nlattr.c - platform/external/strace - Gitiles

 /*
  * Copyright (c) 2016 Fabien Siron <fabien.siron@epita.fr>
  * Copyright (c) 2017 JingPiao Chen <chenjingpiao@gmail.com>
  * Copyright (c) 2016-2018 The strace developers.
  * All rights reserved.
  *
  * 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. The name of the author may not be used to endorse or promote products
  *    derived from this software without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
  */

 #include "defs.h"
 #include <endian.h>
 #include "netlink.h"
 #include "nlattr.h"
 #include <netinet/in.h>
 #include <arpa/inet.h>
 #include <linux/sock_diag.h>
 #include "static_assert.h"

 #include "xlat/netlink_sk_meminfo_indices.h"

 static bool
 fetch_nlattr(struct tcb *const tcp, struct nlattr *const nlattr,
 	     const kernel_ulong_t addr, const unsigned int len,
 	     const bool in_array)
 {
 	if (len < sizeof(struct nlattr)) {
 		printstr_ex(tcp, addr, len, QUOTE_FORCE_HEX);
 		return false;
 	}

 	if (tfetch_obj(tcp, addr, nlattr))
 		return true;

 	if (in_array) {
 		tprints("...");
 		printaddr_comment(addr);
 	} else {
 		printaddr(addr);
 	}

 	return false;
 }

 static void
 print_nlattr(const struct nlattr *const nla,
 	     const struct xlat *const table,
 	     const char *const dflt)
 {
 	static_assert(NLA_TYPE_MASK == ~(NLA_F_NESTED | NLA_F_NET_BYTEORDER),
 		      "wrong NLA_TYPE_MASK");

 	tprintf("{nla_len=%u, nla_type=", nla->nla_len);
 	if (nla->nla_type & NLA_F_NESTED) {
 		print_xlat(NLA_F_NESTED);
 		tprints("|");
 	}
 	if (nla->nla_type & NLA_F_NET_BYTEORDER) {
 		print_xlat(NLA_F_NET_BYTEORDER);
 		tprints("|");
 	}
 	printxval(table, nla->nla_type & NLA_TYPE_MASK, dflt);
 	tprints("}");
 }

 static void
 decode_nlattr_with_data(struct tcb *const tcp,
 			const struct nlattr *const nla,
 			const kernel_ulong_t addr,
 			const unsigned int len,
 			const struct xlat *const table,
 			const char *const dflt,
 			const nla_decoder_t *const decoders,
 			const unsigned int size,
 			const void *const opaque_data)
 {
 	const unsigned int nla_len = MIN(nla->nla_len, len);

 	if (nla_len > NLA_HDRLEN)
 		tprints("{");

 	print_nlattr(nla, table, dflt);

 	if (nla_len > NLA_HDRLEN) {
 		const unsigned int idx =
 			size ? nla->nla_type & NLA_TYPE_MASK : 0;

 		tprints(", ");
 		if (!decoders
 		    || (size && idx >= size)
 		    || !decoders[idx]
 		    || !decoders[idx](
 				tcp, addr + NLA_HDRLEN,
 				nla_len - NLA_HDRLEN,
 				size ? opaque_data
 				     : (const void *) (uintptr_t) nla->nla_type)
 		    )
 			printstr_ex(tcp, addr + NLA_HDRLEN,
 				    nla_len - NLA_HDRLEN, QUOTE_FORCE_HEX);
 		tprints("}");
 	}
 }

 void
 decode_nlattr(struct tcb *const tcp,
 	      kernel_ulong_t addr,
 	      unsigned int len,
 	      const struct xlat *const table,
 	      const char *const dflt,
 	      const nla_decoder_t *const decoders,
 	      const unsigned int size,
 	      const void *const opaque_data)
 {
 	struct nlattr nla;
 	bool is_array = false;
 	unsigned int elt;

 	if (decoders && !size && opaque_data)
 		error_func_msg("[xlat %p, dflt \"%s\", decoders %p] "
 			       "size is zero (going to pass nla_type as "
 			       "decoder argument), but opaque data (%p) is not "
 			       "- will be ignored",
 			       table, dflt, decoders, opaque_data);

