m_tag fixups in preparation for heavier use:

o promote several m_tag_* routines to inline
o add an m_tag_setup inline to set the fixed fields in a packet tag
o add an m_tag_free method pointer to each mtag to support, for example,
  allocating tags from zones
o have m_tag_find check if the tag list is not empty before calling
  m_tag_locate to search

Reviewed by:	brooks, silence from others

2 files changed, 85 insertions, 58 deletions

diff --git a/sys/kern/uipc_mbuf2.c b/sys/kern/uipc_mbuf2.c
index 1b579e3..4d59447 100644
--- a/sys/kern/uipc_mbuf2.c
+++ b/sys/kern/uipc_mbuf2.c
@@ -310,6 +310,17 @@ m_dup1(struct mbuf *m, int off, int len, int wait)
 	return n;
 }
 
+/* Free a packet tag. */
+static void
+_m_tag_free(struct m_tag *t)
+{
+#ifdef MAC
+	if (t->m_tag_id == PACKET_TAG_MACLABEL)
+		mac_destroy_mbuf_tag(t);
+#endif
+	free(t, M_PACKET_TAGS);
+}
+
 /* Get a packet tag structure along with specified data following. */
 struct m_tag *
 m_tag_alloc(u_int32_t cookie, int type, int len, int wait)
@@ -321,39 +332,11 @@ m_tag_alloc(u_int32_t cookie, int type, int len, int wait)
 	t = malloc(len + sizeof(struct m_tag), M_PACKET_TAGS, wait);
 	if (t == NULL)
 		return NULL;
-	t->m_tag_id = type;
-	t->m_tag_len = len;
-	t->m_tag_cookie = cookie;
+	m_tag_setup(t, cookie, type, len);
+	t->m_tag_free = _m_tag_free;
 	return t;
 }
 
-/* Free a packet tag. */
-void
-m_tag_free(struct m_tag *t)
-{
-#ifdef MAC
-	if (t->m_tag_id == PACKET_TAG_MACLABEL)
-		mac_destroy_mbuf_tag(t);
-#endif
-	free(t, M_PACKET_TAGS);
-}
-
-/* Prepend a packet tag. */
-void
-m_tag_prepend(struct mbuf *m, struct m_tag *t)
-{
-	KASSERT(m && t, ("m_tag_prepend: null argument, m %p t %p", m, t));
-	SLIST_INSERT_HEAD(&m->m_pkthdr.tags, t, m_tag_link);
-}
-
-/* Unlink a packet tag. */
-void
-m_tag_unlink(struct mbuf *m, struct m_tag *t)
-{
-	KASSERT(m && t, ("m_tag_unlink: null argument, m %p t %p", m, t));
-	SLIST_REMOVE(&m->m_pkthdr.tags, t, m_tag, m_tag_link);
-}
-
 /* Unlink and free a packet tag. */
 void
 m_tag_delete(struct mbuf *m, struct m_tag *t)
@@ -473,24 +456,3 @@ m_tag_copy_chain(struct mbuf *to, struct mbuf *from, int how)
 	}
 	return 1;
 }
-
-/* Initialize tags on an mbuf. */
-void
-m_tag_init(struct mbuf *m)
-{
-	SLIST_INIT(&m->m_pkthdr.tags);
-}
-
-/* Get first tag in chain. */
-struct m_tag *
-m_tag_first(struct mbuf *m)
-{
-	return SLIST_FIRST(&m->m_pkthdr.tags);
-}
-
-/* Get next tag in chain. */
-struct m_tag *
-m_tag_next(struct mbuf *m, struct m_tag *t)
-{
-	return SLIST_NEXT(t, m_tag_link);
-}
diff --git a/sys/sys/mbuf.h b/sys/sys/mbuf.h
index 6cb01c1..c88e647 100644
--- a/sys/sys/mbuf.h
+++ b/sys/sys/mbuf.h
@@ -83,6 +83,7 @@ struct m_tag {
 	u_int16_t		m_tag_id;	/* Tag ID */
 	u_int16_t		m_tag_len;	/* Length of data */
 	u_int32_t		m_tag_cookie;	/* ABI/Module ID */
+	void			(*m_tag_free)(struct m_tag *);
 };
 
