opts != nil && opts.Classic {
   175  			continue
   176  		}
   177  		if err := h.handle(cfg, ctx); err != nil {
   178  			return err
   179  		}
   180  	}
   181  	return nil
   182  }