/******************************************************************************
  *******************************************************************************
  **
  **  Copyright (C) Sistina Software, Inc.  1997-2003  All rights reserved.
  **  Copyright (C) 2004-2008 Red Hat, Inc.  All rights reserved.
  **
  **  This copyrighted material is made available to anyone wishing to use,
  **  modify, copy, or redistribute it subject to the terms and conditions
  **  of the GNU General Public License v.2.
  **
  *******************************************************************************
  ******************************************************************************/
  
  /*
   * midcomms.c
   *
   * This is the appallingly named "mid-level" comms layer.
   *
   * Its purpose is to take packets from the "real" comms layer,
   * split them up into packets and pass them to the interested
   * part of the locking mechanism.
   *
   * It also takes messages from the locking layer, formats them
   * into packets and sends them to the comms layer.
   */
  
  #include "dlm_internal.h"
  #include "lowcomms.h"
  #include "config.h"
  #include "lock.h"
  #include "midcomms.h"
  
  
  static void copy_from_cb(void *dst, const void *base, unsigned offset,
  			 unsigned len, unsigned limit)
  {
  	unsigned copy = len;
  
  	if ((copy + offset) > limit)
  		copy = limit - offset;
  	memcpy(dst, base + offset, copy);
  	len -= copy;
  	if (len)
  		memcpy(dst + copy, base, len);
  }
  
  /*
   * Called from the low-level comms layer to process a buffer of
   * commands.
   *
   * Only complete messages are processed here, any "spare" bytes from
   * the end of a buffer are saved and tacked onto the front of the next
   * message that comes in. I doubt this will happen very often but we
   * need to be able to cope with it and I don't want the task to be waiting
   * for packets to come in when there is useful work to be done.
   */
  
  int dlm_process_incoming_buffer(int nodeid, const void *base,
  				unsigned offset, unsigned len, unsigned limit)
  {
  	union {
  		unsigned char __buf[DLM_INBUF_LEN];
  		/* this is to force proper alignment on some arches */
  		union dlm_packet p;
  	} __tmp;
  	union dlm_packet *p = &__tmp.p;
  	int ret = 0;
  	int err = 0;
  	uint16_t msglen;
  	uint32_t lockspace;
  
  	while (len > sizeof(struct dlm_header)) {
  
  		/* Copy just the header to check the total length.  The
  		   message may wrap around the end of the buffer back to the
  		   start, so we need to use a temp buffer and copy_from_cb. */
  
  		copy_from_cb(p, base, offset, sizeof(struct dlm_header),
  			     limit);
  
  		msglen = le16_to_cpu(p->header.h_length);
  		lockspace = p->header.h_lockspace;
  
  		err = -EINVAL;
  		if (msglen < sizeof(struct dlm_header))
  			break;
  		if (p->header.h_cmd == DLM_MSG) {
  			if (msglen < sizeof(struct dlm_message))
  				break;
  		} else {
  			if (msglen < sizeof(struct dlm_rcom))
  				break;
  		}
  		err = -E2BIG;
  		if (msglen > dlm_config.ci_buffer_size) {
  			log_print("message size %d from %d too big, buf len %d",
  				  msglen, nodeid, len);
  			break;
  		}
  		err = 0;
  
  		/* If only part of the full message is contained in this
  		   buffer, then do nothing and wait for lowcomms to call
  		   us again later with more data.  We return 0 meaning
  		   we've consumed none of the input buffer. */
  
  		if (msglen > len)
  			break;
  
  		/* Allocate a larger temp buffer if the full message won't fit
  		   in the buffer on the stack (which should work for most
  		   ordinary messages). */
  
  		if (msglen > sizeof(__tmp) && p == &__tmp.p) {
  			p = kmalloc(dlm_config.ci_buffer_size, GFP_NOFS);
  			if (p == NULL)
  				return ret;
  		}
  
  		copy_from_cb(p, base, offset, msglen, limit);
  
  		BUG_ON(lockspace != p->header.h_lockspace);
  
  		ret += msglen;
  		offset += msglen;
  		offset &= (limit - 1);
  		len -= msglen;
  
  		dlm_receive_buffer(p, nodeid);
  	}
  
  	if (p != &__tmp.p)
  		kfree(p);
  
  	return err ? err : ret;
  }