Hi,
Jeremy Harris <jgh@???> (Mi 20 Sep 2017 19:15:18 CEST):
…
> sysctl net.ipv4.tcp_syn_retries ?
Yes, on my system it is set to 6 (retries), so I see 7 SYN packets in a
row, with a doubling time between them.
t dt (s) action
-----------+--------
0 0 SYN
1 1 SYN retry #1
3 2 SYN retry #2
7 4 SYN retry #3
15 8 SYN retry #4
31 16 SYN retry #5
63 32 SYN retry #6
127 64 ETIMEDOUT
I observed it using the LOG target of my firewall (which was set to DROP
packets to the destination host)
---[ edited log from my kernel ]----
1 Sep 21 09:08:20 blade kernel: OUT=wwp0s20f0u6i12 SRC=100.71.138.216 DST=84.19…
+ 1s
2 Sep 21 09:08:21 blade kernel: OUT=wwp0s20f0u6i12 SRC=100.71.138.216 DST=84.19…
+ 2s
3 Sep 21 09:08:23 blade kernel: OUT=wwp0s20f0u6i12 SRC=100.71.138.216 DST=84.19…
+ 4s
4 Sep 21 09:08:27 blade kernel: OUT=wwp0s20f0u6i12 SRC=100.71.138.216 DST=84.19…
+ 8s
5 Sep 21 09:08:35 blade kernel: OUT=wwp0s20f0u6i12 SRC=100.71.138.216 DST=84.19…
+16s
6 Sep 21 09:08:52 blade kernel: OUT=wwp0s20f0u6i12 SRC=100.71.138.216 DST=84.19…
+32s
7 Sep 21 09:09:24 blade kernel: OUT=wwp0s20f0u6i12 SRC=100.71.138.216 DST=84.19…
+64s
Final timeout 09:10:30
---------------------------------
(Note, this connection attempt wasn't initiated by Exim, but by `cat </dev/tcp/84.194…./smtp`
After all, Exim behaves as documented. If the OP whould have taken some
minute to read the docs, he would have discovered:
+------------------------------------------------+
|connect_timeout|Use: smtp|Type: time|Default: 5m|
+------------------------------------------------+
This sets a timeout for the connect() function, which sets up a TCP/IP call to
a remote host. A setting of zero allows the system timeout (typically several
* minutes) to act. To have any effect, the value of this option must be less than
* the system timeout. However, it has been observed that on some systems there is
no system timeout, which is why the default value for this option is 5 minutes,
a value recommended by RFC 1123.
Best regards from Dresden/Germany
Viele Grüße aus Dresden
Heiko Schlittermann
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