rwhod: manually calculate broadcast address

src/server/rwhod/packet_sender.rs

@@ -1,7 +1,7 @@
 use nix::{ifaddrs::getifaddrs, net::if_::InterfaceFlags};
 use std::{
     collections::HashSet,
-    net::{IpAddr, SocketAddr},
+    net::{IpAddr, Ipv4Addr, SocketAddr},
     sync::Arc,
 };
 use tokio::{
@@ -29,6 +29,11 @@ pub struct RwhodSendTarget {
     pub addr: IpAddr,
 }
 
+/// Computes the broadcast address for an IPv4 address/netmask pair
+fn ipv4_broadcast_address(address: Ipv4Addr, netmask: Ipv4Addr) -> Ipv4Addr {
+    Ipv4Addr::from(u32::from(address) | !u32::from(netmask))
+}
+
 /// Find all networks network interfaces suitable for rwhod communication.
 ///
 /// If `allowed_interfaces` is `Some`, only interfaces whose name is contained
@@ -53,24 +58,29 @@ pub fn determine_relevant_interfaces(
             })
             .filter_map(|iface| {
                 let neighbor_addr = if iface.flags.contains(InterfaceFlags::IFF_BROADCAST) {
-                    iface.broadcast
+                    match (
+                        iface.address.as_ref().and_then(|a| a.as_sockaddr_in()),
+                        iface.netmask.as_ref().and_then(|a| a.as_sockaddr_in()),
+                    ) {
+                        (Some(addr), Some(mask)) => {
+                            Some(ipv4_broadcast_address(addr.ip(), mask.ip()).into())
+                        }
+                        _ => None,
+                    }
                 } else if iface.flags.contains(InterfaceFlags::IFF_POINTOPOINT) {
-                    iface.destination
+                    iface.destination.and_then(|addr| {
+                        addr.as_sockaddr_in()
+                            .map(|sa| IpAddr::V4(sa.ip()))
+                            .or_else(|| addr.as_sockaddr_in6().map(|sa| IpAddr::V6(sa.ip())))
+                    })
                 } else {
                     None
                 };
 
-                match neighbor_addr {
-                    Some(addr) => addr
-                        .as_sockaddr_in()
-                        .map(|sa| IpAddr::V4(sa.ip()))
-                        .or_else(|| addr.as_sockaddr_in6().map(|sa| IpAddr::V6(sa.ip())))
-                        .map(|ip_addr| RwhodSendTarget {
-                            name: iface.interface_name,
-                            addr: ip_addr,
-                        }),
-                    None => None,
-                }
+                neighbor_addr.map(|ip_addr| RwhodSendTarget {
+                    name: iface.interface_name,
+                    addr: ip_addr,
+                })
             })
             // keep first occurrence per interface name
             .scan(HashSet::new(), |seen, n| {
@@ -167,6 +177,30 @@ pub async fn rwhod_packet_sender_task(
 mod tests {
     use super::*;
 
+    #[test]
+    fn test_ipv4_broadcast_address() {
+        assert_eq!(
+            ipv4_broadcast_address(
+                Ipv4Addr::new(192, 168, 1, 2),
+                Ipv4Addr::new(255, 255, 255, 0)
+            ),
+            Ipv4Addr::new(192, 168, 1, 255)
+        );
+
+        assert_eq!(
+            ipv4_broadcast_address(Ipv4Addr::new(10, 0, 5, 200), Ipv4Addr::new(255, 0, 0, 0)),
+            Ipv4Addr::new(10, 255, 255, 255)
+        );
+
+        assert_eq!(
+            ipv4_broadcast_address(
+                Ipv4Addr::new(203, 0, 113, 42),
+                Ipv4Addr::new(255, 255, 255, 255)
+            ),
+            Ipv4Addr::new(203, 0, 113, 42)
+        );
+    }
+
     #[test]
     fn test_determine_relevant_interfaces() {
         let interfaces = determine_relevant_interfaces(None).unwrap();