Re: automatic compression over communication channel ?
From: Pascal Bourguignon (spam_at_thalassa.informatimago.com)
Date: 01/29/04
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- In reply to: Vu Pham: "automatic compression over communication channel ?"
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Date: 29 Jan 2004 21:10:37 +0100
"Vu Pham" <vu@sivell.com> writes:
> I am sorry if this question is not appropriate for this forum.
>
> In my client/server app, I compress the data at one end and the other will
> decompress it. To do this, I must implement the zlib api at the
> "application" level : I know in advance how long this transaction will be,
> then I compress it, add a flag and some parameters to notify the other end
> about this compression ...For apps that currently do not have the
> compression, I need to change a lot of codes..
>
> I wonder if there is any way I can implement the compression at a lower
> level - somewhere below my application level and above the tcp level - so
> that I just need to call, say zsend() or zrecv() and these functions will do
> the compression/decompression. stuff.
An easy way to add compression is to use a ppp/ssh tunnel.
To establish such a ppp/ssh tunnel you may use a script including this:
(Edit it to inhib encryption and tune the compression level to fit your needs).
REMOTE_HOST=example.com
REMOTE_USER=example
LOCAL_USER=example
# proxyarp Does not work.
COMMON_OPT="
local
nocrtscts
asyncmap 0
bsdcomp 12,12
nodeflate
noauth
noipdefault
proxyarp ktune
"
CALLER_OPT="
persist
defaultroute
"
PROTO_OPT="
lcp-echo-failure 4
lcp-echo-interval 45
lcp-max-configure 20
lcp-max-failure 10
lcp-max-terminate 3
lcp-restart 3
ipcp-accept-local
ipcp-accept-remote
ipcp-max-configure 10
ipcp-max-failure 10
ipcp-max-terminate 3
ipcp-restart 3
"
PPP_OPTIONS="$COMMON_OPT $CALLER_OPT $PROTO_OPT"
SSH_OPTIONS=$( echo "ssh $SSH_DEBUG -2 -t -x -a -q -C \
-i ~${LOCAL_USER}/.ssh/id_dsa \
-e none \
-o 'CompressionLevel 2' \
-o 'Batchmode yes' \
-c blowfish \
-l ${REMOTE_USER} ${REMOTE_HOST}" | sed -e 's/ */ /g' )
pppd $PPP_DEBUG $PPP_OPTIONS connect-delay 20000 pty "$SSH_OPTIONS"
On the remote host, you must set the REMOTE_USER account such:
example:x:0:1600:VPN:/home/example:/local/sbin/vpn-example
with the vpn-example program:
---(pppsh.c)------------------------------------------------------------
/******************************************************************************
FILE: pppsh.c
LANGUAGE: ANSI-C
SYSTEM: UNIX
USER-INTERFACE: None.
DESCRIPTION
This program encapsulate pppd passing it a compiled-in option file
argument.
USAGE
Compile with -DPPP_OPTION_FILE=\"/etc/ppp/peers/NAME\" \
-o /usr/local/sbin/ppp-NAME
Add an entry in /etc/passwd :
NAME:password:uid:gid:PPP for NAME:/home/NAME:/usr/local/sbin/ppp-NAME
AUTHORS
<PJB> Pascal J. Bourguignon
MODIFICATIONS
2001-12-19 <PJB> Creation.
BUGS
LEGAL
GPL
Copyright Pascal J. Bourguignon 2001 - 2001
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License as
published by the Free Software Foundation; either version 2 of the
License, or (at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; see the file COPYING; if not, write to
the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
Boston, MA 02111-1307 USA
******************************************************************************/
#include <sysexits.h>
#include <unistd.h>
static const char rcsid[]="$Id$";
#ifndef PPPD
#define PPPD "/usr/sbin/pppd"
#endif
#ifndef PPP_OPTION_FILE
#error "Please define PPP_OPTION_FILE"
#endif
int main(int argc,char** argv)
{
char** environment[]={0};
execle(PPPD,PPPD,"file",PPP_OPTION_FILE,0,environment);
perror("pppsh");
exit(EX_OSFILE);
return(EX_OSFILE);
}/*main*/
----(makefile)----------------------------------------------------------
all:
@[ `hostname -s` = host1 ] && localip=192.168.0.1 ./make-peers || true
@[ `hostname -s` = host2 ] && localip=192.168.0.2 ./make-peers || true
users:
./make-users
install:all
@[ `hostname -s` = host1 ] && localip=192.168.0.1 ./make-peers install || true
@[ `hostname -s` = host2 ] && localip=192.168.0.2 ./make-peers install || true
clean:
rm -f vpn-* *.o *~
---(make-peers)---------------------------------------------------------
#!/bin/bash
install=0
for arg ; do
case "$arg" in
install|--install|-i) install=1 ;;
*) ;;
esac
done
PPPD=/usr/sbin/pppd
for ip_peer in \
192.168.0.1-host1 \
192.168.0.2-host2 \
do
remoteip=${ip_peer/-*}
peer=${ip_peer/*-}
PPP_OPTION_FILE=/etc/ppp/peers/vpn-${peer}
if [ "$remoteip" = "$localip" ] ; then
continue
fi
if [ $install -eq 0 ] ; then
echo "Generating VPN link from $localip to $remoteip ($peer)."
cat > vpn-${peer}.ppp <<EOF
ipparam vpn-${peer}
${localip}:${remoteip}
netmask 255.255.255.255
proxyarp
noauth
asyncmap 0
nocrtscts
passive
local
bsdcomp 12,12
deflate 12,12
lcp-echo-interval 15
lcp-echo-failure 8
EOF
gcc \
-o vpn-${peer} pppsh.c \
-DPPP_OPTION_FILE=\"${PPP_OPTION_FILE}\" \
-DPPPD=\"${PPPD}\"
else
echo "Installing VPN link to $remoteip ($peer)."
install -g vpnusers -m 644 vpn-${peer}.ppp ${PPP_OPTION_FILE}
install -g vpnusers -m 750 vpn-${peer} /local/sbin/vpn-${peer}
fi
done
---(/etc/ppp/ip-up.local)-----------------------------------------------
#!/bin/bash
BASENAME=${0##*/}
INTERFACE=$1
DEVICE=$2
SPEED=$3
LOCALIP=$4
REMOTEIP=$5
echo "$@" >> /tmp/ip-up.local.log
case "$INTERFACE" in
ppp*)
route add -net 195.114.85.128/25 metric 3 "$INTERFACE"
route add -net 10.0.0.0/8 metric 3 "$INTERFACE"
;;
esac
------------------------------------------------------------------------
-- __Pascal_Bourguignon__ http://www.informatimago.com/ There is no worse tyranny than to force a man to pay for what he doesn't want merely because you think it would be good for him.--Robert Heinlein http://www.theadvocates.org/
- Next message: Michael B Allen: "Re: linux shared memory synchronization objects"
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- In reply to: Vu Pham: "automatic compression over communication channel ?"
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