githubmirror/iputils

ping6_common.c
1 387 строк36 KB
Sami Kerola
ping: option -N help should output to stdout, and exit with 0
15 апр 2019, 23:17
15 апр 2019, 23:171d628d1
/*
 *
 *	Modified for AF_INET6 by Pedro Roque
 *
 *	<roque@di.fc.ul.pt>
 *
 *	Original copyright notice included below
 */

/*
 * Copyright (c) 1989 The Regents of the University of California.
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Mike Muuss.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */
/*
 *			P I N G . C
 *
 * Using the InterNet Control Message Protocol (ICMP) "ECHO" facility,
 * measure round-trip-delays and packet loss across network paths.
 *
 * Author -
 *	Mike Muuss
 *	U. S. Army Ballistic Research Laboratory
 *	December, 1983
 *
 * Status -
 *	Public Domain.  Distribution Unlimited.
 * Bugs -
 *	More statistics could always be gathered.
 *	If kernel does not support non-raw ICMP sockets or
 *	if -N option is used, this program has to run SUID to ROOT or
 *	with net_cap_raw enabled.
 */
#include <stddef.h>
#include "iputils_common.h"
#include "iputils_ni.h"
#include "ping.h"

ping_func_set_st ping6_func_set = {
	.send_probe = ping6_send_probe,
	.receive_error_msg = ping6_receive_error_msg,
	.parse_reply = ping6_parse_reply,
	.install_filter = ping6_install_filter
};

#ifndef SCOPE_DELIMITER
# define SCOPE_DELIMITER '%'
#endif

uint32_t flowlabel;
uint32_t tclass;

static struct sockaddr_in6 whereto;
static struct sockaddr_in6 firsthop;

static unsigned char cmsgbuf[4096];
static size_t cmsglen = 0;

static int pr_icmph(uint8_t type, uint8_t code, uint32_t info);

struct sockaddr_in6 source6 = { .sin6_family = AF_INET6 };
extern char *device;

#if defined(USE_GCRYPT) || defined(USE_OPENSSL) || defined(USE_NETTLE) || defined(USE_KERNEL_CRYPTO_API)
#include "iputils_md5dig.h"
#define USE_CRYPTO
#endif

/* Node Information query */
int ni_query = -1;
int ni_flag = 0;
void *ni_subject = NULL;
int ni_subject_len = 0;
int ni_subject_type = -1;
char *ni_group;

static inline int ntohsp(uint16_t *p)
{
	uint16_t v;
	memcpy(&v, p, sizeof(v));
	return ntohs(v);
}

unsigned int if_name2index(const char *ifname)
{
	unsigned int i = if_nametoindex(ifname);
	if (!i)
		error(2, 0, _("unknown iface: %s"), ifname);
	return i;
}

struct niquery_option {
	char *name;
	int namelen;
	int has_arg;
	int data;
	int (*handler)(int index, const char *arg);
};

#define NIQUERY_OPTION(_name, _has_arg, _data, _handler)	\
	{							\
		.name = _name,					\
		.namelen = sizeof(_name) - 1,			\
		.has_arg = _has_arg,				\
		.data = _data,					\
		.handler = _handler				\
	}

static int niquery_option_name_handler(int index __attribute__((__unused__)), const char *arg __attribute__((__unused__)));
static int niquery_option_ipv6_handler(int index __attribute__((__unused__)), const char *arg __attribute__((__unused__)));
static int niquery_option_ipv6_flag_handler(int index, const char *arg);
static int niquery_option_ipv4_handler(int index, const char *arg);
static int niquery_option_ipv4_flag_handler(int index, const char *arg);
static int niquery_option_subject_addr_handler(int index, const char *arg);
static int niquery_option_subject_name_handler(int index, const char *arg);
static int niquery_option_help_handler(int index, const char *arg);

struct niquery_option niquery_options[] = {
	NIQUERY_OPTION("name",			0,	0,				niquery_option_name_handler),
	NIQUERY_OPTION("fqdn",			0,	0,				niquery_option_name_handler),
	NIQUERY_OPTION("ipv6",			0,	0,				niquery_option_ipv6_handler),
	NIQUERY_OPTION("ipv6-all",		0,	IPUTILS_NI_IPV6_FLAG_ALL,	niquery_option_ipv6_flag_handler),
	NIQUERY_OPTION("ipv6-compatible",	0,	IPUTILS_NI_IPV6_FLAG_COMPAT,	niquery_option_ipv6_flag_handler),
	NIQUERY_OPTION("ipv6-linklocal",	0,	IPUTILS_NI_IPV6_FLAG_LINKLOCAL,	niquery_option_ipv6_flag_handler),
	NIQUERY_OPTION("ipv6-sitelocal",	0,	IPUTILS_NI_IPV6_FLAG_SITELOCAL,	niquery_option_ipv6_flag_handler),
	NIQUERY_OPTION("ipv6-global",		0,	IPUTILS_NI_IPV6_FLAG_GLOBAL,	niquery_option_ipv6_flag_handler),
	NIQUERY_OPTION("ipv4",			0,	0,				niquery_option_ipv4_handler),
	NIQUERY_OPTION("ipv4-all",		0,	IPUTILS_NI_IPV4_FLAG_ALL,	niquery_option_ipv4_flag_handler),
	NIQUERY_OPTION("subject-ipv6",		1,	IPUTILS_NI_ICMP6_SUBJ_IPV6,	niquery_option_subject_addr_handler),
	NIQUERY_OPTION("subject-ipv4",		1,	IPUTILS_NI_ICMP6_SUBJ_IPV4,	niquery_option_subject_addr_handler),
	NIQUERY_OPTION("subject-name",		1,	0,				niquery_option_subject_name_handler),
	NIQUERY_OPTION("subject-fqdn",		1,	-1,				niquery_option_subject_name_handler),
	NIQUERY_OPTION("help",			0,	0,				niquery_option_help_handler),
	{NULL, 0, 0, 0, NULL}
};

static inline int niquery_is_enabled(void)
{
	return ni_query >= 0;
}

#if PING6_NONCE_MEMORY
uint8_t *ni_nonce_ptr;
#else
struct {
	struct timeval tv;
	pid_t pid;
} ni_nonce_secret;
#endif

static void niquery_init_nonce(void)
{
#if PING6_NONCE_MEMORY
	struct timeval tv;
	unsigned long seed;

	seed = (unsigned long)getpid();
	if (!gettimeofday(&tv, NULL))
		seed ^= tv.tv_usec;
	srand(seed);

	ni_nonce_ptr = calloc(NI_NONCE_SIZE, MAX_DUP_CHK);
	if (!ni_nonce_ptr)
		error(2, errno, "calloc");

	ni_nonce_ptr[0] = ~0;
#else
	gettimeofday(&ni_nonce_secret.tv, NULL);
	ni_nonce_secret.pid = getpid();
#endif
}

