utils: add gsmtap_logread.py a gsmtap log reader

Receive gsmtap logs and feeds it into the python logging
framework. Allows to use generic logging features and
further utilities.

Change-Id: I24478d8e16066c6118e867bdba54c6418c15e170

2 files changed, 167 insertions, 0 deletions

diff --git a/utils/gsmtap.py b/utils/gsmtap.py
new file mode 100644
index 00000000..b7211adf
--- /dev/null
+++ b/utils/gsmtap.py
@@ -0,0 +1,75 @@
+#!/usr/bin/env python
+# License: MIT
+# Copyright 2019 by Sysmocom s.f.m.c. GmbH
+# Author: Alexander Couzens <lynxis@fe80.eu>
+
+import struct
+
+GSMTAP_VERSION = 0x02
+
+GSMTAP_TYPE_OSMOCORE_LOG = 0x10
+
+class TooSmall(RuntimeError):
+    pass
+
+# struct gsmtap_hdr {
+#     uint8_t version;    /*!< version, set to 0x01 currently */
+#     uint8_t hdr_len;    /*!< length in number of 32bit words */
+#     uint8_t type;       /*!< see GSMTAP_TYPE_* */
+#     uint8_t timeslot;   /*!< timeslot (0..7 on Um) */
+#
+#     uint16_t arfcn;     /*!< ARFCN (frequency) */
+#     int8_t signal_dbm;  /*!< signal level in dBm */
+#     int8_t snr_db;      /*!< signal/noise ratio in dB */
+#
+#     uint32_t frame_number;  /*!< GSM Frame Number (FN) */
+#
+#     uint8_t sub_type;   /*!< Type of burst/channel, see above */
+#     uint8_t antenna_nr; /*!< Antenna Number */
+#     uint8_t sub_slot;   /*!< sub-slot within timeslot */
+#     uint8_t res;        /*!< reserved for future use (RFU) */
+#
+# }
+
+class gsmtap_hdr():
+    def __init__(self, data):
+        if len(data) < 2:
+            raise TooSmall()
+        self.version, self.hdr_len = struct.unpack('!BB', data[0:2])
+        self.hdr_len *= 4
+
+        if self.hdr_len >= 3:
+            self.type = struct.unpack('!B', data[2:3])[0]
+
+# /*! Structure of the GSMTAP libosmocore logging header */
+# struct gsmtap_osmocore_log_hdr {
+# 	struct {
+# 		uint32_t sec;
+# 		uint32_t usec;
+# 	} ts;
+# 	char proc_name[16];	/*!< name of process */
+# 	uint32_t pid;		/*!< process ID */
+# 	uint8_t level;		/*!< logging level */
+# 	uint8_t _pad[3];
+# 	/* TODO: color */
+# 	char subsys[16];	/*!< logging sub-system */
+# 	struct {
+# 		char name[32];	/*!< source file name */
+# 		uint32_t line_nr;/*!< line number */
+# 	} src_file;
+# } __attribute__((packed));
+
+class gsmtap_log():
+    def __init__(self, data):
+        packformat = '!II16sIBxxx16s32sI'
+        packlen = struct.calcsize(packformat)
+        if len(data) < packlen:
+            raise TooSmall()
+        self.sec, self.usec, \
+                self.proc_name, self.pid, \
+                self.level, self.subsys, \
+                self.filename, self.fileline_nr = struct.unpack(packformat, data[:packlen])
+
+        message_len = len(data) - packlen
+        if message_len > 0:
+            self.message = data[packlen:].decode('utf-8')
diff --git a/utils/gsmtap_logread.py b/utils/gsmtap_logread.py
new file mode 100644
index 00000000..a29f1491
--- /dev/null
+++ b/utils/gsmtap_logread.py
@@ -0,0 +1,92 @@
+#!/usr/bin/env python
+#
+# License: MIT
+# Copyright 2019 by Sysmocom s.f.m.c. GmbH
+# Author: Alexander Couzens <lynxis@fe80.eu>
+
+import logging
+import socket
+
+from gsmtap import GSMTAP_TYPE_OSMOCORE_LOG, gsmtap_hdr, gsmtap_log, TooSmall
+
+LOG = logging.getLogger("gsmlogreader")
+
+def parse_gsm(packet):
+    hdr = None
+
+    try:
+        hdr = gsmtap_hdr(packet)
+    except TooSmall:
+        return None
+
+    if hdr.type != GSMTAP_TYPE_OSMOCORE_LOG:
+        return None
+
+    if len(packet) <= hdr.hdr_len:
+        return None
+
+    try:
+        return gsmtap_log(packet[hdr.hdr_len:])
+    except TooSmall:
+        return None
+
+def gsmtaplevel_to_loglevel(level):
+    """ convert a gsmtap log level into a python log level """
+    if level <= 1:
+        return logging.DEBUG
+    if level <= 3:
+        return logging.INFO
+    if level <= 5:
+        return logging.WARNING
+
+    return logging.ERROR
+
+def convert_gsmtap_log(gsmtap):
+    level = gsmtaplevel_to_loglevel(gsmtap.level)
+
+    attr = {
+        "name": "gsmtap",
+        "levelno": level,
+        "levelname": gsmtap_get_logname(gsmtap.level),
+        "pathname": gsmtap.filename,
+        "lineno": gsmtap.fileline_nr,
+        "processName": gsmtap.proc_name,
+        "process": gsmtap.pid,
+        "module": gsmtap.subsys,
+        "created": float(gsmtap.sec + gsmtap.usec / 1000000.0),
+        "msec": int(gsmtap.usec / 1000),
+        "msg": gsmtap.message.replace('\n', ' '),
+        }
+    return attr
+
+def gsmtap_get_logname(level):
+    names = {
+        1: "DEBUG",
+        3: "INFO",
+        5: "NOTICE",
+        7: "ERROR",
+        8: "FATAL",
+        }
+    if level in names:
+        return names[level]
+    return "UNKNOWN"
+
+if __name__ == "__main__":
+    # Create a UDP socket
+    sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+    server_address = ('0.0.0.0', 4729)
+    sock.bind(server_address)
+
+    logger = logging.getLogger("gsmtap")
+    logformat = "%(asctime)s %(message)s"
+    logging.basicConfig(format=logformat, level=logging.DEBUG)
+
+
+    while True:
+        data, address = sock.recvfrom(4096)
+        log = parse_gsm(data)
+        if not log:
+            continue
+
+        record = logging.makeLogRecord(convert_gsmtap_log(log))
+        logger.handle(record)