X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~mdw/git/tripe/blobdiff_plain/b9066fbb5c1c160eb305a33a3335b77d17e0f502..0e6502d3341dd870293dacc1aafea005c6dadf0d:/doc/tripe.8

diff --git a/doc/tripe.8 b/doc/tripe.8
index bcfdcbb4..40a5b657 100644
--- a/doc/tripe.8
+++ b/doc/tripe.8
@@ -41,6 +41,8 @@ tripe \- a simple VPN daemon
 .IR addr ]
 .RB [ \-p
 .IR port ]
+.RB [ \-n
+.IR tunnel ]
 .br
 	
 .RB [ \-U
@@ -148,9 +150,9 @@ version number to standard output and exits with status 0.
 .B "\-u, \-\-usage"
 Writes a brief usage summary to standard output and exits with status 0.
 .TP
-.B "\-\-tunnel"
-Writes a string to standard output describing the configured tunnelling
-method and exits with status 0.  This is intended for the use of the
+.B "\-\-tunnels"
+Writes to standard output a list of the configured tunnel drivers, one
+per line, and exits with status 0.  This is intended for the use of the
 start-up script, so that it can check that it will actually work.
 .TP
 .B "\-D, \-\-daemon"
@@ -185,6 +187,9 @@ to tunnel through the VPN.
 Use the specified UDP port for all communications with peers, rather
 than an arbitarary kernel-assigned port.
 .TP
+.BI "\-n, \-\-tunnel=" tunnel
+Use the specified tunnel driver for new peers by default.
+.TP
 .BI "\-U, \-\-setuid=" user
 Set uid to that of
 .I user
@@ -482,25 +487,54 @@ Though not for the faint of heart, it is possible to get
 .B tripe
 to read and write network packets to a pair of file descriptors using
 SLIP encapsulation.  No fancy header compression of any kind is
-supported.  The intended use is that you allocate a pty pair, set the
-slave's line discipline to SLIP, and hand the
+supported.
+.PP
+Two usage modes are supported: a preallocation system, whereby SLIP
+interfaces are created and passed to the
 .B tripe
-server the master end, though in fact any old file descriptors will do.
+server at startup; and a dynamic system, where the server runs a script
+to allocate a new SLIP interface when it needs one.  It is possible to
+use a mixture of these two modes, starting
+.B tripe
+with a few preallocated interfaces and having it allocate more
+dynamically as it needs them.
 .PP
-The SLIP descriptors must be set up and running before the daemon is
-started, and you must inform it about the SLIP descriptors it's meant to
-use in an environment variable
-.BR TRIPE_SLIPIF ,
-whose value must be a colon-separated list of items of the form
+The behaviour of
+.BR tripe 's
+SLIP driver is controlled by the
+.B TRIPE_SLIPIF
+environment variable.  The server will fail to start if this variable is
+not defined.  The variable's value is a colon-delimited list of
+preallocated interfaces, followed optionally by the filename of a script
+to run to dynamically allocate more interfaces.
+.PP
+A static allocation entry has the form
 .IR infd [ \c
 .BI , outfd \c
 .RB ] \c
 .BI = \c
-.IR ifname .
+.IR ifname ,
 If the
 .I outfd
 is omitted, the same file descriptor is used for input and output.
 .PP
+The dynamic allocation script must be named by an absolute or relative
+pathname, beginning with 
+.RB ` / '
+or
+.RB ` . '.
+The server will pass the script an argument, which is the name of the
+peer for which the interface is being created.  The script should
+allocate a new SLIP interface (presumably by creating a pty pair),
+configure it appropriately, and write the interface's name to its
+standard output, followed by a newline.  It should then read and write
+SLIP packets on its stdin and stdout.  The script's stdin will be closed
+when the interface is no longer needed, and the server will attempt to
+send it a
+.B SIGTERM
+signal (though this may fail if the script runs with higher privileges
+than the server).
+.PP
 The output file descriptor should not block unless it really needs to:
 the
 .B tripe
@@ -523,4 +557,4 @@ find one, please inform the author
 .IR "The Trivial IP Encryption Protocol" ,
 .IR "The Wrestlers Protocol" .
 .SH "AUTHOR"
-Mark Wooding, <mdw@nsict.org>
+Mark Wooding, <mdw@distorted.org.uk>