⌘ ~ ❯ ssh -v -J gatekeeper@gateway ubuntu@node -i ~/.ssh/id_rsa
OpenSSH_7.3p1, LibreSSL 2.4.1
[...]
debug1: Authentication succeeded (publickey).
Authenticated to gateway ([35.156.248.245]:22).
debug1: channel_connect_stdio_fwd node:22
debug1: channel 0: new [stdio-forward]
debug1: getpeername failed: Bad file descriptor
debug1: Requesting no-more-sessions@openssh.com
debug1: Entering interactive session.
debug1: pledge: network
debug1: client_input_global_request: rtype keepalive@openssh.com want_reply 1
debug1: client_input_global_request: rtype keepalive@openssh.com want_reply 1
debug1: client_input_global_request: rtype keepalive@openssh.com want_reply 1
debug1: client_input_global_request: rtype keepalive@openssh.com want_reply 1
debug1: client_input_global_request: rtype keepalive@openssh.com want_reply 1
debug1: client_input_global_request: rtype keepalive@openssh.com want_reply 1
debug1: client_input_global_request: rtype keepalive@openssh.com want_reply 1
debug1: client_input_global_request: rtype keepalive@openssh.com want_reply 1
channel 0: open failed: connect failed: Connection timed out
stdio forwarding failed
ssh_exchange_identification: Connection closed by remote host

admin@gateway:~$ grep -e "[7669]" -e "[7739]" /var/log/auth.log
Mar 13 11:01:20 gateway sshd[7669]: Set /proc/self/oom_score_adj to 0
Mar 13 11:01:20 gateway sshd[7669]: rexec line 32: Deprecated option PermitBlacklistedKeys
Mar 13 11:01:20 gateway sshd[7669]: Connection from <laptop-out-ip> port 62113 on <gateway-ip> port 22
Mar 13 11:01:20 gateway sshd[7669]: Postponed publickey for gatekeeper from <laptop-out-ip> port 62113 ssh2 [preauth]
Mar 13 11:01:20 gateway sshd[7669]: Accepted publickey for gatekeeper from <laptop-out-ip> port 62113 ssh2: RSA 8d:7e:9c:53:11:c9:4d:b3:67:7b:ae:04:03:8f:e2:71
Mar 13 11:01:20 gateway sshd[7669]: pam_unix(sshd:session): session opened for user gatekeeper by (uid=0)
Mar 13 11:01:20 gateway sshd[7669]: User child is on pid 7739
Mar 13 11:03:27 gateway sshd[7739]: error: connect_to <node-ip> port 22: failed.
Mar 13 11:03:28 gateway sshd[7739]: Connection closed by <laptop-out-ip>
Mar 13 11:03:28 gateway sshd[7739]: Transferred: sent 2252, received 2864 bytes
Mar 13 11:03:28 gateway sshd[7739]: Closing connection to <laptop-out-ip> port 62113
Mar 13 11:03:28 gateway sshd[7669]: pam_unix(sshd:session): session closed for user gatekeeper