151 lines
3.4 KiB
Go
151 lines
3.4 KiB
Go
/*
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Copyright The containerd Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package cgroups
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import (
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"bufio"
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"fmt"
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"io"
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"os"
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"path/filepath"
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"strings"
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"sync"
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"golang.org/x/sys/unix"
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)
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var (
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nsOnce sync.Once
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inUserNS bool
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checkMode sync.Once
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cgMode CGMode
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)
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const unifiedMountpoint = "/sys/fs/cgroup"
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// CGMode is the cgroups mode of the host system
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type CGMode int
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const (
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// Unavailable cgroup mountpoint
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Unavailable CGMode = iota
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// Legacy cgroups v1
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Legacy
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// Hybrid with cgroups v1 and v2 controllers mounted
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Hybrid
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// Unified with only cgroups v2 mounted
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Unified
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)
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// Mode returns the cgroups mode running on the host
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func Mode() CGMode {
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checkMode.Do(func() {
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var st unix.Statfs_t
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if err := unix.Statfs(unifiedMountpoint, &st); err != nil {
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cgMode = Unavailable
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return
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}
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switch st.Type {
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case unix.CGROUP2_SUPER_MAGIC:
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cgMode = Unified
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default:
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cgMode = Legacy
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if err := unix.Statfs(filepath.Join(unifiedMountpoint, "unified"), &st); err != nil {
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return
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}
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if st.Type == unix.CGROUP2_SUPER_MAGIC {
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cgMode = Hybrid
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}
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}
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})
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return cgMode
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}
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// RunningInUserNS detects whether we are currently running in a user namespace.
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// Copied from github.com/lxc/lxd/shared/util.go
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func RunningInUserNS() bool {
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nsOnce.Do(func() {
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file, err := os.Open("/proc/self/uid_map")
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if err != nil {
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// This kernel-provided file only exists if user namespaces are supported
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return
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}
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defer file.Close()
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buf := bufio.NewReader(file)
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l, _, err := buf.ReadLine()
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if err != nil {
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return
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}
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line := string(l)
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var a, b, c int64
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fmt.Sscanf(line, "%d %d %d", &a, &b, &c)
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/*
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* We assume we are in the initial user namespace if we have a full
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* range - 4294967295 uids starting at uid 0.
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*/
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if a == 0 && b == 0 && c == 4294967295 {
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return
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}
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inUserNS = true
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})
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return inUserNS
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}
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// ParseCgroupFileUnified returns legacy subsystem paths as the first value,
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// and returns the unified path as the second value.
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func ParseCgroupFileUnified(path string) (map[string]string, string, error) {
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f, err := os.Open(path)
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if err != nil {
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return nil, "", err
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}
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defer f.Close()
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return ParseCgroupFromReaderUnified(f)
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}
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// ParseCgroupFromReaderUnified returns legacy subsystem paths as the first value,
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// and returns the unified path as the second value.
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func ParseCgroupFromReaderUnified(r io.Reader) (map[string]string, string, error) {
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var (
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cgroups = make(map[string]string)
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unified = ""
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s = bufio.NewScanner(r)
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)
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for s.Scan() {
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var (
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text = s.Text()
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parts = strings.SplitN(text, ":", 3)
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)
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if len(parts) < 3 {
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return nil, unified, fmt.Errorf("invalid cgroup entry: %q", text)
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}
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for _, subs := range strings.Split(parts[1], ",") {
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if subs == "" {
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unified = parts[2]
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} else {
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cgroups[subs] = parts[2]
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}
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}
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}
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if err := s.Err(); err != nil {
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return nil, unified, err
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}
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return cgroups, unified, nil
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}
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