liboping: use SO_TIMESTAMP when available

Current implementation of liboping relies on getting enough CPU shares
and getting those in a timely manner in order to determine correct ping
response times.

Avoid this limitation when kernel is able to provide packet reception
times using SO_TIMESTAMP. (as is done by iputils's ping utility)

Signed-off-by: Florian Forster <octo@verplant.org>

diff --git a/src/liboping.c b/src/liboping.c
index 4616843..d3fd35c 100644 (file)
--- a/src/liboping.c
+++ b/src/liboping.c
@@ -450,7 +450,7 @@ static int ping_receive_one (pingobj_t *obj, const pinghost_t *ph,
         * reply. The right object will be returned by ping_receive_ipv*(). For
         * now, we can only rely on ph->fd and ph->addrfamily. */
 
-       struct timeval diff;
+       struct timeval diff, pkt_now = *now;
        pinghost_t *host = NULL;
        int recv_ttl;
        uint8_t recv_qos;
@@ -504,6 +504,11 @@ static int ping_receive_one (pingobj_t *obj, const pinghost_t *ph,
                        cmsg != NULL;
                        cmsg = CMSG_NXTHDR (&msghdr, cmsg))
        {
+#ifdef SO_TIMESTAMP
+               if (cmsg->cmsg_level == SOL_SOCKET && cmsg->cmsg_type == SO_TIMESTAMP)
+                       memcpy(&pkt_now, CMSG_DATA(cmsg), sizeof(pkt_now));
+#endif /* SO_TIMESTAMP */
+
                if (ph->addrfamily == AF_INET) /* {{{ */
                {
                        if (cmsg->cmsg_level != IPPROTO_IP)
@@ -578,13 +583,13 @@ static int ping_receive_one (pingobj_t *obj, const pinghost_t *ph,
        }
 
        dprintf ("rcvd: %12i.%06i\n",
-                       (int) now->tv_sec,
-                       (int) now->tv_usec);
+                       (int) pkt_now.tv_sec,
+                       (int) pkt_now.tv_usec);
        dprintf ("sent: %12i.%06i\n",
                        (int) host->timer->tv_sec,
                        (int) host->timer->tv_usec);
 
-       if (ping_timeval_sub (now, host->timer, &diff) < 0)
+       if (ping_timeval_sub (&pkt_now, host->timer, &diff) < 0)
        {
                timerclear (host->timer);
                return (-1);
@@ -1478,7 +1483,13 @@ int ping_host_add (pingobj_t *obj, const char *host)
                        }
                }
 #endif /* SO_BINDTODEVICE */
-
+#ifdef SO_TIMESTAMP
+               if (1)
+               {
+                       int c = 1;
+                       setsockopt(ph->fd, SOL_SOCKET, SO_TIMESTAMP, &c, sizeof(c));
+               }
+#endif /* SO_TIMESTAMP */
                assert (sizeof (struct sockaddr_storage) >= ai_ptr->ai_addrlen);
                memset (ph->addr, '\0', sizeof (struct sockaddr_storage));
                memcpy (ph->addr, ai_ptr->ai_addr, ai_ptr->ai_addrlen);