github.com/ethanhsieh/snapd@v0.0.0-20210615102523-3db9b8e4edc5/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  	"os"
    26  	"path/filepath"
    27  	"strconv"
    28  
    29  	"github.com/snapcore/snapd/dirs"
    30  	"github.com/snapcore/snapd/osutil"
    31  	"github.com/snapcore/snapd/overlord/configstate/config"
    32  	"github.com/snapcore/snapd/systemd"
    33  )
    34  
    35  // see https://www.kernel.org/doc/Documentation/sysctl/kernel.txt
    36  // The idea is that options of the form system.kernel. should
    37  // match the (/proc/)sys/kernel hierarchy etc.
    38  
    39  func init() {
    40  	// add supported configuration of this module
    41  	supportedConfigurations["core.system.kernel.printk.console-loglevel"] = true
    42  }
    43  
    44  const (
    45  	sysctlConfsDir  = "/etc/sysctl.d"
    46  	snapdSysctlConf = "99-snapd.conf"
    47  )
    48  
    49  // these are the sysctl parameters prefixes we handle
    50  var sysctlPrefixes = []string{"kernel.printk"}
    51  
    52  func validateSysctlOptions(tr config.ConfGetter) error {
    53  	consoleLoglevelStr, err := coreCfg(tr, "system.kernel.printk.console-loglevel")
    54  	if err != nil {
    55  		return err
    56  	}
    57  	if consoleLoglevelStr != "" {
    58  		if n, err := strconv.ParseUint(consoleLoglevelStr, 10, 8); err != nil || (n < 0 || n > 7) {
    59  			return fmt.Errorf("console-loglevel must be a number between 0 and 7, not: %s", consoleLoglevelStr)
    60  		}
    61  	}
    62  	return nil
    63  }
    64  
    65  func handleSysctlConfiguration(tr config.ConfGetter, opts *fsOnlyContext) error {
    66  	root := dirs.GlobalRootDir
    67  	if opts != nil {
    68  		root = opts.RootDir
    69  	}
    70  
    71  	consoleLoglevelStr, err := coreCfg(tr, "system.kernel.printk.console-loglevel")
    72  	if err != nil {
    73  		return nil
    74  	}
    75  
    76  	content := bytes.NewBuffer(nil)
    77  	if consoleLoglevelStr != "" {
    78  		content.WriteString(fmt.Sprintf("kernel.printk = %s 4 1 7\n", consoleLoglevelStr))
    79  	} else {
    80  		// Don't write values to content so that the config
    81  		// file gets removed and console-loglevel gets reset
    82  		// to default value from 10-console-messages.conf
    83  
    84  		// TODO: this logic will need more non-obvious work to support
    85  		// kernel parameters that don't have already on-disk defaults.
    86  	}
    87  	dirContent := map[string]osutil.FileState{}
    88  	if content.Len() > 0 {
    89  		dirContent[snapdSysctlConf] = &osutil.MemoryFileState{
    90  			Content: content.Bytes(),
    91  			Mode:    0644,
    92  		}
    93  	}
    94  
    95  	dir := filepath.Join(root, sysctlConfsDir)
    96  	if opts != nil {
    97  		if err := os.MkdirAll(dir, 0755); err != nil {
    98  			return err
    99  		}
   100  	}
   101  
   102  	// write the new config
   103  	glob := snapdSysctlConf
   104  	changed, removed, err := osutil.EnsureDirState(dir, glob, dirContent)
   105  	if err != nil {
   106  		return err
   107  	}
   108  
   109  	if opts == nil {
   110  		if len(changed) > 0 || len(removed) > 0 {
   111  			// apply our configuration or default configuration
   112  			// via systemd-sysctl for the relevant prefixes
   113  			return systemd.Sysctl(sysctlPrefixes)
   114  		}
   115  	}
   116  
   117  	return nil
   118  }