macvlan/macvtap: support 'passthru' mode

Add support for 'passthru' mode when creating a macvlan/macvtap device
which allows takeover of the underlying device and passing it to a KVM
guest using virtio with macvtap backend.

Only one macvlan device is allowed in passthru mode and it inherits
the mac address from the underlying device and sets it in promiscuous
mode to receive and forward all the packets.
Signed-off-by: Sridhar Samudrala <sri@us.ibm.com>

ip/iplink_macvlan.c

@@ -23,14 +23,14 @@
 static void explain(void)
 {
 	fprintf(stderr,
-		"Usage: ... macvlan mode { private | vepa | bridge }\n"
+		"Usage: ... macvlan mode { private | vepa | bridge | passthru }\n"
 	);
 }
 
 static int mode_arg(void)
 {
         fprintf(stderr, "Error: argument of \"mode\" must be \"private\", "
-		"\"vepa\" or \"bridge\"\n");
+		"\"vepa\", \"bridge\" or \"passthru\" \n");
         return -1;
 }
 
@@ -48,6 +48,8 @@ static int macvlan_parse_opt(struct link_util *lu, int argc, char **argv,
 				mode = MACVLAN_MODE_VEPA;
 			else if (strcmp(*argv, "bridge") == 0)
 				mode = MACVLAN_MODE_BRIDGE;
+			else if (strcmp(*argv, "passthru") == 0)
+				mode = MACVLAN_MODE_PASSTHRU;
 			else
 				return mode_arg();
 
@@ -82,6 +84,7 @@ static void macvlan_print_opt(struct link_util *lu, FILE *f, struct rtattr *tb[]
 		  mode == MACVLAN_MODE_PRIVATE ? "private"
 		: mode == MACVLAN_MODE_VEPA    ? "vepa"
 		: mode == MACVLAN_MODE_BRIDGE  ? "bridge"
+		: mode == MACVLAN_MODE_PASSTHRU  ? "passthru"
 		:				 "unknown");
 }
 

ip/iplink_macvtap.c

@@ -20,14 +20,14 @@
 static void explain(void)
 {
 	fprintf(stderr,
-		"Usage: ... macvtap mode { private | vepa | bridge }\n"
+		"Usage: ... macvtap mode { private | vepa | bridge | passthru }\n"
 	);
 }
 
 static int mode_arg(void)
 {
         fprintf(stderr, "Error: argument of \"mode\" must be \"private\", "
-		"\"vepa\" or \"bridge\"\n");
+		"\"vepa\", \"bridge\" or \"passthru\" \n");
         return -1;
 }
 
@@ -45,6 +45,8 @@ static int macvtap_parse_opt(struct link_util *lu, int argc, char **argv,
 				mode = MACVLAN_MODE_VEPA;
 			else if (strcmp(*argv, "bridge") == 0)
 				mode = MACVLAN_MODE_BRIDGE;
+			else if (strcmp(*argv, "passthru") == 0)
+				mode = MACVLAN_MODE_PASSTHRU;
 			else
 				return mode_arg();
 
@@ -79,6 +81,7 @@ static void macvtap_print_opt(struct link_util *lu, FILE *f, struct rtattr *tb[]
 		  mode == MACVLAN_MODE_PRIVATE ? "private"
 		: mode == MACVLAN_MODE_VEPA    ? "vepa"
 		: mode == MACVLAN_MODE_BRIDGE  ? "bridge"
+		: mode == MACVLAN_MODE_PASSTHRU  ? "passthru"
 		:				 "unknown");
 }