How to get client ip address in HttpHandler (Julia Language)? - http

Question

I need to get client's IP address in regular HttpHandler like this:
http = HttpHandler() do req::Request, res::Response
Response( ismatch(r"^/hello/",req.resource) ? string("Hello ", split(req.resource,'/')[3], "!") : 404 )
end
Neither req nor http.sock contain this information.

Answer 1

The Approach
This can be done, if you know the internals of Julia a little. It turns out that Julia uses the library libuv for low level system processing and that library has a function called uv_tcp_getpeername. This function is not exported by Julia.Base, but you can gain access to it via ccall. Also, the module HttpServer allows for way define a callback for various events, including the connect event.
Example Module
module HTTPUtil
export get_server
using HttpServer
function handle_connect(client)
try
buffer = Array(Uint8,32)
bufflen::Int64 = 32
ccall(:uv_tcp_getpeername,Int64,(Ptr{Void},Ptr{Uint8},Ptr{Int64}),client.sock.handle,buffer,&bufflen)
peername::IPv4 = IPv4(buffer[5:8]...)
task_local_storage(:ip,peername)
catch e
println("Error ... $e")
end
end
function get_server()
http = HttpHandler() do req::Request, res::Response
ip = task_local_storage(:ip)
println("Connection received from from $ip")
Response(ismatch(r"^/hello/",req.resource)?string("Hello ",split(req.resource,'/')[3], " $(ip)!") : 404 )
end
http.events["connect"]=(client)->handle_connect(client)
server = Server(http)
end
end
Explained
Each time a connection request is made, a peer socket is created by the server, and the connect handler is called which is defined to be handle_connect. It takes one parameter, client, of type Client. A Client type has a field called sock of type TcpSocket, and a TcpSocket has a field handle which is used by libuv. The object, then is each time a connection request is made, the connect handler is called, which calls uv_tcp_getpeername with the data contained in the TcpSocket handle. A byte array is declared to act as a buffer, which then is cast back to Base.IPv4. The module HTTPServer creates exactly 1 task for each client using #async, so the ip address can be stored local to the client using task_local_storage; thus there is no race condition.
Using it
julia> using HTTPUtil
julia> server = get_server()
Server(HttpHandler((anonymous function),TcpServer(init),Dict{ASCIIString,Function} with 3 entries:
"error" => (anonymous function)
"listen" => (anonymous function)
"connect" => (anonymous function)),nothing)
julia> #async run(server,8000)
Listening on 8000...
Task (queued) #0x000000000767e7a0
julia> Connection received from from 192.168.0.23
Connection received from from 192.168.0.22
... etc
Notes
For illustration, the output is modified so that the server will respond to each browser "Hello ipaddr"
This should be included in Base and/or HttpServer, but currently is not, so you'll need to use this workaround until it is.
The typical looping structure is used in get_server to illustrate there is no requirement for it to change, except to add in the ip address.
Assumes IPv4, but can be improved to allow both IPv4 and IPv6 straightforwardly as libuv supports both.

Answer 2

Thanks to waTeim's answer, but it's from 2014 and things changed in Julia. This works nicely in Julia 6.0 and probably all above:
function ip(socket::TCPSocket)
buffer = Array{UInt8}(32)
bufflen::Int64 = 32
ccall(:uv_tcp_getpeername,Int64,(Ptr{Void},Ptr{UInt8},Ptr{Int64}), socket.handle, buffer, &bufflen)
peername::IPv4 = IPv4(buffer[5:8]...)
end

Answer 3

Building on the excellent answer from waTeim I simplified things a little to work with IPv6, and also for SSL connections:
using MbedTLS
function handle_connect(client)
ip, port = getsockname(isa(client.sock, MbedTLS.SSLContext) ? client.sock.bio : client.sock)
task_local_storage(:ip, ip)
end

Answer 4

(Would have added this as a comment to Josh Bode's answer, but I don't have the necessary reputation.)
Note that it is necessary to use getpeername() instead of getsockname() as of Julia v0.7.
https://github.com/JuliaLang/julia/pull/21825

Answer 5

Depending on your situation, you may be able to pass a linux command.
userIP = strip(readstring(`hostname -i`), ['\n'])