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Need to find the pid of the process that owns caught packet.

Is there any way to do it without long parsing /proc/net/tcp and /proc/<PID>/fd/? Maybe, need to sniff packets in another way? I have to find the fastest way to correlate the packet and its master process in C.

  • My call is "leave open", as getting information about network connections known to the OS is very much specific to the services and interfaces provided by the OS, and not a programming issue in general. Of course the question could be edited to remove the reference to the C language, but it's still going to be the natural language to use for accessing Linux system calls. (File interfaces are easy to access in other ways, of course.) – ilkkachu Mar 22 '17 at 12:34
  • @ilkkachu I am voting to migrate to Stack Overflow because the question is not “how to find this information” (on-topic on Unix & Linux) but “how to find it easily in my preferred programming language” (off-topic since it's about programming in that particular language). – Gilles Mar 22 '17 at 21:42
  • @Gilles, No, the question is "how to do it without parsing files". C is just a hint that the way of parsing output of some utilities (netstat or something like that) in bash or perl is not the answer. – marar Mar 27 '17 at 15:17
  • That's the point: you want a specific technique that's easy in a particular programming language. In a shell script, parsing a file or calling a utility would be the natural way. ilkkachu's answer is exactly what you should expect here. If you want an easier C implementation than parsing the output of netstat, you should ask on Stack Overflow. – Gilles Mar 27 '17 at 22:52
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I don't think there is any other way, /proc/net/* and /proc/*/fd/ seem to be what lsof and netstat -p read. Having a unique mapping from sockets (or tcp ports) to processes would also be impossible since multiple processes can have copies of the same socket. netstat -p seems to show only one of those, lsof of course lists all. Also, since you're starting from a packet, it might not have an originating socket at all: it could come from outside the system, or from a raw/packet socket

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