Doing exec() to a new process but keeping the file descriptors relies on none of the file descriptors having the CLOEXEC (close-on-exec) flag. This flag is, I

Doing exec() to a new process but keeping the file descriptors relies on none of the file descriptors having the CLOEXEC (close-on-exec) flag. This flag is, IIUC, considered best practice for all file descriptors now, and in Python, all file descriptors are now by default created “non-inheritable” (i.e. with the CLOEXEC flag). A working model would instead be to create one inheritable file descriptor, do the fork() (and exec the new process in the child), and then sendmsg() all the normal file descriptors to the new process.