From b98fd94fc691b8b9e14ead3cda7e536fca966e9d Mon Sep 17 00:00:00 2001
From: Sunil Nimmagadda <sunil@nimmagadda.net>
Date: Thu, 21 Nov 2024 22:47:08 +0530
Subject: Implement to_bytes method.

---
 src/vrrpv2.rs | 40 ++++++++++++++++++++++++++++++++++++++--
 1 file changed, 38 insertions(+), 2 deletions(-)

diff --git a/src/vrrpv2.rs b/src/vrrpv2.rs
index c3d5715..9a08801 100644
--- a/src/vrrpv2.rs
+++ b/src/vrrpv2.rs
@@ -1,5 +1,5 @@
-use std::io::Read;
 use std::io::{self, Cursor};
+use std::io::{Read, Write};
 use std::net::Ipv4Addr;
 
 /// A VRRP version 2 packet.
@@ -64,7 +64,7 @@ impl From<std::io::Error> for VRRPv2Error {
     }
 }
 
-#[derive(Debug, PartialEq)]
+#[derive(Clone, Copy, Debug, PartialEq)]
 pub enum VRRPv2AuthType {
     VRRPv2AuthNoAuth = 0x00,
     VRRPv2AuthReserved1 = 0x01,
@@ -97,6 +97,31 @@ impl<T: AsRef<[u8]>> BytesReader for Cursor<T> {
     }
 }
 
+impl VRRPv2 {
+    pub fn to_bytes(&self) -> Result<Vec<u8>, std::io::Error> {
+        let sz = (4 + self.count_ip_addrs) * 4;
+        let bytes: Vec<u8> = Vec::with_capacity(sz.into());
+        let mut wr = Cursor::new(bytes);
+        wr.write(
+            [
+                0x21,
+                self.virtual_router_id,
+                self.priority,
+                self.count_ip_addrs,
+            ]
+            .as_ref(),
+        )?;
+        wr.write([self.auth_type as u8, self.advertisement_interval].as_ref())?;
+        wr.write(self.checksum.to_be_bytes().as_ref())?;
+        for ip in self.ip_addrs.iter() {
+            wr.write(&ip.to_bits().to_be_bytes())?;
+        }
+        wr.write([0; 4].as_ref())?; // Authentication Data 1
+        wr.write([0; 4].as_ref())?; // Authentication Data 2
+        Ok(wr.into_inner())
+    }
+}
+
 fn parse(bytes: &[u8]) -> Result<VRRPv2, VRRPv2Error> {
     let mut rdr = Cursor::new(bytes);
     let vertype = rdr.read_u8()?;
@@ -246,3 +271,14 @@ fn test_checksum_another() {
     let bytes = [0xe3, 0x4f, 0x23, 0x96, 0x44, 0x27, 0x99, 0xf3];
     assert_eq!(checksum(&bytes), 0x1aff);
 }
+
+#[test]
+fn test_to_bytes() {
+    let in_bytes = [
+        0x21, 0x01, 0x64, 0x01, 0x00, 0x01, 0xba, 0x52, 0xc0, 0xa8, 0x00, 0x01, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00,
+    ];
+    let vrrpv2 = from_bytes(&in_bytes).expect("parsing failed");
+    let out_bytes = vrrpv2.to_bytes().expect("conversion failed");
+    assert_eq!(in_bytes.as_ref(), out_bytes);
+}
-- 
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