Randomize fixed bit for compatible peers

quinn-rs · Jan 22, 2022 · e764386 · e764386
1 parent ff642b3
commit e764386
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Showing 2 changed files with 6 additions and 2 deletions.
diff --git a/quinn-proto/src/connection/packet_builder.rs b/quinn-proto/src/connection/packet_builder.rs
@@ -7,7 +7,7 @@ use tracing::{trace, trace_span};
 use super::{spaces::SentPacket, Connection, SentFrames, State};
 use crate::{
     frame::{self, Close},
-    packet::{Header, LongType, PacketNumber, PartialEncode, SpaceId},
+    packet::{Header, LongType, PacketNumber, PartialEncode, SpaceId, FIXED_BIT},
     TransportError, TransportErrorCode,
 };
 
@@ -115,6 +115,10 @@ impl PacketBuilder {
             },
         };
         let partial_encode = header.encode(buffer);
+        if conn.peer_params.grease_quic_bit && conn.rng.gen() {
+            buffer[partial_encode.start] ^= FIXED_BIT;
+        }
+
         let (sample_size, tag_len) = if let Some(ref crypto) = space.crypto {
             (
                 crypto.header.local.sample_size(),

diff --git a/quinn-proto/src/packet.rs b/quinn-proto/src/packet.rs
@@ -770,7 +770,7 @@ impl From<coding::UnexpectedEnd> for PacketDecodeError {
 }
 
 pub(crate) const LONG_HEADER_FORM: u8 = 0x80;
-const FIXED_BIT: u8 = 0x40;
+pub(crate) const FIXED_BIT: u8 = 0x40;
 pub(crate) const SPIN_BIT: u8 = 0x20;
 const SHORT_RESERVED_BITS: u8 = 0x18;
 const LONG_RESERVED_BITS: u8 = 0x0c;