In this question, August Vrubel has some C code that sets up a tun interface and then injects a packet, but the packet seemed to disappear into the ether. In this post, I’d like to take a slightly extended look at my answer because I think it’s a great opportunity for learning a bit more about performing network diagnostics. The original code looked like this: c original sendpacket.c #include <arpa/inet.h> #include <fcntl.

After a recent upgrade of my Fedora 20 system to kernel 3.15.mumble, I started running into a problem (BZ 1121345) with my Docker containers. Operations such as su or runuser would fail with the singularly unhelpful System error message: $ docker run -ti fedora /bin/bash bash-4.2# su -c ‘uptime’ su: System error Hooking up something (like, say, socat unix-listen:/dev/log -) to /dev/log revealed that the system was logging: Jul 19 14:31:18 su: PAM audit_log_acct_message() failed: Operation not permitted Downgrading the kernel to 3.