#if !PING6_NONCE_MEMORY
static int niquery_nonce(uint8_t *nonce, int fill)
{
# ifdef USE_CRYPTO
	static uint8_t digest[MD5_DIGEST_LENGTH];
	static int seq = -1;

	if (fill || seq != *(uint16_t *)nonce || seq < 0) {
		MD5_CTX ctxt;

		MD5_Init(&ctxt);
		MD5_Update(&ctxt, &ni_nonce_secret, sizeof(ni_nonce_secret));
		MD5_Update(&ctxt, nonce, sizeof(uint16_t));
		MD5_Final(digest, &ctxt);

		seq = *(uint16_t *)nonce;
	}

	if (fill) {
		memcpy(nonce + sizeof(uint16_t), digest, NI_NONCE_SIZE - sizeof(uint16_t));
		return 0;
	} else {
		if (memcmp(nonce + sizeof(uint16_t), digest, NI_NONCE_SIZE - sizeof(uint16_t)))
			return -1;
		return ntohsp((uint16_t *)nonce);
	}
# else
	error(3, ENOSYS, _("niquery_nonce() crypto disabled"));
# endif
}
#endif

static inline void niquery_fill_nonce(uint16_t seq, uint8_t *nonce)
{
	uint16_t v = htons(seq);
#if PING6_NONCE_MEMORY
	int i;

	memcpy(&ni_nonce_ptr[NI_NONCE_SIZE * (seq % MAX_DUP_CHK)], &v, sizeof(v));

	for (i = sizeof(v); i < NI_NONCE_SIZE; i++)
		ni_nonce_ptr[NI_NONCE_SIZE * (seq % MAX_DUP_CHK) + i] = 0x100 * (rand() / (RAND_MAX + 1.0));

	memcpy(nonce, &ni_nonce_ptr[NI_NONCE_SIZE * (seq % MAX_DUP_CHK)], NI_NONCE_SIZE);
#else
	memcpy(nonce, &v, sizeof(v));
	niquery_nonce(nonce, 1);
#endif
}

static inline int niquery_check_nonce(uint8_t *nonce)
{
#if PING6_NONCE_MEMORY
	uint16_t seq = ntohsp((uint16_t *)nonce);
	if (memcmp(nonce, &ni_nonce_ptr[NI_NONCE_SIZE * (seq % MAX_DUP_CHK)], NI_NONCE_SIZE))
		return -1;
	return seq;
#else
	return niquery_nonce(nonce, 0);
#endif
}

static int niquery_set_qtype(int type)
{
	if (niquery_is_enabled() && ni_query != type) {
		printf(_("Qtype conflict\n"));
		return -1;
	}
	ni_query = type;
	return 0;
}

static int niquery_option_name_handler(int index __attribute__((__unused__)), const char *arg __attribute__((__unused__)))
{
	if (niquery_set_qtype(IPUTILS_NI_QTYPE_DNSNAME) < 0)
		return -1;
	return 0;
}

static int niquery_option_ipv6_handler(int index __attribute__((__unused__)), const char *arg __attribute__((__unused__)))
{
	if (niquery_set_qtype(IPUTILS_NI_QTYPE_IPV6ADDR) < 0)
		return -1;
	return 0;
}

static int niquery_option_ipv6_flag_handler(int index, const char *arg __attribute__((__unused__)))
{
	if (niquery_set_qtype(IPUTILS_NI_QTYPE_IPV6ADDR) < 0)
		return -1;
	ni_flag |= niquery_options[index].data;
	return 0;
}

static int niquery_option_ipv4_handler(int index __attribute__((__unused__)), const char *arg __attribute__((__unused__)))
{
	if (niquery_set_qtype(IPUTILS_NI_QTYPE_IPV4ADDR) < 0)
		return -1;
	return 0;
}

static int niquery_option_ipv4_flag_handler(int index, const char *arg __attribute__((__unused__)))
{
	if (niquery_set_qtype(IPUTILS_NI_QTYPE_IPV4ADDR) < 0)
		return -1;
	ni_flag |= niquery_options[index].data;
	return 0;
}

static inline int niquery_is_subject_valid(void)
{
	return ni_subject_type >= 0 && ni_subject;
}

static int niquery_set_subject_type(int type)
{
	if (niquery_is_subject_valid() && ni_subject_type != type) {
		printf(_("Subject type conflict\n"));
		return -1;
	}
	ni_subject_type = type;
	return 0;
}

static int niquery_option_subject_addr_handler(int index, const char *arg)
{
	struct addrinfo hints = {
		.ai_family = AF_UNSPEC,
		.ai_socktype = SOCK_DGRAM,
		.ai_flags = getaddrinfo_flags
	};
	struct addrinfo *result, *ai;
	int ret_val;
	int offset;

	if (niquery_set_subject_type(niquery_options[index].data) < 0)
		return -1;

	ni_subject_type = niquery_options[index].data;

	switch (niquery_options[index].data) {
	case IPUTILS_NI_ICMP6_SUBJ_IPV6:
		ni_subject_len = sizeof(struct in6_addr);
		offset = offsetof(struct sockaddr_in6, sin6_addr);
		hints.ai_family = AF_INET6;
		break;
	case IPUTILS_NI_ICMP6_SUBJ_IPV4:
		ni_subject_len = sizeof(struct in_addr);
		offset = offsetof(struct sockaddr_in, sin_addr);
		hints.ai_family = AF_INET;
		break;
	default:
		/* should not happen. */
		offset = -1;
	}

	ret_val = getaddrinfo(arg, 0, &hints, &result);
	if (ret_val) {
		error(0, 0, "%s: %s", arg, gai_strerror(ret_val));
		return -1;
	}

	for (ai = result; ai; ai = ai->ai_next) {
		void *p = malloc(ni_subject_len);
		if (!p)
			continue;
		memcpy(p, (uint8_t *)ai->ai_addr + offset, ni_subject_len);
		free(ni_subject);
		ni_subject = p;
		break;
	}
	freeaddrinfo(result);

	return 0;
}

#ifdef USE_IDN
# if IDN2_VERSION_NUMBER >= 0x02000000
#  define IDN2_FLAGS IDN2_NONTRANSITIONAL
# else
#  define IDN2_FLAGS 0
# endif
#endif

