> I think the socket used for DNS queries is allocated and assigned a port
> number (the latter is done when the descriptor first gets used) but it's
> not listening for arriving datagrams other than replies. It's probably
> just the descriptor used to make DNS queries which is kept open between
> queries.
If thats the case, should it clean up and close the udp listener once it has
received its reply?
>> This is not causing any usability problems, but I do find it
>> interesting. At one point, I was able to netstat the DNS query, and it
>> was sent from a low numbered udp port. Not these high numbers that
>> dkim-milter is listening on after a verify. Are there any concerns with
>> this peculiar behavior?
>
> For the DNS query to come from a low-numbered port (i.e. under 1024), the
> resolver would have to (a) be running as root, and (b) explicitly bind to
> a low port number using bind() or bindresvport(). I don't which resolver
> you're using, but that code certainly does not exist in libar.
Using the built-in libar. My sample from tcpdump shows that you are correct.
Its the DNS query. I could not find the low numbered outbound port that I
had reported on earlier.
> Can you include a sample from tcpdump?
]# tcpdump -n -nn -p -s 0 -t -X -vvv dst or src port 32768
tcpdump: listening on eth0, link-type EN10MB (Ethernet), capture size 65535
bytes
IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto: UDP (17), length:
72) 24.187.214.157.32768 > 167.206.112.138.53: [bad udp cksum a250!] 6763+
TXT? gamma._domainkey.gmail.com. (44)
0x0000: 4500 0048 0000 4000 4011 32f4 18bb d69d [EMAIL
PROTECTED]@.2.....
0x0010: a7ce 708a 8000 0035 0034 07f7 1a6b 0100 ..p....5.4...k..
0x0020: 0001 0000 0000 0000 0567 616d 6d61 0a5f .........gamma._
0x0030: 646f 6d61 696e 6b65 7905 676d 6169 6c03 domainkey.gmail.
0x0040: 636f 6d00 0010 0001 com.....
IP (tos 0x0, ttl 244, id 33532, offset 0, flags [DF], proto: UDP (17),
length: 458) 167.206.112.138.53 > 24.187.214.157.32768: [udp sum ok] 6763
q: TXT? gamma._domainkey.gmail.com. 1/4/4 gamma._domainkey.gmail.com. TXT
"k=rsa; t=y;
p=MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDIhyR3oItOy22ZOaBrIVe9m/iME3RqOJeasANSpg2YTHTYV+Xtp4xwf5gTjCmHQEMOs0qYu0FYiNQPQogJ2t0Mfx9zNu06rfRBDjiIU9tpx2T+NGlWZ8qhbiLo5By8apJavLyqTLavyPSrvsx0B3YzC63T4Age2CDqZYA+OwSMWQIDAQAB"
ns: gmail.com. NS ns2.google.com., gmail.com. NS ns3.google.com., gmail.com.
NS ns4.google.com., gmail.com. NS ns1.google.com. ar: ns1.google.com. A
216.239.32.10, ns2.google.com. A 216.239.34.10, ns3.google.com. A
216.239.36.10, ns4.google.com. A 216.239.38.10 (430)
0x0000: 4500 01ca 82fc 4000 f411 fa74 a7ce 708a [EMAIL PROTECTED]
0x0010: 18bb d69d 0035 8000 01b6 002c 1a6b 8180 .....5.....,.k..
0x0020: 0001 0001 0004 0004 0567 616d 6d61 0a5f .........gamma._
0x0030: 646f 6d61 696e 6b65 7905 676d 6169 6c03 domainkey.gmail.
0x0040: 636f 6d00 0010 0001 c00c 0010 0001 0000 com.............
0x0050: 012c 00e7 e66b 3d72 7361 3b20 743d 793b .,...k=rsa;.t=y;
0x0060: 2070 3d4d 4947 664d 4130 4743 5371 4753 .p=MIGfMA0GCSqGS
0x0070: 4962 3344 5145 4241 5155 4141 3447 4e41 Ib3DQEBAQUAA4GNA
0x0080: 4443 4269 514b 4267 5144 4968 7952 336f DCBiQKBgQDIhyR3o
0x0090: 4974 4f79 3232 5a4f 6142 7249 5665 396d ItOy22ZOaBrIVe9m
0x00a0: 2f69 4d45 3352 714f 4a65 6173 414e 5370 /iME3RqOJeasANSp
0x00b0: 6732 5954 4854 5956 2b58 7470 3478 7766 g2YTHTYV+Xtp4xwf
0x00c0: 3567 546a 436d 4851 454d 4f73 3071 5975 5gTjCmHQEMOs0qYu
0x00d0: 3046 5969 4e51 5051 6f67 4a32 7430 4d66 0FYiNQPQogJ2t0Mf
0x00e0: 7839 7a4e 7530 3672 6652 4244 6a69 4955 x9zNu06rfRBDjiIU
0x00f0: 3974 7078 3254 2b4e 476c 575a 3871 6862 9tpx2T+NGlWZ8qhb
0x0100: 694c 6f35 4279 3861 704a 6176 4c79 7154 iLo5By8apJavLyqT
0x0110: 4c61 7679 5053 7276 7378 3042 3359 7a43 LavyPSrvsx0B3YzC
0x0120: 3633 5434 4167 6532 4344 715a 5941 2b4f 63T4Age2CDqZYA+O
0x0130: 7753 4d57 5149 4441 5141 42c0 1d00 0200 wSMWQIDAQAB.....
0x0140: 0100 0036 8500 0d03 6e73 3206 676f 6f67 ...6....ns2.goog
0x0150: 6c65 c023 c01d 0002 0001 0000 3685 0006 le.#........6...
0x0160: 036e 7333 c12f c01d 0002 0001 0000 3685 .ns3./........6.
0x0170: 0006 036e 7334 c12f c01d 0002 0001 0000 ...ns4./........
0x0180: 3685 0006 036e 7331 c12f c168 0001 0001 6....ns1./.h....
0x0190: 0000 0001 0004 d8ef 200a c12b 0001 0001 ...........+....
0x01a0: 0000 0013 0004 d8ef 220a c144 0001 0001 ........"..D....
0x01b0: 0000 0013 0004 d8ef 240a c156 0001 0001 ........$..V....
0x01c0: 0000 0013 0004 d8ef 260a ........&.
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