diff -r a46fd16cc293 -r 61c484b134c8 src/vrrpv2.rs
--- a/src/vrrpv2.rs	Thu Jan 05 16:03:05 2023 +0530
+++ b/src/vrrpv2.rs	Sat Jan 07 21:11:43 2023 +0530
@@ -77,34 +77,7 @@
     })(input)
 }
 
-// Nightly has a nicer array_chunks API to express it more succinctly.
-// let mut chunks = bytes.array_chunks(2);
-// let mut sum = chunks.map(u16::from_ne_bytes).map(|b| b as u32).sum::<u32>();
-// // handle the remainder
-// if let Some([b]) = chunks.remainder() {
-//     sum += *b as u32
-// }
-
-// Shadowing can be used to avoid `mut`...
-// let sum =...;
-// let sum = (sum & 0xffff) + (sum >> 16);
-// let sum = (sum & 0xffff) + (sum >> 16);
-// manually un-rolling while loop since it's needed atmost twice for an u32.
-fn validate_checksum(bytes: &[u8]) -> bool {
-    let mut sum: u32 = bytes.chunks(2).fold(0, |acc: u32, x| {
-        acc + u32::from(u16::from_ne_bytes(x.try_into().unwrap()))
-    });
-    while (sum >> 16) > 0 {
-        sum = (sum & 0xffff) + (sum >> 16);
-    }
-    let checksum = !(sum as u16);
-    checksum == 0
-}
-
 fn parse(input: &[u8]) -> IResult<&[u8], VRRPv2> {
-    if !validate_checksum(input) {
-        return Err(Err::Error(Error::new(input, ErrorKind::Alt)));
-    }
     let (input, (version, type_)) = parse_version_type(input)?;
     let (input, virtual_router_id) = u8(input)?;
     let (input, priority) = u8(input)?;
@@ -130,7 +103,34 @@
     ))
 }
 
+// Nightly has a nicer array_chunks API to express it more succinctly.
+// let mut chunks = bytes.array_chunks(2);
+// let mut sum = chunks.map(u16::from_ne_bytes).map(|b| b as u32).sum::<u32>();
+// // handle the remainder
+// if let Some([b]) = chunks.remainder() {
+//     sum += *b as u32
+// }
+
+// Shadowing can be used to avoid `mut`...
+// let sum =...;
+// let sum = (sum & 0xffff) + (sum >> 16);
+// let sum = (sum & 0xffff) + (sum >> 16);
+// manually un-rolling while loop since it's needed atmost twice for an u32.
+fn validate_checksum(bytes: &[u8]) -> bool {
+    let mut sum: u32 = bytes.chunks(2).fold(0, |acc: u32, x| {
+        acc + u32::from(u16::from_ne_bytes(x.try_into().unwrap()))
+    });
+    while (sum >> 16) > 0 {
+        sum = (sum & 0xffff) + (sum >> 16);
+    }
+    let checksum = !(sum as u16);
+    checksum == 0
+}
+
 pub fn from_bytes(bytes: &[u8]) -> Result<VRRPv2, VRRPv2Error> {
+    if !validate_checksum(bytes) {
+        return Err(VRRPv2Error::VRRPv2ParseError);
+    }
     match parse(bytes) {
         Ok((_, v)) => Ok(v),
         Err(e) => Err(e.into()),