Take into account tai offset when comparing txtime and timestamp

packet-exchange/src/send_packet.c

@@ -40,7 +40,7 @@
 #define SERVER_PORT_INT 50000
 #define CLOCK_ID CLOCK_TAI
 #define MESSAGE ((uint32_t)0x00FACADE)
-#define NSEC_PER_SEC 1000000000
+#define NSEC_PER_SEC ((uint64_t)1000000000)
 
 static void print_timestamps(struct msghdr *msg, uint64_t txtime);
 static void process_timestamps(uint64_t txtime);
@@ -51,6 +51,8 @@ static unsigned char tx_buffer[1024] = "Hi";
 static size_t tx_buffer_len = sizeof(tx_buffer);
 static int fd;
 
+static int64_t tai_offset;
+
 static int so_timestamping_flags =
     SOF_TIMESTAMPING_TX_SOFTWARE | SOF_TIMESTAMPING_SOFTWARE;
 
@@ -74,6 +76,12 @@ void init_udp_etf(int use_etf, int use_timestamps, int packet_priority,
                   char *network_if) {
   int index;
 
+  struct timespec ts_mon;
+  struct timespec ts_tai;
+  clock_gettime(CLOCK_MONOTONIC, &ts_mon);
+  clock_gettime(CLOCK_TAI, &ts_tai);
+  tai_offset = (ts_mon.tv_sec - ts_tai.tv_sec) * NSEC_PER_SEC + (ts_mon.tv_nsec - ts_tai.tv_nsec);
+
   so_priority = packet_priority;
 
   fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP);
@@ -211,7 +219,7 @@ static void print_timestamps(struct msghdr *msg, uint64_t txtime) {
                 stamp->tv_sec * NSEC_PER_SEC + stamp->tv_nsec;
             printf("SO_TIMESTAMPING ");
             printf("SW %" PRIu64 " - %" PRIu64 " (%" PRIi64 ") ", timestamp_ns,
-                   txtime, ((int64_t)timestamp_ns) - txtime);
+                   txtime, ((int64_t)timestamp_ns) - txtime - tai_offset);
             break;
           }
           default: