Willy Offermans wrote this message on Thu, Mar 27, 2014 at 15:46 +0100: > Hello John-Mark and FreeBSD friends, > > On Wed, Mar 26, 2014 at 04:04:27PM -0700, John-Mark Gurney wrote: > > Willy Offermans wrote this message on Wed, Mar 26, 2014 at 18:22 +0100: > > > Hello John-Mark and FreeBSD friends, > > > > > > On Wed, Mar 26, 2014 at 09:20:35AM -0700, John-Mark Gurney wrote: > > > > Willy Offermans wrote this message on Wed, Mar 26, 2014 at 12:17 +0100: > > > > > On Tue, Mar 25, 2014 at 09:43:16AM -0700, John-Mark Gurney wrote: > > > > > > Willy Offermans wrote this message on Tue, Mar 25, 2014 at 11:39 +0100: > > > > > > > I'm not an expert in tcpdump. Can anyone make sense out of the messages? > > > > > > > > > > > > If you dumped the contents, using -s 0 -X, and look at that last packet > > > > > > you should see 0d 0a 2e 0d 0a at the end.. which is CR/LF/./CR/LF.. If > > > > > > you don't see that, then for some reason sendmail/FreeBSD isn't telling > > > > > > the server that it's done sending which would prevent the receiving > > > > > > side from ack'ing the email causing the timeout... > > > > > > > > > > I followed your suggestions. However I'm not able to distinguish the last > > > > > packet. Is there a way to find this with help of the Flags? The following > > > > > is the output of tcpdump -r /root/tmp/tcpdump -X | grep Flags > > > > > > > > > > 11:57:56.539788 IP MyServer.com.41115 > Smarthost.com.smtp: Flags [S], seq 1001452351, win 65535, options [mss 1448,nop,wscale 6,sackOK,TS val 407239960 ecr 0], length 0 > > > > > 11:57:56.555262 IP Smarthost.com.smtp > MyServer.com.41115: Flags [S.], seq 1277075046, ack 1001452352, win 8192, options [mss 1452], length 0 > > > > > > > > It should look something like: > > > > 09:18:34.723280 IP jmgmac.funkthat.com.64724 > h2.funkthat.com.ssh: Flags [.], ack 177, win 33280, options [nop,nop,TS val 1854905469 ecr 3482476972], length 0 > > > > 0x0000: 4510 0034 d7ac 4000 4006 e1af c0a8 0003 E..4.._at_._at_....... > > > > 0x0010: c0a8 0004 fcd4 0016 7e48 238e d872 43dc ........~H#..rC. > > > > 0x0020: 8010 8200 7c08 0000 0101 080a 6e8f 9c7d ....|.......n..} > > > > 0x0030: cf92 61ac ..a. > > > > > > > > Notice the hex output... I didn't see any of that in your output... > > > > The last packet I was talking about is the last one that had length > > > > 1448 that your server sent... > > > > > > I sent two e-mails consecutively: the first without an attachment, the > > > second with attachment. I dumped tcp of the NIC for port smtp. I got the > > > following: > > > > > > > > > 12:20:55.988622 IP MyServer.com.37191 > Smarthost.com.smtp: Flags [P.], seq 18943:19104, ack 412, win 65535, length 161 > > > 0x0000: 4500 00c9 eebd 4000 4006 0000 c0a8 0004 E....._at_._at_....... > > > 0x0010: d54b 3f0d 9147 0019 4ea0 36dd 15a7 38a0 .K?..G..N.6...8. > > > 0x0020: 5018 ffff 4481 0000 2020 2020 2020 2020 P...D........... > > > 0x0030: 2020 2020 2020 2020 2020 2020 2020 2020 ................ > > > 0x0040: 2020 2020 2020 2020 2020 2020 2020 205c ...............\ > > > 0x0050: 2f20 205c 205e 0d0a 2020 2020 2020 2020 /..\.^.......... > > > 0x0060: 2020 2020 2020 2020 2020 2020 2020 2020 ................ > > > 0x0070: 2020 2020 2020 2020 2020 2020 2020 2020 ................ > > > 0x0080: 2020 202e 5c2e 5f2f 5f29 0d0a 0d0a 2020 ....\._/_)...... > > > 0x0090: 2020 2020 2020 2020 2020 2020 2020 2020 ................ > > > 0x00a0: 2020 2020 2020 2020 2020 2020 2020 2020 ................ > > > 0x00b0: 2020 2020 2077 7777 2e46 7265 6542 5344 .....www.FreeBSD > > > 0x00c0: 2e6f 7267 0d0a 2e0d 0a .org..... > > > > > > As predicted by John-Mark, the first ended with "0d0a 2e0d 0a". However it > > > was not the last packet with length 1448. I hope that this will not spoil > > > the party. Is the Flag [P.] more indicative? It looks like to me, but I'm > > > just learning. > > > > > > Anyway the second mail ended with: > > > > > > 12:22:17.960896 IP MyServer.com.37191 > Smarthost.com.smtp: Flags [.], seq 35127:36575, ack 638, win 65535, length 1448 > > > 0x0000: 4500 05d0 fe9d 4000 4006 0000 c0a8 0004 E....._at_._at_....... > > > <snip> > > > </snip> > > > 0x0560: 5670 6876 4a67 5a5a 5a50 4b2f 4b78 3774 VphvJgZZZPK/Kx7t > > > 0x0570: 382f 4230 594f 6b78 3449 0d0a 4a76 6551 