Possible optimization in ether_output()

[Vijay Singh]

Hi, this patch gives a modest performance improvement here @work.
Please consider.

[/u/vijay/bsd/CODE/cur/sys/net]# svn diff if_ethersubr.c
Index: if_ethersubr.c
===================================================================
--- if_ethersubr.c      (revision 247012)
+++ if_ethersubr.c      (working copy)
@@ -160,6 +160,7 @@
        struct pf_mtag *t;
        int loop_copy = 1;
        int hlen;       /* link layer header length */
+       int use_lle_directly = 0;

        if (ro != NULL) {
                if (!(m->m_flags & (M_BCAST | M_MCAST)))
@@ -184,7 +185,7 @@
 #ifdef INET
        case AF_INET:
                if (lle != NULL && (lle->la_flags & LLE_VALID))
-                       memcpy(edst, &lle->ll_addr.mac16, sizeof(edst));
+                       use_lle_directly = 1;
                else
                        error = arpresolve(ifp, rt0, m, dst, edst, &lle);
                if (error)
@@ -222,7 +223,7 @@
 #ifdef INET6
        case AF_INET6:
                if (lle != NULL && (lle->la_flags & LLE_VALID))
-                       memcpy(edst, &lle->ll_addr.mac16, sizeof(edst));
+                       use_lle_directly = 1;
                else
                        error = nd6_storelladdr(ifp, m, dst, (u_char *)edst, 
&lle);
                if (error)
@@ -317,9 +318,13 @@
        if (m == NULL)
                senderr(ENOBUFS);
        eh = mtod(m, struct ether_header *);
-       (void)memcpy(&eh->ether_type, &type,
-               sizeof(eh->ether_type));
-       (void)memcpy(eh->ether_dhost, edst, sizeof (edst));
+       eh->ether_type = type;
+       if (use_lle_directly) {
+               memcpy(eh->ether_dhost, &lle->ll_addr.mac16,
+                      sizeof(eh->ether_dhost));
+       } else {
+               (void)memcpy(eh->ether_dhost, edst, sizeof (edst));
+       }
        if (hdrcmplt)
                (void)memcpy(eh->ether_shost, esrc,
                        sizeof(eh->ether_shost));
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