netlink_netfilter.c

/*
 * Copyright (c) 2018 Chen Jingpiao <chenjingpiao@gmail.com>
 * Copyright (c) 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"

#ifdef HAVE_LINUX_NETFILTER_NFNETLINK_H

# include "print_fields.h"
# include "nlattr.h"

# include <netinet/in.h>
# include <arpa/inet.h>
# include "netlink.h"
# include <linux/netfilter/nfnetlink.h>

# include "xlat/netfilter_versions.h"
# include "xlat/nl_netfilter_msg_types.h"
# include "xlat/nl_netfilter_subsys_ids.h"

bool
decode_netlink_netfilter(struct tcb *const tcp,
			 const struct nlmsghdr *const nlmsghdr,
			 const kernel_ulong_t addr,
			 const unsigned int len)
{
	if (nlmsghdr->nlmsg_type == NLMSG_DONE)
		return false;

	struct nfgenmsg nfmsg;

	if (len < sizeof(nfmsg))
		printstr_ex(tcp, addr, len, QUOTE_FORCE_HEX);
	else if (!umove_or_printaddr(tcp, addr, &nfmsg)) {
		const uint8_t subsys_id = (uint8_t) (nlmsghdr->nlmsg_type >> 8);
		uint16_t res_id = ntohs(nfmsg.res_id);

		PRINT_FIELD_XVAL("{", nfmsg, nfgen_family, addrfams, "AF_???");
		PRINT_FIELD_XVAL(", ", nfmsg, version, netfilter_versions,
				 "NFNETLINK_???");

		/*
		 * Work around wrong endianness in res_id field,
		 * see linux commit v4.3-rc1~28^2~47^2~1
		 */
		tprints(", res_id=");
		if (subsys_id == NFNL_SUBSYS_NFTABLES
		    && res_id == NFNL_SUBSYS_NFTABLES) {
			tprints("htons(NFNL_SUBSYS_NFTABLES)");
		} else if (subsys_id == NFNL_SUBSYS_NFTABLES
			   && nfmsg.res_id == NFNL_SUBSYS_NFTABLES) {
			tprints("NFNL_SUBSYS_NFTABLES");
		} else {
			tprintf("htons(%d)", res_id);
		}

		const size_t offset = NLMSG_ALIGN(sizeof(nfmsg));
		if (len > offset) {
			tprints(", ");
			if ((nlmsghdr->nlmsg_type >= NFNL_MSG_BATCH_BEGIN
			     && nlmsghdr->nlmsg_type <= NFNL_MSG_BATCH_END)
			    || nlmsghdr->nlmsg_type < NLMSG_MIN_TYPE)
				printstr_ex(tcp, addr + offset,
					    len - offset, QUOTE_FORCE_HEX);
			else
				decode_nlattr(tcp, addr + offset, len - offset,
					      NULL, NULL, NULL, 0, NULL);
		}
	}

	return true;
}

#endif /* HAVE_LINUX_NETFILTER_NFNETLINK_H */