Specify interface as cmd arg

src/main.rs

@@ -11,7 +11,12 @@ use dhcproto::{
         ORO,
     },
 };
-use std::net::SocketAddrV6;
+use ipnetwork;
+use pnet;
+use std::{
+    env,
+    net::SocketAddrV6,
+};
 use tokio::net::UdpSocket;
 
 const scope_id: u32 = 15;
@@ -23,7 +28,31 @@ const DHCP_Relay_Agent_and_Server_port: u16 = 547;
 
 #[tokio::main]
 async fn main() {
-    let socket_addr = SocketAddrV6::new("fe80::e3cf:4290:9165:505d".parse().unwrap(), DHCP_Client_port, 0, scope_id);
+    let mut args = env::args();
+    args.next(); // Skip executable name
+    // First argument is interface name
+    let interface_name = args.next().expect("No interface name specified");
+
+    let all_interfaces = pnet::datalink::interfaces();
+    let selected_interface = all_interfaces
+        .iter()
+        .find(|i| i.name == interface_name)
+        .expect(format!("No interface found with name: {}", interface_name).as_str());
+
+    let ipv6_addresses = selected_interface.ips
+        .iter()
+        .filter_map(|a| match a {
+            ipnetwork::IpNetwork::V6(a) => Some(a),
+            _ => None,
+        });
+    let mut ipv6_link_local_addresses = ipv6_addresses
+        .filter(|a| a.is_subnet_of("fe80::/10".parse().unwrap()));
+
+    // Just take the first address found on the interface
+    let selected_address = ipv6_link_local_addresses.next()
+        .expect("No IPv6 link local address assigned to this interface");
+
+    let socket_addr = SocketAddrV6::new(selected_address.ip(), DHCP_Client_port, 0, selected_interface.index.clone());
     let sock = UdpSocket::bind(socket_addr).await.unwrap();
 
     let remote_addr = SocketAddrV6::new(All_DHCP_Relay_Agents_and_Servers.parse().unwrap(), DHCP_Relay_Agent_and_Server_port, 0, scope_id);