From e0fc82203d677a6f1e808e9a1a46176c109d89be Mon Sep 17 00:00:00 2001 From: Laurent Bercot Date: Mon, 15 Dec 2014 23:08:59 +0000 Subject: Initial commit --- doc/s6-tcpserver4.html | 123 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 123 insertions(+) create mode 100644 doc/s6-tcpserver4.html (limited to 'doc/s6-tcpserver4.html') diff --git a/doc/s6-tcpserver4.html b/doc/s6-tcpserver4.html new file mode 100644 index 0000000..e0270e0 --- /dev/null +++ b/doc/s6-tcpserver4.html @@ -0,0 +1,123 @@ + + + + + s6-networking: the s6-tcpserver4 program + + + + + + +

+ +

The `s6-tcpserver4` program

+ +

+s6-tcpserver4 is a super-server for IPv4 TCP +connections. It accepts connections from clients, and forks a +program to handle each connection. +

+ +

Interface

+ +

+     s6-tcpserver4 [ -1 ] [ -v verbosity ] [ -c maxconn ] [ -C localmaxconn ] [ -b backlog ] [ -G gidlist ] [ -g gid ] [ -u uid ] [ -U ] ip port prog...
+

+ +

s6-tcpserver4 binds to local IPv4 address ip, +port port.
It closes its stdin and stdout.
For every TCP connection to this address and port, it +forks. The child sets some environment variables, then +executes prog... with stdin reading from the network +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.

+ +

Environment variables

+ +

+ For each connection, an instance of prog... is spawned with +the following variables set: +

+ +

PROTO: always set to TCP
TCPREMOTEIP: set to the originating address
TCPREMOTEPORT: set to the originating port
TCPCONNNUM: set to the number of connections originating from +the same IP address

+ +

Options

+ +

-1 : write port to stdout, before +closing it, right after binding and listening to the network socket. +If stdout is suitably redirected, this can be used by monitoring +programs to check when the server is ready to accept connections.
-v verbosity : be more or less verbose. +By default, verbosity is 1: print warning messages to stderr. +0 means only print fatal error messages ; 2 means print status and +connection information for every client.
-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 IP address. +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-tcpserver4'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-tcpserver4's groupid +to gid after binding the socket. This is only valid when run +as root.
-u uid : change s6-tcpserver4's userid +to uid after binding the socket. This is only valid when run +as root.
-U : change s6-tcpserver4'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.

+ +

Signals

+ +

SIGTERM: exit.
SIGHUP: send a SIGTERM and a SIGCONT to all children.
SIGQUIT: send a SIGTERM and a SIGCONT to all children, then exit.
SIGABRT: send a SIGKILL to all children, then exit.

+ +

Notes

+ +

Unlike its ancestor +tcpserver, +s6-tcpserver4 performs just the bare minimum: the point is to have a +very small and very fast process to serve connections with the least +possible overhead. Features such as additional environment variables, +access control and DNS resolution are provided +via the s6-tcpserver-access +program.