Implement Display for VxlanDf

Signed-off-by: Gris Ge <cnfourt@gmail.com>

Author: cathay4t

src/link/link_info/vxlan.rs

@@ -1,6 +1,9 @@
 // SPDX-License-Identifier: MIT
 
-use std::net::{Ipv4Addr, Ipv6Addr};
+use std::{
+    fmt,
+    net::{Ipv4Addr, Ipv6Addr},
+};
 
 use netlink_packet_core::{
     emit_u16_be, emit_u32, emit_u64_be, parse_u16_be, parse_u32, parse_u64_be,
@@ -65,6 +68,17 @@ impl From<u8> for VxlanDf {
     }
 }
 
+impl fmt::Display for VxlanDf {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            VxlanDf::Unset => write!(f, "unset"),
+            VxlanDf::Set => write!(f, "set"),
+            VxlanDf::Inherit => write!(f, "inherit"),
+            VxlanDf::Other(v) => write!(f, "{v}"),
+        }
+    }
+}
+
 impl From<VxlanDf> for u8 {
     fn from(d: VxlanDf) -> Self {
         match d {