 	for (elt = 0; fetch_nlattr(tcp, &nla, addr, len, is_array); elt++) {
 		if (abbrev(tcp) && elt == max_strlen) {
 			tprints("...");
 			break;
 		}

 		const unsigned int nla_len = NLA_ALIGN(nla.nla_len);
 		kernel_ulong_t next_addr = 0;
 		unsigned int next_len = 0;

 		if (nla.nla_len >= NLA_HDRLEN) {
 			next_len = (len >= nla_len) ? len - nla_len : 0;

 			if (next_len && addr + nla_len > addr)
 				next_addr = addr + nla_len;
 		}

 		if (!is_array && next_addr) {
 			tprints("[");
 			is_array = true;
 		}

 		decode_nlattr_with_data(tcp, &nla, addr, len, table, dflt,
 					decoders, size, opaque_data);

 		if (!next_addr)
 			break;

 		tprints(", ");
 		addr = next_addr;
 		len = next_len;
 	}

 	if (is_array) {
 		tprints("]");
 	}
 }

 bool
 decode_nla_str(struct tcb *const tcp,
 	       const kernel_ulong_t addr,
 	       const unsigned int len,
 	       const void *const opaque_data)
 {
 	printstr_ex(tcp, addr, len, QUOTE_0_TERMINATED);

 	return true;
 }

 bool
 decode_nla_strn(struct tcb *const tcp,
 		const kernel_ulong_t addr,
 		const unsigned int len,
 		const void *const opaque_data)
 {
 	printstrn(tcp, addr, len);

 	return true;
 }

 bool
 decode_nla_meminfo(struct tcb *const tcp,
 		   const kernel_ulong_t addr,
 		   const unsigned int len,
 		   const void *const opaque_data)
 {
 	uint32_t mem;
 	const size_t nmemb = len / sizeof(mem);

 	if (!nmemb)
 		return false;

 	unsigned int count = 0;
 	print_array_ex(tcp, addr, nmemb, &mem, sizeof(mem),
 		       tfetch_mem, print_uint32_array_member, &count,
 		       PAF_PRINT_INDICES | PAF_INDEX_XLAT_VALUE_INDEXED
 			| XLAT_STYLE_FMT_U,
 		       ARRSZ_PAIR(netlink_sk_meminfo_indices),
 		       "SK_MEMINFO_???");

 	return true;
 }

 bool
 decode_nla_fd(struct tcb *const tcp,
 	      const kernel_ulong_t addr,
 	      const unsigned int len,
 	      const void *const opaque_data)
 {
 	int fd;

 	if (len < sizeof(fd))
 		return false;
 	else if (!umove_or_printaddr(tcp, addr, &fd))
 		printfd(tcp, fd);

 	return true;
 }

 bool
 decode_nla_uid(struct tcb *const tcp,
 	       const kernel_ulong_t addr,
 	       const unsigned int len,
 	       const void *const opaque_data)
 {
 	uint32_t uid;

 	if (len < sizeof(uid))
 		return false;
 	else if (!umove_or_printaddr(tcp, addr, &uid))
 		printuid("", uid);

 	return true;
 }

 bool
 decode_nla_gid(struct tcb *const tcp,
 	       const kernel_ulong_t addr,
 	       const unsigned int len,
 	       const void *const opaque_data)
 {
 	return decode_nla_uid(tcp, addr, len, opaque_data);
 }

 bool
 decode_nla_ifindex(struct tcb *const tcp,
 	       const kernel_ulong_t addr,
 	       const unsigned int len,
 	       const void *const opaque_data)
 {
 	uint32_t ifindex;

 	if (len < sizeof(ifindex))
 		return false;
 	else if (!umove_or_printaddr(tcp, addr, &ifindex))
 		print_ifindex(ifindex);

 	return true;
 }

 bool
 decode_nla_xval(struct tcb *const tcp,
 		const kernel_ulong_t addr,
 		unsigned int len,
 		const void *const opaque_data)
 {
 	const struct decode_nla_xlat_opts * const opts = opaque_data;
 	union {
 		uint64_t val;
 		uint8_t  bytes[sizeof(uint64_t)];
 	} data = { .val = 0 };

