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f017c1f768
Some applications are stuck to the 20th century and still use
small SO_RCVBUF values.
After the blamed commit, we can drop packets especially
when using LRO/hw-gro enabled NIC and small MSS (1500) values.
LRO/hw-gro NIC pack multiple segments into pages, allowing
tp->scaling_ratio to be set to a high value.
Whenever the receive queue gets full, we can receive a small packet
filling RWIN, but with a high skb->truesize, because most NIC use 4K page
plus sk_buff metadata even when receiving less than 1500 bytes of payload.
Even if we refine how tp->scaling_ratio is estimated,
we could have an issue at the start of the flow, because
the first round of packets (IW10) will be sent based on
the initial tp->scaling_ratio (1/2)
Relax tcp_can_ingest() to use skb->len instead of skb->truesize,
allowing the peer to use final RWIN, assuming a 'perfect'
scaling_ratio of 1.
Fixes: 1d2fbaad7c ("tcp: stronger sk_rcvbuf checks")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20250927092827.2707901-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
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https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.