From bef76b45f480aa41209efdec09fc6bb0bfde7cbe Mon Sep 17 00:00:00 2001 From: Laurent Bercot Date: Sat, 30 Sep 2023 05:40:04 +0000 Subject: Great Tcpserver Unification. Prepare for 2.6.0.0. Signed-off-by: Laurent Bercot --- doc/s6-tcpserverd.html | 113 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 113 insertions(+) create mode 100644 doc/s6-tcpserverd.html (limited to 'doc/s6-tcpserverd.html') diff --git a/doc/s6-tcpserverd.html b/doc/s6-tcpserverd.html new file mode 100644 index 0000000..6600a7b --- /dev/null +++ b/doc/s6-tcpserverd.html @@ -0,0 +1,113 @@ + + + + + + s6-networking: the s6-tcpserverd program + + + + + + +

+ +

The `s6-tcpserverd` program

+ +

+s6-tcpserverd is the serving part of the +s6-tcpserver super-server. +It assumes that its stdin is a bound and listening TCP/IP socket, +and it accepts connections from clients connecting to it, +spawning a program to handle each connection. +

+ +

Interface

+ +

+     s6-tcpserverd [ -1 ] [ -v verbosity ] [ -c maxconn ] [ -C localmaxconn ] prog...
+

+ +

s6-tcpserverd accepts connections from clients to an already +bound and listening TCP socket which is its standard input.
For every TCP connection to this socket, it +spawns a prog... child 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
TCPLOCALIP: set to the server socket's address
TCPLOCALPORT: set to the server socket's port
TCPREMOTEIP: set to the client socket's address
TCPREMOTEPORT: set to the client socket's port
TCPCONNNUM: set to the number of connections originating from +the same IP address

+ +

Options

+ +

-1 : write the local port, followed by newline, +to stdout, and close stdout, right before entering the client-accepting loop. +If stdout is suitably redirected, this can be used by monitoring +programs to check when the server is accepting connections. This can be +used with s6's readiness +notification mechanism to make sure subsequent services do not start +before the server is ready.
-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 16384.
-C localmaxconn : accept at most +localmaxconn connections from the same IP address. +Default is 40. It is impossible to set it higher than maxconn.

+ +

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-tcpserverd performs just the bare minimum: the point is to have a +small and very fast process to serve connections with the least +possible overhead. Features such as access control and DNS resolution +are provided via the s6-tcpserver-access +program.
s6-tcpserverd is meant to be execve'd into by a program that gets +the listening socket. That program is normally +s6-tcpserver-socketbinder, +which creates the socket itself; but it can be a different one if the +socket is to be retrieved by another means, for instance by fd-passing +from a fd-holding daemon (some people call this "socket activation").