Date: Mon, 6 Dec 2004 19:57:09 +0100 From: Hans Petter Selasky <hselasky@c2i.net> To: freebsd-hackers@freebsd.org Subject: hostname lookup problem Message-ID: <20041206195709.A332@curly.tele2.no>
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Hi,
I have come across a problem where res_send() goes into a minute-long wait
loop, waiting for the hostname to be looked up, after a getaddrinfo() call. I
have captured the packets sent/received, and according to the code the
query response does not match. Is this a bug in libc or is it a DNS server
problem?
A temporary patch is to make the code go on with the next packet instead of
waiting for a timeout. Then getaddrinfo only takes a few seconds more, instead
of a minute.
src/lib/libc/net/res_send.c:res_send():
if (!(_res.options & RES_INSECURE2) &&
!res_queriesmatch(buf, buf + buflen,
ans, ans + anssiz)) {
/*
* response contains wrong query? ignore it.
* XXX - potential security hazard could
* be detected here.
*/
DprintQ((_res.options & RES_DEBUG) ||
(_res.pfcode & RES_PRF_REPLY),
(stdout, ";; wrong query name:\n"),
ans, (resplen>anssiz)?anssiz:resplen);
res_close();
goto next_ns;
//goto wait;
}
Trace output from "fetch www.google.com" on a PPP link:
8X (fails):
-- TE->NT - unit:0 - frame:000175 - time:03.12 19:11:46.845441 - length:69 -----
B2:000 ff 03 00 3d c0 00 00 0b 21 45 00 00 3c 02 43 00 ...=....!E..<.C.
B2:010 00 40 11 28 a3 c1 d9 cb 0f c1 d8 01 0a c3 9a 00 .@.(............
B2:020 35 00 28 6d 95 ef aa 01 00 00 01 00 00 00 00 00 5.(m............
B2:030 00 03 77 77 77 06 67 6f 6f 67 6c 65 03 63 6f 6d ..www.google.com
B2:040 00 00 1c 00 01 .....
-- NT->TE - unit:0 - frame:000176 - time:03.12 19:11:46.971341 - length:71 -----
B2:000 ff 03 00 21 45 00 00 43 74 53 40 00 fc 11 ba 8a ...!E..CtS@.....
B2:010 c1 d8 01 0a c1 d9 cb 0f 00 35 c3 9a 00 2f 06 6b .........5.../.k
B2:020 ef aa 81 80 00 01 00 00 00 00 00 00 03 77 77 77 .............www
B2:030 06 67 6f 6f 67 6c 65 06 61 6b 61 64 6e 73 03 6e .google.akadns.n
B2:040 65 74 00 00 1c 00 01 et.....
(above is IPv6 (AAAA), below is IPv4 (A) ??)
1X (succeeds):
-- TE->NT - unit:0 - frame:000211 - time:03.12 19:13:08.633794 - length:69 -----
B2:000 ff 03 00 3d c0 00 00 17 21 45 00 00 3c 02 4b 00 ...=....!E..<.K.
B2:010 00 40 11 28 9b c1 d9 cb 0f c1 d8 01 0a ef 03 00 .@.(............
B2:020 35 00 28 42 46 ef ab 01 00 00 01 00 00 00 00 00 5.(BF...........
B2:030 00 03 77 77 77 06 67 6f 6f 67 6c 65 03 63 6f 6d ..www.google.com
B2:040 00 00 01 00 01 .....
-- NT->TE - unit:0 - frame:000212 - time:03.12 19:13:08.825249 - length:531 ----
B2:000 ff 03 00 21 45 00 02 0f 74 57 40 00 fc 11 b8 ba ...!E...tW@.....
B2:010 c1 d8 01 0a c1 d9 cb 0f 00 35 ef 03 01 fb cc 3d .........5.....=
B2:020 ef ab 81 80 00 01 00 03 00 0d 00 0c 03 77 77 77 .............www
B2:030 06 67 6f 6f 67 6c 65 03 63 6f 6d 00 00 01 00 01 .google.com.....
B2:040 c0 0c 00 05 00 01 00 00 00 1e 00 17 03 77 77 77 .............www
B2:050 06 67 6f 6f 67 6c 65 06 61 6b 61 64 6e 73 03 6e .google.akadns.n
B2:060 65 74 00 c0 2c 00 01 00 01 00 00 00 8e 00 04 42 et..,..........B
B2:070 66 0b 68 c0 2c 00 01 00 01 00 00 00 8e 00 04 42 f.h.,..........B
B2:080 66 0b 63 00 00 02 00 01 00 02 3e 59 00 11 01 41 f.c.......>Y...A
B2:090 0c 52 4f 4f 54 2d 53 45 52 56 45 52 53 c0 3e 00 .ROOT-SERVERS.>.
B2:0a0 00 02 00 01 00 02 3e 59 00 04 01 48 c0 70 00 00 ......>Y...H.p..
B2:0b0 02 00 01 00 02 3e 59 00 04 01 43 c0 70 00 00 02 .....>Y...C.p...
B2:0c0 00 01 00 02 3e 59 00 04 01 47 c0 70 00 00 02 00 ....>Y...G.p....
B2:0d0 01 00 02 3e 59 00 04 01 46 c0 70 00 00 02 00 01 ...>Y...F.p.....
B2:0e0 00 02 3e 59 00 04 01 42 c0 70 00 00 02 00 01 00 ..>Y...B.p......
B2:0f0 02 3e 59 00 04 01 4a c0 70 00 00 02 00 01 00 02 .>Y...J.p.......
B2:100 3e 59 00 04 01 4b c0 70 00 00 02 00 01 00 02 3e >Y...K.p.......>
B2:110 59 00 04 01 4c c0 70 00 00 02 00 01 00 02 3e 59 Y...L.p.......>Y
B2:120 00 04 01 4d c0 70 00 00 02 00 01 00 02 3e 59 00 ...M.p.......>Y.
B2:130 04 01 49 c0 70 00 00 02 00 01 00 02 3e 59 00 04 ..I.p.......>Y..
B2:140 01 45 c0 70 00 00 02 00 01 00 02 3e 59 00 04 01 .E.p.......>Y...
B2:150 44 c0 70 c0 6e 00 01 00 01 00 06 33 f4 00 04 c6 D.p.n......3....
B2:160 29 00 04 c0 8a 00 01 00 01 00 06 33 f4 00 04 80 )..........3....
B2:170 3f 02 35 c0 99 00 01 00 01 00 06 33 f4 00 04 c0 ?.5........3....
B2:180 21 04 0c c0 a8 00 01 00 01 00 06 33 f4 00 04 c0 !..........3....
B2:190 70 24 04 c0 b7 00 01 00 01 00 06 33 f4 00 04 c0 p$.........3....
B2:1a0 05 05 f1 c0 c6 00 01 00 01 00 06 33 f4 00 04 c0 ...........3....
B2:1b0 e4 4f c9 c0 d5 00 01 00 01 00 06 33 89 00 04 c0 .O.........3....
B2:1c0 3a 80 1e c0 e4 00 01 00 01 00 06 33 89 00 04 c1 :..........3....
B2:1d0 00 0e 81 c0 f3 00 01 00 01 00 06 33 89 00 04 c6 ...........3....
B2:1e0 20 40 0c c1 02 00 01 00 01 00 06 33 89 00 04 ca @.........3....
B2:1f0 0c 1b 21 c1 11 00 01 00 01 00 06 33 89 00 04 c0 ..!........3....
B2:200 24 94 11 c1 20 00 01 00 01 00 06 33 f4 00 04 c0 $... ......3....
B2:210 cb e6 0a ...
Yours
-HPS
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