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#!/bin/rc
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# Serve Unix u9fs over SSH
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#
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# Basically, try each of the following until you find one that works:
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#
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# srvssh unix
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# srvssh -r unix
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# srvssh -R unix
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# srvssh -r -s unix
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# srvssh -R -s unix
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#
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# and then never look back. Note that "srvssh unix" should always
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# work. It's just that if you're talking with certain sshd's, you'll get
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# hit by Nagle's algorithm and need to explore the other flags.
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# When using ssh to start u9fs, the only way to turn off
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# Nagle's algorithm (which kills the performance of RPC-based
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# protocols like 9P) is to allocate a pseudo-terminal. The
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# command ssh -Rmp attempts to allocate a pseudo-terminal and
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# then put it in a transparent mode. Especially when
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# connected to older SSH daemons, the connection ends up not
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# quite transparent. To get around this, we explicity set the tty
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# mode on the command line as well. The hope is that -Rmp makes
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# the connection transparent enough for the Tversion, and the stty
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# command will do the rest. If -Rmp doesn't make the connection
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# transparent enough for the Tversion (but the stty commands do
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# make the connection fully transparent) then add "-s 5" to the srv
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# command to tell it to wait 5 seconds before sending the Tversion.
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# That should be enough time for the stty to take effect.
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rfork e
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fn usage {
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echo 'usage: srvssh [-R] [-r] [-s] [-u u9fspath] system [srvname [mtpt]]' >[1=2]
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exit usage
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}
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rawhack=''
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sleephack=()
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u9fspath=u9fs
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rawflags=''
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while(~ $1 -*){
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switch($1){
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case -r
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rawflags='-Rmp'
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shift
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case -R
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rawflags='-Rmp'
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rawhack=('stty raw -echo '';''')
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shift
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case -s
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sleephack=(-s 5)
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shift
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case -u
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shift
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u9fspath=$1
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shift
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case -u*
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u9fspath=`{echo $1 | sed s/-u//}
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shift
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case *
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usage
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}
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}
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if(! ~ $#* 1 2 3)
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usage
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switch($#*){
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case 1
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srv=$1
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mtpt=/n/$1
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case 2
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srv=$2
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mtpt=/n/$1
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case 3
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srv=$2
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mtpt=$3
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}
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x=(srv $sleephack -e \
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'ssh '$rawflags' '$1' '$rawhack' '$u9fspath' -na none -u ''$''USER -l ''$''HOME/u9fs.log' \
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$srv $mtpt)
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$x
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# Sometimes /srv/whatever can be a closed pipe, in which case
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# srv will have been killed for writing to it, without a chance to
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# defend itself. Rerun it in this case.
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ss=$status
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if(~ $ss *'write on closed pipe'*){
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rm -f /srv/$srv
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$x
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ss=$status
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}
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if(! ~ $ss '')
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echo srvssh: $ss >[1=2]
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exit $ss
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