#ifdef USE_CRYPTO
static int niquery_option_subject_name_handler(int index, const char *name)
{
	static char nigroup_buf[INET6_ADDRSTRLEN + 1 + IFNAMSIZ];
	unsigned char *dnptrs[2], **dpp, **lastdnptr;
	int n;
	size_t i;
	char *p;
	char *canonname = NULL, *idn = NULL;
	unsigned char *buf = NULL;
	size_t namelen;
	size_t buflen;
	int dots, fqdn = niquery_options[index].data;
	MD5_CTX ctxt;
	uint8_t digest[MD5_DIGEST_LENGTH];
#ifdef USE_IDN
	int rc;
#endif

	if (niquery_set_subject_type(IPUTILS_NI_ICMP6_SUBJ_FQDN) < 0)
		return -1;

#ifdef USE_IDN
	rc = idn2_lookup_ul(name, &idn, IDN2_FLAGS);
	if (rc)
		error(2, 0, _("IDN encoding error: %s"), idn2_strerror(rc));
#else
	idn = strdup(name);
	if (!idn)
		goto oomexit;
#endif

	p = strchr(idn, SCOPE_DELIMITER);
	if (p) {
		*p = '\0';
		if (strlen(p + 1) >= IFNAMSIZ)
			error(1, 0, _("too long scope name"));
	}

	namelen = strlen(idn);
	canonname = malloc(namelen + 1);
	if (!canonname)
		goto oomexit;

	dots = 0;
	for (i = 0; i < namelen + 1; i++) {
		canonname[i] = isupper(idn[i]) ? tolower(idn[i]) : idn[i];
		if (idn[i] == '.')
			dots++;
	}

	if (fqdn == 0) {
		/* guess if hostname is FQDN */
		fqdn = dots ? 1 : -1;
	}

	buflen = namelen + 3 + 1;	/* dn_comp() requrires strlen() + 3,
					   plus non-fqdn indicator. */
	buf = malloc(buflen);
	if (!buf) {
		error(0, errno, _("memory allocation failed"));
		goto errexit;
	}

	dpp = dnptrs;
	lastdnptr = &dnptrs[ARRAY_SIZE(dnptrs)];

	*dpp++ = (unsigned char *)buf;
	*dpp++ = NULL;

	n = dn_comp(canonname, (unsigned char *)buf, buflen, dnptrs, lastdnptr);
	if (n < 0) {
		error(0, 0, _("inappropriate subject name: %s"), canonname);
		goto errexit;
	} else if ((size_t)n >= buflen) {
		error(0, 0, _("dn_comp() returned too long result"));
		goto errexit;
	}

	MD5_Init(&ctxt);
	MD5_Update(&ctxt, buf, buf[0]);
	MD5_Final(digest, &ctxt);

	sprintf(nigroup_buf, "ff02::2:%02x%02x:%02x%02x%s%s",
		digest[0], digest[1], digest[2], digest[3],
		p ? "%" : "",
		p ? p + 1 : "");

	if (fqdn < 0)
		buf[n] = 0;

	free(ni_subject);

	ni_group = nigroup_buf;
	ni_subject = buf;
	ni_subject_len = n + (fqdn < 0);
	ni_group = nigroup_buf;

	free(canonname);
	free(idn);

	return 0;
oomexit:
	error(0, errno, _("memory allocation failed"));
errexit:
	free(buf);
	free(canonname);
	free(idn);
	exit(1);
}
#else
static int niquery_option_subject_name_handler(int index __attribute__((__unused__)),
					       const char *name __attribute__((__unused__)))
{
	error(3, ENOSYS, _("niquery_option_subject_name_handler() crypto disabled"));
	abort();
}
#endif

int niquery_option_help_handler(int index, const char *arg __attribute__((__unused__)))
{
	fprintf(index ? stdout : stderr,
		      _("ping -6 -N <nodeinfo opt>\n"
			"Help:\n"
			"  help\n"
			"Query:\n"
			"  name\n"
			"  ipv6\n"
			"  ipv6-all\n"
			"  ipv6-compatible\n"
			"  ipv6-global\n"
			"  ipv6-linklocal\n"
			"  ipv6-sitelocal\n"
			"  ipv4\n"
			"  ipv4-all\n"
			"Subject:\n"
			"  subject-ipv6=addr\n"
			"  subject-ipv4=addr\n"
			"  subject-name=name\n"
			"  subject-fqdn=name\n"
		));
	index ? exit(0) : exit(2);
}

int niquery_option_handler(const char *opt_arg)
{
	struct niquery_option *p;
	int i;
	int ret = -1;
	for (i = 0, p = niquery_options; p->name; i++, p++) {
		if (strncmp(p->name, opt_arg, p->namelen))
			continue;
		if (!p->has_arg) {
			if (opt_arg[p->namelen] == '\0') {
				ret = p->handler(i, NULL);
				if (ret >= 0)
					break;
			}
		} else {
			if (opt_arg[p->namelen] == '=') {
				ret = p->handler(i, &opt_arg[p->namelen] + 1);
				if (ret >= 0)
					break;
			}
		}
	}
	if (!p->name)
		ret = niquery_option_help_handler(0, NULL);
	return ret;
}

int ping6_run(int argc, char **argv, struct addrinfo *ai, struct socket_st *sock)
{
	static const struct addrinfo hints = {
		.ai_family = AF_INET6,
		.ai_flags = getaddrinfo_flags
	};
	struct addrinfo *result = NULL;
	int ret_val;
	int hold, packlen;
	unsigned char *packet;
	char *target;
	struct icmp6_filter filter;
	int err;
	static uint32_t scope_id = 0;