 	if (len > sizeof(data) || len < opts->size)
 		return false;

 	if (opts->size)
 		len = MIN(len, opts->size);

 	const size_t bytes_offs = is_bigendian ? sizeof(data) - len : 0;

 	if (!umoven_or_printaddr(tcp, addr, len, data.bytes + bytes_offs)) {
 		if (opts->process_fn)
 			data.val = opts->process_fn(data.val);
 		if (opts->prefix)
 			tprints(opts->prefix);
 		printxval_dispatch_ex(opts->xlat, opts->xlat_size, data.val,
 				      opts->dflt, opts->xt, opts->style);
 		if (opts->suffix)
 			tprints(opts->suffix);
 	}

 	return true;
 }

 static uint64_t
 process_host_order(uint64_t val)
 {
 	return ntohs(val);
 }

 bool
 decode_nla_ether_proto(struct tcb *const tcp,
 		       const kernel_ulong_t addr,
 		       const unsigned int len,
 		       const void *const opaque_data)
 {
 	const struct decode_nla_xlat_opts opts = {
 		.xlat = ethernet_protocols,
 		.xlat_size = ethernet_protocols_size,
 		.dflt = "ETHER_P_???",
 		.xt = XT_SORTED,
 		.prefix = "htons(",
 		.suffix = ")",
 		.size = 2,
 		.process_fn = process_host_order,
 	};

 	return decode_nla_xval(tcp, addr, len, &opts);
 }

 bool
 decode_nla_ip_proto(struct tcb *const tcp,
 		    const kernel_ulong_t addr,
 		    const unsigned int len,
 		    const void *const opaque_data)
 {
 	const struct decode_nla_xlat_opts opts = {
 		.xlat = inet_protocols,
 		.xlat_size = inet_protocols_size,
 		.xt = XT_SORTED,
 		.dflt = "IPPROTO_???",
 		.size = 1,
 	};

 	return decode_nla_xval(tcp, addr, len, &opts);
 }

 bool
 decode_nla_in_addr(struct tcb *const tcp,
 		   const kernel_ulong_t addr,
 		   const unsigned int len,
 		   const void *const opaque_data)
 {
 	struct in_addr in;

 	if (len < sizeof(in))
 		return false;
 	else if (!umove_or_printaddr(tcp, addr, &in))
 		print_inet_addr(AF_INET, &in, sizeof(in), NULL);

 	return true;
 }

 bool
 decode_nla_in6_addr(struct tcb *const tcp,
 		    const kernel_ulong_t addr,
 		    const unsigned int len,
 		    const void *const opaque_data)
 {
 	struct in6_addr in6;

 	if (len < sizeof(in6))
 		return false;
 	else if (!umove_or_printaddr(tcp, addr, &in6))
 		print_inet_addr(AF_INET6, &in6, sizeof(in6), NULL);

 	return true;
 }

 bool
 decode_nla_flags(struct tcb *const tcp,
 		 const kernel_ulong_t addr,
 		 unsigned int len,
 		 const void *const opaque_data)
 {
 	const struct decode_nla_xlat_opts * const opts = opaque_data;
 	union {
 		uint64_t flags;
 		uint8_t  bytes[sizeof(uint64_t)];
 	} data = { .flags = 0 };

 	if (len > sizeof(data) || len < opts->size)
 		return false;

 	if (opts->size)
 		len = MIN(len, opts->size);

 	const size_t bytes_offs = is_bigendian ? sizeof(data) - len : 0;

 	if (opts->xt == XT_INDEXED)
 		error_func_msg("indexed xlats are currently incompatible with "
 			       "printflags");

 	if (!umoven_or_printaddr(tcp, addr, len, data.bytes + bytes_offs)) {
 		if (opts->process_fn)
 			data.flags = opts->process_fn(data.flags);
 		if (opts->prefix)
 			tprints(opts->prefix);
 		printflags_ex(data.flags, opts->dflt, opts->style, opts->xlat,
 			      NULL);
 		if (opts->suffix)
 			tprints(opts->suffix);
 	}

