1/******************************************************************************
2*******************************************************************************
3**
4**  Copyright (C) Sistina Software, Inc.  1997-2003  All rights reserved.
5**  Copyright (C) 2004-2008 Red Hat, Inc.  All rights reserved.
6**
7**  This copyrighted material is made available to anyone wishing to use,
8**  modify, copy, or redistribute it subject to the terms and conditions
9**  of the GNU General Public License v.2.
10**
11*******************************************************************************
12******************************************************************************/
13
14/*
15 * midcomms.c
16 *
17 * This is the appallingly named "mid-level" comms layer.
18 *
19 * Its purpose is to take packets from the "real" comms layer,
20 * split them up into packets and pass them to the interested
21 * part of the locking mechanism.
22 *
23 * It also takes messages from the locking layer, formats them
24 * into packets and sends them to the comms layer.
25 */
26
27#include "dlm_internal.h"
28#include "lowcomms.h"
29#include "config.h"
30#include "lock.h"
31#include "midcomms.h"
32
33
34static void copy_from_cb(void *dst, const void *base, unsigned offset,
35			 unsigned len, unsigned limit)
36{
37	unsigned copy = len;
38
39	if ((copy + offset) > limit)
40		copy = limit - offset;
41	memcpy(dst, base + offset, copy);
42	len -= copy;
43	if (len)
44		memcpy(dst + copy, base, len);
45}
46
47/*
48 * Called from the low-level comms layer to process a buffer of
49 * commands.
50 *
51 * Only complete messages are processed here, any "spare" bytes from
52 * the end of a buffer are saved and tacked onto the front of the next
53 * message that comes in. I doubt this will happen very often but we
54 * need to be able to cope with it and I don't want the task to be waiting
55 * for packets to come in when there is useful work to be done.
56 */
57
58int dlm_process_incoming_buffer(int nodeid, const void *base,
59				unsigned offset, unsigned len, unsigned limit)
60{
61	union {
62		unsigned char __buf[DLM_INBUF_LEN];
63		/* this is to force proper alignment on some arches */
64		union dlm_packet p;
65	} __tmp;
66	union dlm_packet *p = &__tmp.p;
67	int ret = 0;
68	int err = 0;
69	uint16_t msglen;
70	uint32_t lockspace;
71
72	while (len > sizeof(struct dlm_header)) {
73
74		/* Copy just the header to check the total length.  The
75		   message may wrap around the end of the buffer back to the
76		   start, so we need to use a temp buffer and copy_from_cb. */
77
78		copy_from_cb(p, base, offset, sizeof(struct dlm_header),
79			     limit);
80
81		msglen = le16_to_cpu(p->header.h_length);
82		lockspace = p->header.h_lockspace;
83
84		err = -EINVAL;
85		if (msglen < sizeof(struct dlm_header))
86			break;
87		if (p->header.h_cmd == DLM_MSG) {
88			if (msglen < sizeof(struct dlm_message))
89				break;
90		} else {
91			if (msglen < sizeof(struct dlm_rcom))
92				break;
93		}
94		err = -E2BIG;
95		if (msglen > dlm_config.ci_buffer_size) {
96			log_print("message size %d from %d too big, buf len %d",
97				  msglen, nodeid, len);
98			break;
99		}
100		err = 0;
101
102		/* If only part of the full message is contained in this
103		   buffer, then do nothing and wait for lowcomms to call
104		   us again later with more data.  We return 0 meaning
105		   we've consumed none of the input buffer. */
106
107		if (msglen > len)
108			break;
109
110		/* Allocate a larger temp buffer if the full message won't fit
111		   in the buffer on the stack (which should work for most
112		   ordinary messages). */
113
114		if (msglen > sizeof(__tmp) && p == &__tmp.p) {
115			p = kmalloc(dlm_config.ci_buffer_size, GFP_NOFS);
116			if (p == NULL)
117				return ret;
118		}
119
120		copy_from_cb(p, base, offset, msglen, limit);
121
122		BUG_ON(lockspace != p->header.h_lockspace);
123
124		ret += msglen;
125		offset += msglen;
126		offset &= (limit - 1);
127		len -= msglen;
128
129		dlm_receive_buffer(p, nodeid);
130	}
131
132	if (p != &__tmp.p)
133		kfree(p);
134
135	return err ? err : ret;
136}
137