	if (niquery_is_enabled()) {
		niquery_init_nonce();

		if (!niquery_is_subject_valid()) {
			ni_subject = &whereto.sin6_addr;
			ni_subject_len = sizeof(whereto.sin6_addr);
			ni_subject_type = IPUTILS_NI_ICMP6_SUBJ_IPV6;
		}
	}

	if (argc > 1) {
		usage();
	} else if (argc == 1) {
		target = *argv;
	} else {
		if (ni_query < 0 && ni_subject_type != IPUTILS_NI_ICMP6_SUBJ_FQDN)
			usage();
		target = ni_group;
	}

	if (!ai) {
		ret_val = getaddrinfo(target, NULL, &hints, &result);
		if (ret_val)
			error(2, 0, _("%s: %s"), target, gai_strerror(ret_val));
		ai = result;
	}

	memcpy(&whereto, ai->ai_addr, sizeof(whereto));
	whereto.sin6_port = htons(IPPROTO_ICMPV6);

	if (result)
		freeaddrinfo(result);

	if (memchr(target, ':', strlen(target)))
		options |= F_NUMERIC;

	if (IN6_IS_ADDR_UNSPECIFIED(&firsthop.sin6_addr)) {
		memcpy(&firsthop.sin6_addr, &whereto.sin6_addr, 16);
		firsthop.sin6_scope_id = whereto.sin6_scope_id;
		/* Verify scope_id is the same as intermediate nodes */
		if (firsthop.sin6_scope_id && scope_id && firsthop.sin6_scope_id != scope_id)
			error(2, 0, _("scope discrepancy among the nodes"));
		else if (!scope_id)
			scope_id = firsthop.sin6_scope_id;
	}

	hostname = target;

	if (IN6_IS_ADDR_UNSPECIFIED(&source6.sin6_addr)) {
		socklen_t alen;
		int probe_fd = socket(AF_INET6, SOCK_DGRAM, 0);

		if (probe_fd < 0)
			error(2, errno, "socket");
		if (device) {
			unsigned int iface = if_name2index(device);
#ifdef IPV6_RECVPKTINFO
			struct in6_pktinfo ipi;

			memset(&ipi, 0, sizeof(ipi));
			ipi.ipi6_ifindex = iface;
#endif

			if (IN6_IS_ADDR_LINKLOCAL(&firsthop.sin6_addr) ||
			    IN6_IS_ADDR_MC_LINKLOCAL(&firsthop.sin6_addr))
				firsthop.sin6_scope_id = iface;
			enable_capability_raw();
#ifdef IPV6_RECVPKTINFO
			if (setsockopt(probe_fd, IPPROTO_IPV6, IPV6_PKTINFO, &ipi, sizeof ipi) == -1 ||
			    setsockopt(sock->fd, IPPROTO_IPV6, IPV6_PKTINFO, &ipi, sizeof ipi) == -1) {
				error(2, errno, "setsockopt(IPV6_PKTINFO)");
			}
#endif
			if (setsockopt(probe_fd, SOL_SOCKET, SO_BINDTODEVICE, device, strlen(device) + 1) == -1 ||
			    setsockopt(sock->fd, SOL_SOCKET, SO_BINDTODEVICE, device, strlen(device) + 1) == -1) {
				error(2, errno, "setsockopt(SO_BINDTODEVICE) %s", device);
			}
			disable_capability_raw();
		}

		if (!IN6_IS_ADDR_LINKLOCAL(&firsthop.sin6_addr) &&
		    !IN6_IS_ADDR_MC_LINKLOCAL(&firsthop.sin6_addr))
			firsthop.sin6_family = AF_INET6;

		firsthop.sin6_port = htons(1025);
		if (connect(probe_fd, (struct sockaddr *)&firsthop, sizeof(firsthop)) == -1)
			error(2, errno, "connect");
		alen = sizeof source6;
		if (getsockname(probe_fd, (struct sockaddr *)&source6, &alen) == -1)
			error(2, errno, "getsockname");
		source6.sin6_port = 0;
		close(probe_fd);

		if (device) {
			struct ifaddrs *ifa0, *ifa;

			if (getifaddrs(&ifa0))
				error(2, errno, "getifaddrs");

			for (ifa = ifa0; ifa; ifa = ifa->ifa_next) {
				if (!ifa->ifa_name || !ifa->ifa_addr ||
				    ifa->ifa_addr->sa_family != AF_INET6)
					continue;
				if (!strcmp(ifa->ifa_name, device) &&
				    IN6_ARE_ADDR_EQUAL(&((struct sockaddr_in6 *)ifa->ifa_addr)->sin6_addr,
						       &source6.sin6_addr))
					break;
			}
			if (!ifa)
				error(0, 0, _("Warning: source address might be selected on device other than: %s"), device);

			freeifaddrs(ifa0);
		}
	} else if (device && (IN6_IS_ADDR_LINKLOCAL(&source6.sin6_addr) ||
			      IN6_IS_ADDR_MC_LINKLOCAL(&source6.sin6_addr)))
		source6.sin6_scope_id = if_name2index(device);

	if (device) {
		struct cmsghdr *cmsg;
		struct in6_pktinfo *ipi;

		cmsg = (struct cmsghdr *)(cmsgbuf + cmsglen);
		cmsglen += CMSG_SPACE(sizeof(*ipi));
		cmsg->cmsg_len = CMSG_LEN(sizeof(*ipi));
		cmsg->cmsg_level = IPPROTO_IPV6;
		cmsg->cmsg_type = IPV6_PKTINFO;

		ipi = (struct in6_pktinfo *)CMSG_DATA(cmsg);
		memset(ipi, 0, sizeof(*ipi));
		ipi->ipi6_ifindex = if_name2index(device);
	}

	if ((whereto.sin6_addr.s6_addr16[0] & htons(0xff00)) == htons(0xff00)) {
		if (uid) {
			if (interval < 1000)
				error(2, 0, _("multicast ping with too short interval: %d"), interval);
			if (pmtudisc >= 0 && pmtudisc != IPV6_PMTUDISC_DO)
				error(2, 0, _("multicast ping does not fragment"));
		}
		if (pmtudisc < 0)
			pmtudisc = IPV6_PMTUDISC_DO;
	}

