Re: [Dnsmasq-discuss] Scripting with lua
On Wed, 15 May 2024 at 06:32, Geert Stappers wrote:
> I've followed that URL and had to click deeper.
> Now sharing the output of
> $ curl --silent
> https://raw.githubusercontent.com/whitepj/dnsmasq-lua/main/dhcp.lua
Thanks Geert.
Apologies -- it was my intention to keep the actual noise down to a
minimum. You can see from the script that the vast majority of it is
nothing more than comment.
The line that I am having the problem with is that which retrieves
that various variables.
I have tried:
a = (os.getenv("DNSMASQ_TIME_REMAINING") or "blank")
but this returns nothing at all. Since my knowledge of lua is far from
extensive, I'm hoping that someone may know what I'm doing wrong..
Many thanks.
> --[[
>
>LUA script for dnsmasq DHCP leases. Modified from original source at:
>http://lists.thekelleys.org/pipermail/dnsmasq-discuss/2012q1/005425.html
>This script is principally a boilerplate example, to show what is
> possible...
>Tested using dnsmasq v2.90
>
>Run when:
> - Startup (existing leases are invoked with 'old' event
> - SIGHUP ?
> - dhcp lease created, renewed, changed, or destroyed.
> - tftp file transfer completes (not tested)
>
>ENVIRONMENT VARIABLES
>=
> - DNSMASQ_DOMAIN
> - DNSMASQ_SUPPLIED_HOSTNAME
> - DNSMASQ_USER_CLASS0 ... _CLASSn
> - DNSMASQ_LEASE_LENGTH / DNSMASQ_LEASE_EXPIRES
> - DNSMASQ_TIME_REMAINING
> - DNSMASQ_DATA_MISSING
> - DNSMASQ_INTERFACE
> - DNSMASQ_RELAY_ADDRESS
> - DNSMASQ_TAGS
> - DNSMASQ_REQUESTED_OPTIONS
> - DNSMASQ_MUD_URL
>- IPv4 Only
> - DNSMASQ_CLIENT_ID
> - DNSMASQ_CIRCUIT_ID
> - DNSMASQ_SUBSCRIBER_ID
> - DNSMASQ_REMOTE_ID
> - DNSMASQ_VENDOR_CLASS
>- IPv6 Only
> - DNSMASQ_VENDOR_CLASS_ID
> - DNSMASQ_VENDOR_CLASS0 ... _CLASSn
> - DNSMASQ_SERVER_DUID
> - DNSMASQ_IAID
> - DNSMASQ_MAC
>--]]
>
> DBI = require "DBI" -- The ONLY external dependency. On gentoo, use
> emerge dev-lua/luadbi (or use luarocks)
>
> -- Variable Declarations
> counter = 0
> file = nil -- writing to a normal file
> dbh = nil -- our database connection
> dbinsert = nil -- preprepared call to write to a database
>
> local function myenv() -- For testing. How do we retrieve the contents of
> the environment variables?
> a = (os.getenv("DNSMASQ_TIME_REMAINING") or "blank") --
> Help. Always blank.
> return a
> end
>
> local function myerrorhandler(err)
> print("ERROR: " .. err)
> end
>
> function init(a)
> a = (a or "--\n")
> -- MOST of this function will need to be deleted or commented out,
> depending on what functionality is required.
> local ok, err, code = os.rename("/tmp/ilua.db","/tmp/ilua.db")
> if not ok then
> if code == 13 then
> print("DB File exists, but we can't open it! Please
> fix (or delete).")
> os.exit()
> else
> print("No DB file found. Creating...")
> os.execute('sqlite3 --line /tmp/ilua.db "CREATE TABLE
> table1(\"a\");"')
> end
> end
>
> print(a .. "Starting dnsmasq lua
> script...\n==\n")
>
> file = assert(io.open("/tmp/test.log", "a+"))
> -- dbh = assert(DBI.Connect('PostgreSQL', 'db', 'user', 'password' ))
> -- Alternative
> dbh = assert(DBI.Connect('SQLite3','/tmp/ilua.db'))
> dbh:autocommit(true)
> -- dbinsert = assert(dbh:prepare('INSERT INTO table1(a) values ($1)'))
> -- PostgreSQL
> end
>
> local function output(mystring)
> print(mystring) -- In production, I see little point
> in this. Left for testing.
> file:write(mystring)-- We write our data to a standard
> file...
> file:flush()
>
> DBI.Do(dbh, "INSERT INTO table1(a) VALUES ('" .. mystring .. "');")
> -- ... or a SQLite3 file ...
> -- dbinsert:execute(mystring) -- ... or a database (if using
> postgreSQL)
>
> -- See: http:jpmens.net/2013/10/21/tracking-dhcp-leases-with-dnsmasq/
> local cmd = 'mosquitto_pub -h 192.168.1.2 -t "' .. "topic" .. '" -m
> "' .. "payload" .. '" -r'
> print(cmd .. "\n") -- Edit, and change 'print'
> to 'os.execute'
>
> -- What else might we like to do?
> -- Possibly look at a hook for collectd.
> end
>
> function shutdown()
> file:write("Stopping dnsmasq lua
> script..!\n==\n")
> file:close()
> -- dbinsert:close() -- only needed if we have a prepared
> SQL insert function.
