4

You could try strace: strace -e trace=connect your_program with arguments Here is an example output: $ strace -e trace=connect ssh somehost -p 8081 connect(3, {sa_family=AF_LOCAL, sun_path="/var/run/nscd/socket"}, 110) = -1 ENOENT (No such file or directory) connect(3, {sa_family=AF_LOCAL, sun_path="/var/run/nscd/socket"}, 110) = -1 ...


2

No this is perfectly fine to use an ACCEPT policy for the nat table. Using a DROP policy would be an anomaly. A packet traverses various chains in various tables following this schematic: Being accepted, just means the packet gets an other chance of being accepted or dropped in the next round (ie: the next chain and its rules to receive this packet). Being ...


1

A word of warning: Opening up 1433/TCP to the internet (with source: Any) is quite a security risk. Think twice about your intentions here! Install SSMS on the mentioned VM and ensure that you can connect locally to your MSSSQL server. Also ensure that Allow remote connections to this server is ticked (in SSMS go to the properties of your server > ...


1

You need to change one or two kernel tunables - on client machine. To make TCP keepalive (ENABLE=BROKEN) useful. By default Linux kernel sends the 1st TCP keepalive probe after 2 hours: Linux kernel: # cat /proc/sys/net/ipv4/tcp_keepalive_time 7200 Delay before the 1st probe is sent - after 2 hours !!! # cat /proc/sys/net/ipv4/tcp_keepalive_intvl 75 ...


1

Yes, you missed an important detail. But it's not your fault; this is very poorly documented and apparently not well known. The iptables command has a significant design flaw: It doesn't actually display the complete firewall rule unless you use the -v command line option. If you repeat the iptables command and add -v you will see that that rule accepts all ...


1

By default Docker manages its own firewall rules via calling iptables directly. It will allow a port in the firewall when you expose it in your container. These are not visible in ufw.


1

I spoke with my isp and its their fault. They have an weird network. So i always only get an internal ip address from every package that arrive.


1

Seeing verdict drop in the trace is normal. The reject still sends the proper ICMP error, not simply dropping the packet. You can fire up Wireshark and look at them if you wish to be sure. Yes, this is confusing.


1

You can configure your iptables rules to log traffic, and see exactly what traffic was being sent at the time you ran a given program. This won't work well on a busy system, as it doesn't actually tell you which program sent which traffic, but on a light load, you should be able to piece together what's happening. Example for input and output: iptables -A ...


Only top voted, non community-wiki answers of a minimum length are eligible