recvpn.h

#ifndef RECVPN_RECVPN_H
#define RECVPN_RECVPN_H
 
#include "common/platform/sys/syscall.h"
 
/* RFC 9000 13.2: a receiver tracks which packet numbers it has seen so it can
 * drop duplicates and acknowledge the rest. We keep the largest number seen
 * and a sliding bitmap of the window below it, which is enough to detect
 * duplicates and to find the contiguous run for the ACK's first range. */
 
#define RECVPN_WINDOW 64 /* packets below `largest` tracked in the bitmap */

typedef struct {
  u64 largest; 
  u64 bitmap;  
  int any;     
} recvpn;
 
void recvpn_init(recvpn* r);
 
/* Whether packet number pn has already been recorded (a duplicate). */
int recvpn_seen(const recvpn* r, u64 pn);
 
/* Record packet number pn as received. Numbers older than the window are
 * ignored (treated as already acknowledged). */
void recvpn_record(recvpn* r, u64 pn);
 
/* The first ACK range: the count of contiguous packets ending at `largest`
 * that have been received (0 if none recorded). */
u64 recvpn_first_range(const recvpn* r);
 
#endif