Module Linux_ext

sendfile ?pos ?len ~fd sock sends mmap-able data from file descriptor fd to socket sock using offset pos and length len. Returns the number of characters actually written.

NOTE: If the returned value is unequal to what was requested (= the initial size of the data by default), the system call may have been interrupted by a signal, the source file may have been truncated during operation, or a timeout may have occurred on the socket during sending. It is currently impossible to find out which of these events actually happened. Calling sendfile several times on the same descriptor that only partially accepted data due to a timeout will eventually lead to the Unix error EAGAIN.

Raises Unix_error on Unix-errors.

Type for status of SO_BINDTODEVICE socket option. The socket may either restrict the traffic to a given (by name, e.g. "eth0") interface, or do no restriction at all.

gettcpopt_bool sock opt Returns the current value of the boolean TCP socket option opt for socket sock.

settcpopt_bool sock opt v sets the current value of the boolean TCP socket option opt for socket sock to value v.

gettcpopt_string sock opt Returns the current value of the string TCP socket option opt for socket sock.

settcpopt_string sock opt v sets the current value of the string TCP socket option opt for socket sock to value v.

send_nonblocking_no_sigpipe sock ?pos ?len buf tries to do a nonblocking send on socket sock given buffer buf, offset pos and length len. Prevents SIGPIPE, i.e., raises a Unix-error in that case immediately. Returns Some bytes_written or None if the operation would have blocked.

Raises Invalid_argument if the designated buffer range is invalid. Raises Unix_error on Unix-errors.

send_no_sigpipe sock ?pos ?len buf tries to do a blocking send on socket sock given buffer buf, offset pos and length len. Prevents SIGPIPE, i.e., raises a Unix-error in that case immediately. Returns the number of bytes written.

Raises Invalid_argument if the designated buffer range is invalid. Raises Unix_error on Unix-errors.

sendmsg_nonblocking_no_sigpipe sock ?count iovecs tries to do a nonblocking send on socket sock using count I/O-vectors iovecs. Prevents SIGPIPE, i.e., raises a Unix-error in that case immediately. Returns Some bytes_written or None if the operation would have blocked.

Raises Invalid_argument if the designated ranges are invalid. Raises Unix_error on Unix-errors.

peer_credential fd takes a file descriptor of a unix socket. It returns the pid and real ids of the process on the other side, as described in man 7 socket entry for SO_PEERCRED. This is useful in particular in the presence of pid namespace, as the returned pid will be a pid in the current namespace, not the namespace of the other process.

Raises Unix_error if something goes wrong (file descriptor doesn't satisfy the conditions above, no process on the other side of the socket, etc.).

pr_set_pdeathsig s sets the signal s to be sent to the executing process when its parent dies. NOTE: the parent may have died before or while executing this system call. To make sure that you do not miss this event, you should call getppid to get the parent process id after this system call. If the parent has died, the returned parent PID will be 1, i.e., the init process will have adopted the child. You should then either send the signal to yourself using Unix.kill, or execute an appropriate handler.

pr_get_pdeathsig () gets the signal that will be sent to the currently executing process when its parent dies.

pr_set_name_first16 name sets the name of the executing thread to name. Only the first 16 bytes in name will be used; the rest is ignored.

pr_get_name () gets the name of the executing thread. The name is at most 16 bytes long.

file_descr_realpath fd returns the canonicalized absolute pathname of the file associated with file descriptor fd.

Raises Unix_error on errors.

out_channel_realpath oc returns the canonicalized absolute pathname of the file associated with output channel oc.

Raises Unix_error on errors.

in_channel_realpath ic returns the canonicalized absolute pathname of the file associated with input channel ic.

Raises Unix_error on errors.

Setting the CPU affinity causes a thread to only run on the cores chosen. You can find out how many cores a system has in /proc/cpuinfo. This can be useful in two ways: first, it limits a process to a core so that it won't interfere with processes on other cores. Second, you save time by not moving the process back and forth between CPUs, which sometimes invalidates their cache.

See man sched_setaffinity for details.

Note, in particular, that affinity is a "per-thread attribute that can be adjusted independently for each of the threads in a thread group", and so omitting ~pid (or specifying ?pid as None) "will set the attribute for the calling thread", and "passing the value returned from a call to getpid will set the attribute for the main thread of the thread group". (A thread group is what you might think of as a process.)

sched_setaffinity_this_thread is equivalent to sched_setaffinity ?pid:None, though happens to be implemented by using gettid rather than passing pid=0 to sched_setaffinity. It exists for historical reasons, and may be removed in the future.

cores () returns the number of cores on the machine. This may be different than the number of cores available to the calling process.

Parse a kernel %*pbl-format CPU list (e.g. 1,2,3,10-15) into an int list.

isolated_cpus () returns the list of cores marked as isolated.

online_cpus () returns the list of cores online for scheduling.

allowed_cpus ?include_offline ?pid () returns the list of cores allowed for scheduling for this particular PID. If no PID is specified, this checks the current PID. By default, this function automatically filters the returned list of cores to only include online cores. Set include_offline to true to also return CPU cores that the kernel is reporting as allowed, but are currently offline.

cpus_local_to_nic ~ifname returns the list of cores NUMA-local to ifname.

get_terminal_size term returns (rows, cols), the number of rows and columns of the controlling terminal (raises if no controlling terminal), or of the specified file descriptor (useful when writing to stdout, because stdout doesn't have to be the controlling terminal).

Priority.t is what is usually referred to as the "nice" value of a process. It is also known as the "dynamic" priority. It is used with normal (as opposed to real-time) processes that have static priority zero. See Unix.Scheduler.set for setting the static priority.

Set the thread's priority in the Linux scheduler. Omitting the pid argument means that (only) the calling thread will be affected.

Get the thread's priority in the Linux scheduler. Omitting the pid argument means that the calling thread's priority will be retrieved.

get_ipv4_address_for_interface "eth0" returns the IP address assigned to eth0, or throws an exception if no IP address is configured.

get_mac_address returns the mac address of ifname in the canonical form, e.g. "aa:bb:cc:12:34:56".

bind_to_interface fd (Only "eth0") restricts packets from being received/sent on the given file descriptor fd on any interface other than "eth0". Use bind_to_interface fd Any to allow traffic on any interface. The bindings are not cumulative; you may only select one interface, or Any.

Not to be confused with a traditional BSD sockets API bind() call, this Linux-specific socket option (SO_BINDTODEVICE) is used for applications on multi-homed machines with specific security concerns. For similar functionality when using multicast, see Core_unix.mcast_set_ifname.

Set the user identity used for filesystem checks for this thread. Returns the previous user identity.

No error indications are returned even if the call fails. To check if it was successful, you can call getfsuid to check if the fsuid actually updated.

Set the group identity used for filesystem checks for this thread. Returns the previous group identity.

No error indications are returned even if the call fails. To check if it was successful, you can call getfsgid to check if the fsgid actually updated.

Get the user identity used for filesystem checks. This is a wrapper around setfsuid ~fsuid:(-1)

Get the group identity used for filesystem checks. This is a wrapper around setfsgid ~fsgid:(-1)

Extended attributes are name:value pairs associated with inodes (files, directories, symlinks, etc). They are extensions to the normal attributes which are associated with all inodes in the system (i.e. the 'man 2 stat' data). A complete overview of extended attributes concepts can be found in 'man 5 attr'.