[Bug 254366] Severe IPv6 TCP transfer issues on 13.0-RC2 with virtio network adapter

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=254366

--- Comment #19 from commit-hook at FreeBSD.org ---
A commit in branch stable/13 references this bug:

URL:
https://cgit.FreeBSD.org/src/commit/?id=6064ea8172f078c54954bc6e8865625feb7979fe

commit 6064ea8172f078c54954bc6e8865625feb7979fe
Author:     Michael Tuexen <tuexen at FreeBSD.org>
AuthorDate: 2021-03-18 20:25:47 +0000
Commit:     Michael Tuexen <tuexen at FreeBSD.org>
CommitDate: 2021-03-18 20:33:32 +0000

    vtnet: fix TSO for TCP/IPv6

    The decision whether a TCP packet is sent over IPv4 or IPv6 was
    based on ethertype, which works correctly. In D27926 the criteria
    was changed to checking if the CSUM_IP_TSO flag is set in the
    csum-flags and then considering it to be TCP/IPv4.
    However, the TCP stack sets the flag to CSUM_TSO for IPv4 and IPv6,
    where CSUM_TSO is defined as CSUM_IP_TSO|CSUM_IP6_TSO.
    Therefore TCP/IPv6 packets gets mis-classified as TCP/IPv4,
    which breaks TSO for TCP/IPv6.
    This patch bases the check again on the ethertype.
    This fix is instantly MFCed.

    Approved by:            re(gjb)
    PR:                     254366
    Sponsored by:           Netflix, Inc.
    Differential Revision:  https://reviews.freebsd.org/D29331

    (cherry picked from commit d4697a6b56168876fc0ffec1a0bb1b24d25b198e)

 sys/dev/virtio/network/if_vtnet.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

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