tc: Add support for the CBS qdisc

The Credit Based Shaper (CBS) queueing discipline allows bandwidth
reservation with sub-milisecond precision. It is defined by the
802.1Q-2014 specification (section 8.6.8.2 and Annex L).

The syntax is:

tc qdisc add dev DEV parent NODE cbs locredit <LOCREDIT>
   		hicredit <HICREDIT> sendslope <SENDSLOPE>
		idleslope <IDLESLOPE>

(The order is not important)

Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

tc/Makefile

@@ -69,6 +69,7 @@ TCMODULES += q_hhf.o
 TCMODULES += q_clsact.o
 TCMODULES += e_bpf.o
 TCMODULES += f_matchall.o
+TCMODULES += q_cbs.o
 
 TCSO :=
 ifeq ($(TC_CONFIG_ATM),y)

tc/q_cbs.c

@@ -0,0 +1,142 @@
+/*
+ * q_cbs.c		CBS.
+ *
+ *		This program is free software; you can redistribute it and/or
+ *		modify it under the terms of the GNU General Public License
+ *		as published by the Free Software Foundation; either version
+ *		2 of the License, or (at your option) any later version.
+ *
+ * Authors:	Vinicius Costa Gomes <vinicius.gomes@intel.com>
+ *
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <syslog.h>
+#include <fcntl.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+#include <string.h>
+
+#include "utils.h"
+#include "tc_util.h"
+
+static void explain(void)
+{
+	fprintf(stderr, "Usage: ... cbs hicredit BYTES locredit BYTES sendslope BPS idleslope BPS\n");
+	fprintf(stderr, "           [offload 0|1]\n");
+
+}
+
+static void explain1(const char *arg, const char *val)
+{
+	fprintf(stderr, "cbs: illegal value for \"%s\": \"%s\"\n", arg, val);
+}
+
+static int cbs_parse_opt(struct qdisc_util *qu, int argc, char **argv, struct nlmsghdr *n)
+{
+	struct tc_cbs_qopt opt = {};
+	struct rtattr *tail;
+
+	while (argc > 0) {
+		if (matches(*argv, "offload") == 0) {
+			NEXT_ARG();
+			if (opt.offload) {
+				fprintf(stderr, "cbs: duplicate \"offload\" specification\n");
+				return -1;
+			}
+			if (get_u8(&opt.offload, *argv, 0)) {
+				explain1("offload", *argv);
+				return -1;
+			}
+		} else if (matches(*argv, "hicredit") == 0) {
+			NEXT_ARG();
+			if (opt.hicredit) {
+				fprintf(stderr, "cbs: duplicate \"hicredit\" specification\n");
+				return -1;
+			}
+			if (get_s32(&opt.hicredit, *argv, 0)) {
+				explain1("hicredit", *argv);
+				return -1;
+			}
+		} else if (matches(*argv, "locredit") == 0) {
+			NEXT_ARG();
+			if (opt.locredit) {
+				fprintf(stderr, "cbs: duplicate \"locredit\" specification\n");
+				return -1;
+			}
+			if (get_s32(&opt.locredit, *argv, 0)) {
+				explain1("locredit", *argv);
+				return -1;
+			}
+		} else if (matches(*argv, "sendslope") == 0) {
+			NEXT_ARG();
+			if (opt.sendslope) {
+				fprintf(stderr, "cbs: duplicate \"sendslope\" specification\n");
+				return -1;
+			}
+			if (get_s32(&opt.sendslope, *argv, 0)) {
+				explain1("sendslope", *argv);
+				return -1;
+			}
+		} else if (matches(*argv, "idleslope") == 0) {
+			NEXT_ARG();
+			if (opt.idleslope) {
+				fprintf(stderr, "cbs: duplicate \"idleslope\" specification\n");
+				return -1;
+			}
+			if (get_s32(&opt.idleslope, *argv, 0)) {
+				explain1("idleslope", *argv);
+				return -1;
+			}
+		} else if (strcmp(*argv, "help") == 0) {
+			explain();
+			return -1;
+		} else {
+			fprintf(stderr, "cbs: unknown parameter \"%s\"\n", *argv);
+			explain();
+			return -1;
+		}
+		argc--; argv++;
+	}
+
+	tail = NLMSG_TAIL(n);
+	addattr_l(n, 1024, TCA_OPTIONS, NULL, 0);
+	addattr_l(n, 2024, TCA_CBS_PARMS, &opt, sizeof(opt));
+	tail->rta_len = (void *) NLMSG_TAIL(n) - (void *) tail;
+	return 0;
+}
+
+static int cbs_print_opt(struct qdisc_util *qu, FILE *f, struct rtattr *opt)
+{
+	struct rtattr *tb[TCA_CBS_MAX+1];
+	struct tc_cbs_qopt *qopt;
+
+	if (opt == NULL)
+		return 0;
+
+	parse_rtattr_nested(tb, TCA_CBS_MAX, opt);
+
+	if (tb[TCA_CBS_PARMS] == NULL)
+		return -1;
+
+	qopt = RTA_DATA(tb[TCA_CBS_PARMS]);
+	if (RTA_PAYLOAD(tb[TCA_CBS_PARMS])  < sizeof(*qopt))
+		return -1;
+
+	fprintf(f, "hicredit %d ", qopt->hicredit);
+	fprintf(f, "locredit %d ", qopt->locredit);
+	fprintf(f, "sendslope %d ", qopt->sendslope);
+	fprintf(f, "idleslope %d ", qopt->idleslope);
+	fprintf(f, "offload %d ", qopt->offload);
+
+	return 0;
+}
+
+struct qdisc_util cbs_qdisc_util = {
+	.id		= "cbs",
+	.parse_qopt	= cbs_parse_opt,
+	.print_qopt	= cbs_print_opt,
+};