checksum offload for carp

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

Hello,
the attached patch allows use of checksum offload with carp pseudo-interfaces
if the underlying device supports it. I tested this on a netbsd-6 testbed,
and I'm running a backport of this to netbsd-5 on a router with a wm(4)
interface. This decreased CPU time spent in interrupt dramatically.

Does anyone see a problem with this ?

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--

Index: ip_carp.c
===================================================================
RCS file: /cvsroot/src/sys/netinet/ip_carp.c,v
retrieving revision 1.48
diff -u -p -u -r1.48 ip_carp.c
--- ip_carp.c   27 Mar 2012 17:48:17 -0000      1.48
+++ ip_carp.c   2 Aug 2012 10:07:37 -0000
@@ -1552,6 +1552,14 @@ carp_set_ifp(struct carp_softc *sc, stru
                if (ncif != NULL)
                        ifp->if_carp = (void *)ncif;
                sc->sc_carpdev = ifp;
+               sc->sc_if.if_capabilities = ifp->if_capabilities &
+                            (IFCAP_TSOv4 | IFCAP_TSOv6 |
+                             IFCAP_CSUM_IPv4_Tx|IFCAP_CSUM_IPv4_Rx|
+                             IFCAP_CSUM_TCPv4_Tx|IFCAP_CSUM_TCPv4_Rx|
+                             IFCAP_CSUM_UDPv4_Tx|IFCAP_CSUM_UDPv4_Rx|
+                             IFCAP_CSUM_TCPv6_Tx|IFCAP_CSUM_TCPv6_Rx|
+                             IFCAP_CSUM_UDPv6_Tx|IFCAP_CSUM_UDPv6_Rx);
+
                cif = (struct carp_if *)ifp->if_carp;
                TAILQ_FOREACH(vr, &cif->vhif_vrs, sc_list) {
                        if (vr == sc)
@@ -2010,6 +2018,11 @@ carp_ioctl(struct ifnet *ifp, u_long cmd
                error = carp_ether_delmulti(sc, ifr);
                break;
 
+       case SIOCSIFCAP:
+               if ((error = ifioctl_common(ifp, cmd, addr)) == ENETRESET)
+                       error = 0;
+               break;
+
        default:
                error = ether_ioctl(ifp, cmd, data);
        }