From mboxrd@z Thu Jan 1 00:00:00 1970 From: Teemu Koponen Subject: New address announcements in RTMGRP_IPV4_IFADDR netlink group Date: Mon, 6 Jun 2005 11:59:38 -0700 Message-ID: Mime-Version: 1.0 (Apple Message framework v622) Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Return-path: To: netdev@oss.sgi.com Sender: netdev-bounce@oss.sgi.com Errors-to: netdev-bounce@oss.sgi.com List-Id: netdev.vger.kernel.org Netlink developers and gurus, While fine-tuning the handover speed for a certain L3 mobility daemon under Linux 2.6.11.10, I stumbled into the following behavior which intuitively does not follow the semantics of the RTMGRP_IPV4_IFADDR group: 0) A userspace daemon process is running and listening to the broadcast group. 1) Address is inserted to an interface (ip addr add ... at shell). 2) The daemon receives a NEWADDR message, just as is should, but the daemon is unable to bind to the address *immediately* (actually in the function that processes the netlink message). The result is "cannot assign an address" from the bind call. However, if I do insert a single nanosleep, even with an arbitrary low sleep value, before the bind call, the bind then succeeds. So, what is the semantics of NEWADDR? Should the address be bindable right after receiving the message? Or is there a race-condition between userspace and kernel that the inserted sleep helps to overcome by letting the kernel to run again before the bind call? TIA, Teemu --