Merge pull request #155 from d4h0/add-vopono-host-ip-env-variable

Expose $VOPONO_HOST_IP environment variable to the application to run

Author: jamesmcm

USERGUIDE.md

@@ -55,6 +55,35 @@ run itself. `$VOPONO_NS_IP` is useful if you'd like to configure a server
 running within the network namespace to listen on its local IP address only
 (see below, for more information on that).
 
+The application to run within the namespace also has access to
+`$VOPONO_HOST_IP`, to get the IP address of the host.
+
+Note: These environment variables are currently only available from within
+the application/script to run, not on the command line. So the following
+doesn't work:
+
+`vopono exec {other Vopono options} 'echo "HOST IP: $VOPONO_HOST_IP"'`
+
+Output: `HOST IP: $VOPONO_HOST_IP` (the environ variable wasn't expanded).
+
+A work around is to create a executable script, that executes the 
+application you'd like to run:
+
+```bash
+#!/bin/bash
+
+echo "=> NETWORK NAMESPACE IP: $VOPONO_NS_IP"
+echo "=> HOST IP: $VOPONO_HOST_IP"
+```
+
+Execution: `vopono exec {other Vopono options} '/path/to/the/above/script.sh'`
+
+Output:
+
+```
+=> NETWORK NAMESPACE IP: 10.200.1.2
+=> HOST IP: 10.200.1.1
+```
 
 ### Host scripts
 
@@ -65,6 +94,15 @@ Note these scripts run on the host (outside the network namespace), using the cu
 and with the same user as the final application itself (which can be set
 with the `user` argument or config file entry).
 
+Script arguments (e.g. `script.sh arg1 arg1`), are currently not possible, resulting in an error:
+
+```
+$ vopono exec {other Vopono options} --postup 'echo POSTUP' ls
+[...]
+sudo: echo POSTUP: command not found
+[...]
+```
+
 ### Wireguard
 
 Install vopono and use `vopono sync` to

src/exec.rs

@@ -392,12 +392,16 @@ pub fn exec(command: ExecCommand) -> anyhow::Result<()> {
         }
     }
 
+    // Set env var referring to the host IP for the application:
+    std::env::set_var(
+        "VOPONO_HOST_IP",
+        &ns.veth_pair_ips.as_ref().unwrap().host_ip.to_string(),
+    );
+
     let ns = ns.write_lockfile(&command.application)?;
 
     let application = ApplicationWrapper::new(&ns, &command.application, user)?;
 
-    std::env::remove_var("VOPONO_NS_IP");
-
     // Launch TCP proxy server on other threads if forwarding ports
     // TODO: Fix when running as root
     let mut proxy = Vec::new();
@@ -438,6 +442,9 @@ pub fn exec(command: ExecCommand) -> anyhow::Result<()> {
         stay_alive(None, signals);
     }
 
+    std::env::remove_var("VOPONO_NS_IP");
+    std::env::remove_var("VOPONO_HOST_IP");
+
     Ok(())
 }