net: new user space API for time stamping of incoming and outgoing packets

The existing interfaces for getting network packages time stamped are:

* SO_TIMESTAMP

  Generate time stamp for each incoming packet using the (not necessarily

  monotonous!) system time. Result is returned via recv_msg() in a

  control message as timeval (usec resolution).

* SO_TIMESTAMPNS

  Same time stamping mechanism as SO_TIMESTAMP, but returns result as

  timespec (nsec resolution).

* IP_MULTICAST_LOOP + SO_TIMESTAMP[NS]

  Only for multicasts: approximate send time stamp by receiving the looped

  packet and using its receive time stamp.

The following interface complements the existing ones: receive time

stamps can be generated and returned for arbitrary packets and much

closer to the point where the packet is really sent. Time stamps can

be generated in software (as before) or in hardware (if the hardware

has such a feature).

SO_TIMESTAMPING:

Instructs the socket layer which kind of information is wanted. The

parameter is an integer with some of the following bits set. Setting

other bits is an error and doesn't change the current state.

SOF_TIMESTAMPING_TX_HARDWARE:  try to obtain send time stamp in hardware

SOF_TIMESTAMPING_TX_SOFTWARE:  if SOF_TIMESTAMPING_TX_HARDWARE is off or

                               fails, then do it in software

SOF_TIMESTAMPING_RX_HARDWARE:  return the original, unmodified time stamp

                               as generated by the hardware

SOF_TIMESTAMPING_RX_SOFTWARE:  if SOF_TIMESTAMPING_RX_HARDWARE is off or

                               fails, then do it in software

SOF_TIMESTAMPING_RAW_HARDWARE: return original raw hardware time stamp

SOF_TIMESTAMPING_SYS_HARDWARE: return hardware time stamp transformed to

                               the system time base

SOF_TIMESTAMPING_SOFTWARE:     return system time stamp generated in

                               software

SOF_TIMESTAMPING_TX/RX determine how time stamps are generated.

SOF_TIMESTAMPING_RAW/SYS determine how they are reported in the

following control message:

    struct scm_timestamping {

           struct timespec systime;

           struct timespec hwtimetrans;

           struct timespec hwtimeraw;

    };

recvmsg() can be used to get this control message for regular incoming

packets. For send time stamps the outgoing packet is looped back to

the socket's error queue with the send time stamp(s) attached. It can

be received with recvmsg(flags=MSG_ERRQUEUE). The call returns the

original outgoing packet data including all headers preprended down to

and including the link layer, the scm_timestamping control message and

a sock_extended_err control message with ee_errno==ENOMSG and

ee_origin==SO_EE_ORIGIN_TIMESTAMPING. A socket with such a pending

bounced packet is ready for reading as far as select() is concerned.

All three values correspond to the same event in time, but were

generated in different ways. Each of these values may be empty (= all

zero), in which case no such value was available. If the application

is not interested in some of these values, they can be left blank to

avoid the potential overhead of calculating them.

systime is the value of the system time at that moment. This

corresponds to the value also returned via SO_TIMESTAMP[NS]. If the

time stamp was generated by hardware, then this field is

empty. Otherwise it is filled in if SOF_TIMESTAMPING_SOFTWARE is

set.

hwtimeraw is the original hardware time stamp. Filled in if

SOF_TIMESTAMPING_RAW_HARDWARE is set. No assumptions about its

relation to system time should be made.

hwtimetrans is the hardware time stamp transformed so that it

corresponds as good as possible to system time. This correlation is

not perfect; as a consequence, sorting packets received via different

NICs by their hwtimetrans may differ from the order in which they were

received. hwtimetrans may be non-monotonic even for the same NIC.

Filled in if SOF_TIMESTAMPING_SYS_HARDWARE is set. Requires support

by the network device and will be empty without that support.

SIOCSHWTSTAMP:

Hardware time stamping must also be initialized for each device driver

that is expected to do hardware time stamping. The parameter is:

struct hwtstamp_config {

    int flags;           /* no flags defined right now, must be zero */

    int tx_type;         /* HWTSTAMP_TX_* */

    int rx_filter;       /* HWTSTAMP_FILTER_* */

};

Desired behavior is passed into the kernel and to a specific device by

calling ioctl(SIOCSHWTSTAMP) with a pointer to a struct ifreq whose

ifr_data points to a struct hwtstamp_config. The tx_type and

rx_filter are hints to the driver what it is expected to do. If

the requested fine-grained filtering for incoming packets is not

supported, the driver may time stamp more than just the requested types

of packets.

