| 1 | package cgroup |
| 2 | |
| 3 | import ( |
| 4 | "bufio" |
| 5 | "errors" |
| 6 | "fmt" |
| 7 | "os" |
| 8 | "path/filepath" |
| 9 | "strings" |
| 10 | ) |
| 11 | |
| 12 | // hostProcsMaxDepth bounds the walk below a host's cgroup. The platform |
| 13 | // nests at most a few levels (exec group, role child, generation); a tree |
| 14 | // deeper than this is not one it made, and is reported rather than walked. |
| 15 | const hostProcsMaxDepth = 16 |
| 16 | |
| 17 | func hostProcs(root, host, unit string) (int, error) { |
| 18 | if root == "" { |
| 19 | return 0, ErrUnknown |
| 20 | } |
| 21 | if host == "" || strings.ContainsAny(host, "/\x00") || host == "." || host == ".." { |
| 22 | return 0, fmt.Errorf("cgroup: %q is not a host name", host) |
| 23 | } |
| 24 | n, err := countProcs(filepath.Join(root, ExecName(host)), 0) |
| 25 | if err != nil { |
| 26 | return 0, err |
| 27 | } |
| 28 | if unit != "" { |
| 29 | if !filepath.IsAbs(unit) { |
| 30 | return 0, fmt.Errorf("cgroup: the unit cgroup %q is not an absolute path", unit) |
| 31 | } |
| 32 | m, err := countProcs(filepath.Clean(unit), 0) |
| 33 | if err != nil { |
| 34 | return 0, err |
| 35 | } |
| 36 | n += m |
| 37 | } |
| 38 | return n, nil |
| 39 | } |
| 40 | |
| 41 | // countProcs is the number of pids listed in dir's cgroup.procs and in every |
| 42 | // cgroup below it. An absent dir is 0. Symlinks are never followed: cgroupfs |
| 43 | // has none, so a link is not a cgroup. |
| 44 | func countProcs(dir string, depth int) (int, error) { |
| 45 | if depth > hostProcsMaxDepth { |
| 46 | return 0, fmt.Errorf("cgroup: %s is nested deeper than %d levels", dir, hostProcsMaxDepth) |
| 47 | } |
| 48 | st, err := os.Lstat(dir) |
| 49 | if errors.Is(err, os.ErrNotExist) { |
| 50 | return 0, nil |
| 51 | } |
| 52 | if err != nil { |
| 53 | return 0, err |
| 54 | } |
| 55 | if !st.IsDir() { |
| 56 | return 0, fmt.Errorf("cgroup: %s is not a cgroup directory", dir) |
| 57 | } |
| 58 | n, err := readProcsFile(filepath.Join(dir, "cgroup.procs")) |
| 59 | if err != nil { |
| 60 | return 0, err |
| 61 | } |
| 62 | ents, err := os.ReadDir(dir) |
| 63 | if errors.Is(err, os.ErrNotExist) { |
| 64 | return n, nil // removed while read: its processes are gone with it |
| 65 | } |
| 66 | if err != nil { |
| 67 | return 0, err |
| 68 | } |
| 69 | for _, e := range ents { |
| 70 | if !e.IsDir() || e.Type()&os.ModeSymlink != 0 { |
| 71 | continue |
| 72 | } |
| 73 | m, err := countProcs(filepath.Join(dir, e.Name()), depth+1) |
| 74 | if err != nil { |
| 75 | return 0, err |
| 76 | } |
| 77 | n += m |
| 78 | } |
| 79 | return n, nil |
| 80 | } |
| 81 | |
| 82 | // readProcsFile counts the non-empty lines of a cgroup.procs file. A file |
| 83 | // that is gone (the cgroup was removed between the listing and the read) |
| 84 | // lists nothing. |
| 85 | func readProcsFile(path string) (int, error) { |
| 86 | f, err := os.Open(path) |
| 87 | if errors.Is(err, os.ErrNotExist) { |
| 88 | return 0, nil |
| 89 | } |
| 90 | if err != nil { |
| 91 | return 0, err |
| 92 | } |
| 93 | defer f.Close() |
| 94 | n := 0 |
| 95 | sc := bufio.NewScanner(f) |
| 96 | for sc.Scan() { |
| 97 | if strings.TrimSpace(sc.Text()) != "" { |
| 98 | n++ |
| 99 | } |
| 100 | } |
| 101 | if err := sc.Err(); err != nil { |
| 102 | // A cgroup removed while it was read answers ENODEV. |
| 103 | if _, statErr := os.Stat(filepath.Dir(path)); errors.Is(statErr, os.ErrNotExist) { |
| 104 | return 0, nil |
| 105 | } |
| 106 | return 0, err |
| 107 | } |
| 108 | return n, nil |
| 109 | } |
| 110 | |
amadan