strace/netlink.c

/*
 * Copyright (c) 2016 Fabien Siron <fabien.siron@epita.fr>
 * Copyright (c) 2016 Dmitry V. Levin <ldv@altlinux.org>
 * Copyright (c) 2016-2017 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 <sys/socket.h>
#include <linux/audit.h>
#include <linux/netlink.h>
#include <linux/rtnetlink.h>
#include "xlat/netlink_flags.h"
#include "xlat/netlink_protocols.h"
#include "xlat/netlink_types.h"
#include "xlat/nl_audit_types.h"
#include "xlat/nl_route_types.h"
#include "xlat/nl_sock_diag_types.h"

#undef NLMSG_HDRLEN
#define NLMSG_HDRLEN NLMSG_ALIGN(sizeof(struct nlmsghdr))

/*
 * Fetch a struct nlmsghdr from the given address.
 */
static bool
fetch_nlmsghdr(struct tcb *const tcp, struct nlmsghdr *const nlmsghdr,
	       const kernel_ulong_t addr, const kernel_ulong_t len)
{
	if (len < sizeof(struct nlmsghdr)) {
		printstrn(tcp, addr, len);
		return false;
	}

	if (umove_or_printaddr(tcp, addr, nlmsghdr))
		return false;

	return true;
}

enum {
	NL_FAMILY_ERROR = -1,
	NL_FAMILY_DEFAULT = -2
};

static int
get_fd_nl_family(struct tcb *const tcp, const int fd)
{
	const unsigned long inode = getfdinode(tcp, fd);
	if (!inode)
		return NL_FAMILY_ERROR;

	const char *const details = get_sockaddr_by_inode(tcp, fd, inode);
	if (!details)
		return NL_FAMILY_ERROR;

	const char *const nl_details = STR_STRIP_PREFIX(details, "NETLINK:[");
	if (nl_details == details)
		return NL_FAMILY_ERROR;

	const struct xlat *xlats = netlink_protocols;
	for (; xlats->str; ++xlats) {
		const char *name = STR_STRIP_PREFIX(xlats->str, "NETLINK_");
		if (!strncmp(nl_details, name, strlen(name)))
			return xlats->val;
	}

	if (*nl_details >= '0' && *nl_details <= '9')
		return atoi(nl_details);

	return NL_FAMILY_ERROR;
}

static const struct {
	const struct xlat *const xlat;
	const char *const dflt;
} nlmsg_types[] = {
	[NETLINK_AUDIT] = { nl_audit_types, "AUDIT_???" },
	[NETLINK_ROUTE] = { nl_route_types, "RTM_???" },
	[NETLINK_SOCK_DIAG] = { nl_sock_diag_types, "SOCK_DIAG_???" }
};

/*
 * As all valid netlink families are positive integers, use unsigned int
 * for family here to filter out NL_FAMILY_ERROR and NL_FAMILY_DEFAULT.
 */
static void
decode_nlmsg_type(const uint16_t type, const unsigned int family)
{
	if (family < ARRAY_SIZE(nlmsg_types)
	    && nlmsg_types[family].xlat) {
		printxval(nlmsg_types[family].xlat, type, nlmsg_types[family].dflt);
	} else {
		printxval(netlink_types, type, "NLMSG_???");
	}
}

static int
print_nlmsghdr(struct tcb *tcp,
	       const int fd,
	       int family,
	       const struct nlmsghdr *const nlmsghdr)
{
	/* print the whole structure regardless of its nlmsg_len */

	tprintf("{len=%u, type=", nlmsghdr->nlmsg_len);

	const int hdr_family = (nlmsghdr->nlmsg_type < NLMSG_MIN_TYPE)
			       ? NL_FAMILY_DEFAULT
			       : (family != NL_FAMILY_DEFAULT
				  ? family : get_fd_nl_family(tcp, fd));

	decode_nlmsg_type(nlmsghdr->nlmsg_type, hdr_family);

