fix: fix combination of feature flags

The combination `medium-ieee802154` + `medium-ip` + `proto-ipv4` +
`proto-ipv6` did not compile because of `lookup_hardware_addr`.

ci.sh

@@ -30,6 +30,7 @@ FEATURES_TEST=(
     "std,medium-ieee802154,proto-rpl,proto-sixlowpan,proto-sixlowpan-fragmentation,socket-udp"
     "std,medium-ip,proto-ipv4,proto-ipv6,socket-tcp,socket-udp"
     "std,medium-ethernet,medium-ip,medium-ieee802154,proto-ipv4,proto-ipv6,socket-raw,socket-udp,socket-tcp,socket-icmp,socket-dns,async"
+    "std,medium-ieee802154,medium-ip,proto-ipv4,socket-raw"
 )
 
 FEATURES_TEST_NIGHTLY=(

src/iface/interface/mod.rs

@@ -1336,16 +1336,21 @@ impl InterfaceInner {
             let b = dst_addr.as_bytes();
             let hardware_addr = match *dst_addr {
                 #[cfg(feature = "proto-ipv4")]
-                IpAddress::Ipv4(_addr) => {
-                    HardwareAddress::Ethernet(EthernetAddress::from_bytes(&[
+                IpAddress::Ipv4(_addr) => match self.caps.medium {
+                    #[cfg(feature = "medium-ethernet")]
+                    Medium::Ethernet => HardwareAddress::Ethernet(EthernetAddress::from_bytes(&[
                         0x01,
                         0x00,
                         0x5e,
                         b[1] & 0x7F,
                         b[2],
                         b[3],
-                    ]))
-                }
+                    ])),
+                    #[cfg(feature = "medium-ieee802154")]
+                    Medium::Ieee802154 => unreachable!(),
+                    #[cfg(feature = "medium-ip")]
+                    Medium::Ip => unreachable!(),
+                },
                 #[cfg(feature = "proto-ipv6")]
                 IpAddress::Ipv6(_addr) => match self.caps.medium {
                     #[cfg(feature = "medium-ethernet")]
@@ -1376,8 +1381,10 @@ impl InterfaceInner {
         }
 
         match (src_addr, dst_addr) {
-            #[cfg(feature = "proto-ipv4")]
-            (&IpAddress::Ipv4(src_addr), IpAddress::Ipv4(dst_addr)) => {
+            #[cfg(all(feature = "medium-ethernet", feature = "proto-ipv4"))]
+            (&IpAddress::Ipv4(src_addr), IpAddress::Ipv4(dst_addr))
+                if matches!(self.caps.medium, Medium::Ethernet) =>
+            {
                 net_debug!(
                     "address {} not in neighbor cache, sending ARP request",
                     dst_addr

src/iface/neighbor.rs

@@ -146,7 +146,7 @@ impl Cache {
     }
 }
 
-#[cfg(any(feature = "medium-ethernet", feature = "medium-ip"))]
+#[cfg(feature = "medium-ethernet")]
 #[cfg(test)]
 mod test {
     use super::*;