I thought we already had something for this after the misc@ thread a few months ago, but clearly not.
Adapted from FreeBSD if_lagg.c r171661 (which includes capability setting which we already do). http://svnweb.freebsd.org/base/head/sys/net/if_lagg.c?r1=171603&r2=171661 Index: if_trunk.c =================================================================== RCS file: /cvs/src/sys/net/if_trunk.c,v retrieving revision 1.78 diff -u -p -r1.78 if_trunk.c --- if_trunk.c 28 Oct 2011 12:49:43 -0000 1.78 +++ if_trunk.c 22 Feb 2013 12:27:18 -0000 @@ -315,6 +315,20 @@ trunk_port_create(struct trunk_softc *tr if (ifp->if_type != IFT_ETHER) return (EPROTONOSUPPORT); + /* Take MTU from the first member port */ + if (SLIST_EMPTY(&tr->tr_ports)) { + if (tr->tr_ifflags & IFF_DEBUG) + printf("%s: first port, setting trunk mtu %u\n", + tr->tr_ifname, ifp->if_mtu); + tr->tr_ac.ac_if.if_mtu = ifp->if_mtu; + tr->tr_ac.ac_if.if_hardmtu = ifp->if_mtu; + } + else if (tr->tr_ac.ac_if.if_mtu != ifp->if_mtu) { + printf("%s: adding %s failed, MTU %u != %u\n", tr->tr_ifname, + ifp->if_xname, ifp->if_mtu, tr->tr_ac.ac_if.if_mtu); + return (EINVAL); + } + if ((error = ifpromisc(ifp, 1)) != 0) return (error); @@ -510,6 +524,10 @@ trunk_port_ioctl(struct ifnet *ifp, u_lo } trunk_port2req(tp, rp); + break; + case SIOCSIFMTU: + /* Do not allow the MTU to be changed once joined */ + error = EINVAL; break; default: error = ENOTTY;
