From 66d0c056bece7ec0cd2d11513eaae88d6478d231 Mon Sep 17 00:00:00 2001
From: John Baldwin <jhb@FreeBSD.org>
Date: Sat, 29 Jun 2019 00:51:38 +0000
Subject: [PATCH] Support IFCAP_NOMAP in vlan(4).

Enable IFCAP_NOMAP for a vlan interface if it is supported by the
underlying trunk device.

Reviewed by:	gallatin, hselasky, rrs
Sponsored by:	Netflix
Differential Revision:	https://reviews.freebsd.org/D20616
---
 sys/net/if_vlan.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/sys/net/if_vlan.c b/sys/net/if_vlan.c
index 5f29eb61b470..681d651e7796 100644
--- a/sys/net/if_vlan.c
+++ b/sys/net/if_vlan.c
@@ -1731,6 +1731,16 @@ vlan_capabilities(struct ifvlan *ifv)
 	ena |= (mena & IFCAP_TXRTLMT);
 #endif
 
+	/*
+	 * If the parent interface supports unmapped mbufs, so does
+	 * the VLAN interface.  Note that this should be fine even for
+	 * interfaces that don't support hardware tagging as headers
+	 * are prepended in normal mbufs to unmapped mbufs holding
+	 * payload data.
+	 */
+	cap |= (p->if_capabilities & IFCAP_NOMAP);
+	ena |= (mena & IFCAP_NOMAP);
+
 	ifp->if_capabilities = cap;
 	ifp->if_capenable = ena;
 	ifp->if_hwassist = hwa;