 	return true;
 }

 bool
 decode_nla_be16(struct tcb *const tcp,
 		const kernel_ulong_t addr,
 		const unsigned int len,
 		const void *const opaque_data)
 {
 	uint16_t num;

 	if (len < sizeof(num))
 		return false;
 	else if (!umove_or_printaddr(tcp, addr, &num))
 		tprintf("htons(%u)", ntohs(num));

 	return true;
 }

 bool
 decode_nla_be64(struct tcb *const tcp,
 		const kernel_ulong_t addr,
 		const unsigned int len,
 		const void *const opaque_data)
 {
 #if defined HAVE_BE64TOH || defined be64toh
 	uint64_t num;

 	if (len < sizeof(num))
 		return false;
 	else if (!umove_or_printaddr(tcp, addr, &num))
 		tprintf("htobe64(%" PRIu64 ")", be64toh(num));

 	return true;
 #else
 	return false;
 #endif
 }

 #define DECODE_NLA_INTEGER(name, type, fmt)		\
 bool							\
 decode_nla_ ## name(struct tcb *const tcp,		\
 		    const kernel_ulong_t addr,		\
 		    const unsigned int len,		\
 		    const void *const opaque_data)	\
 {							\
 	type num;					\
 							\
 	if (len < sizeof(num))				\
 		return false;				\
 	if (!umove_or_printaddr(tcp, addr, &num))	\
 		tprintf(fmt, num);			\
 	return true;					\
 }

 DECODE_NLA_INTEGER(x8, uint8_t, "%#" PRIx8)
 DECODE_NLA_INTEGER(x16, uint16_t, "%#" PRIx16)
 DECODE_NLA_INTEGER(x32, uint32_t, "%#" PRIx32)
 DECODE_NLA_INTEGER(x64, uint64_t, "%#" PRIx64)
 DECODE_NLA_INTEGER(u8, uint8_t, "%" PRIu8)
 DECODE_NLA_INTEGER(u16, uint16_t, "%" PRIu16)
 DECODE_NLA_INTEGER(u32, uint32_t, "%" PRIu32)
 DECODE_NLA_INTEGER(u64, uint64_t, "%" PRIu64)
 DECODE_NLA_INTEGER(s8, int8_t, "%" PRId8)
 DECODE_NLA_INTEGER(s16, int16_t, "%" PRId16)
 DECODE_NLA_INTEGER(s32, int32_t, "%" PRId32)
 DECODE_NLA_INTEGER(s64, int64_t, "%" PRId64)
	/*
	* Copyright (c) 2016 Fabien Siron <fabien.siron@epita.fr>
	* Copyright (c) 2017 JingPiao Chen <chenjingpiao@gmail.com>
	* Copyright (c) 2016-2018 The strace developers.
	* All rights reserved.
	*
	* 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. The name of the author may not be used to endorse or promote products
	* derived from this software without specific prior written permission.
	*
	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
	*/

	#include "defs.h"
	#include <endian.h>
	#include "netlink.h"
	#include "nlattr.h"
	#include <netinet/in.h>
	#include <arpa/inet.h>
	#include <linux/sock_diag.h>
	#include "static_assert.h"

	#include "xlat/netlink_sk_meminfo_indices.h"

	static bool
	fetch_nlattr(struct tcb const tcp, struct nlattr const nlattr,
	const kernel_ulong_t addr, const unsigned int len,
	const bool in_array)
	{
	if (len < sizeof(struct nlattr)) {
	printstr_ex(tcp, addr, len, QUOTE_FORCE_HEX);
	return false;
	}

	if (tfetch_obj(tcp, addr, nlattr))
	return true;

	if (in_array) {
	tprints("...");
	printaddr_comment(addr);
	} else {
	printaddr(addr);
	}

	return false;
	}

	static void
	print_nlattr(const struct nlattr *const nla,
	const struct xlat *const table,
	const char *const dflt)
	{
	static_assert(NLA_TYPE_MASK == ~(NLA_F_NESTED \| NLA_F_NET_BYTEORDER),
	"wrong NLA_TYPE_MASK");

