Hello Hideaki, Back in 2.6.20, I believe you added TCP_MD5SIG. Currently, there is no documentation for this option in the tcp(7) man page. Would you be willing to send in a patch? Cheers, Michael -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Author of "The Linux Programming Interface"; http://man7.org/tlpi/ -- 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