Add m_demote(struct mbuf *m, int all) to clean up mbuf (chain) from

any tags and packet headers.  If "all" is set then the first mbuf
in the chain will be cleaned too.

This function is used before an mbuf, that arrived as packet with
m->flags & M_PKTHDR, is appended to an mbuf chain using m->m_next
(not m->m_nextpkt).

Reviewed by:	glebius

2 files changed, 25 insertions, 0 deletions

diff --git a/sys/kern/uipc_mbuf.c b/sys/kern/uipc_mbuf.c
index 6a0e9ba..6932245 100644
--- a/sys/kern/uipc_mbuf.c
+++ b/sys/kern/uipc_mbuf.c
@@ -270,6 +270,30 @@ mb_free_ext(struct mbuf *m)
 }
 
 /*
+ * Clean up mbuf (chain) from any tags and packet headers.
+ * If "all" is set then the first mbuf in the chain will be
+ * cleaned too.
+ */
+void
+m_demote(struct mbuf *m0, int all)
+{
+	struct mbuf *m;
+
+	for (m = all ? m0 : m0->m_next; m != NULL; m = m->m_next) {
+		if (m->m_flags & M_PKTHDR) {
+			m_tag_delete_chain(m, NULL);
+			m->m_flags &= ~M_PKTHDR;
+			bzero(&m->m_pkthdr, sizeof(struct pkthdr));
+		}
+		if (m->m_type & MT_HEADER)
+			m->m_type = MT_DATA;
+		if (m != m0 && m->m_nextpkt)
+			m->m_nextpkt = NULL;
+		m->m_flags = m->m_flags & (M_EXT|M_EOR|M_RDONLY|M_FREELIST);
+	}
+}
+
+/*
  * "Move" mbuf pkthdr from "from" to "to".
  * "from" must have M_PKTHDR set, and "to" must be empty.
  */
diff --git a/sys/sys/mbuf.h b/sys/sys/mbuf.h
index a07b685..7f2b540 100644
--- a/sys/sys/mbuf.h
+++ b/sys/sys/mbuf.h
@@ -577,6 +577,7 @@ struct	mbuf	*m_copypacket(struct mbuf *, int);
 void		 m_copy_pkthdr(struct mbuf *, struct mbuf *);
 struct	mbuf	*m_copyup(struct mbuf *n, int len, int dstoff);
 struct	mbuf	*m_defrag(struct mbuf *, int);
+void		 m_demote(struct mbuf *, int);
 struct	mbuf	*m_devget(char *, int, int, struct ifnet *,
 		    void (*)(char *, caddr_t, u_int));
 struct	mbuf	*m_dup(struct mbuf *, int);