	if (pmtudisc >= 0) {
		if (setsockopt(sock->fd, IPPROTO_IPV6, IPV6_MTU_DISCOVER, &pmtudisc, sizeof pmtudisc) == -1)
			error(2, errno, "IPV6_MTU_DISCOVER");
	}

	if ((options & F_STRICTSOURCE) &&
	    bind(sock->fd, (struct sockaddr *)&source6, sizeof source6) == -1)
		error(2, errno, "bind icmp socket");

	if ((ssize_t)datalen >= (ssize_t)sizeof(struct timeval) && (ni_query < 0)) {
		/* can we time transfer */
		timing = 1;
	}
	packlen = datalen + 8 + 4096 + 40 + 8; /* 4096 for rthdr */
	if (!(packet = (unsigned char *)malloc((unsigned int)packlen)))
		error(2, errno, _("memory allocation failed"));

	/* Estimate memory eaten by single packet. It is rough estimate.
	 * Actually, for small datalen's it depends on kernel side a lot. */
	hold = datalen + 8;
	hold += ((hold + 511) / 512) * (40 + 16 + 64 + 160);
	sock_setbufs(sock, hold);

#ifdef __linux__
	if (sock->socktype == SOCK_RAW) {
		int csum_offset = 2;
		int sz_opt = sizeof(int);

		err = setsockopt(sock->fd, SOL_RAW, IPV6_CHECKSUM, &csum_offset, sz_opt);
		if (err < 0) {
			/* checksum should be enabled by default and setting this
			 * option might fail anyway.
			 */
			error(0, errno, _("setsockopt(RAW_CHECKSUM) failed - try to continue"));
		}
#else
	{
#endif

		/*
		 *	select icmp echo reply as icmp type to receive
		 */

		ICMP6_FILTER_SETBLOCKALL(&filter);

		ICMP6_FILTER_SETPASS(ICMP6_DST_UNREACH, &filter);
		ICMP6_FILTER_SETPASS(ICMP6_PACKET_TOO_BIG, &filter);
		ICMP6_FILTER_SETPASS(ICMP6_TIME_EXCEEDED, &filter);
		ICMP6_FILTER_SETPASS(ICMP6_PARAM_PROB, &filter);

		if (niquery_is_enabled())
			ICMP6_FILTER_SETPASS(IPUTILS_NI_ICMP6_REPLY, &filter);
		else
			ICMP6_FILTER_SETPASS(ICMP6_ECHO_REPLY, &filter);

		err = setsockopt(sock->fd, IPPROTO_ICMPV6, ICMP6_FILTER, &filter, sizeof filter);

		if (err < 0)
			error(2, errno, "setsockopt(ICMP6_FILTER)");
	}

	if (options & F_NOLOOP) {
		int loop = 0;
		if (setsockopt(sock->fd, IPPROTO_IPV6, IPV6_MULTICAST_LOOP, &loop, sizeof loop) == -1)
			error(2, errno, _("can't disable multicast loopback"));
	}
	if (options & F_TTL) {
		if (setsockopt(sock->fd, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &ttl, sizeof ttl) == -1)
			error(2, errno, _("can't set multicast hop limit"));
		if (setsockopt(sock->fd, IPPROTO_IPV6, IPV6_UNICAST_HOPS, &ttl, sizeof ttl) == -1)
			error(2, errno, _("can't set unicast hop limit"));
	}

	const int on = 1;
	if (
#ifdef IPV6_RECVHOPLIMIT
	    setsockopt(sock->fd, IPPROTO_IPV6, IPV6_RECVHOPLIMIT, &on, sizeof on) == -1 &&
	    setsockopt(sock->fd, IPPROTO_IPV6, IPV6_2292HOPLIMIT, &on, sizeof on) == -1
#else
	    setsockopt(sock->fd, IPPROTO_IPV6, IPV6_HOPLIMIT, &on, sizeof on) == -1
#endif
	   )
		error(2, errno, _("can't receive hop limit"));

	if (options & F_TCLASS) {
#ifdef IPV6_TCLASS
		if (setsockopt(sock->fd, IPPROTO_IPV6, IPV6_TCLASS, &tclass, sizeof tclass) == -1)
			error(2, errno, _("setsockopt(IPV6_TCLASS)"));
#else
		error(0, 0, _("traffic class is not supported"));
#endif
	}

	if (options & F_FLOWINFO) {
#ifdef IPV6_FLOWLABEL_MGR
		char freq_buf[CMSG_ALIGN(sizeof(struct in6_flowlabel_req)) + cmsglen];
		struct in6_flowlabel_req *freq = (struct in6_flowlabel_req *)freq_buf;
		int freq_len = sizeof(*freq);
		memset(freq, 0, sizeof(*freq));
		freq->flr_label = htonl(flowlabel & IPV6_FLOWINFO_FLOWLABEL);
		freq->flr_action = IPV6_FL_A_GET;
		freq->flr_flags = IPV6_FL_F_CREATE;
		freq->flr_share = IPV6_FL_S_EXCL;
		memcpy(&freq->flr_dst, &whereto.sin6_addr, 16);
		if (setsockopt(sock->fd, IPPROTO_IPV6, IPV6_FLOWLABEL_MGR, freq, freq_len) == -1)
			error(2, errno, _("can't set flowlabel"));
		flowlabel = freq->flr_label;
#else
		error(2, 0, _("flow labels are not supported"));
#endif

