Hi, Found by looking at kernel source: http://elixir.free-electrons.com/linux/v4.14-rc6/source/net/ipv4/tcp.c#L1134 --- man2/send.2 2017-10-24 17:13:12.503137552 +0200 +++ man2/send.2.fix 2017-10-17 17:14:32.260107294 +0200 @@ -353,6 +353,9 @@ in .BR ip (7). .TP +.B EALREADY +Another Fast Open is in progress. +.TP .B EBADF .I sockfd is not a valid open file descriptor. Regards, Gregory (Sorry for duplicate, forgot to send as plaintext) -- Grégory Vander Schueren | R&D Engineer gregory.vanderschueren@xxxxxxxxxxxx | Tessares SA | Hybrid Access Solutions www.tessares.net 6 Rue Louis de Geer, 1348 Louvain-la-Neuve, Belgium -- ------------------------------ DISCLAIMER. This email and any files transmitted with it are confidential and intended solely for the use of the individual or entity to whom they are addressed. If you have received this email in error please notify the system manager. This message contains confidential information and is intended only for the individual named. If you are not the named addressee you should not disseminate, distribute or copy this e-mail. Please notify the sender immediately by e-mail if you have received this e-mail by mistake and delete this e-mail from your system. If you are not the intended recipient you are notified that disclosing, copying, distributing or taking any action in reliance on the contents of this information is strictly prohibited. -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html