/*
 * Copyright (c) 2016 Oracle. All rights reserved.
 * Copyright (c) 2005-2006 Network Appliance, Inc. All rights reserved.
 *
 * This software is available to you under a choice of one of two
 * licenses.  You may choose to be licensed under the terms of the GNU
 * General Public License (GPL) Version 2, available from the file
 * COPYING in the main directory of this source tree, or the BSD-type
 * license below:
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *      Redistributions of source code must retain the above copyright
 *      notice, this list of conditions and the following disclaimer.
 *
 *      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.
 *
 *      Neither the name of the Network Appliance, Inc. 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 COPYRIGHT HOLDERS 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 COPYRIGHT
 * OWNER 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.
 *
 * Author: Tom Tucker <tom@opengridcomputing.com>
 */

#include <linux/sunrpc/xdr.h>
#include <linux/sunrpc/debug.h>
#include <asm/unaligned.h>
#include <linux/sunrpc/rpc_rdma.h>
#include <linux/sunrpc/svc_rdma.h>

#define RPCDBG_FACILITY	RPCDBG_SVCXPRT

static __be32 *xdr_check_read_list(__be32 *p, __be32 *end)
{
	__be32 *next;

	while (*p++ != xdr_zero) {
		next = p + rpcrdma_readchunk_maxsz - 1;
		if (next > end)
			return NULL;
		p = next;
	}
	return p;
}

static __be32 *xdr_check_write_list(__be32 *p, __be32 *end)
{
	__be32 *next;

	while (*p++ != xdr_zero) {
		next = p + 1 + be32_to_cpup(p) * rpcrdma_segment_maxsz;
		if (next > end)
			return NULL;
		p = next;
	}
	return p;
}

static __be32 *xdr_check_reply_chunk(__be32 *p, __be32 *end)
{
	__be32 *next;

	if (*p++ != xdr_zero) {
		next = p + 1 + be32_to_cpup(p) * rpcrdma_segment_maxsz;
		if (next > end)
			return NULL;
		p = next;
	}
	return p;
}

/**
 * svc_rdma_xdr_decode_req - Parse incoming RPC-over-RDMA header
 * @rq_arg: Receive buffer
 *
 * On entry, xdr->head[0].iov_base points to first byte in the
 * RPC-over-RDMA header.
 *
 * On successful exit, head[0] points to first byte past the
 * RPC-over-RDMA header. For RDMA_MSG, this is the RPC message.
 * The length of the RPC-over-RDMA header is returned.
 */
int svc_rdma_xdr_decode_req(struct xdr_buf *rq_arg)
{
	__be32 *p, *end, *rdma_argp;
	unsigned int hdr_len;

	/* Verify that there's enough bytes for header + something */
	if (rq_arg->len <= RPCRDMA_HDRLEN_ERR)
		goto out_short;

	rdma_argp = rq_arg->head[0].iov_base;
	if (*(rdma_argp + 1) != rpcrdma_version)
		goto out_version;

	switch (*(rdma_argp + 3)) {
	case rdma_msg:
	case rdma_nomsg:
		break;

	case rdma_done:
		goto out_drop;

	case rdma_error:
		goto out_drop;

	default:
		goto out_proc;
	}

	end = (__be32 *)((unsigned long)rdma_argp + rq_arg->len);
	p = xdr_check_read_list(rdma_argp + 4, end);
	if (!p)
		goto out_inval;
	p = xdr_check_write_list(p, end);
	if (!p)
		goto out_inval;
	p = xdr_check_reply_chunk(p, end);
	if (!p)
		goto out_inval;
	if (p > end)
		goto out_inval;

	rq_arg->head[0].iov_base = p;
	hdr_len = (unsigned long)p - (unsigned long)rdma_argp;
	rq_arg->head[0].iov_len -= hdr_len;
	return hdr_len;

out_short:
	dprintk("svcrdma: header too short = %d\n", rq_arg->len);
	return -EINVAL;

out_version:
	dprintk("svcrdma: bad xprt version: %u\n",
		be32_to_cpup(rdma_argp + 1));
	return -EPROTONOSUPPORT;

out_drop:
	dprintk("svcrdma: dropping RDMA_DONE/ERROR message\n");
	return 0;

out_proc:
	dprintk("svcrdma: bad rdma procedure (%u)\n",
		be32_to_cpup(rdma_argp + 3));
	return -EINVAL;

out_inval:
	dprintk("svcrdma: failed to parse transport header\n");
	return -EINVAL;
}