#ifdef IPV6_FLOWINFO_SEND
		whereto.sin6_flowinfo = flowlabel;
		if (setsockopt(sock->fd, IPPROTO_IPV6, IPV6_FLOWINFO_SEND, &on, sizeof on) == -1)
			error(2, errno, _("can't send flowinfo"));
#else
		error(2, 0, _("flowinfo is not supported"));
#endif
	}

	printf(_("PING %s(%s) "), hostname, pr_addr(&whereto, sizeof whereto));
	if (flowlabel)
		printf(_(", flow 0x%05x, "), (unsigned)ntohl(flowlabel));
	if (device || (options & F_STRICTSOURCE)) {
		int saved_options = options;

		options |= F_NUMERIC;
		printf(_("from %s %s: "), pr_addr(&source6, sizeof source6), device ? device : "");
		options = saved_options;
	}
	printf(_("%d data bytes\n"), datalen);

	setup(sock);

	drop_capabilities();

	main_loop(&ping6_func_set, sock, packet, packlen);
}

int ping6_receive_error_msg(socket_st *sock)
{
	ssize_t res;
	char cbuf[512];
	struct iovec iov;
	struct msghdr msg;
	struct cmsghdr *cmsg;
	struct sock_extended_err *e;
	struct icmp6_hdr icmph;
	struct sockaddr_in6 target;
	int net_errors = 0;
	int local_errors = 0;
	int saved_errno = errno;

	iov.iov_base = &icmph;
	iov.iov_len = sizeof(icmph);
	msg.msg_name = (void *)&target;
	msg.msg_namelen = sizeof(target);
	msg.msg_iov = &iov;
	msg.msg_iovlen = 1;
	msg.msg_flags = 0;
	msg.msg_control = cbuf;
	msg.msg_controllen = sizeof(cbuf);

	res = recvmsg(sock->fd, &msg, MSG_ERRQUEUE | MSG_DONTWAIT);
	if (res < 0)
		goto out;

	e = NULL;
	for (cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) {
		if (cmsg->cmsg_level == IPPROTO_IPV6) {
			if (cmsg->cmsg_type == IPV6_RECVERR)
				e = (struct sock_extended_err *)CMSG_DATA(cmsg);
		}
	}
	if (e == NULL)
		abort();

	if (e->ee_origin == SO_EE_ORIGIN_LOCAL) {
		local_errors++;
		if (options & F_QUIET)
			goto out;
		if (options & F_FLOOD)
			write_stdout("E", 1);
		else if (e->ee_errno != EMSGSIZE)
			error(0, e->ee_errno, _("local error"));
		else
			error(0, 0, _("local error: message too long, mtu: %u"), e->ee_info);
		nerrors++;
	} else if (e->ee_origin == SO_EE_ORIGIN_ICMP6) {
		struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)(e + 1);

		if ((size_t)res < sizeof(icmph) ||
		    memcmp(&target.sin6_addr, &whereto.sin6_addr, 16) ||
		    icmph.icmp6_type != ICMP6_ECHO_REQUEST ||
		    !is_ours(sock, icmph.icmp6_id)) {
			/* Not our error, not an error at all. Clear. */
			saved_errno = 0;
			goto out;
		}

		net_errors++;
		nerrors++;
		if (options & F_QUIET)
			goto out;
		if (options & F_FLOOD) {
			write_stdout("\bE", 2);
		} else {
			print_timestamp();
			printf(_("From %s icmp_seq=%u "), pr_addr(sin6, sizeof *sin6), ntohs(icmph.icmp6_seq));
			pr_icmph(e->ee_type, e->ee_code, e->ee_info);
			putchar('\n');
			fflush(stdout);
		}
	}

out:
	errno = saved_errno;
	return net_errors ? net_errors : -local_errors;
}

/*
 * pinger --
 * 	Compose and transmit an ICMP ECHO REQUEST packet.  The IP packet
 * will be added on by the kernel.  The ID field is our UNIX process ID,
 * and the sequence number is an ascending integer.  The first several bytes
 * of the data portion are used to hold a UNIX "timeval" struct in VAX
 * byte-order, to compute the round-trip time.
 */
int build_echo(uint8_t *_icmph, unsigned packet_size __attribute__((__unused__)))
{
	struct icmp6_hdr *icmph;
	int cc;

	icmph = (struct icmp6_hdr *)_icmph;
	icmph->icmp6_type = ICMP6_ECHO_REQUEST;
	icmph->icmp6_code = 0;
	icmph->icmp6_cksum = 0;
	icmph->icmp6_seq = htons(ntransmitted + 1);
	icmph->icmp6_id = ident;

	if (timing)
		gettimeofday((struct timeval *)&_icmph[8],
		    (struct timezone *)NULL);

	cc = datalen + 8;			/* skips ICMP portion */

	return cc;
}


int build_niquery(uint8_t *_nih, unsigned packet_size __attribute__((__unused__)))
{
	struct ni_hdr *nih;
	int cc;

	nih = (struct ni_hdr *)_nih;
	nih->ni_cksum = 0;

	nih->ni_type = IPUTILS_NI_ICMP6_QUERY;
	cc = sizeof(*nih);
	datalen = 0;

	niquery_fill_nonce(ntransmitted + 1, nih->ni_nonce);
	nih->ni_code = ni_subject_type;
	nih->ni_qtype = htons(ni_query);
	nih->ni_flags = ni_flag;
	memcpy(nih + 1, ni_subject, ni_subject_len);
	cc += ni_subject_len;

	return cc;
}

int ping6_send_probe(socket_st *sock, void *packet, unsigned packet_size)
{
	int len, cc;

	rcvd_clear(ntransmitted + 1);

	if (niquery_is_enabled())
		len = build_niquery(packet, packet_size);
	else
		len = build_echo(packet, packet_size);

	if (cmsglen == 0) {
		cc = sendto(sock->fd, (char *)packet, len, confirm,
			    (struct sockaddr *)&whereto,
			    sizeof(struct sockaddr_in6));
	} else {
		struct msghdr mhdr;
		struct iovec iov;

		iov.iov_len = len;
		iov.iov_base = packet;

		memset(&mhdr, 0, sizeof(mhdr));
		mhdr.msg_name = &whereto;
		mhdr.msg_namelen = sizeof(struct sockaddr_in6);
		mhdr.msg_iov = &iov;
		mhdr.msg_iovlen = 1;
		mhdr.msg_control = cmsgbuf;
		mhdr.msg_controllen = cmsglen;

		cc = sendmsg(sock->fd, &mhdr, confirm);
	}
	confirm = 0;

	return (cc == len ? 0 : cc);
}

void pr_echo_reply(uint8_t *_icmph, int cc __attribute__((__unused__)))
{
	struct icmp6_hdr *icmph = (struct icmp6_hdr *)_icmph;

