From 87c5b2118efcee65eeda3f743d081ea9c2b866d9 Mon Sep 17 00:00:00 2001 From: Laurent Bercot Date: Thu, 15 Jan 2015 20:14:44 +0000 Subject: Move Unix domain utilities and access control utilites, as well as the accessrules library, from s6-networking to here --- doc/s6-ipcserver.html | 173 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 173 insertions(+) create mode 100644 doc/s6-ipcserver.html (limited to 'doc/s6-ipcserver.html') diff --git a/doc/s6-ipcserver.html b/doc/s6-ipcserver.html new file mode 100644 index 0000000..855fe4b --- /dev/null +++ b/doc/s6-ipcserver.html @@ -0,0 +1,173 @@ + + + + + s6: the s6-ipcserver program + + + + + + +

+s6
+Software
+skarnet.org +

+ +

The `s6-ipcserver` program

+ +

+s6-ipcserver is an +UCSPI server tool for +Unix domain sockets, i.e. a super-server. +It accepts connections from clients, and forks a +program to handle each connection. +

+ +

Interface

+ +

+     s6-ipcserver [ -1 ] [ -q | -Q | -v ] [ -d | -D ] [ -P | -p ] [ -c maxconn ] [ -C localmaxconn ] [ -b backlog ] [ -G gidlist ] [ -g gid ] [ -u uid ] [ -U ] path prog...
+

+ +

s6-ipcserver binds a Unix domain socket to path.
It can drop its root privileges.
It closes its stdin and stdout.
For every client connection to this socket, it +forks. The child sets some environment variables, then +executes prog... with stdin reading from the socket and +stdout writing to it.
Depending on the verbosity level, it logs what it does to stderr.
It runs until killed by a signal. Depending on the received +signal, it may kill its children before exiting.
s6-ipcserver actually doesn't do any of this itself. It is +a wrapper, rewriting the command line and executing into a chain +of programs that perform those duties.

+ +

Implementation

+ +

s6-ipcserver parses the options and arguments it is given, and +builds a new command line with them. It then executes into that new +command line.
The first program s6-ipcserver executes into is +s6-ipcserver-socketbinder. +It will create and bind a Unix domain socket to path, then +execute into the rest of the command line.
If a privilege-dropping operation has been requested, the +program that s6-ipcserver-socketbinder executes into is +s6-applyuidgid. +It will drop the root privileges, then execute into the rest of the +command line.
The next program in the chain is +s6-ipcserverd. It is executed into +by s6-applyuidgid, or directly by s6-ipcserver-socketbinder if no +privilege-dropping operation has been requested. s6-ipcserverd is +the long-lived process, the "daemon" itself, accepting connections +from clients.
For every client, s6-ipcserverd will spawn an instance of +prog..., the remainder of the command line.

+ + +

Options

+ +

-1 : write path, followed by a newline, +to stdout, before +closing it, right after binding and listening to the Unix socket. +If stdout is suitably redirected, this can be used by monitoring +programs to check when the server is ready to accept connections.
-q : be quiet.
-Q : be normally verbose. This is the default.
-v : be verbose.
-d : allow instant rebinding to the same path +even if it has been used not long ago - this is the SO_REUSEADDR flag to +setsockopt() +and is generally used with server programs. This is the default. Note that +path will be deleted if it already exists at program start time.
-D : disallow instant rebinding to the same path.
-P : disable client credentials lookups. The +IPCREMOTEEUID and IPCREMOTEEGID environment variables will be unset +in every instance of prog.... This is the portable option, +because not every system supports credential lookup across Unix domain +sockets; but it is not as secure.
-p : enable client credentials lookups. This +is the default; it works at least on Linux, Solaris, and +*BSD systems. On systems that do not support it, every connection +attempt will fail with a warning message.
-c maxconn : accept at most +maxconn concurrent connections. Default is 40. It is +impossible to set it higher than 1000.
-C localmaxconn : accept at most +localmaxconn connections from the same user ID. +Default is 40. It is impossible to set it higher than maxconn.
-b backlog : set a maximum of +backlog backlog connections on the socket. Extra +connection attempts will rejected by the kernel.
-G gidlist : change s6-ipcserver's +supplementary group list to gidlist after binding the socket. +This is only valid when run as root. gidlist must be a +comma-separated list of numerical group IDs.
-g gid : change s6-ipcserver's groupid +to gid after binding the socket. This is only valid when run +as root.
-u uid : change s6-ipcserver's userid +to uid after binding the socket. This is only valid when run +as root.
-U : change s6-ipcserver's user id, group id and +supplementary group list +according to the values of the UID, GID and GIDLIST environment variables +after binding the socket. This is only valid when run as root. +This can be used with the +s6-envuidgid +program to easily script a service that binds to a privileged socket +then drops its privileges to those of a named non-root account.

+ +

Implementation

+ +

s6-ipcserver parses the options and arguments it is given, and +builds a new command line with them. It then executes into that new +command line.
The first program s6-ipcserver executes into is +s6-ipcserver-socketbinder. +It will create and bind a Unix domain socket to path, then +execute into the rest of the command line.
If a privilege-dropping operation has been requested, the +program that s6-ipcserver-socketbinder executes into is +s6-applyuidgid. +It will drop the root privileges, then execute into the rest of the +command line.
The next program in the chain is +s6-ipcserverd. It is executed into +by s6-applyuidgid, or directly by s6-ipcserver-socketbinder if no +privilege-dropping operation has been requested. s6-ipcserverd is +the long-lived process, the "daemon" itself, accepting connections +from clients.
For every client, s6-ipcserverd will spawn an instance of +prog..., the remainder of the command line.

+ +

Notes

+ +

s6-ipcserver does not interpret its options itself. It just +dispatches them to the appropriate program on the command line that +it builds.
Previous versions of s6-ipcserver were +monolithic: it did the work of s6-ipcserver-socketbinder, +s6-applyuidgid and s6-ipcserverd itself. The functionality has now +been split into several different programs because some service startup +schemes require the daemon to get its socket from an external +program instead of creating and binding it itself. The most obvious +application of this is upgrading a long-lived process without +losing existing connections.

+ + + -- cgit v1.3.1

The s6-ipcserver program

Interface

Implementation

Options

Implementation

Notes

The `s6-ipcserver` program