netdev - [PATCH iproute2-next 2/2] tc: q_red: Support 'nodrop' flag

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Date:   Wed, 18 Mar 2020 14:18:28 +0200
From:   Petr Machata <petrm@...lanox.com>
To:     netdev@...r.kernel.org
Cc:     Petr Machata <petrm@...lanox.com>, David Ahern <dsahern@...il.com>
Subject: [PATCH iproute2-next 2/2] tc: q_red: Support 'nodrop' flag

Recognize the new configuration option of the RED Qdisc, "nodrop". Add
support for passing flags through TCA_RED_FLAGS, and always use it for
passing RED flags.

Signed-off-by: Petr Machata <petrm@...lanox.com>
---
 man/man8/tc-red.8 |  6 +++++-
 tc/q_red.c        | 22 +++++++++++++++++-----
 tc/tc_red.c       |  5 +++++
 3 files changed, 27 insertions(+), 6 deletions(-)

diff --git a/man/man8/tc-red.8 b/man/man8/tc-red.8
index dd1ab74c..b5aaa986 100644
--- a/man/man8/tc-red.8
+++ b/man/man8/tc-red.8
@@ -13,7 +13,7 @@ bytes
 bytes
 .B [ burst
 packets
-.B ] [ ecn ] [ harddrop] [ bandwidth
+.B ] [ ecn ] [ harddrop ] [ nodrop ] [ bandwidth
 rate
 .B ] [ probability
 chance
@@ -123,6 +123,10 @@ If average flow queue size is above
 .B max
 bytes, this parameter forces a drop instead of ecn marking.
 .TP
+nodrop
+With this parameter, traffic that should be marked, but is not ECN-capable, is
+enqueued. Without the parameter it is early-dropped.
+.TP
 adaptive
 (Added in linux-3.3) Sets RED in adaptive mode as described in http://icir.org/floyd/papers/adaptiveRed.pdf
 .nf
diff --git a/tc/q_red.c b/tc/q_red.c
index 6256420f..ee81803e 100644
--- a/tc/q_red.c
+++ b/tc/q_red.c
@@ -30,12 +30,17 @@ static void explain(void)
 	fprintf(stderr,
 		"Usage: ... red	limit BYTES [min BYTES] [max BYTES] avpkt BYTES [burst PACKETS]\n"
 		"		[adaptive] [probability PROBABILITY] [bandwidth KBPS]\n"
-		"		[ecn] [harddrop]\n");
+		"		[ecn] [harddrop] [nodrop]\n");
 }
 
+#define RED_SUPPORTED_FLAGS (TC_RED_HISTORIC_FLAGS | TC_RED_NODROP)
+
 static int red_parse_opt(struct qdisc_util *qu, int argc, char **argv,
 			 struct nlmsghdr *n, const char *dev)
 {
+	struct nla_bitfield32 flags_bf = {
+		.selector = RED_SUPPORTED_FLAGS,
+	};
 	struct tc_red_qopt opt = {};
 	unsigned int burst = 0;
 	unsigned int avpkt = 0;
@@ -95,13 +100,15 @@ static int red_parse_opt(struct qdisc_util *qu, int argc, char **argv,
 				return -1;
 			}
 		} else if (strcmp(*argv, "ecn") == 0) {
-			opt.flags |= TC_RED_ECN;
+			flags_bf.value |= TC_RED_ECN;
 		} else if (strcmp(*argv, "harddrop") == 0) {
-			opt.flags |= TC_RED_HARDDROP;
+			flags_bf.value |= TC_RED_HARDDROP;
+		} else if (strcmp(*argv, "nodrop") == 0) {
+			flags_bf.value |= TC_RED_NODROP;
 		} else if (strcmp(*argv, "adaptative") == 0) {
-			opt.flags |= TC_RED_ADAPTATIVE;
+			flags_bf.value |= TC_RED_ADAPTATIVE;
 		} else if (strcmp(*argv, "adaptive") == 0) {
-			opt.flags |= TC_RED_ADAPTATIVE;
+			flags_bf.value |= TC_RED_ADAPTATIVE;
 		} else if (strcmp(*argv, "help") == 0) {
 			explain();
 			return -1;
@@ -154,6 +161,7 @@ static int red_parse_opt(struct qdisc_util *qu, int argc, char **argv,
 	addattr_l(n, 1024, TCA_RED_STAB, sbuf, 256);
 	max_P = probability * pow(2, 32);
 	addattr_l(n, 1024, TCA_RED_MAX_P, &max_P, sizeof(max_P));
+	addattr_l(n, 1024, TCA_RED_FLAGS, &flags_bf, sizeof(flags_bf));
 	addattr_nest_end(n, tail);
 	return 0;
 }
@@ -183,6 +191,10 @@ static int red_print_opt(struct qdisc_util *qu, FILE *f, struct rtattr *opt)
 	    RTA_PAYLOAD(tb[TCA_RED_MAX_P]) >= sizeof(__u32))
 		max_P = rta_getattr_u32(tb[TCA_RED_MAX_P]);
 
+	if (tb[TCA_RED_FLAGS] &&
+	    RTA_PAYLOAD(tb[TCA_RED_FLAGS]) >= sizeof(__u32))
+		qopt->flags = rta_getattr_u32(tb[TCA_RED_FLAGS]);
+
 	print_uint(PRINT_JSON, "limit", NULL, qopt->limit);
 	print_string(PRINT_FP, NULL, "limit %s ", sprint_size(qopt->limit, b1));
 	print_uint(PRINT_JSON, "min", NULL, qopt->qth_min);
diff --git a/tc/tc_red.c b/tc/tc_red.c
index 681ca297..88f5ff35 100644
--- a/tc/tc_red.c
+++ b/tc/tc_red.c
@@ -116,4 +116,9 @@ void tc_red_print_flags(__u32 flags)
 		print_bool(PRINT_ANY, "adaptive", "adaptive ", true);
 	else
 		print_bool(PRINT_ANY, "adaptive", NULL, false);
+
+	if (flags & TC_RED_NODROP)
+		print_bool(PRINT_ANY, "nodrop", "nodrop ", true);
+	else
+		print_bool(PRINT_ANY, "nodrop", NULL, false);
 }
-- 
2.20.1