	tprintf("{nla_len=%u, nla_type=", nla->nla_len);
	if (nla->nla_type & NLA_F_NESTED) {
	print_xlat(NLA_F_NESTED);
	tprints("\|");
	}
	if (nla->nla_type & NLA_F_NET_BYTEORDER) {
	print_xlat(NLA_F_NET_BYTEORDER);
	tprints("\|");
	}
	printxval(table, nla->nla_type & NLA_TYPE_MASK, dflt);
	tprints("}");
	}

	static void
	decode_nlattr_with_data(struct tcb *const tcp,
	const struct nlattr *const nla,
	const kernel_ulong_t addr,
	const unsigned int len,
	const struct xlat *const table,
	const char *const dflt,
	const nla_decoder_t *const decoders,
	const unsigned int size,
	const void *const opaque_data)
	{
	const unsigned int nla_len = MIN(nla->nla_len, len);

	if (nla_len > NLA_HDRLEN)
	tprints("{");

	print_nlattr(nla, table, dflt);

	if (nla_len > NLA_HDRLEN) {
	const unsigned int idx =
	size ? nla->nla_type & NLA_TYPE_MASK : 0;

	tprints(", ");
	if (!decoders
	\|\| (size && idx >= size)
	\|\| !decoders[idx]
	\|\| !decoders[idx](
	tcp, addr + NLA_HDRLEN,
	nla_len - NLA_HDRLEN,
	size ? opaque_data
	: (const void *) (uintptr_t) nla->nla_type)
	)
	printstr_ex(tcp, addr + NLA_HDRLEN,
	nla_len - NLA_HDRLEN, QUOTE_FORCE_HEX);
	tprints("}");
	}
	}

	void
	decode_nlattr(struct tcb *const tcp,
	kernel_ulong_t addr,
	unsigned int len,
	const struct xlat *const table,
	const char *const dflt,
	const nla_decoder_t *const decoders,
	const unsigned int size,
	const void *const opaque_data)
	{
	struct nlattr nla;
	bool is_array = false;
	unsigned int elt;

	if (decoders && !size && opaque_data)
	error_func_msg("[xlat %p, dflt \"%s\", decoders %p] "
	"size is zero (going to pass nla_type as "
	"decoder argument), but opaque data (%p) is not "
	"- will be ignored",
	table, dflt, decoders, opaque_data);

	for (elt = 0; fetch_nlattr(tcp, &nla, addr, len, is_array); elt++) {
	if (abbrev(tcp) && elt == max_strlen) {
	tprints("...");
	break;
	}

	const unsigned int nla_len = NLA_ALIGN(nla.nla_len);
	kernel_ulong_t next_addr = 0;
	unsigned int next_len = 0;

	if (nla.nla_len >= NLA_HDRLEN) {
	next_len = (len >= nla_len) ? len - nla_len : 0;

	if (next_len && addr + nla_len > addr)
	next_addr = addr + nla_len;
	}

	if (!is_array && next_addr) {
	tprints("[");
	is_array = true;
	}

	decode_nlattr_with_data(tcp, &nla, addr, len, table, dflt,
	decoders, size, opaque_data);

	if (!next_addr)
	break;

	tprints(", ");
	addr = next_addr;
	len = next_len;
	}

	if (is_array) {
	tprints("]");
	}
	}

	bool
	decode_nla_str(struct tcb *const tcp,
	const kernel_ulong_t addr,
	const unsigned int len,
	const void *const opaque_data)
	{
	printstr_ex(tcp, addr, len, QUOTE_0_TERMINATED);

	return true;
	}

	bool
	decode_nla_strn(struct tcb *const tcp,
	const kernel_ulong_t addr,
	const unsigned int len,
	const void *const opaque_data)
	{
	printstrn(tcp, addr, len);

	return true;
	}

	bool
	decode_nla_meminfo(struct tcb *const tcp,
	const kernel_ulong_t addr,
	const unsigned int len,
	const void *const opaque_data)
	{
	uint32_t mem;
	const size_t nmemb = len / sizeof(mem);

	if (!nmemb)
	return false;

