Absolutely. I'm a fairly technical user, if it can help to debug on my end, give me a few pointers and I'll do what I can. I don't have years of experience debugging Linux software, but I'll do whatever I can if it's straightforward enough.
In the following output, I have used "bogus" as the key. I have also changed the destination from the real one to example.org. Note that the issue still occurs if I use a destination IP address instead of hostname. I understand that redacting information can hurt debugging, so let me know if that information being redacted specifically causes problem for you. Here's me running the command three times: gp@steel:~$ fwknop -A tcp/22 -s -D example.org -v -v -v argument string too long, exiting. gp@steel:~$ fwknop -A tcp/22 -s -D example.org -v -v -v Enter encryption password: FKO Field Values: ================= Random Value: 1811307673174552 Username: gp Timestamp: 1374778453 FKO Version: 1.9.12 Message Type: 1 Message String: 0.0.0.0,tcp/22 Nat Access: <NULL> Server Auth: <NULL> Client Timeout: 0 Digest Type: 3 Encoded Data: 1811307673174552:Z3A:1374778453:1.9.12:1:MC4wLjAuMCx0Y3AvMjI SPA Data Digest: U9gMhFFP8YmhyMEGwMJ2VJYvY0/ivXEVEouuZ/9Rz2E Final Packed/Encrypted/Encoded Data: 9ZgVRQZr4ANfL5CxloY6NmGVZaVPCICGF7KjSdY/1T75x/IeaqSVv4HdY7HyCbY8LgKftmf9eVRHCtGM8k6TyjOI3wMyAbRYTACDWcDu+bJ6wx9BPE1LBWh+XEKcIISPOD4dRA54gCqPAo4nlA0Rgl45ZvBVQ4Odc Generating SPA packet: protocol: udp port: 62201 send_spa_packet: bytes sent: 161 gp@steel:~$ fwknop -A tcp/22 -s -D example.org -v -v -v argument string too long, exiting. gp@steel:~$