clarify the max size of the CMSG buffer

quinn-rs · Nov 9, 2023 · 054d252 · 054d252
1 parent 3717e8d
commit 054d252
Showing 1 changed file with 2 additions and 1 deletion.
diff --git a/quinn-udp/src/windows.rs b/quinn-udp/src/windows.rs
@@ -14,7 +14,8 @@ use crate::EcnCodepoint;
 
 use super::{cmsg, log_sendmsg_error, RecvMeta, Transmit, UdpSockRef, IO_ERROR_LOG_INTERVAL};
 
-const CMSG_LEN: usize = 128; // FIXME arbitrary value, same as unix ?, is it too small/much ?
+// Enough to store max(IP_PKTINFO + IP_ECN, IPV6_PKTINFO + IPV6_ECN) bytes (header + data) and some extra margin
+const CMSG_LEN: usize = 128;
 
 // FIXME this could use [`std::sync::OnceLock`] once the MSRV is bumped to 1.70 and upper
 static WSARECVMSG_PTR: OnceCell<WinSock::LPFN_WSARECVMSG> = OnceCell::new();