On Tue, Dec 15, 2015 at 04:07:57PM +0100, Thibaut Collet wrote: > After a migration, to avoid netwotk outage, all interfaces of the guest > must send a packet to update switches mapping (ideally a GARP). > As some interfaces do not do it QEMU does it in behalf of the guest by > sending a RARP (his RARP is not forged by the guest but by QEMU). This is > the qemu_self_announce purpose that "spoofs" a RARP to all backend of guest > ethernet interfaces. For vhost-user backend, QEMU can not do it directly > and asks to the vhost-user backend to do it with the VHOST_USER_SEND_RARP > request that contains the MAC address of the guest interface. > > Thibaut.
Hi, Thibaut, Thanks for the explaination. Two more questions: 1. if vhost-user backend (or say, DPDK) supports GUEST_ANNOUNCE, and send another RARP (or say, GARP, I will use RARP as example), then there will be two RARP later on the line, right? (since the QEMU one is sent unconditionally from qemu_announce_self). 2. if the only thing vhost-user backend is to send another same RARP when got SEND_RARP request, why would it bother if QEMU will unconditionally send one? (or say, I still do not know why we need this SEND_RARP request, if the vhost-user backend is going to do the same thing again as QEMU already does) Thanks in advance. Peter