A driver which supports hardware time stamping shall update the struct

with the actual, possibly more permissive configuration. If the

requested packets cannot be time stamped, then nothing should be

changed and ERANGE shall be returned (in contrast to EINVAL, which

indicates that SIOCSHWTSTAMP is not supported at all).

Only a processes with admin rights may change the configuration. User

space is responsible to ensure that multiple processes don't interfere

with each other and that the settings are reset.

/* possible values for hwtstamp_config->tx_type */

enum {

	/*

	 * no outgoing packet will need hardware time stamping;

	 * should a packet arrive which asks for it, no hardware

	 * time stamping will be done

	 */

	HWTSTAMP_TX_OFF,

	/*

	 * enables hardware time stamping for outgoing packets;

	 * the sender of the packet decides which are to be

	 * time stamped by setting SOF_TIMESTAMPING_TX_SOFTWARE

	 * before sending the packet

	 */

	HWTSTAMP_TX_ON,

};

/* possible values for hwtstamp_config->rx_filter */

enum {

	/* time stamp no incoming packet at all */

	HWTSTAMP_FILTER_NONE,

	/* time stamp any incoming packet */

	HWTSTAMP_FILTER_ALL,

        /* return value: time stamp all packets requested plus some others */

        HWTSTAMP_FILTER_SOME,

	/* PTP v1, UDP, any kind of event packet */

	HWTSTAMP_FILTER_PTP_V1_L4_EVENT,

        ...

};

DEVICE IMPLEMENTATION

A driver which supports hardware time stamping must support the

SIOCSHWTSTAMP ioctl. Time stamps for received packets must be stored

in the skb with skb_hwtstamp_set().

Time stamps for outgoing packets are to be generated as follows:

- In hard_start_xmit(), check if skb_hwtstamp_check_tx_hardware()

  returns non-zero. If yes, then the driver is expected

  to do hardware time stamping.

- If this is possible for the skb and requested, then declare

  that the driver is doing the time stamping by calling

  skb_hwtstamp_tx_in_progress(). A driver not supporting

  hardware time stamping doesn't do that. A driver must never

  touch sk_buff::tstamp! It is used to store how time stamping

  for an outgoing packets is to be done.

- As soon as the driver has sent the packet and/or obtained a

  hardware time stamp for it, it passes the time stamp back by

  calling skb_hwtstamp_tx() with the original skb, the raw

  hardware time stamp and a handle to the device (necessary

  to convert the hardware time stamp to system time). If obtaining

  the hardware time stamp somehow fails, then the driver should

  not fall back to software time stamping. The rationale is that

  this would occur at a later time in the processing pipeline

  than other software time stamping and therefore could lead

  to unexpected deltas between time stamps.

- If the driver did not call skb_hwtstamp_tx_in_progress(), then

  dev_hard_start_xmit() checks whether software time stamping

  is wanted as fallback and potentially generates the time stamp.

timestamping

CPPFLAGS = -I../../../include

timestamping: timestamping.c

clean:

	rm -f timestamping

/*

 * This program demonstrates how the various time stamping features in

 * the Linux kernel work. It emulates the behavior of a PTP

 * implementation in stand-alone master mode by sending PTPv1 Sync

 * multicasts once every second. It looks for similar packets, but

 * beyond that doesn't actually implement PTP.

 *

 * Outgoing packets are time stamped with SO_TIMESTAMPING with or

 * without hardware support.

 *

 * Incoming packets are time stamped with SO_TIMESTAMPING with or

 * without hardware support, SIOCGSTAMP[NS] (per-socket time stamp) and

 * SO_TIMESTAMP[NS].

 *

 * Copyright (C) 2009 Intel Corporation.

 * Author: Patrick Ohly <patrick.ohly@intel.com>

 *

 * This program is free software; you can redistribute it and/or modify it

 * under the terms and conditions of the GNU General Public License,

 * version 2, as published by the Free Software Foundation.

