github.com/hugh712/snapd@v0.0.0-20200910133618-1a99902bd583/overlord/configstate/configcore/sysctl.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  	"bytes"
    24  	"fmt"
    25  	"path/filepath"
    26  	"strconv"
    27  
    28  	"github.com/snapcore/snapd/dirs"
    29  	"github.com/snapcore/snapd/osutil"
    30  	"github.com/snapcore/snapd/overlord/configstate/config"
    31  	"github.com/snapcore/snapd/systemd"
    32  )
    33  
    34  // see https://www.kernel.org/doc/Documentation/sysctl/kernel.txt
    35  // The idea is that options of the form system.kernel. should
    36  // match the (/proc/)sys/kernel hierarchy etc.
    37  
    38  func init() {
    39  	// add supported configuration of this module
    40  	supportedConfigurations["core.system.kernel.printk.console-loglevel"] = true
    41  }
    42  
    43  const (
    44  	sysctlConfsDir  = "/etc/sysctl.d"
    45  	snapdSysctlConf = "99-snapd.conf"
    46  )
    47  
    48  // these are the sysctl parameters prefixes we handle
    49  var sysctlPrefixes = []string{"kernel.printk"}
    50  
    51  func validateSysctlOptions(tr config.ConfGetter) error {
    52  	consoleLoglevelStr, err := coreCfg(tr, "system.kernel.printk.console-loglevel")
    53  	if err != nil {
    54  		return err
    55  	}
    56  	if consoleLoglevelStr != "" {
    57  		if n, err := strconv.ParseUint(consoleLoglevelStr, 10, 8); err != nil || (n < 0 || n > 7) {
    58  			return fmt.Errorf("console-loglevel must be a number between 0 and 7, not: %s", consoleLoglevelStr)
    59  		}
    60  	}
    61  	return nil
    62  }
    63  
    64  func handleSysctlConfiguration(tr config.ConfGetter, opts *fsOnlyContext) error {
    65  	root := dirs.GlobalRootDir
    66  	if opts != nil {
    67  		root = opts.RootDir
    68  	}
    69  
    70  	consoleLoglevelStr, err := coreCfg(tr, "system.kernel.printk.console-loglevel")
    71  	if err != nil {
    72  		return nil
    73  	}
    74  
    75  	content := bytes.NewBuffer(nil)
    76  	if consoleLoglevelStr != "" {
    77  		content.WriteString(fmt.Sprintf("kernel.printk = %s 4 1 7\n", consoleLoglevelStr))
    78  	} else {
    79  		// Don't write values to content so that the config
    80  		// file gets removed and console-loglevel gets reset
    81  		// to default value from 10-console-messages.conf
    82  
    83  		// TODO: this logic will need more non-obvious work to support
    84  		// kernel parameters that don't have already on-disk defaults.
    85  	}
    86  	dirContent := map[string]osutil.FileState{}
    87  	if content.Len() > 0 {
    88  		dirContent[snapdSysctlConf] = &osutil.MemoryFileState{
    89  			Content: content.Bytes(),
    90  			Mode:    0644,
    91  		}
    92  	}
    93  
    94  	// write the new config
    95  	dir := filepath.Join(root, sysctlConfsDir)
    96  	glob := snapdSysctlConf
    97  	changed, removed, err := osutil.EnsureDirState(dir, glob, dirContent)
    98  	if err != nil {
    99  		return err
   100  	}
   101  
   102  	if opts == nil {
   103  		if len(changed) > 0 || len(removed) > 0 {
   104  			// apply our configuration or default configuration
   105  			// via systemd-sysctl for the relevant prefixes
   106  			return systemd.Sysctl(sysctlPrefixes)
   107  		}
   108  	}
   109  
   110  	return nil
   111  }