On Tue, 2016-06-14 at 11:40 +0000, Eggert, Lars wrote: > On 2016-06-14, at 13:28, Pavel Emelyanov <xe...@virtuozzo.com> wrote: > > Andrey (in Cc) has played with TCP_REPAIR recently, I guess he can know > > something. > > Thanks for CC'ing him. We looked a little bit more into this: > > When TCP_REPAIR is on, tcp_connect() directly calls tcp_finish_connect() > before returning, passing NULL for skb, which causes sk_rx_dst_set() to be > bypassed. Later, when TCP_REPAIR is being turned off, do_tcp_setsockopt() > just does tcp_send_window_probe(), but apparently all the "dst" stuff is > being bypassed then also, so the mss remains at TCP_MSS_DEFAULT. > > Lars
What gives : sysctl net/ipv4/ip_no_pmtu_disc net/ipv4/tcp_mtu_probing
