improve handling of CID retirement

CMakeLists.txt

@@ -59,7 +59,6 @@ SET(QUICLY_LIBRARY_FILES
     lib/rate.c
     lib/recvstate.c
     lib/remote_cid.c
-    lib/retire_cid.c
     lib/sendstate.c
     lib/sentmap.c
     lib/streambuf.c
@@ -77,7 +76,6 @@ SET(UNITTEST_SOURCE_FILES
     t/ranges.c
     t/rate.c
     t/remote_cid.c
-    t/retire_cid.c
     t/sentmap.c
     t/simple.c
     t/stream-concurrency.c

include/quicly/remote_cid.h

@@ -84,6 +84,13 @@ typedef struct st_quicly_remote_cid_set_t {
      * we expect to receive CIDs with sequence number smaller than or equal to this number
      */
     uint64_t _largest_sequence_expected;
+    /**
+     * queue containing CID sequence numbers that should be sent using RETIRE_CONNECTION_ID frames
+     */
+    struct {
+        uint64_t cids[QUICLY_LOCAL_ACTIVE_CONNECTION_ID_LIMIT * 2];
+        size_t count;
+    } retired;
 } quicly_remote_cid_set_t;
 
 /**
@@ -93,16 +100,24 @@ typedef struct st_quicly_remote_cid_set_t {
  */
 void quicly_remote_cid_init_set(quicly_remote_cid_set_t *set, ptls_iovec_t *initial_cid, void (*random_bytes)(void *, size_t));
 /**
- * registers received connection ID
+ * registers received connection ID at the same time pushing CIDs to the retired queue, if any
  * returns 0 if successful (registered or ignored because of duplication/stale information), transport error code otherwise
  */
 int quicly_remote_cid_register(quicly_remote_cid_set_t *set, uint64_t sequence, const uint8_t *cid, size_t cid_len,
-                               const uint8_t srt[QUICLY_STATELESS_RESET_TOKEN_LEN], uint64_t retire_prior_to,
-                               uint64_t unregistered_seqs[QUICLY_LOCAL_ACTIVE_CONNECTION_ID_LIMIT], size_t *num_unregistered_seqs);
+                               const uint8_t srt[QUICLY_STATELESS_RESET_TOKEN_LEN], uint64_t retire_prior_to);
+/**
+ * Unregisters specified CID from the store, pushing the unregistered CID onto the retired queue. The former always succeeds, while
+ * the latter might fail due to overflow. In case of the latter, an error is returned.
+ */
+int quicly_remote_cid_unregister(quicly_remote_cid_set_t *set, uint64_t sequence);
+/**
+ * pushes a CID sequence number to the retired queue
+ */
+int quicly_remote_cid_push_retired(quicly_remote_cid_set_t *set, uint64_t sequence);
 /**
- * unregisters specified CID from the store
+ * removed the first `count` sequence numbers from the retired queue
  */
-void quicly_remote_cid_unregister(quicly_remote_cid_set_t *set, uint64_t sequence);
+void quicly_remote_cid_shift_retired(quicly_remote_cid_set_t *set, size_t count);
 
 #ifdef __cplusplus
 }