	printf(_(" icmp_seq=%u"), ntohs(icmph->icmp6_seq));
}

static void putchar_safe(char c)
{
	if (isprint(c))
		putchar(c);
	else
		printf("\\%03o", c);
}

static
void pr_niquery_reply_name(struct ni_hdr *nih, int len)
{
	uint8_t *h = (uint8_t *)(nih + 1);
	uint8_t *p = h + 4;
	uint8_t *end = (uint8_t *)nih + len;
	int continued = 0;
	char buf[1024];
	int ret;

	len -= sizeof(struct ni_hdr) + 4;

	if (len < 0) {
		printf(_(" parse error (too short)"));
		return;
	}
	while (p < end) {
		int fqdn = 1;
		size_t i;

		memset(buf, 0xff, sizeof(buf));

		if (continued)
			putchar(',');

		ret = dn_expand(h, end, p, buf, sizeof(buf));
		if (ret < 0) {
			printf(_(" parse error (truncated)"));
			break;
		}
		if (p + ret < end && *(p + ret) == '\0')
			fqdn = 0;

		putchar(' ');
		for (i = 0; i < strlen(buf); i++)
			putchar_safe(buf[i]);
		if (fqdn)
			putchar('.');

		p += ret + !fqdn;

		continued = 1;
	}
}

static
void pr_niquery_reply_addr(struct ni_hdr *nih, int len)
{
	uint8_t *h = (uint8_t *)(nih + 1);
	uint8_t *p;
	uint8_t *end = (uint8_t *)nih + len;
	int af;
	int aflen;
	int continued = 0;
	int truncated;
	char buf[1024];

	switch (ntohs(nih->ni_qtype)) {
	case IPUTILS_NI_QTYPE_IPV4ADDR:
		af = AF_INET;
		aflen = sizeof(struct in_addr);
		truncated = nih->ni_flags & IPUTILS_NI_IPV6_FLAG_TRUNCATE;
		break;
	case IPUTILS_NI_QTYPE_IPV6ADDR:
		af = AF_INET6;
		aflen = sizeof(struct in6_addr);
		truncated = nih->ni_flags & IPUTILS_NI_IPV4_FLAG_TRUNCATE;
		break;
	default:
		/* should not happen */
		af = aflen = truncated = 0;
	}
	p = h;
	if (len < 0) {
		printf(_(" parse error (too short)"));
		return;
	}

	while (p < end) {
		if (continued)
			putchar(',');

		if (p + sizeof(uint32_t) + aflen > end) {
			printf(_(" parse error (truncated)"));
			break;
		}
		if (!inet_ntop(af, p + sizeof(uint32_t), buf, sizeof(buf)))
			printf(_(" unexpeced error in inet_ntop(%s)"),
			       strerror(errno));
		else
			printf(" %s", buf);
		p += sizeof(uint32_t) + aflen;

		continued = 1;
	}
	if (truncated)
		printf(_(" (truncated)"));
}

static
void pr_niquery_reply(uint8_t *_nih, int len)
{
	struct ni_hdr *nih = (struct ni_hdr *)_nih;

	switch (nih->ni_code) {
	case IPUTILS_NI_ICMP6_SUCCESS:
		switch (ntohs(nih->ni_qtype)) {
		case IPUTILS_NI_QTYPE_DNSNAME:
			pr_niquery_reply_name(nih, len);
			break;
		case IPUTILS_NI_QTYPE_IPV4ADDR:
		case IPUTILS_NI_QTYPE_IPV6ADDR:
			pr_niquery_reply_addr(nih, len);
			break;
		default:
			printf(_(" unknown qtype(0x%02x)"), ntohs(nih->ni_qtype));
		}
		break;
	case IPUTILS_NI_ICMP6_REFUSED:
		printf(_(" refused"));
		break;
	case IPUTILS_NI_ICMP6_UNKNOWN:
		printf(_(" unknown"));
		break;
	default:
		printf(_(" unknown code(%02x)"), ntohs(nih->ni_code));
	}
	printf(_("; seq=%u;"), ntohsp((uint16_t *)nih->ni_nonce));
}

/*
 * parse_reply --
 *	Print out the packet, if it came from us.  This logic is necessary
 * because ALL readers of the ICMP socket get a copy of ALL ICMP packets
 * which arrive ('tis only fair).  This permits multiple copies of this
 * program to be run without having intermingled output (or statistics!).
 */
int
ping6_parse_reply(socket_st *sock, struct msghdr *msg, int cc, void *addr, struct timeval *tv)
{
	struct sockaddr_in6 *from = addr;
	uint8_t *buf = msg->msg_iov->iov_base;
	struct cmsghdr *c;
	struct icmp6_hdr *icmph;
	int hops = -1;

	for (c = CMSG_FIRSTHDR(msg); c; c = CMSG_NXTHDR(msg, c)) {
		if (c->cmsg_level != IPPROTO_IPV6)
			continue;
		switch (c->cmsg_type) {
		case IPV6_HOPLIMIT:
#ifdef IPV6_2292HOPLIMIT
		case IPV6_2292HOPLIMIT:
#endif
			if (c->cmsg_len < CMSG_LEN(sizeof(int)))
				continue;
			memcpy(&hops, CMSG_DATA(c), sizeof(hops));
		}
	}


	/* Now the ICMP part */

	icmph = (struct icmp6_hdr *)buf;
	if (cc < 8) {
		if (options & F_VERBOSE)
			error(0, 0, _("packet too short: %d bytes"), cc);
		return 1;
	}

	if (icmph->icmp6_type == ICMP6_ECHO_REPLY) {
		if (!is_ours(sock, icmph->icmp6_id))
			return 1;
	       if (!contains_pattern_in_payload((uint8_t *)(icmph + 1)))
			return 1;	/* 'Twas really not our ECHO */
		if (gather_statistics((uint8_t *)icmph, sizeof(*icmph), cc,
				      ntohs(icmph->icmp6_seq),
				      hops, 0, tv, pr_addr(from, sizeof *from),
				      pr_echo_reply)) {
			fflush(stdout);
			return 0;
		}
	} else if (icmph->icmp6_type == IPUTILS_NI_ICMP6_REPLY) {
		struct ni_hdr *nih = (struct ni_hdr *)icmph;
		int seq = niquery_check_nonce(nih->ni_nonce);
		if (seq < 0)
			return 1;
		if (gather_statistics((uint8_t *)icmph, sizeof(*icmph), cc,
				      seq,
				      hops, 0, tv, pr_addr(from, sizeof *from),
				      pr_niquery_reply))
			return 0;
	} else {
		int nexthdr;
		struct ip6_hdr *iph1 = (struct ip6_hdr *)(icmph + 1);
		struct icmp6_hdr *icmph1 = (struct icmp6_hdr *)(iph1 + 1);

