rtc watchdog for v3

1 files changed, 119 insertions, 0 deletions

diff --git a/kvmd/apps/watchdog/__init__.py b/kvmd/apps/watchdog/__init__.py
new file mode 100644
index 00000000..0caa39a6
--- /dev/null
+++ b/kvmd/apps/watchdog/__init__.py
@@ -0,0 +1,119 @@
+# ========================================================================== #
+#                                                                            #
+#    KVMD - The main PiKVM daemon.                                           #
+#                                                                            #
+#    Copyright (C) 2018-2021  Maxim Devaev <[email protected]>               #
+#                                                                            #
+#    This program is free software: you can redistribute it and/or modify    #
+#    it under the terms of the GNU General Public License as published by    #
+#    the Free Software Foundation, either version 3 of the License, or       #
+#    (at your option) any later version.                                     #
+#                                                                            #
+#    This program is distributed in the hope that it will be useful,         #
+#    but WITHOUT ANY WARRANTY; without even the implied warranty of          #
+#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the           #
+#    GNU General Public License for more details.                            #
+#                                                                            #
+#    You should have received a copy of the GNU General Public License       #
+#    along with this program.  If not, see <https://www.gnu.org/licenses/>.  #
+#                                                                            #
+# ========================================================================== #
+
+
+import argparse
+import errno
+import time
+
+from typing import List
+from typing import Optional
+
+from ...logging import get_logger
+
+from ...yamlconf import Section
+
+from ... import env
+
+from .. import init
+
+
+# =====
+class RtcIsNotAvailableError(Exception):
+    pass
+
+
+# =====
+def _join_rtc(device: int, key: str) -> str:
+    return f"{env.SYSFS_PREFIX}/sys/class/rtc/rtc{device}/{key}"
+
+
+def _read_int(device: int, key: str) -> int:
+    with open(_join_rtc(device, key)) as value_file:
+        return int(value_file.read().strip() or "0")
+
+
+def _write_int(device: int, key: str, value: int) -> None:
+    with open(_join_rtc(device, key), "w") as value_file:
+        value_file.write(str(value))
+
+
+def _reset_alarm(device: int, timeout: int) -> None:
+    now = _read_int(device, "since_epoch")
+    if now == 0:
+        raise RtcIsNotAvailableError("Current UNIX time == 0")
+    try:
+        for wake in [0, now + timeout]:
+            _write_int(device, "wakealarm", wake)
+    except OSError as err:
+        if err.errno != errno.EIO:
+            raise
+        raise RtcIsNotAvailableError("IO error, probably the supercapacitor is not charged")
+
+
+# =====
+def _cmd_run(config: Section) -> None:
+    logger = get_logger(0)
+    logger.info("Running watchdog loop on RTC%d ...", config.device)
+    fail = False
+    try:
+        while True:
+            try:
+                _reset_alarm(config.device, config.timeout)
+            except RtcIsNotAvailableError as err:
+                if not fail:
+                    logger.error("RTC%d is not available now: %s; waiting ...", config.device, err)
+                    fail = True
+            else:
+                if fail:
+                    logger.info("RTC%d is available, working ...", config.device)
+                    fail = False
+            time.sleep(config.interval)
+    except (SystemExit, KeyboardInterrupt):
+        if not fail:
+            _reset_alarm(config.device, config.timeout)
+            logger.info("The watchdog remains alarmed. Use 'kvmd-watchdog cancel' to disarm it")
+    logger.info("Bye-bye")
+
+
+def _cmd_cancel(config: Section) -> None:
+    _write_int(config.device, "wakealarm", 0)
+
+
+# =====
+def main(argv: Optional[List[str]]=None) -> None:
+    (parent_parser, argv, config) = init(add_help=False, argv=argv)
+    parser = argparse.ArgumentParser(
+        prog="kvmd-watchdog",
+        description="RTC-based hardware watchdog",
+        parents=[parent_parser],
+    )
+    parser.set_defaults(cmd=(lambda *_: parser.print_help()))
+    subparsers = parser.add_subparsers()
+
+    cmd_run_parser = subparsers.add_parser("run", help="Run watchdog loop")
+    cmd_run_parser.set_defaults(cmd=_cmd_run)
+
+    cmd_cancel_parser = subparsers.add_parser("cancel", help="Cancel armed timeout")
+    cmd_cancel_parser.set_defaults(cmd=_cmd_cancel)
+
+    options = parser.parse_args(argv[1:])
+    options.cmd(config.watchdog)