From 416ef5e2bf59bb2e45066a1d5d91ac677c0f48e5 Mon Sep 17 00:00:00 2001 From: Laurent Bercot Date: Wed, 10 Dec 2014 03:05:47 +0000 Subject: Initial commit --- doc/skadns/skadnsd.html | 120 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 120 insertions(+) create mode 100644 doc/skadns/skadnsd.html (limited to 'doc/skadns/skadnsd.html') diff --git a/doc/skadns/skadnsd.html b/doc/skadns/skadnsd.html new file mode 100644 index 0000000..e8316b8 --- /dev/null +++ b/doc/skadns/skadnsd.html @@ -0,0 +1,120 @@ + + + + + s6-dns: the skadnsd internal program + + + + + + +libskadns
+s6-dns
+Software
+skarnet.org

+ +

The skadnsd program

+ +

+skadnsd is the skadns daemon. It reads a series of +queries from the client on stdin, resolves them asynchronously, +and writes +the answers to the client as soon as it gets them. It exits 0 +when its stdin closes. It exits 111 on any serious error, +writing the error message to stderr. +

+ +

+skadnsd is a stub resolver. It reads /etc/resolv.conf +at start looking for a "nameserver" line containing +the address of a DNS cache (aka full resolver). It will exit 111 if it cannot +find any valid cache address in /etc/resolv.conf. If the +DNSCACHEIP environment variable is set, its value overrides +what /etc/resolv.conf says. +

+ +

Interface

+ +

+skadnsd does not fork, does not background itself automatically, +and does not use syslog. It is not meant to be run directly by the +user: it will be invoked and spawned by the skadns library calls. +

+ +

+ There are 2 ways to use skadnsd: +

+
    +
  1. (preferred) Use the skadns_startf() library call. +A skadnsd child will then be spawned from your +calling process, and automatically reaped when you call +skadns_end(). It requires care with applications that +trap SIGCHLD.
    2. +
  2. Use the skadns_start() library call, together with +a skadnsd service.
    3. +
+ +

Running skadnsd as a child process

+ +

+ This is the simplest and safest way of using skadns. Forget +about skadnsd: just start your library calls with +skadns_startf() and end them with skadns_end(). +Be careful though: if you're using SIGCHLD handlers, make sure they do +not interfere with the child processes your application has without +knowing. This is a general Unix programming rule. +

+ +

Running a skadnsd as a daemon: the skadnsd service

+ +

+ In this mode, you set up a daemon listening on a Unix domain socket, +and clients connect to this socket to access the service. The +advantage of this setup is that it works even with badly written +clients that have trouble handling a child process; the drawback is +that it requires support from the system administrator. +

+ +

+skadnsd has no "standalone" mode: it is designed to work with a Unix +domain superserver, like +s6-ipcserver. +skadnsd follows the UCSPI" +interface, it can be directly executed from the superserver. +

+ +

+You should run skadnsd (and its Unix superserver) under a specific user +and group, for elementary security reasons; and you should run its +dedicated logger as another specific user. Do NOT run skadnsd as root; +check your super-server documentation to find how +to run it under a specific account. +

+ +

Notes

+ + + + + -- cgit v1.2.3