David, I see a recent change in inet_connection_sock.c that uses sysctl_tcp_synack_retries suspiciously.
Previously, sysctl_tcp_synack_retries was a global variable, and now it has been moved into the fragment (really netns_ipv4). In reqsk_timer_handler (inet_connection_sock.c) near line 563 it is used as the default max_retries value in case icsk->icsk_syn_retries is not set. Previously, other transports (dccp?) would use the TCP global variable as a default. Now that the defaults come from the fragment, I suspect the fragment variable is not set for other transports. (I can't find where it's set for dccp.) Of course, this will only show in non-TCP transport protocols when the icsk retries value is not set, so it's a rare case. Perhaps it's an unreachable case, since I don't know all the kernel paths. Maybe the problem is that the default shouldn't be to a TCP value, but should be a 'transport' value. This code is somewhat convoluted, so I am not sure of my analysis, but I wanted you to consider it. John Light Intel OTC comms
