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Commit 9c29e361 authored by Paolo Abeni's avatar Paolo Abeni Committed by David S. Miller
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mptcp: fix DSS map generation on fin retransmission



The RFC 8684 mandates that no-data DATA FIN packets should carry
a DSS with 0 sequence number and data len equal to 1. Currently,
on FIN retransmission we re-use the existing mapping; if the previous
fin transmission was part of a partially acked data packet, we could
end-up writing in the egress packet a non-compliant DSS.

The above will be detected by a "Bad mapping" warning on the receiver
side.

This change addresses the issue explicitly checking for 0 len packet
when adding the DATA_FIN option.

Fixes: 6d0060f6 ("mptcp: Write MPTCP DSS headers to outgoing data packets")
Reported-by: default avatar <syzbot+42a07faa5923cfaeb9c9@syzkaller.appspotmail.com>
Tested-by: default avatarChristoph Paasch <cpaasch@apple.com>
Reviewed-by: default avatarChristoph Paasch <cpaasch@apple.com>
Reviewed-by: default avatarMat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: default avatarPaolo Abeni <pabeni@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 5eff0690
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