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119 lines
4.8 KiB
Python
Executable file
119 lines
4.8 KiB
Python
Executable file
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# This module "prints" log messages to UDP broadcasts to port 514.
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from helpers import prettyMac
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from configmodule import getConfigValue, getConfigValueBool
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class udplog():
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def fillMac(self, macbytearray, position=6): # position 6 is the source MAC
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for i in range(0, 6):
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self.EthTxFrame[6+i] = macbytearray[i]
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def log(self, s, purpose=""):
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# return # activate this line to disable the logging completely
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#
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# The frame format follows the Syslog protocol, https://en.wikipedia.org/wiki/Syslog
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# Level consists of
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# Facility = 1 = "user"
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# Severity = 7 = "debug"
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# print("[UDPLOG] Logging " + s)
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if (purpose==""):
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if (not self.isUpdSyslogEnabled):
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# If no special purpose, and the logging is disabled, we stop here.
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return
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# Logging is not suppressed, so continue to construct the message:
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strLevel="<15>"
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# The String to be logged. Terminated by 00.
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if (len(s)>700):
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s = s[0:700] # Limit the length. Too long messages crash the transmit. Todo: Find out the real limit.
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strMessage=s+"\0"
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lenPayLoad = 4 + len(strMessage) # length of level is 4
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buffer=bytearray(lenPayLoad+28) # prepare the IPv4 buffer. Including 28 bytes IP header.
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# syslog level (4 characters)
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for i in range(0, len(strLevel)):
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buffer[28+i] = ord(strLevel[i])
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# the message, terminated by 00
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for i in range(0, len(strMessage)):
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buffer[32+i] = ord(strMessage[i])
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buffer[0] = 0x45 # IP header len
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buffer[1] = 0
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iplen=len(buffer) # including IP header and all payload
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buffer[2] = iplen >> 8
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buffer[3] = (iplen & 0xff)
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ipid = 0x8a9f
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buffer[4] = ipid >> 8
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buffer[5] = (ipid & 0xff)
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fragoffset = 0
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buffer[6] = fragoffset >> 8
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buffer[7] = (fragoffset & 0xff)
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buffer[8] = 0x80 # ttl
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buffer[9] = 0x11 # proto
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checksum = 0
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buffer[10] = checksum >> 8
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buffer[11] = (checksum & 0xff)
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# source ip 4 bytes
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buffer[12] = 192 # does this really matter?
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buffer[13] = 168
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buffer[14] = self.ownMac[4] # quick&dirty: we just fill the last two bytes of the MAC here.
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buffer[15] = self.ownMac[5] #
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# destination ip 4 bytes: broadcast
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buffer[16] = 0xff
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buffer[17] = 0xff
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buffer[18] = 0xff
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buffer[19] = 0xff
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# source port
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buffer[20] = 0xff
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buffer[21] = 0x95
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# destination port. 0x0202 = 514 = the official Syslog UDP port
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buffer[22] = 0x02
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buffer[23] = 0x02
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udplen = lenPayLoad + 8 # payload plus 8 byte udp header
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buffer[24] = udplen >> 8
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buffer[25] = (udplen & 0xff)
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udpchecksum = 0 # checksum 0 has the special meaning: no checksum. Receiver ignores it.
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buffer[26] = udpchecksum >> 8
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buffer[27] = (udpchecksum & 0xff)
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# packs the IP packet into an ethernet packet
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self.EthTxFrame = bytearray(len(buffer) + 6 + 6 + 2) # Ethernet header needs 14 bytes:
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# 6 bytes destination MAC
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# 6 bytes source MAC
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# 2 bytes EtherType
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# fill the destination MAC with broadcast MAC
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self.EthTxFrame[0] = 0xFF
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self.EthTxFrame[1] = 0xFF
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self.EthTxFrame[2] = 0xFF
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self.EthTxFrame[3] = 0xFF
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self.EthTxFrame[4] = 0xFF
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self.EthTxFrame[5] = 0xFF
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self.fillMac(self.ownMac) # bytes 6 to 11 are the source MAC
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self.EthTxFrame[12] = 0x08 # 0800 is IPv4
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self.EthTxFrame[13] = 0x00
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for i in range(0, len(buffer)): # copy the IPv4 buffer content into the Ethernet buffer
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self.EthTxFrame[14+i] = buffer[i]
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self.transmit(self.EthTxFrame) # and finally transmit the Ethernet frame
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def __init__(self, transmitCallback, addressManager):
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self.transmit = transmitCallback
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self.addressManager = addressManager
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self.ownMac = self.addressManager.getLocalMacAddress()
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print("udplog started with ownMac " + prettyMac(self.ownMac))
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self.isUpdSyslogEnabled = getConfigValueBool("udp_syslog_enable")
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if (self.isUpdSyslogEnabled):
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print("logging to UDP Syslog is enabled")
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else:
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print("logging to UDP Syslog is disabled")
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def udplog_init(transmitCallback, addressManager):
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global udplogger
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udplogger = udplog(transmitCallback, addressManager) # create a global logger object
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def udplog_log(s, purpose=""):
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global udplogger
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udplogger.log(s, purpose) |