	unsigned int count = 0;
	print_array_ex(tcp, addr, nmemb, &mem, sizeof(mem),
	tfetch_mem, print_uint32_array_member, &count,
	PAF_PRINT_INDICES \| PAF_INDEX_XLAT_VALUE_INDEXED
	\| XLAT_STYLE_FMT_U,
	ARRSZ_PAIR(netlink_sk_meminfo_indices),
	"SK_MEMINFO_???");

	return true;
	}

	bool
	decode_nla_fd(struct tcb *const tcp,
	const kernel_ulong_t addr,
	const unsigned int len,
	const void *const opaque_data)
	{
	int fd;

	if (len < sizeof(fd))
	return false;
	else if (!umove_or_printaddr(tcp, addr, &fd))
	printfd(tcp, fd);

	return true;
	}

	bool
	decode_nla_uid(struct tcb *const tcp,
	const kernel_ulong_t addr,
	const unsigned int len,
	const void *const opaque_data)
	{
	uint32_t uid;

	if (len < sizeof(uid))
	return false;
	else if (!umove_or_printaddr(tcp, addr, &uid))
	printuid("", uid);

	return true;
	}

	bool
	decode_nla_gid(struct tcb *const tcp,
	const kernel_ulong_t addr,
	const unsigned int len,
	const void *const opaque_data)
	{
	return decode_nla_uid(tcp, addr, len, opaque_data);
	}

	bool
	decode_nla_ifindex(struct tcb *const tcp,
	const kernel_ulong_t addr,
	const unsigned int len,
	const void *const opaque_data)
	{
	uint32_t ifindex;

	if (len < sizeof(ifindex))
	return false;
	else if (!umove_or_printaddr(tcp, addr, &ifindex))
	print_ifindex(ifindex);

	return true;
	}

	bool
	decode_nla_xval(struct tcb *const tcp,
	const kernel_ulong_t addr,
	unsigned int len,
	const void *const opaque_data)
	{
	const struct decode_nla_xlat_opts * const opts = opaque_data;
	union {
	uint64_t val;
	uint8_t bytes[sizeof(uint64_t)];
	} data = { .val = 0 };

	if (len > sizeof(data) \|\| len < opts->size)
	return false;

	if (opts->size)
	len = MIN(len, opts->size);

	const size_t bytes_offs = is_bigendian ? sizeof(data) - len : 0;

	if (!umoven_or_printaddr(tcp, addr, len, data.bytes + bytes_offs)) {
	if (opts->process_fn)
	data.val = opts->process_fn(data.val);
	if (opts->prefix)
	tprints(opts->prefix);
	printxval_dispatch_ex(opts->xlat, opts->xlat_size, data.val,
	opts->dflt, opts->xt, opts->style);
	if (opts->suffix)
	tprints(opts->suffix);
	}

	return true;
	}

	static uint64_t
	process_host_order(uint64_t val)
	{
	return ntohs(val);
	}

	bool
	decode_nla_ether_proto(struct tcb *const tcp,
	const kernel_ulong_t addr,
	const unsigned int len,
	const void *const opaque_data)
	{
	const struct decode_nla_xlat_opts opts = {
	.xlat = ethernet_protocols,
	.xlat_size = ethernet_protocols_size,
	.dflt = "ETHER_P_???",
	.xt = XT_SORTED,
	.prefix = "htons(",
	.suffix = ")",
	.size = 2,
	.process_fn = process_host_order,
	};

	return decode_nla_xval(tcp, addr, len, &opts);
	}

	bool
	decode_nla_ip_proto(struct tcb *const tcp,
	const kernel_ulong_t addr,
	const unsigned int len,
	const void *const opaque_data)
	{
	const struct decode_nla_xlat_opts opts = {
	.xlat = inet_protocols,
	.xlat_size = inet_protocols_size,
	.xt = XT_SORTED,
	.dflt = "IPPROTO_???",
	.size = 1,
	};

	return decode_nla_xval(tcp, addr, len, &opts);
	}

	bool
	decode_nla_in_addr(struct tcb *const tcp,
	const kernel_ulong_t addr,
	const unsigned int len,
	const void *const opaque_data)
	{
	struct in_addr in;

