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From: Andrew Boyer <aboyer@averesystems.com>
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Date: Thu, 12 Jul 2012 14:26:08 -0400
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References: <86liiqrnnq.wl%gnn@neville-neil.com> <4FFDF6C7.3030301@FreeBSD.org>
	<C06D346A-97BE-4498-B4E5-0ED85731A8BD@freebsd.org>
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To: Jason Hellenthal <jhellenthal@dataix.net>
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Cc: George Neville-Neil <gnn@freebsd.org>, Navdeep Parhar <np@freebsd.org>,
	net@freebsd.org
Subject: Re: Interface MTU question...
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On Jul 12, 2012, at 12:55 PM, Jason Hellenthal wrote:
> Something else to look into ... 
> 
> # ifconfig lagg0 mtu 1492
> ifconfig: ioctl (set mtu): Invalid argument
> 
> This is on stable/8 r238264 when the interface was up/up and down/down
> 
> Also attempted on the member interfaces dc0 and dc1


It's disabled by default, but I don't know why.  This seems to work for us.

-Andrew

Index: sys/net/if_lagg.c
===================================================================
--- sys/net/if_lagg.c	(revision 238402)
+++ sys/net/if_lagg.c	(working copy)
@@ -752,8 +752,18 @@
 		break;
 
 	case SIOCSIFMTU:
-		/* Do not allow the MTU to be changed once joined */
-		error = EINVAL;
+		LAGG_WLOCK(sc);
+		SLIST_FOREACH(lp, &sc->sc_ports, lp_entries) {
+			if (!error) {
+				/* Call the base ioctl for each port */
+				error = (*lp->lp_ioctl)(lp->lp_ifp, cmd, data);
+			}
+		}
+		if (!error) {
+			/* Update the aggregate MTU */
+			sc->sc_ifp->if_mtu = ifr->ifr_mtu;
+		}
+		LAGG_WUNLOCK(sc);
 		break;
 
 	default:

--------------------------------------------------
Andrew Boyer	aboyer@averesystems.com