Small fixes for if_oerrors in vlan(4), mpe(4) and pppx

[Christiano F. Haesbaert]

Hi, vlan_start() was increasing packet counts before checking if the
packet was successfully enqueued. I made a hunt for similar errors.

Index: net/if_mpe.c
===================================================================
RCS file: /cvs/src/sys/net/if_mpe.c,v
retrieving revision 1.25
diff -d -u -p -w -r1.25 if_mpe.c
--- net/if_mpe.c        28 Jan 2011 14:58:24 -0000      1.25
+++ net/if_mpe.c        20 Aug 2011 04:06:29 -0000
@@ -265,7 +265,7 @@ mpeoutput(struct ifnet *ifp, struct mbuf
        if (error) {
                /* mbuf is already freed */
                splx(s);
-               return (error);
+               goto out;
        }
        if_start(ifp);
        splx(s);
Index: net/if_pppx.c
===================================================================
RCS file: /cvs/src/sys/net/if_pppx.c,v
retrieving revision 1.9
diff -d -u -p -w -r1.9 if_pppx.c
--- net/if_pppx.c       7 Jul 2011 20:42:56 -0000       1.9
+++ net/if_pppx.c       20 Aug 2011 05:37:48 -0000
@@ -1057,6 +1057,10 @@ pppx_if_output(struct ifnet *ifp, struct
 
        s = splnet();
        IFQ_ENQUEUE(&ifp->if_snd, m, NULL, error);
+       if (error) {
+               splx(s);
+               goto out;
+       }
        if_start(ifp);
        splx(s);
 
Index: net/if_vlan.c
===================================================================
RCS file: /cvs/src/sys/net/if_vlan.c,v
retrieving revision 1.87
diff -d -u -p -w -r1.87 if_vlan.c
--- net/if_vlan.c       18 Feb 2011 17:06:45 -0000      1.87
+++ net/if_vlan.c       20 Aug 2011 03:58:05 -0000
@@ -251,15 +251,15 @@ vlan_start(struct ifnet *ifp)
                 * Send it, precisely as ether_output() would have.
                 * We are already running at splnet.
                 */
-               p->if_obytes += m->m_pkthdr.len;
-               if (m->m_flags & M_MCAST)
-                       p->if_omcasts++;
                IFQ_ENQUEUE(&p->if_snd, m, NULL, error);
                if (error) {
                        /* mbuf is already freed */
                        ifp->if_oerrors++;
                        continue;
                }
+               p->if_obytes += m->m_pkthdr.len;
+               if (m->m_flags & M_MCAST)
+                       p->if_omcasts++;
 
                ifp->if_opackets++;
                if_start(p);