daemon: allow per-request variables in Lua

The handlers in Lua can now store per-request variables that are automatically GC'd when the request is finished. This is useful for stateful modules, such as DNS64 that uses internal option flags for state tracking, or stats that previously couldn't be implemented in Lua

The layers can now get a variable table like so:

local vars = kres.request_t(r):vars()
vars.hello = true

The variables are persisted between different layers for each request.

TODO:

• Add to to basic resolve tests
• Update DNS64 module
• Add to library documentation

I very much like this, I was wondering about the same when I saw DNS64 module internals. Thank you!

added feature label

marked the checklist item Add to to basic resolve tests as completed

marked the checklist item Add to to basic resolve tests as incomplete

added 188 commits

• 3a8f8170...d316da92 - 187 commits from branch master
• 4384af52 - daemon: allow per-request variables in Lua

Compare with previous version

unmarked as a Work In Progress

changed the description

marked the checklist item Add to to basic resolve tests as completed

marked the checklist item Update DNS64 module as completed

marked the checklist item Add to library documentation as completed

For me, the mechanism which allows to store per-request variables is OK.

But changes in DNS64 module looks a bit problematic due to forwarding mode. Unfortunately, for now resolver must to know if answer was synthesized. Otherwise it could make problems with validation.

https://gitlab.labs.nic.cz/knot/knot-resolver/blob/master/lib/resolve.c#L1002

Example. config

...
modules = {
...
    "policy",
    "dns64",
...
}
...
dns64.config('fe80::21b:aabb:0:0')
...
policy.add(policy.all(policy.TLS_FORWARD({{ "1.1.1.1", insecure = true }})))
...

master

kdig alza.cz AAAA @127.0.0.1 -p 53000 +dnssec
;; ->>HEADER<<- opcode: QUERY; status: NOERROR; id: 58086
;; Flags: qr rd ra; QUERY: 1; ANSWER: 1; AUTHORITY: 4; ADDITIONAL: 1

;; EDNS PSEUDOSECTION:
;; Version: 0; flags: do; UDP size: 4096 B; ext-rcode: NOERROR

;; QUESTION SECTION:
;; alza.cz.            		IN	AAAA

;; ANSWER SECTION:
alza.cz.            	271	IN	AAAA	fe80::21b:aabb:b9b5:b013

;; AUTHORITY SECTION:
....blahblahblah...

;; Received 458 B
;; Time 2018-05-30 14:58:54 CEST
;; From 127.0.0.1@53000(UDP) in 81.0 ms

vs this branch

kdig alza.cz AAAA @127.0.0.1 -p 53000 +dnssec
;; ->>HEADER<<- opcode: QUERY; status: SERVFAIL; id: 13368
;; Flags: qr rd ra; QUERY: 1; ANSWER: 0; AUTHORITY: 0; ADDITIONAL: 0

;; QUESTION SECTION:
;; alza.cz.            		IN	AAAA

;; Received 25 B
;; Time 2018-05-30 14:58:16 CEST
;; From 127.0.0.1@53000(UDP) in 39.9 ms

Could we consider using DNS64_MARK flag in query flags along with per request lua variables?

marked the checklist item Update DNS64 module as incomplete

added 1 commit

• 14de9110 - daemon: allow per-request variables in Lua

Compare with previous version

@gdemidov uh, that's annoying. I'll remove it for now, but this should really be transparent.

changed the description

merged

mentioned in commit 7fae33f4

mentioned in issue #363