 /*
@@ -569,19 +570,82 @@ struct	mbuf	*m_split(struct mbuf *, int, int);
 
 /* Packet tag routines. */
 struct	m_tag 	*m_tag_alloc(u_int32_t, int, int, int);
-void		 m_tag_free(struct m_tag *);
-void		 m_tag_prepend(struct mbuf *, struct m_tag *);
-void		 m_tag_unlink(struct mbuf *, struct m_tag *);
 void		 m_tag_delete(struct mbuf *, struct m_tag *);
 void		 m_tag_delete_chain(struct mbuf *, struct m_tag *);
 struct	m_tag	*m_tag_locate(struct mbuf *, u_int32_t, int, struct m_tag *);
 struct	m_tag	*m_tag_copy(struct m_tag *, int);
 int		 m_tag_copy_chain(struct mbuf *, struct mbuf *, int);
-void		 m_tag_init(struct mbuf *);
-struct	m_tag	*m_tag_first(struct mbuf *);
-struct	m_tag	*m_tag_next(struct mbuf *, struct m_tag *);
 void		 m_tag_delete_nonpersistent(struct mbuf *);
 
+/*
+ * Initialize the list of tags associated with an mbuf.
+ */
+static __inline void
+m_tag_init(struct mbuf *m)
+{
+	SLIST_INIT(&m->m_pkthdr.tags);
+}
+
+/*
+ * Setup the contents of a tag.  Note that this does not
+ * fillin the free method; the caller is expected to do that.
+ *
+ * XXX probably should be called m_tag_init; but that was
+ * already taken.
+ */
+static __inline void
+m_tag_setup(struct m_tag *t, u_int32_t cookie, int type, int len)
+{
+	t->m_tag_id = type;
+	t->m_tag_len = len;
+	t->m_tag_cookie = cookie;
+}
+
+/*
+ * Reclaim resources associated with a tag.
+ */
+static __inline void
+m_tag_free(struct m_tag *t)
+{
+	(*t->m_tag_free)(t);
+}
+
+/*
+ * Return the first tag associated with an mbuf.
+ */
+static __inline struct m_tag *
+m_tag_first(struct mbuf *m)
+{
+	return SLIST_FIRST(&m->m_pkthdr.tags);
+}
+
+/*
+ * Return the next tag in the list of tags associated with an mbuf.
+ */
+static __inline struct m_tag *
+m_tag_next(struct mbuf *m, struct m_tag *t)
+{
+	return SLIST_NEXT(t, m_tag_link);
+}
+
+/*
+ * Prepend a tag to the list of tags associated with an mbuf.
+ */
+static __inline void
+m_tag_prepend(struct mbuf *m, struct m_tag *t)
+{
+	SLIST_INSERT_HEAD(&m->m_pkthdr.tags, t, m_tag_link);
+}
+
+/*
+ * Unlink a tag from the list of tags associated with an mbuf.
+ */
+static __inline void
+m_tag_unlink(struct mbuf *m, struct m_tag *t)
+{
+	SLIST_REMOVE(&m->m_pkthdr.tags, t, m_tag, m_tag_link);
+}
+
 /* These are for OpenBSD compatibility. */
 #define	MTAG_ABI_COMPAT		0		/* compatibility ABI */
 
@@ -594,7 +658,8 @@ m_tag_get(int type, int length, int wait)
 static __inline struct m_tag *
 m_tag_find(struct mbuf *m, int type, struct m_tag *start)
 {
-	return m_tag_locate(m, MTAG_ABI_COMPAT, type, start);
+	return SLIST_EMPTY(&m->m_pkthdr.tags) ?
+		NULL : m_tag_locate(m, MTAG_ABI_COMPAT, type, start);
 }
 #endif /* _KERNEL */