Re: [PATCH net-next v3 0/5] net: gso: restore outer ip ids correctly

[Jakub Kicinski]

On Thu, 21 Aug 2025 09:30:42 +0200 Richard Gobert wrote:
> GRO currently ignores outer IPv4 header IDs for encapsulated packets
> that have their don't-fragment flag set. GSO, however, always assumes
> that outer IP IDs are incrementing. This results in GSO mangling the
> outer IDs when they aren't incrementing. For example, GSO mangles the
> outer IDs of IPv6 packets that were converted to IPv4, which must
> have an ID of 0 according to RFC 6145, sect. 5.1.
> 
> GRO+GSO is supposed to be entirely transparent by default. GSO already
> correctly restores inner IDs and IDs of non-encapsulated packets. The
> tx-tcp-mangleid-segmentation feature can be enabled to allow the
> mangling of such IDs so that TSO can be used.
> 
> This series fixes outer ID restoration for encapsulated packets when
> tx-tcp-mangleid-segmentation is disabled. It also allows GRO to merge
> packets with fixed IDs that don't have their don't-fragment flag set.


This series appears to break GSO_PARTIAL:

https://netdev-3.bots.linux.dev/vmksft-fbnic-qemu/results/263201/6-tso-py/stdout
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