1.. SPDX-License-Identifier: GPL-2.0
  2
  3===============================================
  4Generic networking statistics for netlink users
  5===============================================
  6
  7Statistic counters are grouped into structs:
  8
  9==================== ===================== =====================
 10Struct               TLV type              Description
 11==================== ===================== =====================
 12gnet_stats_basic     TCA_STATS_BASIC       Basic statistics
 13gnet_stats_rate_est  TCA_STATS_RATE_EST    Rate estimator
 14gnet_stats_queue     TCA_STATS_QUEUE       Queue statistics
 15none                 TCA_STATS_APP         Application specific
 16==================== ===================== =====================
 17
 18
 19Collecting:
 20-----------
 21
 22Declare the statistic structs you need::
 23
 24	struct mystruct {
 25		struct gnet_stats_basic	bstats;
 26		struct gnet_stats_queue	qstats;
 27		...
 28	};
 29
 30Update statistics, in dequeue() methods only, (while owning qdisc->running)::
 31
 32	mystruct->tstats.packet++;
 33	mystruct->qstats.backlog += skb->pkt_len;
 34
 35
 36Export to userspace (Dump):
 37---------------------------
 38
 39::
 40
 41    my_dumping_routine(struct sk_buff *skb, ...)
 42    {
 43	    struct gnet_dump dump;
 44
 45	    if (gnet_stats_start_copy(skb, TCA_STATS2, &mystruct->lock, &dump,
 46				    TCA_PAD) < 0)
 47		    goto rtattr_failure;
 48
 49	    if (gnet_stats_copy_basic(&dump, &mystruct->bstats) < 0 ||
 50		gnet_stats_copy_queue(&dump, &mystruct->qstats) < 0 ||
 51		    gnet_stats_copy_app(&dump, &xstats, sizeof(xstats)) < 0)
 52		    goto rtattr_failure;
 53
 54	    if (gnet_stats_finish_copy(&dump) < 0)
 55		    goto rtattr_failure;
 56	    ...
 57    }
 58
 59TCA_STATS/TCA_XSTATS backward compatibility:
 60--------------------------------------------
 61
 62Prior users of struct tc_stats and xstats can maintain backward
 63compatibility by calling the compat wrappers to keep providing the
 64existing TLV types::
 65
 66    my_dumping_routine(struct sk_buff *skb, ...)
 67    {
 68	if (gnet_stats_start_copy_compat(skb, TCA_STATS2, TCA_STATS,
 69					TCA_XSTATS, &mystruct->lock, &dump,
 70					TCA_PAD) < 0)
 71		    goto rtattr_failure;
 72	    ...
 73    }
 74
 75A struct tc_stats will be filled out during gnet_stats_copy_* calls
 76and appended to the skb. TCA_XSTATS is provided if gnet_stats_copy_app
 77was called.
 78
 79
 80Locking:
 81--------
 82
 83Locks are taken before writing and released once all statistics have
 84been written. Locks are always released in case of an error. You
 85are responsible for making sure that the lock is initialized.
 86
 87
 88Rate Estimator:
 89---------------
 90
 910) Prepare an estimator attribute. Most likely this would be in user
 92   space. The value of this TLV should contain a tc_estimator structure.
 93   As usual, such a TLV needs to be 32 bit aligned and therefore the
 94   length needs to be appropriately set, etc. The estimator interval
 95   and ewma log need to be converted to the appropriate values.
 96   tc_estimator.c::tc_setup_estimator() is advisable to be used as the
 97   conversion routine. It does a few clever things. It takes a time
 98   interval in microsecs, a time constant also in microsecs and a struct
 99   tc_estimator to  be populated. The returned tc_estimator can be
100   transported to the kernel.  Transfer such a structure in a TLV of type
101   TCA_RATE to your code in the kernel.
102
103In the kernel when setting up:
104
1051) make sure you have basic stats and rate stats setup first.
1062) make sure you have initialized stats lock that is used to setup such
107   stats.
1083) Now initialize a new estimator::
109
110    int ret = gen_new_estimator(my_basicstats,my_rate_est_stats,
111	mystats_lock, attr_with_tcestimator_struct);
112
113    if ret == 0
114	success
115    else
116	failed
117
118From now on, every time you dump my_rate_est_stats it will contain
119up-to-date info.
120
121Once you are done, call gen_kill_estimator(my_basicstats,
122my_rate_est_stats) Make sure that my_basicstats and my_rate_est_stats
123are still valid (i.e still exist) at the time of making this call.
124
125
126Authors:
127--------
128- Thomas Graf <tgraf@suug.ch>
129- Jamal Hadi Salim <hadi@cyberus.ca>