Support plug qdisc - queue traffic until explicit release

The plug qdisc supports two operations - plug and unplug. When the
qdisc receives a plug ("buffer") command via netlink request,
packets arriving henceforth are buffered until a corresponding unplug
command is received. Depending on the type of unplug ("release_one"
or "release_indefinite"), the queue can be unplugged indefinitely or
selectively.

The plug qdisc allows a user to implement network output buffering
(aka output commit), used commonly in checkpoint based fault tolerance
systems. It also supports a general purpose queue plug/unplug
functionality.

The associated kernel module is available in David Miller's net-next
tree, commit: c3059be16c9ef29c05f0876a9df5fea21f29724f

This patch introduces userspace tools and API, to control the qdisc
via netlink messages.

Signed-off-by: Shriram Rajagopalan <rshriram@cs.ubc.ca>
Signed-off-by: Thomas Graf <tgraf@redhat.com>

1 files changed, 113 insertions, 0 deletions

diff --git a/lib/cli/qdisc/plug.c b/lib/cli/qdisc/plug.c
new file mode 100644
index 0000000..2b8d5d6
--- /dev/null
+++ b/lib/cli/qdisc/plug.c
@@ -0,0 +1,113 @@
+
+/*
+ * src/lib/cli/qdisc/plug.c     	plug module for CLI lib
+ *
+ *	This library is free software; you can redistribute it and/or
+ *	modify it under the terms of the GNU Lesser General Public
+ *	License as published by the Free Software Foundation version 2.1
+ *	of the License.
+ *
+ * Copyright (c) 2012 Shriram Rajagopalan <rshriram@cs.ubc.ca>
+ */
+
+#include <netlink/cli/utils.h>
+#include <netlink/cli/tc.h>
+#include <netlink/route/qdisc/plug.h>
+
+static void print_usage(void)
+{
+	printf(
+"Usage: nl-qdisc-add [...] plug [OPTIONS]...\n"
+"\n"
+"OPTIONS\n"
+"     --help                Show this help text.\n"
+"     --limit               Maximum queue length in bytes.\n"
+"     --buffer              create a new buffer(plug) and queue incoming traffic into it.\n"
+"     --release-one         release traffic from previous buffer.\n"
+"     --release-indefinite  stop buffering and release all (buffered and new) packets.\n"
+"\n"
+"EXAMPLE"
+"    # Attach plug qdisc with 32KB queue size to ifb0\n"
+"    nl-qdisc-add --dev=ifb0 --parent=root plug --limit=32768\n"
+"    # Plug network traffic arriving at ifb0\n"
+"    nl-qdisc-add --dev=ifb0 --parent=root --update plug --buffer\n"
+"    # Unplug traffic arriving at ifb0 indefinitely\n"
+"    nl-qdisc-add --dev=ifb0 --parent=root --update plug --release-indefinite\n\n"
+"    # If operating in output buffering mode:\n"
+"    # at time t=t0, create a new output buffer b0 to hold network output\n"
+"    nl-qdisc-add --dev=ifb0 --parent=root --update plug --buffer\n\n"
+"    # at time t=t1, take a checkpoint c0, create a new output buffer b1\n"
+"    nl-qdisc-add --dev=ifb0 --parent=root --update plug --buffer\n"
+"    # at time t=t1+r, after c0 is committed, release b0\n"
+"    nl-qdisc-add --dev=ifb0 --parent=root --update plug --release-one\n\n"
+"    # at time t=t2, take a checkpoint c1, create a new output buffer b2\n"
+"    nl-qdisc-add --dev=ifb0 --parent=root --update plug --buffer\n"
+"    # at time t=t2+r, after c1 is committed, release b1\n"
+"    nl-qdisc-add --dev=ifb0 --parent=root --update plug --release-one\n");
+}
+
+static void plug_parse_argv(struct rtnl_tc *tc, int argc, char **argv)
+{
+	struct rtnl_qdisc *qdisc = (struct rtnl_qdisc *) tc;
+
+	for (;;) {
+		int c, optidx = 0;
+		enum {
+			ARG_LIMIT              = 257,
+			ARG_BUFFER             = 258,
+			ARG_RELEASE_ONE        = 259,
+			ARG_RELEASE_INDEFINITE = 260,
+		};
+		static struct option long_opts[] = {
+			{ "help", 0, 0, 'h' },
+			{ "limit", 1, 0, ARG_LIMIT },
+			{ "buffer", 0, 0, ARG_BUFFER },
+			{ "release-one", 0, 0, ARG_RELEASE_ONE },
+			{ "release-indefinite", 0, 0, ARG_RELEASE_INDEFINITE },
+			{ 0, 0, 0, 0 }
+		};
+	
+		c = getopt_long(argc, argv, "h", long_opts, &optidx);
+		if (c == -1)
+			break;
+
+		switch (c) {
+		case 'h':
+			print_usage();
+			return;
+
+		case ARG_LIMIT:
+			rtnl_qdisc_plug_set_limit(qdisc, nl_cli_parse_u32(optarg));
+			break;
+
+		case ARG_BUFFER:
+			rtnl_qdisc_plug_buffer(qdisc);
+			break;
+
+		case ARG_RELEASE_ONE:
+		        rtnl_qdisc_plug_release_one(qdisc);
+			break;
+
+		case ARG_RELEASE_INDEFINITE:
+			rtnl_qdisc_plug_release_indefinite(qdisc);
+			break;
+		}
+ 	}
+}
+
+static struct nl_cli_tc_module plug_module =
+{
+	.tm_name		= "plug",
+	.tm_type		= RTNL_TC_TYPE_QDISC,
+	.tm_parse_argv		= plug_parse_argv,
+};
+
+static void __init plug_init(void)
+{
+	nl_cli_tc_register(&plug_module);
+}
+
+static void __exit plug_exit(void)
+{
+	nl_cli_tc_unregister(&plug_module);
+}