Constant OUTER_INITIAL_MTU 

pub const OUTER_INITIAL_MTU: u16 = 1350 /* 1_350u16 */;

Available on crate feature masque only.

Initial MTU for a QUIC connection to a MASQUE proxy that carries tunnels as HTTP/3 datagrams: an inner QUIC packet needs 1200 bytes plus the outer packet’s overhead, which QUIC’s default of 1200 leaves no room for. Configure it on both sides of that connection.