MEDIUM: filters/lua: Support declaration of some filter callback functions in lua
It is now possible to write some filter callback functions in lua. All
filter callbacks are not supported yet but the mechanism to call them is now
in place. Following method may be defined in the Lua filter class to be
bound on filter callbacks:
* Filter:start_analyse(txn, chn)
* Filter:end_analyse(txn, chn)
* Filter:tcp_payload(txn, chn, offset, length)
hlua_filter_callback() function is responsible to call the good lua function
depending on the filter callback function. Using some flags it is possible
to allow a lua call to yield or not, to retrieve a return value or not, and
to specify if a channel or an http message must be passed as second
argument. For now, the HTTP part has not been added yet. It is also possible
to add extra argument adding them on the stack before the call.
3 new functions are exposed by the global object "filter". The first one,
filter.wake_time(ms_delay), to set the wake_time when a Lua callback
function yields (if allowed). The two others,
filter.register_data_filter(filter, chn) and
filter.unregister_data_filter(filter, chn), to enable or disable the data
filtering on a channel for a specific lua filter instance.
start_analyse() and end_analyse() may return one of the constant
filter.CONTINUE, filter.WAIT or filter.ERROR. If nothing is returned,
filter.CONTINUE is used as the default value. On its side, tcp_payload() may
return the amount of data to forward. If nothing is returned, all incoming
data are forwarded.
For now, these functions are not allowed to yield because this interferes
with the filter workflow.
Here is a simple example :
MyFilter = {}
MyFilter.id = "My Lua filter"
MyFilter.flags = filter.FLT_CFG_FL_HTX
MyFilter.__index = MyFilter
function MyFilter:new()
flt = {}
setmetatable(flt, MyFilter)
flt.req_len = 0
flt.res_len = 0
return flt
end
function MyFilter:start_analyze(txn, chn)
filter.register_data_filter(self, chn)
end
function MyFilter:end_analyze(txn, chn)
print("<Total> request: "..self.req_len.." - response: "..self.res_len)
end
function MyFilter:tcp_payload(txn, chn)
offset = chn:ouput()
len = chn:input()
if chn:is_resp() then
self.res_len = self.res_len + len
print("<TCP:Response> offset: "..offset.." - length: "..len)
else
self.req_len = self.req_len + len
print("<TCP:Request> offset: "..offset.." - length: "..len)
end
end
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