 *

 * This program is distributed in the hope it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE. * See the GNU General Public License for

 * more details.

 *

 * You should have received a copy of the GNU General Public License along with

 * this program; if not, write to the Free Software Foundation, Inc.,

 * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.

 */

#include <stdio.h>

#include <stdlib.h>

#include <errno.h>

#include <string.h>

#include <sys/time.h>

#include <sys/socket.h>

#include <sys/select.h>

#include <sys/ioctl.h>

#include <arpa/inet.h>

#include <net/if.h>

#include "asm/types.h"

#include "linux/net_tstamp.h"

#include "linux/errqueue.h"

#ifndef SO_TIMESTAMPING

# define SO_TIMESTAMPING         37

# define SCM_TIMESTAMPING        SO_TIMESTAMPING

#endif

#ifndef SO_TIMESTAMPNS

# define SO_TIMESTAMPNS 35

#endif

#ifndef SIOCGSTAMPNS

# define SIOCGSTAMPNS 0x8907

#endif

#ifndef SIOCSHWTSTAMP

# define SIOCSHWTSTAMP 0x89b0

#endif

static void usage(const char *error)

{

	if (error)

		printf("invalid option: %s\n", error);

	printf("timestamping interface option*\n\n"

	       "Options:\n"

	       "  IP_MULTICAST_LOOP - looping outgoing multicasts\n"

	       "  SO_TIMESTAMP - normal software time stamping, ms resolution\n"

	       "  SO_TIMESTAMPNS - more accurate software time stamping\n"

	       "  SOF_TIMESTAMPING_TX_HARDWARE - hardware time stamping of outgoing packets\n"

	       "  SOF_TIMESTAMPING_TX_SOFTWARE - software fallback for outgoing packets\n"

	       "  SOF_TIMESTAMPING_RX_HARDWARE - hardware time stamping of incoming packets\n"

	       "  SOF_TIMESTAMPING_RX_SOFTWARE - software fallback for incoming packets\n"

	       "  SOF_TIMESTAMPING_SOFTWARE - request reporting of software time stamps\n"

	       "  SOF_TIMESTAMPING_SYS_HARDWARE - request reporting of transformed HW time stamps\n"

	       "  SOF_TIMESTAMPING_RAW_HARDWARE - request reporting of raw HW time stamps\n"

	       "  SIOCGSTAMP - check last socket time stamp\n"

	       "  SIOCGSTAMPNS - more accurate socket time stamp\n");

	exit(1);

}

static void bail(const char *error)

{

	printf("%s: %s\n", error, strerror(errno));

	exit(1);

}

static const unsigned char sync[] = {

	0x00, 0x01, 0x00, 0x01,

	0x5f, 0x44, 0x46, 0x4c,

	0x54, 0x00, 0x00, 0x00,

	0x00, 0x00, 0x00, 0x00,

	0x00, 0x00, 0x00, 0x00,

	0x01, 0x01,

	/* fake uuid */

	0x00, 0x01,

	0x02, 0x03, 0x04, 0x05,

	0x00, 0x01, 0x00, 0x37,

	0x00, 0x00, 0x00, 0x08,

	0x00, 0x00, 0x00, 0x00,

	0x49, 0x05, 0xcd, 0x01,

	0x29, 0xb1, 0x8d, 0xb0,

	0x00, 0x00, 0x00, 0x00,

	0x00, 0x01,

	/* fake uuid */

	0x00, 0x01,

	0x02, 0x03, 0x04, 0x05,

	0x00, 0x00, 0x00, 0x37,

	0x00, 0x00, 0x00, 0x04,

	0x44, 0x46, 0x4c, 0x54,

	0x00, 0x00, 0xf0, 0x60,

	0x00, 0x01, 0x00, 0x00,

	0x00, 0x00, 0x00, 0x01,

	0x00, 0x00, 0xf0, 0x60,

	0x00, 0x00, 0x00, 0x00,

	0x00, 0x00, 0x00, 0x04,

	0x44, 0x46, 0x4c, 0x54,

	0x00, 0x01,

	/* fake uuid */

	0x00, 0x01,

	0x02, 0x03, 0x04, 0x05,

	0x00, 0x00, 0x00, 0x00,

	0x00, 0x00, 0x00, 0x00,

	0x00, 0x00, 0x00, 0x00,

	0x00, 0x00, 0x00, 0x00

};

static void sendpacket(int sock, struct sockaddr *addr, socklen_t addr_len)

