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docs: net: render the checksum comment in checksum-offloads.rst

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checksum-offloads.rst seems like a better place to render
the checksum comment than skbuff.rst.

Remove the stale references to sections in that comment
(it no longer has A, B, C, D, E sections).

Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20260526160151.2793354-10-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Jakub Kicinski 2026-05-26 09:01:50 -07:00
parent 6686e7f03f
commit 25bfb3a8ed
2 changed files with 10 additions and 14 deletions
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18
Documentation/networking/checksum-offloads.rst
View File

@ -25,10 +25,8 @@ Things that should be documented here but aren't yet:
TX Checksum Offload
===================
The interface for offloading a transmit checksum to a device is explained in
detail in comments near the top of include/linux/skbuff.h.
In brief, it allows to request the device fill in a single ones-complement
In brief, Tx checksum offload allows to request the device fill in a single
ones-complement
checksum defined by the sk_buff fields skb->csum_start and skb->csum_offset.
The device should compute the 16-bit ones-complement checksum (i.e. the
'IP-style' checksum) from csum_start to the end of the packet, and fill in the
@ -47,8 +45,7 @@ mechanism such as LCO or RCO.
SCTP CRC32c can also be offloaded using this interface, by means of filling
skb->csum_start and skb->csum_offset as described above, setting
skb->csum_not_inet, and advertising NETIF_F_SCTP_CRC. Drivers must not treat
ordinary IP checksum offload as SCTP CRC32c support. See the skbuff.h comment
(section 'D') for more details.
ordinary IP checksum offload as SCTP CRC32c support.
No offloading of the IP header checksum is performed; it is always done in
software. This is OK because when we build the IP header, we obviously have it
@ -56,8 +53,7 @@ in cache, so summing it isn't expensive. It's also rather short.
The requirements for GSO are more complicated, because when segmenting an
encapsulated packet both the inner and outer checksums may need to be edited or
recomputed for each resulting segment. See the skbuff.h comment (section 'E')
for more details.
recomputed for each resulting segment.
A driver declares its offload capabilities in netdev->hw_features; see
Documentation/networking/netdev-features.rst for more. NETIF_F_IP_CSUM and
@ -154,3 +150,9 @@ or left at ``CHECKSUM_NONE``. Drivers **must not discard** packets with
bad TCP/UDP checksum and must not configure the device to drop them.
Checksum validation is relatively inexpensive and having bad packets reflected
in SNMP counters is crucial for network monitoring.
skb checksum documentation
==========================
.. kernel-doc:: include/linux/skbuff.h
:doc: skb checksums

6
Documentation/networking/skbuff.rst
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@ -29,9 +29,3 @@ dataref and headerless skbs
.. kernel-doc:: include/linux/skbuff.h
:doc: dataref and headerless skbs
Checksum information
--------------------
.. kernel-doc:: include/linux/skbuff.h
:doc: skb checksums