Documentation/networking/nexthop-group-resilient.rst

1 .. SPDX-License-Identifier: GPL-2.0
4 Resilient Next-hop Groups
7 Resilient groups are a type of next-hop group that is aimed at minimizing
12 the legacy multipath next-hop group, which uses the hash-threshold
15 To select a next hop, hash-threshold algorithm first assigns a range of
22              +-------+-------+-------+-------+-------+
24              +-------+-+-----+---+---+-----+-+-------+
26              +---------+---------+---------+---------+
29 	      under the hash-threshold algorithm.
32 and 4 in favor of 5. While there will usually be some overlap between the
36 If a multipath group is used for load-balancing between multiple servers,
41 If a multipath group is used for load-balancing among available paths to
46 To mitigate the above-mentioned flow redirection, resilient next-hop groups
52 This indirection brings an important feature. In the hash-threshold
58 	    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
60 	    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
62 	    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
64 	    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
71 traffic, and use those to satisfy the new next-hop distribution demands,
74 the next-hop group change.
77 ---------
91 Each bucket maintains a last-used timer. Every time a packet is forwarded
94 amount of time that a bucket must not be hit by traffic in order for it to
107 future time.
113 non-zero value, the value represents the period of time that the table is
119 4) whose next hop is overweight, and the amount of time that the table has
120    been out of balance exceeds the unbalanced timer, if that is non-zero,
125 ----------------------------
131 - Full group notification with the type
133   created and buckets populated for the first time.
135 - Single-bucket notifications of the type
137   individual migrations within an already-established group.
139 - Pre-replace notification, ``NEXTHOP_EVENT_RES_TABLE_PRE_REPLACE``. This
143 Some single-bucket notifications are forced, as indicated by the "force"
148 Non-forced notifications can be overridden by the driver by returning an
161 ------------
187 Requests to get resilient next-hop groups use the ``RTM_GETNEXTHOP``
205   ``NHA_ID``          ID of the next-hop group that the bucket belongs to.
223   ``NHA_ID``          If specified, limits the dump to just the next-hop group
240 -----
249 The last command creates a resilient next-hop group. It will have 8 buckets
255 Changing next-hop weights leads to change in bucket allocation::
271 Note the two buckets that have a shorter idle time. Those are the ones that
272 were migrated after the next-hop replace command to satisfy the new demand
276 ---------
280 For example, the following will mark bucket 23 in next-hop group 10 as