{

	struct timeval now;

	int res;

	res = sendto(sock, sync, sizeof(sync), 0,

		addr, addr_len);

	gettimeofday(&now, 0);

	if (res < 0)

		printf("%s: %s\n", "send", strerror(errno));

	else

		printf("%ld.%06ld: sent %d bytes\n",

		       (long)now.tv_sec, (long)now.tv_usec,

		       res);

}

static void printpacket(struct msghdr *msg, int res,

			char *data,

			int sock, int recvmsg_flags,

			int siocgstamp, int siocgstampns)

{

	struct sockaddr_in *from_addr = (struct sockaddr_in *)msg->msg_name;

	struct cmsghdr *cmsg;

	struct timeval tv;

	struct timespec ts;

	struct timeval now;

	gettimeofday(&now, 0);

	printf("%ld.%06ld: received %s data, %d bytes from %s, %d bytes control messages\n",

	       (long)now.tv_sec, (long)now.tv_usec,

	       (recvmsg_flags & MSG_ERRQUEUE) ? "error" : "regular",

	       res,

	       inet_ntoa(from_addr->sin_addr),

	       msg->msg_controllen);

	for (cmsg = CMSG_FIRSTHDR(msg);

	     cmsg;

	     cmsg = CMSG_NXTHDR(msg, cmsg)) {

		printf("   cmsg len %d: ", cmsg->cmsg_len);

		switch (cmsg->cmsg_level) {

		case SOL_SOCKET:

			printf("SOL_SOCKET ");

			switch (cmsg->cmsg_type) {

			case SO_TIMESTAMP: {

				struct timeval *stamp =

					(struct timeval *)CMSG_DATA(cmsg);

				printf("SO_TIMESTAMP %ld.%06ld",

				       (long)stamp->tv_sec,

				       (long)stamp->tv_usec);

				break;

			}

			case SO_TIMESTAMPNS: {

				struct timespec *stamp =

					(struct timespec *)CMSG_DATA(cmsg);

				printf("SO_TIMESTAMPNS %ld.%09ld",

				       (long)stamp->tv_sec,

				       (long)stamp->tv_nsec);

				break;

			}

			case SO_TIMESTAMPING: {

				struct timespec *stamp =

					(struct timespec *)CMSG_DATA(cmsg);

				printf("SO_TIMESTAMPING ");

				printf("SW %ld.%09ld ",

				       (long)stamp->tv_sec,

				       (long)stamp->tv_nsec);

				stamp++;

				printf("HW transformed %ld.%09ld ",

				       (long)stamp->tv_sec,

				       (long)stamp->tv_nsec);

				stamp++;

				printf("HW raw %ld.%09ld",

				       (long)stamp->tv_sec,

				       (long)stamp->tv_nsec);

				break;

			}

			default:

				printf("type %d", cmsg->cmsg_type);

				break;

			}

			break;

		case IPPROTO_IP:

			printf("IPPROTO_IP ");

			switch (cmsg->cmsg_type) {

			case IP_RECVERR: {

				struct sock_extended_err *err =

					(struct sock_extended_err *)CMSG_DATA(cmsg);

				printf("IP_RECVERR ee_errno '%s' ee_origin %d => %s",

					strerror(err->ee_errno),

					err->ee_origin,

#ifdef SO_EE_ORIGIN_TIMESTAMPING

					err->ee_origin == SO_EE_ORIGIN_TIMESTAMPING ?

