sslobodr | d046be8 | 2019-01-16 10:02:22 -0500 | [diff] [blame] | 1 | // Copyright 2015 CoreOS, Inc. |
| 2 | // |
| 3 | // Licensed under the Apache License, Version 2.0 (the "License"); |
| 4 | // you may not use this file except in compliance with the License. |
| 5 | // You may obtain a copy of the License at |
| 6 | // |
| 7 | // http://www.apache.org/licenses/LICENSE-2.0 |
| 8 | // |
| 9 | // Unless required by applicable law or agreed to in writing, software |
| 10 | // distributed under the License is distributed on an "AS IS" BASIS, |
| 11 | // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 12 | // See the License for the specific language governing permissions and |
| 13 | // limitations under the License. |
| 14 | |
| 15 | // Package journal provides write bindings to the local systemd journal. |
| 16 | // It is implemented in pure Go and connects to the journal directly over its |
| 17 | // unix socket. |
| 18 | // |
| 19 | // To read from the journal, see the "sdjournal" package, which wraps the |
| 20 | // sd-journal a C API. |
| 21 | // |
| 22 | // http://www.freedesktop.org/software/systemd/man/systemd-journald.service.html |
| 23 | package journal |
| 24 | |
| 25 | import ( |
| 26 | "bytes" |
| 27 | "encoding/binary" |
| 28 | "errors" |
| 29 | "fmt" |
| 30 | "io" |
| 31 | "io/ioutil" |
| 32 | "net" |
| 33 | "os" |
| 34 | "strconv" |
| 35 | "strings" |
| 36 | "syscall" |
| 37 | ) |
| 38 | |
| 39 | // Priority of a journal message |
| 40 | type Priority int |
| 41 | |
| 42 | const ( |
| 43 | PriEmerg Priority = iota |
| 44 | PriAlert |
| 45 | PriCrit |
| 46 | PriErr |
| 47 | PriWarning |
| 48 | PriNotice |
| 49 | PriInfo |
| 50 | PriDebug |
| 51 | ) |
| 52 | |
| 53 | var conn net.Conn |
| 54 | |
| 55 | func init() { |
| 56 | var err error |
| 57 | conn, err = net.Dial("unixgram", "/run/systemd/journal/socket") |
| 58 | if err != nil { |
| 59 | conn = nil |
| 60 | } |
| 61 | } |
| 62 | |
| 63 | // Enabled returns true if the local systemd journal is available for logging |
| 64 | func Enabled() bool { |
| 65 | return conn != nil |
| 66 | } |
| 67 | |
| 68 | // Send a message to the local systemd journal. vars is a map of journald |
| 69 | // fields to values. Fields must be composed of uppercase letters, numbers, |
| 70 | // and underscores, but must not start with an underscore. Within these |
| 71 | // restrictions, any arbitrary field name may be used. Some names have special |
| 72 | // significance: see the journalctl documentation |
| 73 | // (http://www.freedesktop.org/software/systemd/man/systemd.journal-fields.html) |
| 74 | // for more details. vars may be nil. |
| 75 | func Send(message string, priority Priority, vars map[string]string) error { |
| 76 | if conn == nil { |
| 77 | return journalError("could not connect to journald socket") |
| 78 | } |
| 79 | |
| 80 | data := new(bytes.Buffer) |
| 81 | appendVariable(data, "PRIORITY", strconv.Itoa(int(priority))) |
| 82 | appendVariable(data, "MESSAGE", message) |
| 83 | for k, v := range vars { |
| 84 | appendVariable(data, k, v) |
| 85 | } |
| 86 | |
| 87 | _, err := io.Copy(conn, data) |
| 88 | if err != nil && isSocketSpaceError(err) { |
| 89 | file, err := tempFd() |
| 90 | if err != nil { |
| 91 | return journalError(err.Error()) |
| 92 | } |
| 93 | defer file.Close() |
| 94 | _, err = io.Copy(file, data) |
| 95 | if err != nil { |
