feature: tarpit() filter

[szuecs]

feature: tarpit() filter to let connection to the client open until it closes the connection

[AlexanderYastrebov]

I think this is equivalent in behavior with

$ bin/skipper -inline-routes='* -> chunks(1, "1s") -> dropResponseHeader("Content-Length") -> repeatContent("X", 1000000000) -> status(200) -> <shunt>'
...
~$ nc localhost 9090
GET / HTTP/1.1        
Host: localhost:9090

HTTP/1.1 200 OK
Server: Skipper
Date: Fri, 01 Dec 2023 09:32:40 GMT
Transfer-Encoding: chunked

1
X
1
X
1
X
1
X
1
X
1
X
1
X
1
X
^C

-- it responds with Transfer-Encoding: chunked and sends chunks of 1 byte.

If we do not drop Content-Length then it just slowly sends response:

$ bin/skipper -inline-routes='* -> chunks(1, "1s") -> repeatContent("X", 10000) -> status(200) -> <shunt>'
...
~$ nc localhost 9090
GET / HTTP/1.1 
Host: localhost:9090

HTTP/1.1 200 OK
Content-Length: 10000
Server: Skipper
Date: Fri, 01 Dec 2023 09:33:42 GMT

XXXXXX^C

If we want to have second behavior for tarpit then we need to tell content length:

$ bin/skipper -inline-routes='* -> setResponseHeader("Content-Length", "10000") -> tarpit("1s") -> <shunt>
...
~$ nc localhost 9090
GET / HTTP/1.1
Host: localhost:9090

HTTP/1.1 200 OK
Content-Length: 10000
Server: Skipper
Date: Fri, 01 Dec 2023 09:35:19 GMT

   ^C

[szuecs]

👍

[AlexanderYastrebov]

👍