QUIC WIRE: Utility function to determine if PN is in an ACK frame

Reviewed-by: NTomas Mraz <tomas@openssl.org>
Reviewed-by: NMatt Caswell <matt@openssl.org>
Reviewed-by: NPaul Dale <pauli@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/21029)

include/internal/quic_wire.h

@@ -159,6 +159,9 @@ typedef struct ossl_quic_frame_ack_st {
     unsigned int                ecn_present : 1;
 } OSSL_QUIC_FRAME_ACK;
 
+/* Returns 1 if the given frame contains the given PN. */
+int ossl_quic_frame_ack_contains_pn(const OSSL_QUIC_FRAME_ACK *ack, QUIC_PN pn);
+
 /* QUIC Frame: STREAM */
 typedef struct ossl_quic_frame_stream_st {
     uint64_t                stream_id;  /* Stream ID */

ssl/quic/quic_wire.c

@@ -15,6 +15,18 @@
 
 OSSL_SAFE_MATH_UNSIGNED(uint64_t, uint64_t)
 
+int ossl_quic_frame_ack_contains_pn(const OSSL_QUIC_FRAME_ACK *ack, QUIC_PN pn)
+{
+    size_t i;
+
+    for (i = 0; i < ack->num_ack_ranges; ++i)
+        if (pn >= ack->ack_ranges[i].start
+            && pn <= ack->ack_ranges[i].end)
+            return 1;
+
+    return 0;
+}
+
 /*
  * QUIC Wire Format Encoding
  * =========================