nanog mailing list archives
Re: Common operational misconceptions
From: Mark Andrews <marka () isc org>
Date: Fri, 17 Feb 2012 09:40:16 +1100
In message <CA+ycCUOoLgwAMUn_aSBf8FFiPczWmt2oo7T45jOnqthJWx+xpg () mail gmail com>, Daniel Griggs writes:
--001636c5b8ca93b4eb04b91b7066 Content-Type: text/plain; charset=ISO-8859-1 Seems like dig doesn't always advertise a big enough buffer, I was having the same issue as you. If you set the buffer size on the command line it works as directed.
Well you were supposed to ask your recursive server, not ask the authoritative server directly. We were talking about testing the path from the recursive server (which you may not have log in access to) to the authoritative server. If you want to ask the authoritative server directly then +edns=0 or +dnssec or +bufsize=4096 or you can use dig from BIND 9.9.0 which sets the ad flag and enables edns (version 0) by default. % dig edns-v6-ok.isc.org txt ;; Truncated, retrying in TCP mode. ; <<>> DiG 9.7.3-P3 <<>> edns-v6-ok.isc.org txt ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 46198 ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 1, ADDITIONAL: 1 ;; QUESTION SECTION: ;edns-v6-ok.isc.org. IN TXT ;; ANSWER SECTION: edns-v6-ok.isc.org. 0 IN TXT "EDNS-4096-OK" "EDNS-4096-OK" <snipped> ;; AUTHORITY SECTION: edns-v6-ok.isc.org. 7199 IN NS edns-v6-ok.isc.org. ;; ADDITIONAL SECTION: edns-v6-ok.isc.org. 7199 IN AAAA 2001:4f8:0:2::8 ;; Query time: 174 msec ;; SERVER: 127.0.0.1#53(127.0.0.1) ;; WHEN: Fri Feb 17 09:36:37 2012 ;; MSG SIZE rcvd: 4127 %
Daniels-Mac-mini:~ daniel$ dig edns-v4-ok.isc.org txt @149.20.64.58 ;; Truncated, retrying in TCP mode. ;; Connection to 149.20.64.58#53(149.20.64.58) for edns-v4-ok.isc.orgfailed: connection refused. Daniels-Mac-mini:~ daniel$ dig edns-v4-ok.isc.org txt @149.20.64.58+bufsize=4096 ; <<>> DiG 9.7.3-P3 <<>> edns-v4-ok.isc.org txt @149.20.64.58 +bufsize=4096 ;; global options: +cmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 18209 ;; flags: qr aa rd; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1 ;; WARNING: recursion requested but not available ;; OPT PSEUDOSECTION: ; EDNS: version: 0, flags:; udp: 4096 ;; QUESTION SECTION: ;edns-v4-ok.isc.org. IN TXT ;; ANSWER SECTION: edns-v4-ok.isc.org. 0 IN TXT "EDNS-4096-OK" "EDNS-4096-OK" "EDNS-4096-OK" "EDNS-4096-OK" "EDNS-4096-OK" "EDNS-4096-OK" <snip> "EDNS-4" ;; Query time: 176 msec ;; SERVER: 149.20.64.58#53(149.20.64.58) ;; WHEN: Fri Feb 17 10:22:08 2012 ;; MSG SIZE rcvd: 4096 On 17 February 2012 05:53, Phil Regnauld <regnauld () nsrc org> wrote:Borderline dns-ops, sorry folks! - but this is interesting as we've been talking about ipv6 being operational, and this is part of it... Mark Andrews (marka) writes:If you are seeing TC between the resolver and the server and the TCPquery is being answers thensomething in the path is intercepting the DNS queries.TC is on the answer from the remote server to my resolver, so yeah, seems like something is messing with the packets.Don't see any v6 fragments (that'd be a problem since PF doesn'thandlethem