		/* We must not ever fall here. All the messages but
		 * echo reply are blocked by filter and error are
		 * received with IPV6_RECVERR. Ugly code is preserved
		 * however, just to remember what crap we avoided
		 * using RECVRERR. :-)
		 */

		if (cc < (int)(8 + sizeof(struct ip6_hdr) + 8))
			return 1;

		if (memcmp(&iph1->ip6_dst, &whereto.sin6_addr, 16))
			return 1;

		nexthdr = iph1->ip6_nxt;

		if (nexthdr == 44) {
			nexthdr = *(uint8_t *)icmph1;
			icmph1++;
		}
		if (nexthdr == IPPROTO_ICMPV6) {
			if (icmph1->icmp6_type != ICMP6_ECHO_REQUEST ||
			    !is_ours(sock, icmph1->icmp6_id))
				return 1;
			acknowledge(ntohs(icmph1->icmp6_seq));
			nerrors++;
			if (options & F_FLOOD) {
				write_stdout("\bE", 2);
				return 0;
			}
			print_timestamp();
			printf(_("From %s: icmp_seq=%u "), pr_addr(from, sizeof *from), ntohs(icmph1->icmp6_seq));
		} else {
			/* We've got something other than an ECHOREPLY */
			if (!(options & F_VERBOSE) || uid)
				return 1;
			print_timestamp();
			printf(_("From %s: "), pr_addr(from, sizeof *from));
		}
		pr_icmph(icmph->icmp6_type, icmph->icmp6_code, ntohl(icmph->icmp6_mtu));
	}

	if (options & F_AUDIBLE) {
		putchar('\a');
		if (options & F_FLOOD)
			fflush(stdout);
	}
	if (!(options & F_FLOOD)) {
		putchar('\n');
		fflush(stdout);
	}
	return 0;
}


int pr_icmph(uint8_t type, uint8_t code, uint32_t info)
{
	switch (type) {
	case ICMP6_DST_UNREACH:
		printf(_("Destination unreachable: "));
		switch (code) {
		case ICMP6_DST_UNREACH_NOROUTE:
			printf(_("No route"));
			break;
		case ICMP6_DST_UNREACH_ADMIN:
			printf(_("Administratively prohibited"));
			break;
		case ICMP6_DST_UNREACH_BEYONDSCOPE:
			printf(_("Beyond scope of source address"));
			break;
		case ICMP6_DST_UNREACH_ADDR:
			printf(_("Address unreachable"));
			break;
		case ICMP6_DST_UNREACH_NOPORT:
			printf(_("Port unreachable"));
			break;
		default:
			printf(_("Unknown code %d"), code);
			break;
		}
		break;
	case ICMP6_PACKET_TOO_BIG:
		printf(_("Packet too big: mtu=%u"), info);
		if (code)
			printf(_(", code=%d"), code);
		break;
	case ICMP6_TIME_EXCEEDED:
		printf(_("Time exceeded: "));
		if (code == ICMP6_TIME_EXCEED_TRANSIT)
			printf(_("Hop limit"));
		else if (code == ICMP6_TIME_EXCEED_REASSEMBLY)
			printf(_("Defragmentation failure"));
		else
			printf(_("code %d"), code);
		break;
	case ICMP6_PARAM_PROB:
		printf(_("Parameter problem: "));
		if (code == ICMP6_PARAMPROB_HEADER)
			printf(_("Wrong header field "));
		else if (code == ICMP6_PARAMPROB_NEXTHEADER)
			printf(_("Unknown header "));
		else if (code == ICMP6_PARAMPROB_OPTION)
			printf(_("Unknown option "));
		else
			printf(_("code %d "), code);
		printf(_("at %u"), info);
		break;
	case ICMP6_ECHO_REQUEST:
		printf(_("Echo request"));
		break;
	case ICMP6_ECHO_REPLY:
		printf(_("Echo reply"));
		break;
	case MLD_LISTENER_QUERY:
		printf(_("MLD Query"));
		break;
	case MLD_LISTENER_REPORT:
		printf(_("MLD Report"));
		break;
	case MLD_LISTENER_REDUCTION:
		printf(_("MLD Reduction"));
		break;
	default:
		printf(_("unknown icmp type: %u"), type);

	}
	return 0;
}

void ping6_install_filter(socket_st *sock)
{
	static int once;
	static struct sock_filter insns[] = {
		BPF_STMT(BPF_LD	 | BPF_H   | BPF_ABS, 4),	/* Load icmp echo ident */
		BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, 0xAAAA, 0, 1), /* Ours? */
		BPF_STMT(BPF_RET | BPF_K, ~0U),			/* Yes, it passes. */
		BPF_STMT(BPF_LD  | BPF_B   | BPF_ABS, 0),	/* Load icmp type */
		BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, ICMP6_ECHO_REPLY, 1, 0), /* Echo? */
		BPF_STMT(BPF_RET | BPF_K, ~0U),		/* No. It passes. This must not happen. */
		BPF_STMT(BPF_RET | BPF_K, 0), 		/* Echo with wrong ident. Reject. */
	};
	static struct sock_fprog filter = {
		sizeof insns / sizeof(insns[0]),
		insns
	};

	if (once)
		return;
	once = 1;

	/* Patch bpflet for current identifier. */
	insns[1] = (struct sock_filter)BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, htons(ident), 0, 1);

	if (setsockopt(sock->fd, SOL_SOCKET, SO_ATTACH_FILTER, &filter, sizeof(filter)))
		error(0, errno, _("WARNING: failed to install socket filter"));
}