	if (len < sizeof(in))
	return false;
	else if (!umove_or_printaddr(tcp, addr, &in))
	print_inet_addr(AF_INET, &in, sizeof(in), NULL);

	return true;
	}

	bool
	decode_nla_in6_addr(struct tcb *const tcp,
	const kernel_ulong_t addr,
	const unsigned int len,
	const void *const opaque_data)
	{
	struct in6_addr in6;

	if (len < sizeof(in6))
	return false;
	else if (!umove_or_printaddr(tcp, addr, &in6))
	print_inet_addr(AF_INET6, &in6, sizeof(in6), NULL);

	return true;
	}

	bool
	decode_nla_flags(struct tcb *const tcp,
	const kernel_ulong_t addr,
	unsigned int len,
	const void *const opaque_data)
	{
	const struct decode_nla_xlat_opts * const opts = opaque_data;
	union {
	uint64_t flags;
	uint8_t bytes[sizeof(uint64_t)];
	} data = { .flags = 0 };

	if (len > sizeof(data) \|\| len < opts->size)
	return false;

	if (opts->size)
	len = MIN(len, opts->size);

	const size_t bytes_offs = is_bigendian ? sizeof(data) - len : 0;

	if (opts->xt == XT_INDEXED)
	error_func_msg("indexed xlats are currently incompatible with "
	"printflags");

	if (!umoven_or_printaddr(tcp, addr, len, data.bytes + bytes_offs)) {
	if (opts->process_fn)
	data.flags = opts->process_fn(data.flags);
	if (opts->prefix)
	tprints(opts->prefix);
	printflags_ex(data.flags, opts->dflt, opts->style, opts->xlat,
	NULL);
	if (opts->suffix)
	tprints(opts->suffix);
	}

	return true;
	}

	bool
	decode_nla_be16(struct tcb *const tcp,
	const kernel_ulong_t addr,
	const unsigned int len,
	const void *const opaque_data)
	{
	uint16_t num;

	if (len < sizeof(num))
	return false;
	else if (!umove_or_printaddr(tcp, addr, &num))
	tprintf("htons(%u)", ntohs(num));

	return true;
	}

	bool
	decode_nla_be64(struct tcb *const tcp,
	const kernel_ulong_t addr,
	const unsigned int len,
	const void *const opaque_data)
	{
	#if defined HAVE_BE64TOH \|\| defined be64toh
	uint64_t num;

	if (len < sizeof(num))
	return false;
	else if (!umove_or_printaddr(tcp, addr, &num))
	tprintf("htobe64(%" PRIu64 ")", be64toh(num));

	return true;
	#else
	return false;
	#endif
	}

	#define DECODE_NLA_INTEGER(name, type, fmt) \
	bool \
	decode_nla_ ## name(struct tcb *const tcp, \
	const kernel_ulong_t addr, \
	const unsigned int len, \
	const void *const opaque_data) \
	{ \
	type num; \
	\
	if (len < sizeof(num)) \
	return false; \
	if (!umove_or_printaddr(tcp, addr, &num)) \
	tprintf(fmt, num); \
	return true; \
	}

	DECODE_NLA_INTEGER(x8, uint8_t, "%#" PRIx8)
	DECODE_NLA_INTEGER(x16, uint16_t, "%#" PRIx16)
	DECODE_NLA_INTEGER(x32, uint32_t, "%#" PRIx32)
	DECODE_NLA_INTEGER(x64, uint64_t, "%#" PRIx64)
	DECODE_NLA_INTEGER(u8, uint8_t, "%" PRIu8)
	DECODE_NLA_INTEGER(u16, uint16_t, "%" PRIu16)
	DECODE_NLA_INTEGER(u32, uint32_t, "%" PRIu32)
	DECODE_NLA_INTEGER(u64, uint64_t, "%" PRIu64)
	DECODE_NLA_INTEGER(s8, int8_t, "%" PRId8)
	DECODE_NLA_INTEGER(s16, int16_t, "%" PRId16)
	DECODE_NLA_INTEGER(s32, int32_t, "%" PRId32)
	DECODE_NLA_INTEGER(s64, int64_t, "%" PRId64)