					"bounced packet" : "unexpected origin"

#else

					"probably SO_EE_ORIGIN_TIMESTAMPING"

#endif

					);

				if (res < sizeof(sync))

					printf(" => truncated data?!");

				else if (!memcmp(sync, data + res - sizeof(sync),

							sizeof(sync)))

					printf(" => GOT OUR DATA BACK (HURRAY!)");

				break;

			}

			case IP_PKTINFO: {

				struct in_pktinfo *pktinfo =

					(struct in_pktinfo *)CMSG_DATA(cmsg);

				printf("IP_PKTINFO interface index %u",

					pktinfo->ipi_ifindex);

				break;

			}

			default:

				printf("type %d", cmsg->cmsg_type);

				break;

			}

			break;

		default:

			printf("level %d type %d",

				cmsg->cmsg_level,

				cmsg->cmsg_type);

			break;

		}

		printf("\n");

	}

	if (siocgstamp) {

		if (ioctl(sock, SIOCGSTAMP, &tv))

			printf("   %s: %s\n", "SIOCGSTAMP", strerror(errno));

		else

			printf("SIOCGSTAMP %ld.%06ld\n",

			       (long)tv.tv_sec,

			       (long)tv.tv_usec);

	}

	if (siocgstampns) {

		if (ioctl(sock, SIOCGSTAMPNS, &ts))

			printf("   %s: %s\n", "SIOCGSTAMPNS", strerror(errno));

		else

			printf("SIOCGSTAMPNS %ld.%09ld\n",

			       (long)ts.tv_sec,

			       (long)ts.tv_nsec);

	}

}

static void recvpacket(int sock, int recvmsg_flags,

		       int siocgstamp, int siocgstampns)

{

	char data[256];

	struct msghdr msg;

	struct iovec entry;

	struct sockaddr_in from_addr;

	struct {

		struct cmsghdr cm;

		char control[512];

	} control;

	int res;

	memset(&msg, 0, sizeof(msg));

	msg.msg_iov = &entry;

	msg.msg_iovlen = 1;

	entry.iov_base = data;

	entry.iov_len = sizeof(data);

	msg.msg_name = (caddr_t)&from_addr;

	msg.msg_namelen = sizeof(from_addr);

	msg.msg_control = &control;

	msg.msg_controllen = sizeof(control);

	res = recvmsg(sock, &msg, recvmsg_flags|MSG_DONTWAIT);

	if (res < 0) {

		printf("%s %s: %s\n",

		       "recvmsg",

		       (recvmsg_flags & MSG_ERRQUEUE) ? "error" : "regular",

		       strerror(errno));

	} else {

		printpacket(&msg, res, data,

			    sock, recvmsg_flags,

			    siocgstamp, siocgstampns);

	}

}

int main(int argc, char **argv)

{

	int so_timestamping_flags = 0;

	int so_timestamp = 0;

	int so_timestampns = 0;

	int siocgstamp = 0;

	int siocgstampns = 0;

	int ip_multicast_loop = 0;

	char *interface;

	int i;

	int enabled = 1;

	int sock;

	struct ifreq device;

	struct ifreq hwtstamp;

	struct hwtstamp_config hwconfig, hwconfig_requested;

	struct sockaddr_in addr;

	struct ip_mreq imr;

	struct in_addr iaddr;

	int val;

	socklen_t len;

	struct timeval next;

	if (argc < 2)

		usage(0);

	interface = argv[1];

	for (i = 2; i < argc; i++) {

		if (!strcasecmp(argv[i], "SO_TIMESTAMP"))

			so_timestamp = 1;

		else if (!strcasecmp(argv[i], "SO_TIMESTAMPNS"))

			so_timestampns = 1;

		else if (!strcasecmp(argv[i], "SIOCGSTAMP"))

			siocgstamp = 1;

		else if (!strcasecmp(argv[i], "SIOCGSTAMPNS"))

			siocgstampns = 1;

		else if (!strcasecmp(argv[i], "IP_MULTICAST_LOOP"))

			ip_multicast_loop = 1;

		else if (!strcasecmp(argv[i], "SOF_TIMESTAMPING_TX_HARDWARE"))

			so_timestamping_flags |= SOF_TIMESTAMPING_TX_HARDWARE;

		else if (!strcasecmp(argv[i], "SOF_TIMESTAMPING_TX_SOFTWARE"))

			so_timestamping_flags |= SOF_TIMESTAMPING_TX_SOFTWARE;

		else if (!strcasecmp(argv[i], "SOF_TIMESTAMPING_RX_HARDWARE"))

			so_timestamping_flags |= SOF_TIMESTAMPING_RX_HARDWARE;

