Timeout indicates search_high should be set to the new mtu corresponding to
current_mss no
matter how we change search_low. So the best shot here IMO would be updating
search_high
with current_mss, which in return makes the search window *slide* from right
to left, and
the probing will converge in good speed eventually.

So my thoughts is:

@@ -113,6 +113,7 @@ static void tcp_mtu_probing(struct inet_connection_sock

*icsk, struct sock *sk)
                        struct tcp_sock *tp = tcp_sk(sk);
                        int mss;

+                       icsk_mtup.search_high = tcp_mss_to_mtu(sk,
tcp_current_mss(sk));
                        mss = tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low)

quoted

quoted

1;

                        mss = min(net->ipv4.sysctl_tcp_base_mss, mss);
                        mss = max(mss, 68 - tp->tcp_header_len);