tc: gred: Add support for TCA_GRED_LIMIT attribute

Allow the qdisc limit to be set, which is particularly useful when
the default VQ is not configured with RED parameters.
Signed-off-by: David Ward <david.ward@ll.mit.edu>

tc/q_gred.c

@@ -38,7 +38,7 @@
 static void explain(void)
 {
 	fprintf(stderr, "Usage: tc qdisc { add | replace | change } ... gred setup vqs NUMBER\n");
-	fprintf(stderr, "           default DEFAULT_VQ [ grio ]\n");
+	fprintf(stderr, "           default DEFAULT_VQ [ grio ] [ limit BYTES ]\n");
 	fprintf(stderr, "       tc qdisc change ... gred vq VQ [ prio VALUE ] limit BYTES\n");
 	fprintf(stderr, "           min BYTES max BYTES avpkt BYTES [ burst PACKETS ]\n");
 	fprintf(stderr, "           [ probability PROBABILITY ] [ bandwidth KBPS ]\n");
@@ -50,6 +50,7 @@ static int init_gred(struct qdisc_util *qu, int argc, char **argv,
 
 	struct rtattr *tail;
 	struct tc_gred_sopt opt = { 0 };
+	__u32 limit = 0;
 
 	opt.def_DP = MAX_DPs;
 
@@ -83,6 +84,12 @@ static int init_gred(struct qdisc_util *qu, int argc, char **argv,
 			}
 		} else if (strcmp(*argv, "grio") == 0) {
 			opt.grio = 1;
+		} else if (strcmp(*argv, "limit") == 0) {
+			NEXT_ARG();
+			if (get_size(&limit, *argv)) {
+				fprintf(stderr, "Illegal \"limit\"\n");
+				return -1;
+			}
 		} else if (strcmp(*argv, "help") == 0) {
 			explain();
 			return -1;
@@ -104,6 +111,8 @@ static int init_gred(struct qdisc_util *qu, int argc, char **argv,
 	tail = NLMSG_TAIL(n);
 	addattr_l(n, 1024, TCA_OPTIONS, NULL, 0);
 	addattr_l(n, 1024, TCA_GRED_DPS, &opt, sizeof(struct tc_gred_sopt));
+	if (limit)
+		addattr32(n, 1024, TCA_GRED_LIMIT, limit);
 	tail->rta_len = (void *) NLMSG_TAIL(n) - (void *) tail;
 	return 0;
 }
@@ -264,6 +273,7 @@ static int gred_print_opt(struct qdisc_util *qu, FILE *f, struct rtattr *opt)
 	struct tc_gred_sopt *sopt;
 	struct tc_gred_qopt *qopt;
 	__u32 *max_p = NULL;
+	__u32 *limit = NULL;
 	unsigned i;
 	SPRINT_BUF(b1);
 	SPRINT_BUF(b2);
@@ -281,6 +291,10 @@ static int gred_print_opt(struct qdisc_util *qu, FILE *f, struct rtattr *opt)
 	    RTA_PAYLOAD(tb[TCA_GRED_MAX_P]) >= sizeof(__u32) * MAX_DPs)
 		max_p = RTA_DATA(tb[TCA_GRED_MAX_P]);
 
+	if (tb[TCA_GRED_LIMIT] &&
+	    RTA_PAYLOAD(tb[TCA_GRED_LIMIT]) == sizeof(__u32))
+		limit = RTA_DATA(tb[TCA_GRED_LIMIT]);
+
 	sopt = RTA_DATA(tb[TCA_GRED_DPS]);
 	qopt = RTA_DATA(tb[TCA_GRED_PARMS]);
 	if (RTA_PAYLOAD(tb[TCA_GRED_DPS]) < sizeof(*sopt) ||
@@ -296,6 +310,10 @@ static int gred_print_opt(struct qdisc_util *qu, FILE *f, struct rtattr *opt)
 		sopt->def_DP,
 		sopt->grio ? "grio " : "");
 
+	if (limit)
+		fprintf(f, "limit %s ",
+			sprint_size(*limit, b1));
+
 	for (i=0;i<MAX_DPs;i++, qopt++) {
 		if (qopt->DP >= MAX_DPs) continue;
 		fprintf(f, "\n vq %u prio %hhu limit %s min %s max %s ",