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Diffstat (limited to 'lib/route/qdisc/plug.c')
| -rw-r--r-- | lib/route/qdisc/plug.c | 177 |
1 files changed, 177 insertions, 0 deletions
diff --git a/lib/route/qdisc/plug.c b/lib/route/qdisc/plug.c new file mode 100644 index 0000000..a99b9be --- /dev/null +++ b/lib/route/qdisc/plug.c @@ -0,0 +1,177 @@ +/* + * lib/route/qdisc/plug.c PLUG Qdisc + * + * 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> + */ + +/** + * @ingroup qdisc + * @defgroup qdisc_plug Plug/Unplug Traffic (PLUG) + * @brief + * + * Queue traffic until an explicit release command. + * + * There are two ways to use this qdisc: + * 1. A simple "instantaneous" plug/unplug operation, by issuing an alternating + * sequence of TCQ_PLUG_BUFFER & TCQ_PLUG_RELEASE_INDEFINITE commands. + * + * 2. For network output buffering (a.k.a output commit) functionality. + * Output commit property is commonly used by applications using checkpoint + * based fault-tolerance to ensure that the checkpoint from which a system + * is being restored is consistent w.r.t outside world. + * + * Consider for e.g. Remus - a Virtual Machine checkpointing system, + * wherein a VM is checkpointed, say every 50ms. The checkpoint is replicated + * asynchronously to the backup host, while the VM continues executing the + * next epoch speculatively. + * + * The following is a typical sequence of output buffer operations: + * 1.At epoch i, start_buffer(i) + * 2. At end of epoch i (i.e. after 50ms): + * 2.1 Stop VM and take checkpoint(i). + * 2.2 start_buffer(i+1) and Resume VM + * 3. While speculatively executing epoch(i+1), asynchronously replicate + * checkpoint(i) to backup host. + * 4. When checkpoint_ack(i) is received from backup, release_buffer(i) + * Thus, this Qdisc would receive the following sequence of commands: + * TCQ_PLUG_BUFFER (epoch i) + * .. TCQ_PLUG_BUFFER (epoch i+1) + * ....TCQ_PLUG_RELEASE_ONE (epoch i) + * ......TCQ_PLUG_BUFFER (epoch i+2) + * ........ + * + * + * State of the queue, when used for network output buffering: + * + * plug(i+1) plug(i) head + * ------------------+--------------------+----------------> + * | | + * | | + * pkts_current_epoch| pkts_last_epoch |pkts_to_release + * ----------------->|<--------+--------->|+---------------> + * v v + * + * + * @{ + */ + +#include <netlink-local.h> +#include <netlink-tc.h> +#include <netlink/netlink.h> +#include <netlink/utils.h> +#include <netlink/route/tc-api.h> +#include <netlink/route/qdisc/plug.h> + +static int plug_msg_fill(struct rtnl_tc *tc, void *data, struct nl_msg *msg) +{ + struct rtnl_plug *plug = data; + struct tc_plug_qopt opts; + + if (!plug) + return -NLE_INVAL; + + opts.action = plug->action; + opts.limit = plug->limit; + + return nlmsg_append(msg, &opts, sizeof(opts), NL_DONTPAD); +} + +/** + * @name Attribute Modification + * @{ + */ + +/** + * Insert a plug into the qdisc and buffer any incoming + * network traffic. + * @arg qdisc PLUG qdisc to be modified. + */ +int rtnl_qdisc_plug_buffer(struct rtnl_qdisc *qdisc) +{ + struct rtnl_plug *plug; + + if (!(plug = rtnl_tc_data(TC_CAST(qdisc)))) + return -NLE_NOMEM; + + plug->action = TCQ_PLUG_BUFFER; + return 0; +} + +/** + * Unplug the qdisc, releasing packets from queue head + * to the last complete buffer, while new traffic + * continues to be buffered. + * @arg qdisc PLUG qdisc to be modified. + */ +int rtnl_qdisc_plug_release_one(struct rtnl_qdisc *qdisc) +{ + struct rtnl_plug *plug; + + if (!(plug = rtnl_tc_data(TC_CAST(qdisc)))) + return -NLE_NOMEM; + + plug->action = TCQ_PLUG_RELEASE_ONE; + return 0; +} + +/** + * Indefinitely unplug the qdisc, releasing all packets. + * Network traffic will not be buffered until the next + * buffer command is issued. + * @arg qdisc PLUG qdisc to be modified. + */ +int rtnl_qdisc_plug_release_indefinite(struct rtnl_qdisc *qdisc) +{ + struct rtnl_plug *plug; + + if (!(plug = rtnl_tc_data(TC_CAST(qdisc)))) + return -NLE_NOMEM; + + plug->action = TCQ_PLUG_RELEASE_INDEFINITE; + return 0; +} + +/** + * Set limit of PLUG qdisc. + * @arg qdisc PLUG qdisc to be modified. + * @arg limit New limit. + * @return 0 on success or a negative error code. + */ +int rtnl_qdisc_plug_set_limit(struct rtnl_qdisc *qdisc, int limit) +{ + struct rtnl_plug *plug; + + if (!(plug = rtnl_tc_data(TC_CAST(qdisc)))) + return -NLE_NOMEM; + + plug->action = TCQ_PLUG_LIMIT; + plug->limit = limit; + + return 0; +} + +/** @} */ + +static struct rtnl_tc_ops plug_ops = { + .to_kind = "plug", + .to_type = RTNL_TC_TYPE_QDISC, + .to_size = sizeof(struct rtnl_plug), + .to_msg_fill = plug_msg_fill, +}; + +static void __init plug_init(void) +{ + rtnl_tc_register(&plug_ops); +} + +static void __exit plug_exit(void) +{ + rtnl_tc_unregister(&plug_ops); +} + +/** @} */ |