Don't panic in Drop (#12)

* Allow communication with host

* Clarify missing root privileges message

README.md

@@ -20,12 +20,12 @@ And assumes that:
 
 ## Installing
 
-For proper functioning Softnet binary requires two things:
+For proper functioning, Softnet binary requires two things:
 
-* a [SUID-bit](https://en.wikipedia.org/wiki/Setuid#SUID) is set on the binary or [passwordless sudo](https://serverfault.com/questions/160581/how-to-setup-passwordless-sudo-on-linux) is enabled, which effectively gives the binary `root` privileges
+* a [SUID-bit](https://en.wikipedia.org/wiki/Setuid#SUID) to be set on the binary or a [passwordless sudo](https://serverfault.com/questions/160581/how-to-setup-passwordless-sudo-on-linux) to be configured, which effectively gives the binary `root` privileges
-  * this is needed in order to create [`vmnet.framework`](https://developer.apple.com/documentation/vmnet) interface and perform DHCP-related tweaks
+  * these privileges are needed to create [`vmnet.framework`](https://developer.apple.com/documentation/vmnet) interface and perform DHCP-related system tweaks
   * the privileges will be dropped automatically to that of the calling user (or those represented by the `--user` and `--group` command-line arguments) once all of the initialization is completed
-* the binary is available in `PATH`
+* the binary to be available in `PATH`
   * so that the Tart will be able to find it
 
 ## Running

lib/host.rs

@@ -107,7 +107,7 @@ impl Host {
             .map_err(|err| Error::VmnetFailed { source: err })?;
 
         // Now let the callback finish
-        self.callback_can_continue_tx.send(()).unwrap();
+        let _ = self.callback_can_continue_tx.send(());
 
         self.interface
             .finalize()

lib/proxy/host.rs

@@ -12,7 +12,9 @@ impl Proxy {
 
         // Snoop bootpd(8) replies from the host to
         // figure out the IP assigned to the VM
-        self.snoop(frame);
+        if frame.dst_addr() == self.vm_mac_address {
+            self.snoop(frame);
+        }
 
         self.vm
             .write(frame.as_ref())

lib/proxy/vm.rs

@@ -68,6 +68,11 @@ impl Proxy {
             }
         }
 
+        // Allow communication with host
+        if ipv4_pkt.dst_addr() == self.host.gateway_ip {
+            return Some(());
+        }
+
         if ipv4_pkt.protocol() == IpProtocol::Udp {
             let udp_pkt = UdpPacket::new_checked(ipv4_pkt.payload()).ok()?;
 
@@ -77,11 +82,8 @@ impl Proxy {
                 return Some(());
             }
 
-            // Allow DHCP communication with the bootpd(8) on host
+            // Allow DHCP communication with the bootpd(8) on host via broadcast address
-            let allowed_dhcp_target =
+            if udp_pkt.is_dhcp_request() && ipv4_pkt.dst_addr().is_broadcast() {
-                ipv4_pkt.dst_addr().is_broadcast() || ipv4_pkt.dst_addr() == self.host.gateway_ip;
-
-            if udp_pkt.is_dhcp_request() && allowed_dhcp_target {
                 return Some(());
             }
         }

src/main.rs

@@ -27,7 +27,7 @@ struct Args {
     #[clap(
         long,
         help = "set bootpd(8) lease time to this value (in seconds) before starting the VM",
-        default_value_t = 60
+        default_value_t = 600
     )]
     bootpd_lease_time: u32,
 
@@ -92,7 +92,7 @@ fn try_main() -> Result<(), Box<dyn std::error::Error>> {
                 .exec();
         }
 
-        return Err("root privileges are required to run".into());
+        return Err("root privileges are required to run and passwordless sudo was not available".into());
     }
 
     // Set bootpd(8) min/max lease time while still having the root privileges