> dbh:close()
> end
>
> local function tabletostring(table)
> local k,v
> local line = ""
> for k,v in pairs(table) do line = line
Re: [Dnsmasq-discuss] Scripting with lua
On 14/05/2024 23:09, White, Phil via Dnsmasq-discuss wrote: * and (tentatively / hypothetically), could the actions taken by dnsmasq in granting/renewing a lease be modified following the results of running the lua script? For example, if the lua script modified the DNSMASQ_TAGS variable. The lua script (or non-lua script) is run after dnsmasq replies, so the answer is no. ___ Dnsmasq-discuss mailing list Dnsmasq-discuss@lists.thekelleys.org.uk https://lists.thekelleys.org.uk/cgi-bin/mailman/listinfo/dnsmasq-discuss
Re: [Dnsmasq-discuss] Scripting with lua
On Tue, May 14, 2024 at 10:09:12PM +0100, White, Phil via Dnsmasq-discuss wrote:
> Hi All,
>
> Feeling inquisitive about the options --dhcp-luascript, script-arp,
> and script-on-renewal, I've been exploring what possibilities this
> brings. Knowing absolutely nothing about lua, I have pulled together a
> simple logging script that works -- but I've run up against a problem
> in accessing the stored variables. Therefore, this is probably more of
> a query about lua than it is about dnsmasq.
>
> The man page states that the environment inherits a number of
> variables (example: DNSMASQ_TAGS) which I am trying to retrieve -- but
> my current approach is returning nil (eg. tags =
> os.getenv("DNSMASQ_TAGS"))
>
> Questions:
> * How can I retrieve the contents of the DNSMASQ_ variables (if set)
> * Does the dnsmasq log the return status if there is an error?
> * and (tentatively / hypothetically), could the actions taken by
> dnsmasq in granting/renewing a lease be modified following the results
> of running the lua script? For example, if the lua script modified the
> DNSMASQ_TAGS variable.
>
> Note: This is NOT a feature request -- purely thinking about what
> might be possible...
>
> I've uploaded my current test script to:
> https://github.com/whitepj/dnsmasq-lua if this makes anything clearer.
I've followed that URL and had to click deeper.
Now sharing the output of
$ curl --silent
https://raw.githubusercontent.com/whitepj/dnsmasq-lua/main/dhcp.lua
--[[
LUA script for dnsmasq DHCP leases. Modified from original source at:
http://lists.thekelleys.org/pipermail/dnsmasq-discuss/2012q1/005425.html
This script is principally a boilerplate example, to show what is possible...
Tested using dnsmasq v2.90
Run when:
- Startup (existing leases are invoked with 'old' event
- SIGHUP ?
- dhcp lease created, renewed, changed, or destroyed.
- tftp file transfer completes (not tested)
WHY?
Gives us another way to monitor dhcp leases.
ENVIRONMENT VARIABLES
=
- DNSMASQ_DOMAIN
- DNSMASQ_SUPPLIED_HOSTNAME
- DNSMASQ_USER_CLASS0 ... _CLASSn
- DNSMASQ_LEASE_LENGTH / DNSMASQ_LEASE_EXPIRES
- DNSMASQ_TIME_REMAINING
- DNSMASQ_DATA_MISSING
- DNSMASQ_INTERFACE
- DNSMASQ_RELAY_ADDRESS
- DNSMASQ_TAGS
- DNSMASQ_REQUESTED_OPTIONS
- DNSMASQ_MUD_URL
- IPv4 Only
- DNSMASQ_CLIENT_ID
- DNSMASQ_CIRCUIT_ID
- DNSMASQ_SUBSCRIBER_ID
- DNSMASQ_REMOTE_ID
- DNSMASQ_VENDOR_CLASS
- IPv6 Only
- DNSMASQ_VENDOR_CLASS_ID
- DNSMASQ_VENDOR_CLASS0 ... _CLASSn
- DNSMASQ_SERVER_DUID
- DNSMASQ_IAID
- DNSMASQ_MAC
FUNCTIONS & ARGUMENTS
=
- init
- shutdown
- lease
- add
- old
- del
- arp
- arp-add
- arp-del
- relay-snoop ??? or is this relay(arg), where arg='snoop'?
- tftp ??? not yet tested
dnsmasq CONFIGURATION
=
dhcp-scriptuser = WHATEVER
dhcp-luascript = /usr/local/etc/dnsmasq.d/THIS_SCRIPT.lua
script-on-renewal
script-arp
--]]
DBI = require "DBI" -- The ONLY external dependency. On gentoo, use emerge
dev-lua/luadbi (or use luarocks)
-- Variable Declarations
counter = 0
file = nil -- writing to a normal file
dbh = nil -- our database connection
dbinsert = nil -- preprepared call to write to a database
local function myenv() -- For testing. How do we retrieve the contents of the
environment variables?
a = (os.getenv("DNSMASQ_TIME_REMAINING") or "blank")--
Help. Always blank.
return a
end
local function myerrorhandler(err)
print("ERROR: " .. err)
end
function init(a)
a = (a or "--\n")
-- MOST of this function will need to be deleted or commented out,
depending on what functionality is required.
local ok, err, code = os.rename("/tmp/ilua.db","/tmp/ilua.db")
if not ok then
if code == 13 then
print("DB File exists, but we can't open it! Please fix
(or delete).")
os.exit()
else
print("No DB file found. Creating...")
os.execute('sqlite3 --line /tmp/ilua.db "CREATE TABLE
table1(\"a\");"')
end
end
print(a .. "Starting dnsmasq lua
script...\n==\n")
file = assert(io.open("/tmp/test.log", "a+"))
-- dbh = assert(DBI.Connect('PostgreSQL', 'db', 'user', 'password' ))
-- Alternative
dbh = assert(DBI.Connect('SQLite3','/tmp/ilua.db'))
dbh:autocommit(true)
-- dbinsert = assert(dbh:prepare('INSERT INTO table1(a) values ($1)'))
-- PostgreSQL
end
local function output(mystring)
print(mystring) -- In
