/*

 * Copyright (c) 1995 Danny Gasparovski

 *

 * Please read the file COPYRIGHT for the

 * terms and conditions of the copyright.

 */

/*

 * mbuf's in SLiRP are much simpler than the real mbufs in

 * FreeBSD.  They are fixed size, determined by the MTU,

 * so that one whole packet can fit.  Mbuf's cannot be

 * chained together.  If there's more data than the mbuf

 * could hold, an external malloced buffer is pointed to

 * by m_ext (and the data pointers) and M_EXT is set in

 * the flags

 */

#include <slirp.h>

int mbuf_alloced = 0;

struct mbuf m_freelist, m_usedlist;

#define MBUF_THRESH 30

int mbuf_max = 0;

/*

 * Find a nice value for msize

 * XXX if_maxlinkhdr already in mtu

 */

#define SLIRP_MSIZE (IF_MTU + IF_MAXLINKHDR + sizeof(struct m_hdr ) + 6)

void

m_init()

{

	m_freelist.m_next = m_freelist.m_prev = &m_freelist;

	m_usedlist.m_next = m_usedlist.m_prev = &m_usedlist;

}

/*

 * Get an mbuf from the free list, if there are none

 * malloc one

 *

 * Because fragmentation can occur if we alloc new mbufs and

 * free old mbufs, we mark all mbufs above mbuf_thresh as M_DOFREE,

 * which tells m_free to actually free() it

 */

struct mbuf *

m_get()

{

	register struct mbuf *m;

	int flags = 0;

	DEBUG_CALL("m_get");

	if (m_freelist.m_next == &m_freelist) {

		m = (struct mbuf *)malloc(SLIRP_MSIZE);

		if (m == NULL) goto end_error;

		mbuf_alloced++;

		if (mbuf_alloced > MBUF_THRESH)

			flags = M_DOFREE;

		if (mbuf_alloced > mbuf_max)

			mbuf_max = mbuf_alloced;

	} else {

		m = m_freelist.m_next;

		remque(m);

	}

	/* Insert it in the used list */

	insque(m,&m_usedlist);

	m->m_flags = (flags | M_USEDLIST);

	/* Initialise it */

	m->m_size = SLIRP_MSIZE - sizeof(struct m_hdr);

	m->m_data = m->m_dat;

	m->m_len = 0;

	m->m_nextpkt = 0;

	m->m_prevpkt = 0;

end_error:

	DEBUG_ARG("m = %lx", (long )m);

	return m;

}

void

m_free(m)

	struct mbuf *m;

{

  DEBUG_CALL("m_free");

  DEBUG_ARG("m = %lx", (long )m);

  if(m) {

	/* Remove from m_usedlist */

	if (m->m_flags & M_USEDLIST)

	   remque(m);

	/* If it's M_EXT, free() it */

	if (m->m_flags & M_EXT)

	   free(m->m_ext);

	/*

	 * Either free() it or put it on the free list

	 */

	if (m->m_flags & M_DOFREE) {

		free(m);

		mbuf_alloced--;

	} else if ((m->m_flags & M_FREELIST) == 0) {

		insque(m,&m_freelist);

		m->m_flags = M_FREELIST; /* Clobber other flags */

	}

  } /* if(m) */

}

/*

 * Copy data from one mbuf to the end of

 * the other.. if result is too big for one mbuf, malloc()

 * an M_EXT data segment

 */

void

m_cat(m, n)

	register struct mbuf *m, *n;

{

	/*

	 * If there's no room, realloc

	 */

	if (M_FREEROOM(m) < n->m_len)

		m_inc(m,m->m_size+MINCSIZE);

	memcpy(m->m_data+m->m_len, n->m_data, n->m_len);

	m->m_len += n->m_len;

	m_free(n);

}

/* make m size bytes large */

void

m_inc(m, size)

        struct mbuf *m;

        int size;

{

	int datasize;

	/* some compiles throw up on gotos.  This one we can fake. */

        if(m->m_size>size) return;

        if (m->m_flags & M_EXT) {

	  datasize = m->m_data - m->m_ext;

	  m->m_ext = (char *)realloc(m->m_ext,size);

/*		if (m->m_ext == NULL)

 *			return (struct mbuf *)NULL;

 */

	  m->m_data = m->m_ext + datasize;

        } else {

	  char *dat;

	  datasize = m->m_data - m->m_dat;

	  dat = (char *)malloc(size);

/*		if (dat == NULL)

 *			return (struct mbuf *)NULL;

 */

	  memcpy(dat, m->m_dat, m->m_size);

	  m->m_ext = dat;

	  m->m_data = m->m_ext + datasize;

	  m->m_flags |= M_EXT;

        }

        m->m_size = size;

}

void

m_adj(m, len)

	struct mbuf *m;

	int len;

{

	if (m == NULL)

		return;

	if (len >= 0) {

		/* Trim from head */

		m->m_data += len;

		m->m_len -= len;

	} else {

		/* Trim from tail */

		len = -len;

		m->m_len -= len;

	}

}

/*

 * Copy len bytes from m, starting off bytes into n

 */

int

m_copy(n, m, off, len)

	struct mbuf *n, *m;

	int off, len;

{

	if (len > M_FREEROOM(n))

		return -1;

	memcpy((n->m_data + n->m_len), (m->m_data + off), len);

	n->m_len += len;

	return 0;

}

/*

 * Given a pointer into an mbuf, return the mbuf

 * XXX This is a kludge, I should eliminate the need for it

 * Fortunately, it's not used often

 */

struct mbuf *

dtom(dat)

	void *dat;

{

	struct mbuf *m;

	DEBUG_CALL("dtom");

	DEBUG_ARG("dat = %lx", (long )dat);

	/* bug corrected for M_EXT buffers */

	for (m = m_usedlist.m_next; m != &m_usedlist; m = m->m_next) {

	  if (m->m_flags & M_EXT) {

	    if( (char *)dat>=m->m_ext && (char *)dat<(m->m_ext + m->m_size) )

	      return m;

	  } else {

	    if( (char *)dat >= m->m_dat && (char *)dat<(m->m_dat + m->m_size) )

	      return m;

	  }

	}

	DEBUG_ERROR((dfd, "dtom failed"));

	return (struct mbuf *)0;

}