	tprints(", flags=");
	printflags(netlink_flags, nlmsghdr->nlmsg_flags, "NLM_F_???");

	tprintf(", seq=%u, pid=%u}", nlmsghdr->nlmsg_seq,
		nlmsghdr->nlmsg_pid);

	return family != NL_FAMILY_DEFAULT ? family : hdr_family;
}

static void
decode_nlmsghdr_with_payload(struct tcb *const tcp,
			     const int fd,
			     int family,
			     const struct nlmsghdr *const nlmsghdr,
			     const kernel_ulong_t addr,
			     const kernel_ulong_t len);

static void
decode_nlmsgerr(struct tcb *const tcp,
		const int fd,
		const int family,
		kernel_ulong_t addr,
		kernel_ulong_t len)
{
	struct nlmsgerr err;

	if (len < sizeof(err.error)) {
		printstrn(tcp, addr, len);
		return;
	}

	if (umove_or_printaddr(tcp, addr, &err.error))
		return;

	tprints("{error=");
	if (err.error < 0 && (unsigned) -err.error < nerrnos) {
		tprintf("-%s", errnoent[-err.error]);
	} else {
		tprintf("%d", err.error);
	}

	addr += offsetof(struct nlmsgerr, msg);
	len -= offsetof(struct nlmsgerr, msg);

	if (len) {
		tprints(", msg=");
		if (fetch_nlmsghdr(tcp, &err.msg, addr, len)) {
			decode_nlmsghdr_with_payload(tcp, fd, family,
						     &err.msg, addr, len);
		}
	}

	tprints("}");
}

static void
decode_payload(struct tcb *const tcp,
	       const int fd,
	       const int family,
	       const struct nlmsghdr *const nlmsghdr,
	       const kernel_ulong_t addr,
	       const kernel_ulong_t len)
{
	if (nlmsghdr->nlmsg_type == NLMSG_ERROR) {
		decode_nlmsgerr(tcp, fd, family, addr, len);
		return;
	} else if (nlmsghdr->nlmsg_type == NLMSG_DONE && len == sizeof(int)) {
		int num;

		if (!umove_or_printaddr(tcp, addr, &num))
			tprintf("%d", num);
		return;
	}

	printstrn(tcp, addr, len);
}

static void
decode_nlmsghdr_with_payload(struct tcb *const tcp,
			     const int fd,
			     int family,
			     const struct nlmsghdr *const nlmsghdr,
			     const kernel_ulong_t addr,
			     const kernel_ulong_t len)
{
	tprints("{");

	family = print_nlmsghdr(tcp, fd, family, nlmsghdr);

	unsigned int nlmsg_len =
		nlmsghdr->nlmsg_len > len ? len : nlmsghdr->nlmsg_len;
	if (nlmsg_len > NLMSG_HDRLEN) {
		tprints(", ");
		decode_payload(tcp, fd, family, nlmsghdr, addr + NLMSG_HDRLEN,
						     nlmsg_len - NLMSG_HDRLEN);
	}

	tprints("}");
}

void
decode_netlink(struct tcb *const tcp,
	       const int fd,
	       kernel_ulong_t addr,
	       kernel_ulong_t len)
{
	struct nlmsghdr nlmsghdr;
	bool print_array = false;
	unsigned int elt;

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

		unsigned int nlmsg_len = NLMSG_ALIGN(nlmsghdr.nlmsg_len);
		kernel_ulong_t next_addr = 0;
		kernel_ulong_t next_len = 0;

		if (nlmsghdr.nlmsg_len >= NLMSG_HDRLEN) {
			next_len = (len >= nlmsg_len) ? len - nlmsg_len : 0;

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

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

		decode_nlmsghdr_with_payload(tcp, fd, NL_FAMILY_DEFAULT,
					     &nlmsghdr, addr, len);

		if (!next_addr)
			break;

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

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