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slirp/mbuf.c

@@ -0,0 +1,218 @@
+/*
+ * 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"
+
+#define MBUF_THRESH 30
+
+/*
+ * Find a nice value for msize
+ * XXX if_maxlinkhdr already in mtu
+ */
+#define SLIRP_MSIZE (IF_MTU + IF_MAXLINKHDR + offsetof(struct mbuf, m_dat) + 6)
+
+void
+m_init(Slirp *slirp)
+{
+    slirp->m_freelist.m_next = slirp->m_freelist.m_prev = &slirp->m_freelist;
+    slirp->m_usedlist.m_next = slirp->m_usedlist.m_prev = &slirp->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(Slirp *slirp)
+{
+	register struct mbuf *m;
+	int flags = 0;
+
+	DEBUG_CALL("m_get");
+
+	if (slirp->m_freelist.m_next == &slirp->m_freelist) {
+		m = (struct mbuf *)malloc(SLIRP_MSIZE);
+		if (m == NULL) goto end_error;
+		slirp->mbuf_alloced++;
+		if (slirp->mbuf_alloced > MBUF_THRESH)
+			flags = M_DOFREE;
+		m->slirp = slirp;
+	} else {
+		m = slirp->m_freelist.m_next;
+		remque(m);
+	}
+
+	/* Insert it in the used list */
+	insque(m,&slirp->m_usedlist);
+	m->m_flags = (flags | M_USEDLIST);
+
+	/* Initialise it */
+	m->m_size = SLIRP_MSIZE - offsetof(struct mbuf, m_dat);
+	m->m_data = m->m_dat;
+	m->m_len = 0;
+        m->m_nextpkt = NULL;
+        m->m_prevpkt = NULL;
+end_error:
+	DEBUG_ARG("m = %lx", (long )m);
+	return m;
+}
+
+void
+m_free(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) {
+		m->slirp->mbuf_alloced--;
+		free(m);
+	} else if ((m->m_flags & M_FREELIST) == 0) {
+		insque(m,&m->slirp->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(struct mbuf *m, struct mbuf *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(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);
+	  m->m_data = m->m_ext + datasize;
+        } else {
+	  char *dat;
+	  datasize = m->m_data - m->m_dat;
+	  dat = (char *)malloc(size);
+	  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(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(struct mbuf *n, struct mbuf *m, int off, int 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(Slirp *slirp, void *dat)
+{
+	struct mbuf *m;
+
+	DEBUG_CALL("dtom");
+	DEBUG_ARG("dat = %lx", (long )dat);
+
+	/* bug corrected for M_EXT buffers */
+	for (m = slirp->m_usedlist.m_next; m != &slirp->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;
+}