Hello, My name is Darek Ostolski, I'm computer enthusiast and hobbyst (also a developer). If this is incorrect mailing list excuse me and please point to the appropriate place to ask this kind of question. I couldn't find any other more appropriate place. I have a process that is in the separate net namespace (basically a container) and I want to check opened connections for that process. I have a kernel 4.3.3. My experiments showed that this information is available in /proc/[pid]/net/tcp|tcp6 files. For example for a global /proc/net/tcp6 shows following opened ports: root@host:~# cat /proc/net/tcp6 sl local_address remote_address st tx_queue rx_queue tr tm->when retrnsmt uid timeout inode 0: 00000000000000000000000000000000:01BD 00000000000000000000000000000000:0000 0A 00000000:00000000 00:00000000 00000000 0 0 22882 1 ffff88040de7b240 100 0 0 10 0 1: 00000000000000000000000000000000:008B 00000000000000000000000000000000:0000 0A 00000000:00000000 00:00000000 00000000 0 0 22883 1 ffff88040de7a9c0 100 0 0 10 0 2: 00000000000000000000000000000000:0050 00000000000000000000000000000000:0000 0A 00000000:00000000 00:00000000 00000000 0 0 1214363 1 ffff880077ed9340 100 0 0 10 0 3: 00000000000000000000000000000000:0016 00000000000000000000000000000000:0000 0A 00000000:00000000 00:00000000 00000000 0 0 21933 1 ffff880400a33140 100 0 0 10 0 4: 00000000000000000000000000000000:445C 00000000000000000000000000000000:0000 0A 00000000:00000000 00:00000000 00000000 1000 0 29904 1 ffff880400a32040 100 0 0 10 0 And for a process running in container I have: root@host:~# cat /proc/30518/net/tcp6 sl local_address remote_address st tx_queue rx_queue tr tm->when retrnsmt uid timeout inode 0: 0000000000000000FFFF00000100007F:1F45 00000000000000000000000000000000:0000 0A 00000000:00000000 00:00000000 00000000 0 0 1211206 1 ffff880364fcb380 100 0 0 10 0 1: 00000000000000000000000000000000:1F49 00000000000000000000000000000000:0000 0A 00000000:00000000 00:00000000 00000000 0 0 1215425 1 ffff8802befd0200 100 0 0 10 0 2: 00000000000000000000000000000000:1F90 00000000000000000000000000000000:0000 0A 00000000:00000000 00:00000000 00000000 0 0 1215421 1 ffff880077ed8240 100 0 0 10 0 So I see that there are opened ports that are not visible on host level but are visible at a container level for example 1F90 -> which is basically 8080. I'd like to ask following questions: 1. Where can I find documentation for /proc/[pid]/net/tcp|tcp6 files? All I could find was documentation about global file(i.e. /proc/net/tcp|tcp6) and there is no information about network namespaces at all (google, stackoverflow, man pages, kernel docs) 2. Could You confirm that in these files I'll see all connections that are specific for a given process even if this process is in separate network namespace? (so I dont have to enter target net/pid namespace to read their global /proc/net/tcp|tcp6 files) 3. I've grep kernel source code and tried to find where /proc/[pid]/net/tcp|tcp6 files are created but I couldn't (I've found functions for global files, maybe they are the same). I'd like to check when these files where introduced (from what kernel version they are available) and if I can confirm my findings directly from kernel sources (that I'll see connections from separate net namespace without actually entering that namespace). This is source code that I've found: http://lxr.free-electrons.com/source/net/ipv4/tcp_ipv4.c?v=4.3#L2261 But as I wrote I don't know how it is related to to files from /proc/[pid]/net/tcp|tcp6 Thank You in advance for your help. -- Regards, Darek