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a6bb5b9e7c
". If" gets interpreted as a macro, so move the period to the previous
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33: warning: macro `If' not defined
Fixes: 141b55f854 ("Add SKB Priority qdisc support in tc(8)")
Signed-off-by: Luca Boccassi <bluca@debian.org>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
71 lines
2.4 KiB
Groff
71 lines
2.4 KiB
Groff
.TH SKBPRIO 8 "13 August 2018" "iproute2" "Linux"
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.SH NAME
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skbprio \- SKB Priority Queue
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.SH SYNOPSIS
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.B tc qdisc ... add skbprio
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.B [ limit
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packets
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.B ]
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.SH DESCRIPTION
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SKB Priority Queue is a queueing discipline intended to prioritize
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the most important packets during a denial-of-service (
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.B DoS
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) attack. The priority of a packet is given by
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.B skb->priority
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, where a higher value places the packet closer to the exit of the queue. When
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the queue is full, the lowest priority packet in the queue is dropped to make
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room for the packet to be added if it has higher priority. If the packet to be
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added has lower priority than all packets in the queue, it is dropped.
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Without SKB priority queue, queue length limits must be imposed
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on individual sub-queues, and there is no straightforward way to enforce
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a global queue length limit across all priorities. SKBprio queue enforces
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a global queue length limit while not restricting the lengths of
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individual sub-queues.
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While SKB Priority Queue is agnostic to how
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.B skb->priority
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is assigned. A typical use case is to copy
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the 6-bit DS field of IPv4 and IPv6 packets using
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.BR tc-skbedit (8).
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If
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.B skb->priority
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is greater or equal to 64, the priority is assumed to be 63.
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Priorities less than 64 are taken at face value.
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SKB Priority Queue enables routers to locally decide which
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packets to drop under a DoS attack.
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Priorities should be assigned to packets such that the higher the priority,
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the more expected behavior a source shows.
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So sources have an incentive to play by the rules.
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.SH ALGORITHM
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Skbprio maintains 64 lists (priorities go from 0 to 63).
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When a packet is enqueued, it gets inserted at the
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.B tail
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of its priority list. When a packet needs to be sent out to the network, it is
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taken from the head of the highest priority list. When the queue is full,
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the packet at the tail of the lowest priority list is dropped to serve the
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ingress packet - if it is of higher priority, otherwise the ingress packet is
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dropped. This algorithm allocates as much bandwidth as possible to high
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priority packets, while only servicing low priority packets when
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there is enough bandwidth.
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.SH PARAMETERS
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.TP
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limit
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Maximum queue size specified in packets. It defaults to 64.
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The range for this parameter is [0, UINT32_MAX].
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.SH SEE ALSO
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.BR tc-prio (8),
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.BR tc-skbedit (8)
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.SH AUTHORS
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Nishanth Devarajan <devarajn@uci.edu>, Michel Machado <michel@digirati.com.br>
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This manpage maintained by Bert Hubert <ahu@ds9a.nl>
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