bond: add FromStr/Display for BondLacpRate

Add FromStr and Display trait implementations for BondLacpRate using
"slow"/"fast" strings.

Unit test included.

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

Author: cathay4t

src/link/link_info/bond.rs

@@ -720,6 +720,32 @@ impl From<BondLacpRate> for u8 {
     }
 }
 
+impl std::fmt::Display for BondLacpRate {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            BondLacpRate::Slow => f.write_str("slow"),
+            BondLacpRate::Fast => f.write_str("fast"),
+            BondLacpRate::Other(v) => write!(f, "{v}"),
+        }
+    }
+}
+
+impl std::str::FromStr for BondLacpRate {
+    type Err = DecodeError;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        Ok(match s {
+            "slow" => Self::Slow,
+            "fast" => Self::Fast,
+            _ => {
+                return Err(DecodeError::from(format!(
+                    "unknown bond lacp rate: {s}"
+                )))
+            }
+        })
+    }
+}
+
 const BOND_AD_STABLE: u8 = 0;
 const BOND_AD_BANDWIDTH: u8 = 1;
 const BOND_AD_COUNT: u8 = 2;

src/link/tests/bond.rs

@@ -316,3 +316,11 @@ fn test_bond_ad_select_from_str() {
     );
     assert!(BondAdSelect::from_str("bogus").is_err());
 }
+
+#[test]
+fn test_bond_lacp_rate_from_str() {
+    use std::str::FromStr;
+    assert_eq!(BondLacpRate::Slow, "slow".parse().unwrap());
+    assert_eq!(BondLacpRate::Fast, "fast".parse().unwrap());
+    assert!(BondLacpRate::from_str("bogus").is_err());
+}