From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=networkplumber-org.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=r2uKp2/WcQXgpvkYrcWFEL0hVjFKRI1erLruelY4s0E=; b=IHrRp1TghLJAkvJYkAe6xh1y9y0dJjwspSy8mqbwLLKhN7vCRf8m0yu9D2s8/A1DxF Eo+d+NErL03Lwjt9YuyN04u2lHdboxl2sY6JVjk8fjGCWfTMKnbpxazLTsByJQUQRARk D/akncBSdQrcCm+9MYZJEOUqGYZ/NDRC/dz/MiTV4EOyQ9DLw0nU3pTaSYa+B2Zx3HcG fhUWiIbeHMR6xJVHTtUEhuFU3j5x7mLxBw4ESEsj+9zUYbGOiHkmzn9oTBM1sUVI1cOp +I4I4TESIWlKij6UCXo6Yy6wGA0U14O368efGs4bXqGsNy5ez7jSiuSn4YHXz0ieQLzy Lz+Q== Date: Fri, 15 Dec 2017 17:47:09 -0800 From: Stephen Hemminger Message-ID: <20171215174709.4cea5b98@xeon-e3> In-Reply-To: References: <20171215075512.6138a258@xeon-e3> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: Re: [Bridge] linux bridge does not forward arp reply back packets in a vmware vm List-Id: Linux Ethernet Bridging List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Adrian P Cc: bridge@lists.linux-foundation.org On Fri, 15 Dec 2017 18:29:58 +0200 Adrian P wrote: > On Fri, Dec 15, 2017 at 5:55 PM, Stephen Hemminger > wrote: > > On Fri, 15 Dec 2017 15:37:39 +0200 > > Adrian P wrote: > > > >> Hello, > >> > >> I have a strange issue with a linux bridge created by > >> openstack-neutron (pike release). This linux bridge is hosted in a > >> vmware VM running latest CentOS 7, with a single network interface in > >> promiscuous mode. > >> > >> From openstack neutron perspective, the networking setup is simple: a > >> single flat external provider network, with a single cirros VM > >> instance connected to it. > >> > >> Therefore, in the linux bridge running in the vmware host, I have 3 interfaces: > >> > >> # brctl show > >> bridge name bridge id STP enabled interfaces > >> brq025a9a94-58 8000.005056a6b378 no ens160 > >> tap2eb4cad6-cd > >> <----- neutron DHCP agent tap interface > >> tap6d31a191-9f > >> <----- cirros VM instance tap interface > >> > >> The ens160 is the "physical" CentOS 7 host interface, that is in > >> promiscuous mode. > >> > >> The tap2eb4cad6-cd tap interface is the neutron DHCP agent interface, > >> and the tap6d31a191-9f tap interface is used by the cirros VM > >> instance. > >> > >> The problem is the following: > >> > >> With a tcpdump, I am able to see the arp request (ARP, Request who-has > >> 10.20.21.1 tell 10.20.21.233) going out from the cirros VM instance on > >> tap interface tap6d31a191-9f, and well as on the bridge itself > >> (brq025a9a94-58). However, the reply back to the arp request (Reply > >> 10.20.21.1 is-at 00:17:08:c4:52:80) does not reach the cirros VM > >> instance anymore. With tcpdump, I am able to see the arp reply back > >> packets in the bridge (brq025a9a94-58), however they do not show up > >> anymore on the cirros VM instance tap interface tap6d31a191-9f. > >> > >> To me it seems that for whatever reason, the bridge does not forward > >> the arp reply back packets to the cirros VM tap interface, and I do > >> not understand why. The strange thing is that after a while, for > >> apparently no reason, a single arp reply back packet gets through the > >> bridge and the tap interface, and the arp table gets updated with > >> correct IP address in the cirros VM instance. However, if I clean up > >> the arp table in the cirros VM instance, it takes again 10 to 15 > >> minutes of continuously sending arp requests, until a single arp reply > >> back packets gets through. > >> > >> I was banging my head to the table for a few days with this issue, and > >> finally, for apparent no reason, I manually configured the bridge max > >> aging time to 0, to convert it in a hub, and from that moment > >> everything started to work without any issue. Still, I do no > >> understand why is this happening, and obviously I cannot manually set > >> up the bridge aging time to 0 all the time in all the bridges > >> openstack neutron creates automatically. > >> > >> Any thoughts? > >> > >> Many thanks in advance. > >> > >> Best regards, > >> Adrian > > > > Does each tap instance and the ens160 have a different and valid Ethernet > > address? Also make sure the these are in the bridge forwarding table. > > Yes, they have valid Ethernet addresses, and they do show up in the > forwarding table twice, see below: > > # ip addr > <...> > 2: ens160: mtu 1500 qdisc mq master > brq025a9a94-58 state UP qlen 1000 > link/ether 00:50:56:a6:b3:78 brd ff:ff:ff:ff:ff:ff > inet6 fe80::250:56ff:fea6:b378/64 scope link > valid_lft forever preferred_lft forever > 4: tap2eb4cad6-cd@if2: mtu 1500 > qdisc noqueue master brq025a9a94-58 state UP qlen 1000 > link/ether 8a:b2:15:4c:96:55 brd ff:ff:ff:ff:ff:ff link-netnsid 0 > 5: brq025a9a94-58: mtu 1500 qdisc > noqueue state UP qlen 1000 > link/ether 00:50:56:a6:b3:78 brd ff:ff:ff:ff:ff:ff > inet 10.20.21.249/24 brd 10.20.21.255 scope global brq025a9a94-58 > valid_lft forever preferred_lft forever > inet6 fe80::803d:d0ff:fe2e:3ae4/64 scope link > valid_lft forever preferred_lft forever > 6: tap6d31a191-9f: mtu 1500 qdisc > pfifo_fast master brq025a9a94-58 state UNKNOWN qlen 1000 > link/ether fe:16:3e:9a:04:95 brd ff:ff:ff:ff:ff:ff > inet6 fe80::fc16:3eff:fe9a:495/64 scope link > valid_lft forever preferred_lft forever > > # brctl showmacs brq025a9a94-58 > port no mac addr is local? ageing timer > 1 00:50:56:a6:b3:78 yes 0.00 > 1 00:50:56:a6:b3:78 yes 0.00 > 2 8a:b2:15:4c:96:55 yes 0.00 > 2 8a:b2:15:4c:96:55 yes 0.00 > 3 fe:16:3e:9a:04:95 yes 0.00 > 3 fe:16:3e:9a:04:95 yes 0.00 Since there are multiple entries per port maybe you are also using VLANs?