From 7481ba561822ae1a75029bc53f79cb7f4a892f93 Mon Sep 17 00:00:00 2001
From: Trent Nelson <trent@solana.com>
Date: Wed, 11 Nov 2020 19:27:03 -0700
Subject: [PATCH] ip-echo-server: Add helper to compute reply length

---
 net-utils/src/ip_echo_server.rs | 8 ++------
 net-utils/src/lib.rs            | 4 ++++
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/net-utils/src/ip_echo_server.rs b/net-utils/src/ip_echo_server.rs
index 52dc7c0e25..4ba62a6ea1 100644
--- a/net-utils/src/ip_echo_server.rs
+++ b/net-utils/src/ip_echo_server.rs
@@ -1,4 +1,4 @@
-use crate::HEADER_LENGTH;
+use crate::{ip_echo_server_reply_length, HEADER_LENGTH};
 use bytes::Bytes;
 use log::*;
 use serde_derive::{Deserialize, Serialize};
@@ -177,11 +177,7 @@ pub fn ip_echo_server(tcp: std::net::TcpListener) -> IpEchoServer {
                     } else {
                         // "\0\0\0\0" header is added to ensure a valid response will never
                         // conflict with the first four bytes of a valid HTTP response.
-                        let mut bytes = vec![
-                            0;
-                            HEADER_LENGTH + bincode::serialized_size(&peer_addr.ip()).unwrap()
-                                as usize
-                        ];
+                        let mut bytes = vec![0u8; ip_echo_server_reply_length()];
                         bincode::serialize_into(&mut bytes[HEADER_LENGTH..], &peer_addr.ip())
                             .unwrap();
                         Ok(Bytes::from(bytes))
diff --git a/net-utils/src/lib.rs b/net-utils/src/lib.rs
index 547ee4f9fc..72f6057f2d 100644
--- a/net-utils/src/lib.rs
+++ b/net-utils/src/lib.rs
@@ -23,6 +23,10 @@ pub struct UdpSocketPair {
 pub type PortRange = (u16, u16);
 
 pub(crate) const HEADER_LENGTH: usize = 4;
+pub(crate) fn ip_echo_server_reply_length() -> usize {
+    let largest_ip_addr = IpAddr::from([0u16; 8]); // IPv6 variant
+    HEADER_LENGTH + bincode::serialized_size(&largest_ip_addr).unwrap() as usize
+}
 
 fn ip_echo_server_request(
     ip_echo_server_addr: &SocketAddr,