Thinking about UDP packet routing (redsocks+TPROXY)

pkt-route.dot

digraph routing {
    subgraph interfaces {
        node [shape = folder];
        host_if_inet;
        host_if_lxc;
        lxc_if;
        lxc_if;
    }

    lxc_default_route [label = "default route"];
    host_default_route [label = "default route"];
    internet [style = filled, fillcolor = green, shape = hexagon];
    app [style = filled, fillcolor = yellow, shape = tab];
    redsocks [style = filled, fillcolor = yellow, shape = tab];

    subgraph cluster_host {
        label = "host";
        edge [style = dashed];

        // req
        app -> "mangle/OUTPUT -j MARK" -> "ip rule fwmark …" -> host_if_lxc [color = red];
        host_if_lxc -> "nat/POSTROUTING -j MASQUERADE" -> host_default_route -> host_if_inet [color = orange];

        // reply
        host_if_inet -> "demasq-dnat" -> host_if_lxc [color = lightblue];
        host_if_lxc -> "rp_filter" -> app [color = blue];
    }

    host_if_lxc -> lxc_if [color = red];
    lxc_if -> host_if_lxc [color = orange];
    host_if_inet -> internet [color = orange];
    internet -> host_if_inet [color = lightblue];
    host_if_lxc -> lxc_if [color = lightblue];
    lxc_if -> host_if_lxc [color = blue];

    subgraph cluster_lxc {
        label = "lxc";
        edge [style = dashed];

        lxc_if -> "PREROUTING: ! -d me -j TPROXY" -> redsocks [color = red];
        redsocks -> lxc_default_route -> lxc_if [color = orange];
        lxc_if -> redsocks [color = lightblue];
        subgraph cluster_redsocks {
            label = "redsocks";
            redsocks -> "bind(nonlocal)" [color = blue];
        }
        "bind(nonlocal)" -> lxc_default_route -> lxc_if [color = blue];
    }
}