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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal>Thanks Numan, that makes more sense. I got the impression no special routing was needed.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>John Lang<o:p></o:p></p><p class=MsoNormal>w (303) 272-5457<o:p></o:p></p><p class=MsoNormal>c (970) 231-3724<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><b>From:</b> Numan Siddique <numans@ovn.org> <br><b>Sent:</b> Tuesday, June 9, 2020 12:25 PM<br><b>To:</b> John Lang <john.x.lang@oracle.com><br><b>Cc:</b> ovs-discuss <ovs-discuss@openvswitch.org><br><b>Subject:</b> Re: [ovs-discuss] OVN DNS support questions<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><div><div><p class=MsoNormal><o:p> </o:p></p></div><p class=MsoNormal><o:p> </o:p></p><div><div><p class=MsoNormal>On Tue, Jun 9, 2020 at 11:49 PM John Lang <<a href="mailto:john.x.lang@oracle.com">john.x.lang@oracle.com</a>> wrote:<o:p></o:p></p></div><blockquote style='border:none;border-left:solid #CCCCCC 1.0pt;padding:0in 0in 0in 6.0pt;margin-left:4.8pt;margin-right:0in'><div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>Numan,<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>Earlier I had send an e-mail with the following question that you responded to. I maybe should have asked if the pipeline would redirect the DNS request to another DNS server to OVN.<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p><p class=gmail-m2837967426429165787gmail-m-8743985617076697658gmail-m4188889267868020159msolistparagraph style='margin-left:.75in'>1.<span style='font-size:7.0pt;font-family:"Times New Roman",serif'> </span>If OVN can’t answer a DNS request, does the pipeline forward it on the another DNS server? How is that server address set? Though the DHCP options?<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;margin-left:.25in'> <o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;margin-left:.25in'>Yes. If OVN can't anwer it resumes the packet pipeline. So if there are any other DNS servers, they should get the packet.<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>I was looking at the flows in my OVN setup configured for DNS, and I don’t see how the DNS request is redirected to a server external to OVN.<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;margin-left:.5in'> table=16(ls_in_dns_lookup ), priority=100 , match=(udp.dst == 53), action=(reg0[4] = dns_lookup(); next;)<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;margin-left:.5in'> table=16(ls_in_dns_lookup ), priority=0 , match=(1), action=(next;)<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;margin-left:.5in'> table=17(ls_in_dns_response ), priority=100 , match=(udp.dst == 53 && reg0[4]), action=(eth.dst <-> eth.src; ip6.src <-> ip6.dst; udp.dst = udp.src; udp.src = 53; outport = inport; flags.loopback = 1; output;)<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;margin-left:.5in'> table=17(ls_in_dns_response ), priority=100 , match=(udp.dst == 53 && reg0[4]), action=(eth.dst <-> eth.src; ip4.src <-> ip4.dst; udp.dst = udp.src; udp.src = 53; outport = inport; flags.loopback = 1; output;)<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto;margin-left:.5in'> table=17(ls_in_dns_response ), priority=0 , match=(1), action=(next;)<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>Based on these flows it looks like all udp.dst requests on port 53 are sent to dns_lookup. If dns_lookup resolves the request it send the reply (either IPV4 or IPV6). If not, it proceeds to table 18, and I think eventually the request gets dropped. Is there some later flow I should be looking for that would redirect the request to another DNS server (or is there something I’m missing in dns_lookup that does the redirect)? If so, how does OVN/OVS know the ip address of that server?<o:p></o:p></p></div></div></blockquote><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>OVN is not aware of any external DNS servers if any. So if OVN can't resolve the DNS, the packet resumes the pipeline<o:p></o:p></p></div><div><p class=MsoNormal>and is treated like any other packet. If the DNS server IP is to be routed it will be routed. Let me know If I'm not clear.<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>Thanks<o:p></o:p></p></div><div><p class=MsoNormal>Numan<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><blockquote style='border:none;border-left:solid #CCCCCC 1.0pt;padding:0in 0in 0in 6.0pt;margin-left:4.8pt;margin-right:0in'><div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>John Lang<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>w (303) 272-5457<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>c (970) 231-3724<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p></div></div><p class=MsoNormal>_______________________________________________<br>discuss mailing list<br><a href="mailto:discuss@openvswitch.org" target="_blank">discuss@openvswitch.org</a><br><a href="https://mail.openvswitch.org/mailman/listinfo/ovs-discuss" target="_blank">https://mail.openvswitch.org/mailman/listinfo/ovs-discuss</a><o:p></o:p></p></blockquote></div></div></div></body></html>