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Merge pull request #1395 from vyos/mergify/bp/sagitta/pr-1390

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ethernet: Add details about LRO/GRO (backport #1390)
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Robert Göhler 2024-04-18 14:49:11 +02:00 committed by GitHub
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docs/configuration/interfaces/ethernet.rst
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@ -61,6 +61,22 @@ Offloading
Enable different types of hardware offloading on the given NIC. Enable different types of hardware offloading on the given NIC.
:abbr:`LRO (Large Receive Offload)` is a technique designed to boost the
efficiency of how your computer's network interface card (NIC) processes
incoming network traffic. Typically, network data arrives in smaller chunks
called packets. Processing each packet individually consumes CPU (central
processing unit) resources. Lots of small packets can lead to a performance
bottleneck. Instead of handing the CPU each packet as it comes in, LRO
instructs the NIC to combine multiple incoming packets into a single, larger
packet. This larger packet is then passed to the CPU for processing.
.. note:: Under some circumstances, LRO is known to modify the packet headers
of forwarded traffic, which breaks the end-to-end principle of computer
networking. LRO is also only able to offload TCP segments encapsulated in
IPv4 packets. Due to these limitations, it is recommended to use GRO
(Generic Receive Offload) where possible. More information on the
limitations of LRO can be found here: https://lwn.net/Articles/358910/
:abbr:`GSO (Generic Segmentation Offload)` is a pure software offload that is :abbr:`GSO (Generic Segmentation Offload)` is a pure software offload that is
meant to deal with cases where device drivers cannot perform the offloads meant to deal with cases where device drivers cannot perform the offloads
described above. What occurs in GSO is that a given skbuff will have its data described above. What occurs in GSO is that a given skbuff will have its data
@ -87,13 +103,13 @@ Offloading
placing the packet on the desired CPU's backlog queue and waking up the CPU placing the packet on the desired CPU's backlog queue and waking up the CPU
for processing. RPS has some advantages over RSS: for processing. RPS has some advantages over RSS:
- it can be used with any NIC, - it can be used with any NIC
- software filters can easily be added to hash over new protocols, - software filters can easily be added to hash over new protocols
- it does not increase hardware device interrupt rate (although it does - it does not increase hardware device interrupt rate, although it does
introduce inter-processor interrupts (IPIs)). introduce inter-processor interrupts (IPIs)
.. note:: In order to use TSO/LRO with VMXNET3 adaters one must also enable .. note:: In order to use TSO/LRO with VMXNET3 adapters, the SG offloading
the SG offloading option. option must also be enabled.
Authentication (EAPoL) Authentication (EAPoL)
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