8/B0YOkx4I..JveQ > > > 0x0580: 2b6e 7765 5647 2f33 6e79 6231 6133 496f +nweVG/3nyb1a3Io > > > 0x0590: 5474 554f 4d61 4374 696b 714b 436b 4959 TtUOMaCtikqKCkIY > > > 0x05a0: 704a 7668 3055 416d 6c33 4754 4f4c 6455 pJvh0UAml3GTOLdU > > > 0x05b0: 774b 4145 7151 5741 7841 4141 5a66 7647 wKAEqQWAxAAAZfvG > > > 0x05c0: 706b 6c36 0d0a 7a4e 6234 745a 6633 5a6c pkl6..zNb4tZf3Zl > > > > > > Being packet with length 1448 and sent from my side. The code "0d0a 2e0d > > > 0a" is missing. Immediately thereafter the following packets: > > > > We clearly haven't gotten the last mime-boundary, we are still in the > > base64 encoded data of the attachment... > > > > > 12:22:18.003557 IP Smarthost.com.smtp > MyServer.com.37191: Flags [.], ack 36575, win 65160, length 0 > > > 0x0000: 4500 0028 11fb 4000 7a06 19d0 d54b 3f0d E..(.._at_.z....K?. > > > 0x0010: c0a8 0004 0019 9147 15a7 3982 4ea0 7bbd .......G..9.N.{. > > > 0x0020: 5010 fe88 315f 0000 0000 0000 0000 P...1_........ > > > > The remote acking that it got your last packet... > > > > > 12:22:37.665889 IP MyServer.com.37191 > Smarthost.com.smtp: Flags [R.], seq 39471, ack 638, win 65535, length 0 > > > 0x0000: 4500 0028 492c 4000 4006 0000 c0a8 0004 E..(I,_at_._at_....... > > > 0x0010: d54b 3f0d 9147 0019 4ea0 870d 15a7 3982 .K?..G..N.....9. > > > 0x0020: 5014 ffff 2494 0000 P...$... > > > > Local host closing down the connection because of time out... > > > > > 12:22:37.680857 IP Smarthost.com.smtp > MyServer.com.37191: Flags [.], ack 36575, win 65160, length 0 > > > 0x0000: 4500 0028 0584 0000 f906 e746 d54b 3f0d E..(.......F.K?. > > > 0x0010: c0a8 0004 0019 9147 15a7 3982 4ea0 7bbd .......G..9.N.{. > > > 0x0020: 5010 fe88 315f 0000 0000 0000 0000 P...1_........ > > > 12:22:37.680920 IP MyServer.com.37191 > Smarthost.com.smtp: Flags [R], seq 1319140285, win 0, length 0 > > > 0x0000: 4500 0028 4935 4000 4006 0000 c0a8 0004 E..(I5_at_._at_....... > > > 0x0010: d54b 3f0d 9147 0019 4ea0 7bbd 0000 0000 .K?..G..N.{..... > > > 0x0020: 5004 0000 7f1d 0000 P....... > > > > > > It looks like Smarthost.com asks for more, but there is not more to sent. > > > The final packet seems to be absent. I cannot look for the closing remark > > > "www.FreeBSD.org", since there is the attachment at the end of the second > > > mail. Is there any connection between the encoded attachment in the second > > > mail and the output of tcpdump? > > > > > > Am I the only one noticing this error? I can hardly believe this. > > > > > > Is there a way to force the insertion of <CRLF>.<CRLF>? > > > > So, this is more looking like a kernel problem where the last packet(s) > > aren't being sent out... Could you possibly catch the output of > > netstat -anfinet of the connection between the last packet and the > > reset? It'll be interesting to see if there is data in the send-q > > for the connection (third column)... If it's zero, that seems to imply > > that the server process hasn't sent all the data necessary... Then > > the next bit of investigation would be to run ktrace on the sendmail > > process and make sure that it writes all the correct data to the > > socket... > > > > Do you know what OS the remote side is running? You could use nmap > > to try to figure it out, as it could be a TCP stack interaction issue.. > > netstat -anfinet gave: > > tcp4 0 33304 MyServerIP.35395 SmarthostIP.25 ESTABLISHED > > So there is still data to be sent, if I interpret correctly. What is next > to be investigated? Yeh, if there is data in the send-q (per above) and you aren't seeing any more packets, someone on -net with some TCP clue should help you debug this... Also, did you figure out what the OS is of the other end? Knowing that will also help them... For -net's reference, the opening syns look like: 11:57:56.539788 IP MyServer.com.41115 > Smarthost.com.smtp: Flags [S], seq 1001452351, win 65535, options [mss 1448,nop,wscale 6,sackOK,TS val 407239960 ecr 0], length 0 11:57:56.555262 IP Smarthost.com.smtp > MyServer.com.41115: Flags [S.], seq 1277075046, ack 1001452352, win 8192, options [mss 1452], length 0 -- John-Mark Gurney Voice: +1 415 225 5579 "All that I will do, has been done, All that I have, has not."Received on Fri Mar 28 2014 - 02:27:10 UTC
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