svn commit: r291953 - head/sys/dev/usb/net

[Hans Petter Selasky]

Author: hselasky
Date: Mon Dec  7 18:55:33 2015
New Revision: 291953
URL: https://svnweb.freebsd.org/changeset/base/291953

Log:
  When setting up VLANs on a Raspberry Pi ethernet port, the MTU drops
  from 1500 to 1496 bytes. The MTU should remain at 1500, extending the
  frame size as per IEEE 802.3. Adding IFCAP_VLAN_MTU to the
  if_capabilities field in the smsc driver solves the problem.  The
  datasheet for the LAN9512 chip, section 3.2.3 states that the chip
  supports the extended frame.
  
  Submitted by:	rpp at ci.com.au
  MFC after:	1 week
  PR:		205050

Modified:
  head/sys/dev/usb/net/if_smsc.c

Modified: head/sys/dev/usb/net/if_smsc.c
==============================================================================
--- head/sys/dev/usb/net/if_smsc.c	Mon Dec  7 18:45:55 2015	(r291952)
+++ head/sys/dev/usb/net/if_smsc.c	Mon Dec  7 18:55:33 2015	(r291953)
@@ -1707,7 +1707,7 @@ smsc_attach_post_sub(struct usb_ether *u
 	/* The chip supports TCP/UDP checksum offloading on TX and RX paths, however
 	 * currently only RX checksum is supported in the driver (see top of file).
 	 */
-	ifp->if_capabilities |= IFCAP_RXCSUM;
+	ifp->if_capabilities |= IFCAP_RXCSUM | IFCAP_VLAN_MTU;
 	ifp->if_hwassist = 0;
 	
 	/* TX checksuming is disabled (for now?)