From b9b97bbb9d3503381de4b1beb5fcbf69e8e4c68d Mon Sep 17 00:00:00 2001
From: Smitty <me@smitop.com>
Date: Fri, 9 Jul 2021 12:54:02 -0400
Subject: [PATCH] Reject too-long IPs quicker

Now that there can't be a bunch of leading zeros, parsing can be
optimized a bit.
---
 library/std/src/net/parser.rs | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/library/std/src/net/parser.rs b/library/std/src/net/parser.rs
index d43d40400aba..df6bbdeab899 100644
--- a/library/std/src/net/parser.rs
+++ b/library/std/src/net/parser.rs
@@ -289,7 +289,12 @@ impl FromStr for IpAddr {
 impl FromStr for Ipv4Addr {
     type Err = AddrParseError;
     fn from_str(s: &str) -> Result<Ipv4Addr, AddrParseError> {
-        Parser::new(s).parse_with(|p| p.read_ipv4_addr())
+        // don't try to parse if too long
+        if s.len() > 15 {
+            Err(AddrParseError(()))
+        } else {
+            Parser::new(s).parse_with(|p| p.read_ipv4_addr())
+        }
     }
 }