iproute2: sch_rr support in tc

This patch applies on top of Patrick McHardy's RTNETLINK
patches to add nested compat attributes.  This is needed to maintain
ABI for sch_{rr|prio} in the kernel with respect to tc.  A new option,
namely multiqueue, was added to sch_prio and sch_rr.  This will allow
a user to turn multiqueue support on for sch_prio or sch_rr at loadtime.
Also, tc qdisc ls will display whether or not multiqueue is enabled on
that qdisc.  When in multiqueue mode, a user can specify a value of 0 for
bands, and the number of bands will be created to match the number of
queues on the device.

This patch is to support the new sch_rr (round-robin) qdisc being proposed
in NET for multiqueue network device support in the Linux network stack.
It uses q_prio.c as the template, since the qdiscs are nearly identical,
outside of the ->dequeue() routine.

Signed-off-by: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@intel.com>
diff --git a/tc/q_prio.c b/tc/q_prio.c
index d696e1b..6883edb 100644
--- a/tc/q_prio.c
+++ b/tc/q_prio.c
@@ -29,7 +29,7 @@
 
 static void explain(void)
 {
-	fprintf(stderr, "Usage: ... prio bands NUMBER priomap P1 P2...\n");
+	fprintf(stderr, "Usage: ... prio bands NUMBER priomap P1 P2...[multiqueue]\n");
 }
 
 #define usage() return(-1)
@@ -40,6 +40,8 @@
 	int pmap_mode = 0;
 	int idx = 0;
 	struct tc_prio_qopt opt={3,{ 1, 2, 2, 2, 1, 2, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1 }};
+	struct rtattr *nest;
+	unsigned char mq = 0;
 
 	while (argc > 0) {
 		if (strcmp(*argv, "bands") == 0) {
@@ -57,6 +59,8 @@
 				return -1;
 			}
 			pmap_mode = 1;
+		} else if (strcmp(*argv, "multiqueue") == 0) {
+			mq = 1;
 		} else if (strcmp(*argv, "help") == 0) {
 			explain();
 			return -1;
@@ -90,7 +94,10 @@
 			opt.priomap[idx] = opt.priomap[TC_PRIO_BESTEFFORT];
 	}
 */
-	addattr_l(n, 1024, TCA_OPTIONS, &opt, sizeof(opt));
+	nest = addattr_nest_compat(n, 1024, TCA_OPTIONS, &opt, sizeof(opt));
+	if (mq)
+		addattr_l(n, 1024, TCA_PRIO_MQ, NULL, 0);
+	addattr_nest_compat_end(n, nest);
 	return 0;
 }
 
@@ -98,16 +105,23 @@
 {
 	int i;
 	struct tc_prio_qopt *qopt;
+	struct rtattr *tb[TCA_PRIO_MAX+1];
 
 	if (opt == NULL)
 		return 0;
 
-	if (RTA_PAYLOAD(opt)  < sizeof(*qopt))
-		return -1;
-	qopt = RTA_DATA(opt);
+	if (parse_rtattr_nested_compat(tb, TCA_PRIO_MAX, opt, qopt,
+					sizeof(*qopt)))
+                return -1;
+
 	fprintf(f, "bands %u priomap ", qopt->bands);
 	for (i=0; i<=TC_PRIO_MAX; i++)
 		fprintf(f, " %d", qopt->priomap[i]);
+
+	if (tb[TCA_PRIO_MQ])
+		fprintf(f, " multiqueue: %s ",
+		    *(unsigned char *)RTA_DATA(tb[TCA_PRIO_MQ]) ? "on" : "off");
+
 	return 0;
 }