On Fri, 29 Sep 2023 17:04:45 +0200 Stefano Brivio <sbrivio(a)redhat.com> wrote:It looks like we need it as workaround for this situation, readily reproducible at least with a 6.5 Linux kernel, with default rmem_max and wmem_max values: - an iperf3 client on the host sends about 160 KiB, typically segmented into five frames by passt. We read this data using MSG_PEEK - the iperf3 server on the guest starts receiving - meanwhile, the host kernel advertised a zero-sized window to the receiver, as expectedGosh, sorry, I forgot all the s/receiver/whatever/ here. Fixed locally and not reposting, unless there's something else... -- Stefano