on this host).You should see something like this on the wire. The second query is toanswerdig's query over TCP.I'm not seeing fragments as you are. Here's what I see: 14:40:20.955876 IP6 2001:2000:1080:d::2.64561 > 2001:4f8:0:2::8.53: 52841 TXT? edns-v6-ok.isc.org. (36) 14:40:21.141948 IP6 2001:4f8:0:2::8.53 > 2001:2000:1080:d::2.64561: 52841*-| 0/0/0 (36) 14:40:21.142259 IP6 2001:2000:1080:d::2.53262 > 2001:4f8:0:2::8.53: Flags [S], seq 1112939462, win 65535, options [mss 1440,nop,wscale 6,sackOK,TS val 2571957531 ecr 0], length 0 14:40:21.327895 IP6 2001:4f8:0:2::8.53 > 2001:2000:1080:d::2.53262: Flags [R.], seq 0, ack 1112939463, win 0, length 0 Cheers, Phil-- Daniel Griggs Network Operations e: daniel () fx net nz d: +64 4 4989567 --001636c5b8ca93b4eb04b91b7066 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable <br>Seems like dig doesn't always advertise a big enough buffer, I was = having the same issue as you. If you set the buffer size on the command lin= e it works as directed.<br><br>Daniels-Mac-mini:~ daniel$ dig <a href=3D"ht= tp://edns-v4-ok.isc.org">edns-v4-ok.isc.org</a> txt @<a href=3D"http://149.= 20.64.58">149.20.64.58</a><br> ;; Truncated, retrying in TCP mode.<br>;; Connection to 149.20.64.58#53(149= .20.64.58) for <a href=3D"http://edns-v4-ok.isc.org">edns-v4-ok.isc.org</a>= failed: connection refused.<br>Daniels-Mac-mini:~ daniel$ dig <a href=3D"h= ttp://edns-v4-ok.isc.org">edns-v4-ok.isc.org</a> txt @<a href=3D"http://149= .20.64.58">149.20.64.58</a> +bufsize=3D4096<br> <br>; <<>> DiG 9.7.3-P3 <<>> <a href=3D"http://edns= -v4-ok.isc.org">edns-v4-ok.isc.org</a> txt @<a href=3D"http://149.20.64.58"=149.20.64.58</a> +bufsize=3D4096<br>;; global options: +cmd<br>;; Got answ=er:<br> ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 18209<br>;;= flags: qr aa rd; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1<br>;; WA= RNING: recursion requested but not available<br><br>;; OPT PSEUDOSECTION:<b= r> ; EDNS: version: 0, flags:; udp: 4096<br>;; QUESTION SECTION:<br>;<a href= =3D"http://edns-v4-ok.isc.org">edns-v4-ok.isc.org</a>.=A0=A0=A0 =A0=A0=A0 I= N=A0=A0=A0 TXT<br><br>;; ANSWER SECTION:<br><a href=3D"http://edns-v4-ok.is= c.org">edns-v4-ok.isc.org</a>.=A0=A0=A0 0=A0=A0=A0 IN=A0=A0=A0 TXT=A0=A0=A0= "EDNS-4096-OK" "EDNS-4096-OK" "EDNS-4096-OK"= "EDNS-4096-OK" "EDNS-4096-OK" "EDNS-4096-OK"= <br> <snip><br>"EDNS-4"<br><br>;; Query time: 176 msec<br>;; SER= VER: 149.20.64.58#53(149.20.64.58)<br>;; WHEN: Fri Feb 17 10:22:08 2012<br>= ;; MSG SIZE=A0 rcvd: 4096<br><br><br><br><br><div class=3D"gmail_quote">On = 17 February 2012 05:53, Phil Regnauld <span dir=3D"ltr"><<a href=3D"mail= to:regnauld () nsrc org">regnauld () nsrc org</a>></span> wrote:<br> <blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p= x #ccc solid;padding-left:1ex"> =A0 =A0 =A0 =A0Borderline dns-ops, sorry fo= lks! - but this is interesting<br> =A0 =A0 =A0 =A0as we've been talking about ipv6 being operational, and= this<br> =A0 =A0 =A0 =A0is part of it...