If mbuf refcnt was > 1 then rte_vlan_insert() would incorrectly
modify the original copy. Original code was expecting clone to make
a copy (it doesn't). Better to let the caller deal with making
a copy or setting up mbuf chain to allow for header to be added.

Also fix docbook comment about parameters (function takes
pointer to mbuf).

Fixes: c974021a5949 ("ether: add soft vlan encap/decap")
Signed-off-by: Stephen Hemminger <sthem...@microsoft.com>
---
 lib/librte_net/rte_ether.h | 15 ++++-----------
 1 file changed, 4 insertions(+), 11 deletions(-)

diff --git a/lib/librte_net/rte_ether.h b/lib/librte_net/rte_ether.h
index c2c5e249ffe9..bab2b198fa79 100644
--- a/lib/librte_net/rte_ether.h
+++ b/lib/librte_net/rte_ether.h
@@ -374,7 +374,7 @@ static inline int rte_vlan_strip(struct rte_mbuf *m)
  * Software version of VLAN unstripping
  *
  * @param m
- *   The packet mbuf.
+ *   Pointer to the packet mbuf.
  * @return
  *   - 0: On success
  *   -EPERM: mbuf is is shared overwriting would be unsafe
@@ -385,16 +385,9 @@ static inline int rte_vlan_insert(struct rte_mbuf **m)
        struct ether_hdr *oh, *nh;
        struct vlan_hdr *vh;
 
-       /* Can't insert header if mbuf is shared */
-       if (rte_mbuf_refcnt_read(*m) > 1) {
-               struct rte_mbuf *copy;
-
-               copy = rte_pktmbuf_clone(*m, (*m)->pool);
-               if (unlikely(copy == NULL))
-                       return -ENOMEM;
-               rte_pktmbuf_free(*m);
-               *m = copy;
-       }
+       /* Can't directly insert header if mbuf is shared */
+       if (rte_mbuf_refcnt_read(*m) > 1)
+               return -EPERM;
 
        oh = rte_pktmbuf_mtod(*m, struct ether_hdr *);
        nh = (struct ether_hdr *)
-- 
2.17.1

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