From 2ed0677286cc83deea230e8ceea0f73899acaab0 Mon Sep 17 00:00:00 2001
From: Nils Andreas Svee <me@lochnair.net>
Date: Thu, 7 May 2026 20:34:34 +0700
Subject: [PATCH] fix(client): harden ancillary receive parsing

---
 crates/irtt-client/src/receive/linux.rs | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/crates/irtt-client/src/receive/linux.rs b/crates/irtt-client/src/receive/linux.rs
index c6e52e0..f1b2361 100644
--- a/crates/irtt-client/src/receive/linux.rs
+++ b/crates/irtt-client/src/receive/linux.rs
@@ -66,6 +66,12 @@ pub(crate) fn recv_datagram(
     if len < 0 {
         return Err(io::Error::last_os_error());
     }
+    let len = usize::try_from(len).map_err(|_| {
+        io::Error::new(
+            io::ErrorKind::InvalidData,
+            "recvmsg returned an unrepresentable datagram length",
+        )
+    })?;
     let received_at = ClientTimestamp::now();
     let meta = unsafe {
         // SAFETY: `msg` was initialized by a successful `recvmsg` call. The
@@ -75,7 +81,7 @@ pub(crate) fn recv_datagram(
     };
 
     Ok(ReceivedDatagram {
-        len: len as usize,
+        len,
         received_at,
         meta,
     })