Index: usr.sbin/bhyve/bhyve.8
===================================================================
--- usr.sbin/bhyve/bhyve.8
+++ usr.sbin/bhyve/bhyve.8
@@ -24,7 +24,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd December 13, 2019
+.Dd January 23, 2020
 .Dt BHYVE 8
 .Os
 .Sh NAME
@@ -584,6 +584,11 @@
   -A -H -P -m 24G bigvm
 .Ed
 .Pp
+The virtio-net device accepts an additional option to explicitely enable
+or disable the virtio-net `mergeable rx buffers` feature. If the option
+is not specified, bhyve will advertise the feature only when the vale(4)
+net backend is used.
+.Pp
 Run an 8GB quad-CPU virtual machine with 8 AHCI SATA disks, an AHCI ATAPI
 CD-ROM, a single virtio network port, an AMD hostbridge, and the console
 port connected to an
Index: usr.sbin/bhyve/net_backends.c
===================================================================
--- usr.sbin/bhyve/net_backends.c
+++ usr.sbin/bhyve/net_backends.c
@@ -279,7 +279,6 @@
 static uint64_t
 tap_get_cap(struct net_backend *be)
 {
-
 	return (0); /* no capabilities for now */
 }
 
Index: usr.sbin/bhyve/net_utils.c
===================================================================
--- usr.sbin/bhyve/net_utils.c
+++ usr.sbin/bhyve/net_utils.c
@@ -44,21 +44,19 @@
 net_parsemac(char *mac_str, uint8_t *mac_addr)
 {
         struct ether_addr *ea;
-        char *tmpstr;
         char zero_addr[ETHER_ADDR_LEN] = { 0, 0, 0, 0, 0, 0 };
 
-        tmpstr = strsep(&mac_str,"=");
+	if (mac_str == NULL)
+		return (EINVAL);
 
-        if ((mac_str != NULL) && (!strcmp(tmpstr,"mac"))) {
-                ea = ether_aton(mac_str);
+	ea = ether_aton(mac_str);
 
-                if (ea == NULL || ETHER_IS_MULTICAST(ea->octet) ||
-                    memcmp(ea->octet, zero_addr, ETHER_ADDR_LEN) == 0) {
-			EPRINTLN("Invalid MAC %s", mac_str);
-                        return (EINVAL);
-                } else
-                        memcpy(mac_addr, ea->octet, ETHER_ADDR_LEN);
-        }
+	if (ea == NULL || ETHER_IS_MULTICAST(ea->octet) ||
+	    memcmp(ea->octet, zero_addr, ETHER_ADDR_LEN) == 0) {
+		EPRINTLN("Invalid MAC %s", mac_str);
+		return (EINVAL);
+	} else
+		memcpy(mac_addr, ea->octet, ETHER_ADDR_LEN);
 
         return (0);
 }
Index: usr.sbin/bhyve/pci_e82545.c
===================================================================
--- usr.sbin/bhyve/pci_e82545.c
+++ usr.sbin/bhyve/pci_e82545.c
@@ -2328,18 +2328,38 @@
 	mac_provided = 0;
 	sc->esc_be = NULL;
 	if (opts != NULL) {
-		int err;
+		int err = 0;
 
 		devname = vtopts = strdup(opts);
 		(void) strsep(&vtopts, ",");
 
-		if (vtopts != NULL) {
-			err = net_parsemac(vtopts, sc->esc_mac.octet);
-			if (err != 0) {
-				free(devname);
-				return (err);
+		/*
+		 * Parse the list of options in the form
+		 *     key1=value1,...,keyN=valueN.
+		 */
+		while (vtopts != NULL) {
+			char *value = vtopts;
+			char *key;
+
+			key = strsep(&value, "=");
+			if (value == NULL) {
+				break;
+			}
+			vtopts = value;
+			(void) strsep(&vtopts, ",");
+
+			if (strcmp(key, "mac") == 0) {
+				err = net_parsemac(value, sc->esc_mac.octet);
+				if (err) {
+					break;
+				}
+				mac_provided = 1;
 			}
-			mac_provided = 1;
+		}
+
+		if (err) {
+			free(devname);
+			return (err);
 		}
 
 		err = netbe_init(&sc->esc_be, devname, e82545_rx_callback, sc);
Index: usr.sbin/bhyve/pci_virtio_net.c
===================================================================
--- usr.sbin/bhyve/pci_virtio_net.c
+++ usr.sbin/bhyve/pci_virtio_net.c
@@ -464,21 +464,52 @@
 	 */
 	mac_provided = 0;
 	if (opts != NULL) {
+		int mrg_rxbuf_enabled = 0;
+		int mrg_rxbuf_disabled = 0;
 		char *devname;
 		char *vtopts;
-		int err;
+		int err = 0;
 
+		/* Get the device name. */
 		devname = vtopts = strdup(opts);
 		(void) strsep(&vtopts, ",");
 
-		if (vtopts != NULL) {
-			err = net_parsemac(vtopts, sc->vsc_config.mac);
-			if (err != 0) {
-				free(devname);
-				free(sc);
-				return (err);
+		/*
+		 * Parse the list of options in the form
+		 *     key1=value1,...,keyN=valueN.
+		 */
+		while (vtopts != NULL) {
+			char *value = vtopts;
+			char *key;
+
+			key = strsep(&value, "=");
+			if (value == NULL) {
+				break;
+			}
+			vtopts = value;
+			(void) strsep(&vtopts, ",");
+
+			if (strcmp(key, "mac") == 0) {
+				err = net_parsemac(value, sc->vsc_config.mac);
+				if (err) {
+					break;
+				}
+				mac_provided = 1;
+			} else if (strcmp(key, "mrgrxbuf") == 0) {
+				if (strcmp(value, "on") == 0) {
+					mrg_rxbuf_enabled = 1;
+					mrg_rxbuf_disabled = 0;
+				} else {
+					mrg_rxbuf_disabled = 1;
+					mrg_rxbuf_enabled = 0;
+				}
 			}
-			mac_provided = 1;
+		}
+
+		if (err) {
+			free(devname);
+			free(sc);
+			return (err);
 		}
 
 		err = netbe_init(&sc->vsc_be, devname, pci_vtnet_rx_callback,
@@ -489,6 +520,11 @@
 			return (err);
 		}
 		sc->vsc_consts.vc_hv_caps |= netbe_get_cap(sc->vsc_be);
+		if (mrg_rxbuf_enabled)
+			sc->vsc_consts.vc_hv_caps |= VIRTIO_NET_F_MRG_RXBUF;
+		else if (mrg_rxbuf_disabled)
+			sc->vsc_consts.vc_hv_caps &= ~VIRTIO_NET_F_MRG_RXBUF;
+
 	}
 
 	if (!mac_provided) {