I am writing an application that does packet sniffing using a Pcap library. For that to work, I need to give the java binary network sniffing capabilities to avoid having to run it as root:
sudo setcap cap_net_raw,cap_net_admin=eip /path/to/bin/java
When I run any program, every few seconds, I get a Full Thread Dump to stdout. Here is an example of such a full thread dump (the rest of the repo is irrelevant). The program otherwise seems to run successfully: except for the dump, I couldn't find a difference in the execution.
The code below is sufficient to reproduce the issue:
package main;
import java.io.IOException;
public class StdinTest {
public static void main(String[] args) throws IOException {
System.in.read();
}
}
When I remove the capabilities from the java binary with the command below, things go back to normal and I no longer get the Full Thread Dumps to stdout.
sudo setcap -r /path/to/bin/java
I'm not sure it's a problem since the program seems to run fine, but it doesn't look normal.
I haven't found anyone who seems to have a similar issue, I'm a bit lost...
Any help is appreciated, thanks in advance!
Details:
- OS: reproduced on ArchLinux (kernel 5.12.9) & Ubuntu 20.04 (kernel 5.8.0)
- JDK: reproduced on Adopt OpenJDK 11, 15 & 16, openjdk.java.net 15 & 16.
EDIT:
Not reproduceable if the program is ran in command line:
java -classpath target/classes main.StdinTest
I only get the symptoms when starting it from IntelliJ Idea Ultimate. I haven't tried with other IDEs.