		else if (!strcasecmp(argv[i], "SOF_TIMESTAMPING_RX_SOFTWARE"))

			so_timestamping_flags |= SOF_TIMESTAMPING_RX_SOFTWARE;

		else if (!strcasecmp(argv[i], "SOF_TIMESTAMPING_SOFTWARE"))

			so_timestamping_flags |= SOF_TIMESTAMPING_SOFTWARE;

		else if (!strcasecmp(argv[i], "SOF_TIMESTAMPING_SYS_HARDWARE"))

			so_timestamping_flags |= SOF_TIMESTAMPING_SYS_HARDWARE;

		else if (!strcasecmp(argv[i], "SOF_TIMESTAMPING_RAW_HARDWARE"))

			so_timestamping_flags |= SOF_TIMESTAMPING_RAW_HARDWARE;

		else

			usage(argv[i]);

	}

	sock = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP);

	if (socket < 0)

		bail("socket");

	memset(&device, 0, sizeof(device));

	strncpy(device.ifr_name, interface, sizeof(device.ifr_name));

	if (ioctl(sock, SIOCGIFADDR, &device) < 0)

		bail("getting interface IP address");

	memset(&hwtstamp, 0, sizeof(hwtstamp));

	strncpy(hwtstamp.ifr_name, interface, sizeof(hwtstamp.ifr_name));

	hwtstamp.ifr_data = (void *)&hwconfig;

	memset(&hwconfig, 0, sizeof(&hwconfig));

	hwconfig.tx_type =

		(so_timestamping_flags & SOF_TIMESTAMPING_TX_HARDWARE) ?

		HWTSTAMP_TX_ON : HWTSTAMP_TX_OFF;

	hwconfig.rx_filter =

		(so_timestamping_flags & SOF_TIMESTAMPING_RX_HARDWARE) ?

		HWTSTAMP_FILTER_PTP_V1_L4_SYNC : HWTSTAMP_FILTER_NONE;

	hwconfig_requested = hwconfig;

	if (ioctl(sock, SIOCSHWTSTAMP, &hwtstamp) < 0) {

		if ((errno == EINVAL || errno == ENOTSUP) &&

		    hwconfig_requested.tx_type == HWTSTAMP_TX_OFF &&

		    hwconfig_requested.rx_filter == HWTSTAMP_FILTER_NONE)

			printf("SIOCSHWTSTAMP: disabling hardware time stamping not possible\n");

		else

			bail("SIOCSHWTSTAMP");

	}

	printf("SIOCSHWTSTAMP: tx_type %d requested, got %d; rx_filter %d requested, got %d\n",

	       hwconfig_requested.tx_type, hwconfig.tx_type,

	       hwconfig_requested.rx_filter, hwconfig.rx_filter);

	/* bind to PTP port */

	addr.sin_family = AF_INET;

	addr.sin_addr.s_addr = htonl(INADDR_ANY);

	addr.sin_port = htons(319 /* PTP event port */);

	if (bind(sock,

		 (struct sockaddr *)&addr,

		 sizeof(struct sockaddr_in)) < 0)

		bail("bind");

	/* set multicast group for outgoing packets */

	inet_aton("224.0.1.130", &iaddr); /* alternate PTP domain 1 */

	addr.sin_addr = iaddr;

	imr.imr_multiaddr.s_addr = iaddr.s_addr;

	imr.imr_interface.s_addr =

		((struct sockaddr_in *)&device.ifr_addr)->sin_addr.s_addr;

	if (setsockopt(sock, IPPROTO_IP, IP_MULTICAST_IF,

		       &imr.imr_interface.s_addr, sizeof(struct in_addr)) < 0)

		bail("set multicast");

	/* join multicast group, loop our own packet */

	if (setsockopt(sock, IPPROTO_IP, IP_ADD_MEMBERSHIP,

		       &imr, sizeof(struct ip_mreq)) < 0)

		bail("join multicast group");

	if (setsockopt(sock, IPPROTO_IP, IP_MULTICAST_LOOP,

		       &ip_multicast_loop, sizeof(enabled)) < 0) {

		bail("loop multicast");