| 96 | return journalError(err.Error()) |
| 97 | } |
| 98 | |
| 99 | rights := syscall.UnixRights(int(file.Fd())) |
| 100 | |
| 101 | /* this connection should always be a UnixConn, but better safe than sorry */ |
| 102 | unixConn, ok := conn.(*net.UnixConn) |
| 103 | if !ok { |
| 104 | return journalError("can't send file through non-Unix connection") |
| 105 | } |
| 106 | _, _, err = unixConn.WriteMsgUnix([]byte{}, rights, nil) |
| 107 | if err != nil { |
| 108 | return journalError(err.Error()) |
| 109 | } |
| 110 | } else if err != nil { |
| 111 | return journalError(err.Error()) |
| 112 | } |
| 113 | return nil |
| 114 | } |
| 115 | |
| 116 | // Print prints a message to the local systemd journal using Send(). |
| 117 | func Print(priority Priority, format string, a ...interface{}) error { |
| 118 | return Send(fmt.Sprintf(format, a...), priority, nil) |
| 119 | } |
| 120 | |
| 121 | func appendVariable(w io.Writer, name, value string) { |
| 122 | if err := validVarName(name); err != nil { |
| 123 | journalError(err.Error()) |
| 124 | } |
| 125 | if strings.ContainsRune(value, '\n') { |
| 126 | /* When the value contains a newline, we write: |
| 127 | * - the variable name, followed by a newline |
| 128 | * - the size (in 64bit little endian format) |
| 129 | * - the data, followed by a newline |
| 130 | */ |
| 131 | fmt.Fprintln(w, name) |
| 132 | binary.Write(w, binary.LittleEndian, uint64(len(value))) |
| 133 | fmt.Fprintln(w, value) |
| 134 | } else { |
| 135 | /* just write the variable and value all on one line */ |
| 136 | fmt.Fprintf(w, "%s=%s\n", name, value) |
| 137 | } |
| 138 | } |
| 139 | |
| 140 | // validVarName validates a variable name to make sure it journald will accept it. |
| 141 | // The variable name must be in uppercase and consist only of characters, |
| 142 | // numbers and underscores, and may not begin with an underscore. (from the docs) |
| 143 | // https://www.freedesktop.org/software/systemd/man/sd_journal_print.html |
| 144 | func validVarName(name string) error { |
| 145 | if name == "" { |
| 146 | return errors.New("Empty variable name") |
| 147 | } else if name[0] == '_' { |
| 148 | return errors.New("Variable name begins with an underscore") |
| 149 | } |
| 150 | |
| 151 | for _, c := range name { |
| 152 | if !(('A' <= c && c <= 'Z') || ('0' <= c && c <= '9') || c == '_') { |
| 153 | return errors.New("Variable name contains invalid characters") |
| 154 | } |
| 155 | } |
| 156 | return nil |
| 157 | } |
| 158 | |
| 159 | func isSocketSpaceError(err error) bool { |
| 160 | opErr, ok := err.(*net.OpError) |
| 161 | if !ok { |
| 162 | return false |
| 163 | } |
| 164 | |
| 165 | sysErr, ok := opErr.Err.(syscall.Errno) |
| 166 | if !ok { |
| 167 | return false |
| 168 | } |
| 169 | |
| 170 | return sysErr == syscall.EMSGSIZE || sysErr == syscall.ENOBUFS |
| 171 | } |
| 172 | |
| 173 | func tempFd() (*os.File, error) { |
| 174 | file, err := ioutil.TempFile("/dev/shm/", "journal.XXXXX") |
| 175 | if err != nil { |
| 176 | return nil, err |
| 177 | } |
| 178 | err = syscall.Unlink(file.Name()) |
| 179 | if err != nil { |
| 180 | return nil, err |
| 181 | } |
| 182 | return file, nil |
| 183 | } |
| 184 | |
| 185 | func journalError(s string) error { |
| 186 | s = "journal error: " + s |
| 187 | fmt.Fprintln(os.Stderr, s) |
| 188 | return errors.New(s) |
| 189 | } |