From 650198b760185b2d7b84338c946fa9ba0141fcfd Mon Sep 17 00:00:00 2001
From: An Long <aisk1988@gmail.com>
Date: Thu, 25 Jun 2026 00:09:04 +0900
Subject: [PATCH] =?UTF-8?q?=F0=9F=90=9B=20Fix=20ICMP=20reply=20decoding=20?=
 =?UTF-8?q?robustness?=
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---
 src/errors.rs      | 2 --
 src/packet/icmp.rs | 6 ++++--
 src/ping.rs        | 5 ++++-
 3 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/src/errors.rs b/src/errors.rs
index ece84c3..2d5cca5 100644
--- a/src/errors.rs
+++ b/src/errors.rs
@@ -6,8 +6,6 @@ pub enum Error {
     InvalidProtocol,
     #[error("internal error")]
     InternalError,
-    #[error("Decode V4 error occurred while processing the IPv4 packet.")]
-    DecodeV4Error,
     #[error("Decode echo reply error occurred while processing the ICMP echo reply.")]
     DecodeEchoReplyError,
     #[error("io error: {error}")]
diff --git a/src/packet/icmp.rs b/src/packet/icmp.rs
index 9ccc7bd..f049dfd 100644
--- a/src/packet/icmp.rs
+++ b/src/packet/icmp.rs
@@ -2,6 +2,8 @@ use std::io::Write;
 use thiserror::Error;
 
 pub const HEADER_SIZE: usize = 8;
+/// Size of the correlation token carried as the echo payload.
+pub const PAYLOAD_SIZE: usize = 24;
 
 #[derive(Debug, Error)]
 pub enum Error {
@@ -68,7 +70,7 @@ pub struct EchoReply<'a> {
 
 impl<'a> EchoReply<'a> {
     pub fn decode<P: Proto>(buffer: &'a [u8]) -> Result<Self, Error> {
-        if buffer.as_ref().len() < HEADER_SIZE {
+        if buffer.as_ref().len() < HEADER_SIZE + PAYLOAD_SIZE {
             return Err(Error::InvalidSize);
         }
 
@@ -80,7 +82,7 @@ impl<'a> EchoReply<'a> {
 
         let ident = (u16::from(buffer[4]) << 8) + u16::from(buffer[5]);
         let seq_cnt = (u16::from(buffer[6]) << 8) + u16::from(buffer[7]);
-        let payload = &buffer[HEADER_SIZE..(HEADER_SIZE + 24)];
+        let payload = &buffer[HEADER_SIZE..(HEADER_SIZE + PAYLOAD_SIZE)];
 
         Ok(EchoReply {
             ident,
diff --git a/src/ping.rs b/src/ping.rs
index 54af08b..599fc96 100644
--- a/src/ping.rs
+++ b/src/ping.rs
@@ -137,9 +137,12 @@ fn ping_with_socktype(
                     Err(_) => continue,
                 }
             } else {
+                // Skip undecodable IP packets (malformed, truncated, or
+                // unrelated ICMP traffic from other hosts on a RAW socket)
+                // instead of failing the whole ping; keep waiting for our reply.
                 let ipv4_packet = match IpV4Packet::decode(&buffer) {
                     Ok(packet) => packet,
-                    Err(_) => return Err(Error::DecodeV4Error.into()),
+                    Err(_) => continue,
                 };
                 recv_ttl = Some(ipv4_packet.ttl);
                 match EchoReply::decode::<IcmpV4>(ipv4_packet.data) {