	}

	/* set socket options for time stamping */

	if (so_timestamp &&

		setsockopt(sock, SOL_SOCKET, SO_TIMESTAMP,

			   &enabled, sizeof(enabled)) < 0)

		bail("setsockopt SO_TIMESTAMP");

	if (so_timestampns &&

		setsockopt(sock, SOL_SOCKET, SO_TIMESTAMPNS,

			   &enabled, sizeof(enabled)) < 0)

		bail("setsockopt SO_TIMESTAMPNS");

	if (so_timestamping_flags &&

		setsockopt(sock, SOL_SOCKET, SO_TIMESTAMPING,

			   &so_timestamping_flags,

			   sizeof(so_timestamping_flags)) < 0)

		bail("setsockopt SO_TIMESTAMPING");

	/* request IP_PKTINFO for debugging purposes */

	if (setsockopt(sock, SOL_IP, IP_PKTINFO,

		       &enabled, sizeof(enabled)) < 0)

		printf("%s: %s\n", "setsockopt IP_PKTINFO", strerror(errno));

	/* verify socket options */

	len = sizeof(val);

	if (getsockopt(sock, SOL_SOCKET, SO_TIMESTAMP, &val, &len) < 0)

		printf("%s: %s\n", "getsockopt SO_TIMESTAMP", strerror(errno));

	else

		printf("SO_TIMESTAMP %d\n", val);

	if (getsockopt(sock, SOL_SOCKET, SO_TIMESTAMPNS, &val, &len) < 0)

		printf("%s: %s\n", "getsockopt SO_TIMESTAMPNS",

		       strerror(errno));

	else

		printf("SO_TIMESTAMPNS %d\n", val);

	if (getsockopt(sock, SOL_SOCKET, SO_TIMESTAMPING, &val, &len) < 0) {

		printf("%s: %s\n", "getsockopt SO_TIMESTAMPING",

		       strerror(errno));

	} else {

		printf("SO_TIMESTAMPING %d\n", val);

		if (val != so_timestamping_flags)

			printf("   not the expected value %d\n",

			       so_timestamping_flags);

	}

	/* send packets forever every five seconds */

	gettimeofday(&next, 0);

	next.tv_sec = (next.tv_sec + 1) / 5 * 5;

	next.tv_usec = 0;

	while (1) {

		struct timeval now;

		struct timeval delta;

		long delta_us;

		int res;

		fd_set readfs, errorfs;

		gettimeofday(&now, 0);

		delta_us = (long)(next.tv_sec - now.tv_sec) * 1000000 +

			(long)(next.tv_usec - now.tv_usec);

		if (delta_us > 0) {

			/* continue waiting for timeout or data */

			delta.tv_sec = delta_us / 1000000;

			delta.tv_usec = delta_us % 1000000;

			FD_ZERO(&readfs);

			FD_ZERO(&errorfs);

			FD_SET(sock, &readfs);

			FD_SET(sock, &errorfs);

			printf("%ld.%06ld: select %ldus\n",

			       (long)now.tv_sec, (long)now.tv_usec,

			       delta_us);

			res = select(sock + 1, &readfs, 0, &errorfs, &delta);

			gettimeofday(&now, 0);

			printf("%ld.%06ld: select returned: %d, %s\n",

			       (long)now.tv_sec, (long)now.tv_usec,

			       res,

			       res < 0 ? strerror(errno) : "success");

			if (res > 0) {

				if (FD_ISSET(sock, &readfs))

					printf("ready for reading\n");

				if (FD_ISSET(sock, &errorfs))

					printf("has error\n");

				recvpacket(sock, 0,

					   siocgstamp,

					   siocgstampns);

				recvpacket(sock, MSG_ERRQUEUE,

					   siocgstamp,

					   siocgstampns);

			}

		} else {

			/* write one packet */

			sendpacket(sock,

				   (struct sockaddr *)&addr,

				   sizeof(addr));

			next.tv_sec += 5;

			continue;

		}

	}

	return 0;

}

#define SO_MARK			36

#define SO_TIMESTAMPING		37

#define SCM_TIMESTAMPING	SO_TIMESTAMPING

/* O_NONBLOCK clashes with the bits used for socket types.  Therefore we

 * have to define SOCK_NONBLOCK to a different value here.