Compare txtime to timestamp

packet-exchange/src/send_packet.c

@@ -14,6 +14,7 @@
 #include <error.h>
 #include <fcntl.h>
 #include <ifaddrs.h>
+#include <inttypes.h>
 #include <linux/errqueue.h>
 #include <linux/ethtool.h>
 #include <linux/net_tstamp.h>
@@ -41,8 +42,8 @@
 #define MESSAGE ((uint32_t)0x00FACADE)
 #define NSEC_PER_SEC 1000000000
 
-static void print_timestamps(struct msghdr *msg);
-static void process_timestamps();
+static void print_timestamps(struct msghdr *msg, uint64_t txtime);
+static void process_timestamps(uint64_t txtime);
 
 static int so_priority = 3;
 static struct sock_txtime sk_txtime;
@@ -160,17 +161,16 @@ void send_udp_packet(int use_etf, int use_timestamps, uint64_t txtime,
   if (sendmsgerr < 0)
     error(EXIT_FAILURE, errno, "sendmsg failed, ret value: %d\n", sendmsgerr);
 
-  if(use_timestamps) {
-
+  if (use_timestamps) {
     res = poll(&poll_fd, 1, 0);
     if (res > 0)
-      process_timestamps();
+      process_timestamps(txtime);
     else
       fprintf(stderr, "select failed\n");
   }
 }
 
-static void process_timestamps() {
+static void process_timestamps(uint64_t txtime) {
   char data[256];
   struct msghdr msg;
   struct iovec entry;
@@ -192,13 +192,12 @@ static void process_timestamps() {
 
   if (recvmsg(fd, &msg, MSG_ERRQUEUE | MSG_DONTWAIT) == -1) {
     fprintf(stderr, "recvmsg failed\n");
-  }
-  else {
-    print_timestamps(&msg);
+  } else {
+    print_timestamps(&msg, txtime);
   }
 }
 
-static void print_timestamps(struct msghdr *msg) {
+static void print_timestamps(struct msghdr *msg, uint64_t txtime) {
   struct cmsghdr *cmsg;
 
   for (cmsg = CMSG_FIRSTHDR(msg); cmsg; cmsg = CMSG_NXTHDR(msg, cmsg)) {
@@ -208,8 +207,11 @@ static void print_timestamps(struct msghdr *msg) {
         switch (cmsg->cmsg_type) {
           case SO_TIMESTAMPING: {
             struct timespec *stamp = (struct timespec *)CMSG_DATA(cmsg);
+            uint64_t timestamp_ns =
+                stamp->tv_sec * NSEC_PER_SEC + stamp->tv_nsec;
             printf("SO_TIMESTAMPING ");
-            printf("SW %ld.%09ld ", (long)stamp->tv_sec, (long)stamp->tv_nsec);
+            printf("SW %" PRIu64 " - %" PRIu64 " (%" PRIi64 ") ", timestamp_ns,
+                   txtime, ((int64_t)timestamp_ns) - txtime);
             break;
           }
           default:
@@ -246,7 +248,6 @@ static int process_socket_error_queue() {
                        .msg_control = msg_control,
                        .msg_controllen = sizeof(msg_control)};
 
-
   if (recvmsg(fd, &msg, MSG_ERRQUEUE) == -1) {
     fprintf(stderr, "recvmsg failed");
     return -1;