<br> <div class=3D"im"><br> Mark Andrews (marka) writes:<br> ><br> > If you are seeing TC between the resolver and the server and the TCP q= uery is being answers then<br> > something in the path is intercepting the DNS queries.<br> <br> </div> =A0 =A0 =A0 =A0TC is on the answer from the remote server to my reso= lver, so yeah, seems<br> =A0 =A0 =A0 =A0like something is messing with the packets.<br> <div class=3D"im"><br> > > =A0 =A0 Don't see any v6 fragments (that'd be a problem s= ince PF doesn't handle<br> > > =A0 =A0 them on this host).<br> ><br> > You should see something like this on the wire. =A0The second query is= to answer<br> > dig's query over TCP.<br> <br> </div> =A0 =A0 =A0 =A0I'm not seeing fragments as you are.<br> <br> =A0 =A0 =A0 =A0Here's what I see:<br> <br> 14:40:20.955876 IP6 2001:2000:1080:d::2.64561 > 2001:4f8:0:2::8.53: 5284= 1 TXT? <a href=3D"http://edns-v6-ok.isc.org" target=3D"_blank">edns-v6-ok.i= sc.org</a>. (36)<br> 14:40:21.141948 IP6 2001:4f8:0:2::8.53 > 2001:2000:1080:d::2.64561: 5284= 1*-| 0/0/0 (36)<br> 14:40:21.142259 IP6 2001:2000:1080:d::2.53262 > 2001:4f8:0:2::8.53: Flag= s [S], seq 1112939462, win 65535, options [mss 1440,nop,wscale 6,sackOK,TS = val 2571957531 ecr 0], length 0<br> 14:40:21.327895 IP6 2001:4f8:0:2::8.53 > 2001:2000:1080:d::2.53262: Flag= s [R.], seq 0, ack 1112939463, win 0, length 0<br> <br> =A0 =A0 =A0 =A0Cheers,<br> =A0 =A0 =A0 =A0Phil<br> <br> </blockquote></div><br><br clear=3D"all"><br>-- <br>Daniel Griggs<br>Networ= k Operations<br>e: <a href=3D"mailto:daniel () fx net nz" target=3D"_blank">da= niel () fx net nz</a><br>d: +64 4 4989567<br> --001636c5b8ca93b4eb04b91b7066--
-- Mark Andrews, ISC 1 Seymour St., Dundas Valley, NSW 2117, Australia PHONE: +61 2 9871 4742 INTERNET: marka () isc org
Current thread:
- Re: Common operational misconceptions, (continued)
- Re: Common operational misconceptions Steve Bertrand (Feb 15)
- Re: Common operational misconceptions sthaug (Feb 16)
- Re: Common operational misconceptions Mark Andrews (Feb 16)
- Re: Common operational misconceptions Jeroen Massar (Feb 16)
- Re: Common operational misconceptions Mark Andrews (Feb 16)
- Re: Common operational misconceptions Phil Regnauld (Feb 16)
- Re: Common operational misconceptions Mark Andrews (Feb 16)
- Re: Common operational misconceptions Phil Regnauld (Feb 16)
- Re: Common operational misconceptions Mark Andrews (Feb 16)
- Re: Common operational misconceptions Daniel Griggs (Feb 16)
- Re: Common operational misconceptions Mark Andrews (Feb 16)
- Re: Common operational misconceptions Owen DeLong (Feb 15)
- Re: Common operational misconceptions Paul Thornton (Feb 16)
- Re: Common operational misconceptions Jared Mauch (Feb 16)
- Re: Common operational misconceptions Owen DeLong (Feb 16)
- Re: Common operational misconceptions Ray Soucy (Feb 16)
- Re: Common operational misconceptions Jeff Kell (Feb 16)
- Re: Common operational misconceptions Chuck Anderson (Feb 16)
- Re: Common operational misconceptions Jack Bates (Feb 16)
- Re: Common operational misconceptions Carsten Bormann (Feb 16)
- Re: Common operational misconceptions Paul Graydon (Feb 16)