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# -*- test-case-name: twisted.conch.test.test_channel -*-
# Copyright (c) 2001-2008 Twisted Matrix Laboratories.
# See LICENSE for details.
#
"""
The parent class for all the SSH Channels. Currently implemented channels
are session. direct-tcp, and forwarded-tcp.
Maintainer: Paul Swartz
"""
from twisted.python import log
from twisted.internet import interfaces
from zope.interface import implements
class SSHChannel(log.Logger):
"""
A class that represents a multiplexed channel over an SSH connection.
The channel has a local window which is the maximum amount of data it will
receive, and a remote which is the maximum amount of data the remote side
will accept. There is also a maximum packet size for any individual data
packet going each way.
@ivar name: the name of the channel.
@type name: C{str}
@ivar localWindowSize: the maximum size of the local window in bytes.
@type localWindowSize: C{int}
@ivar localWindowLeft: how many bytes are left in the local window.
@type localWindowLeft: C{int}
@ivar localMaxPacket: the maximum size of packet we will accept in bytes.
@type localMaxPacket: C{int}
@ivar remoteWindowLeft: how many bytes are left in the remote window.
@type remoteWindowLeft: C{int}
@ivar remoteMaxPacket: the maximum size of a packet the remote side will
accept in bytes.
@type remoteMaxPacket: C{int}
@ivar conn: the connection this channel is multiplexed through.
@type conn: L{SSHConnection}
@ivar data: any data to send to the other size when the channel is
requested.
@type data: C{str}
@ivar avatar: an avatar for the logged-in user (if a server channel)
@ivar localClosed: True if we aren't accepting more data.
@type localClosed: C{bool}
@ivar remoteClosed: True if the other size isn't accepting more data.
@type remoteClosed: C{bool}
"""
implements(interfaces.ITransport)
name = None # only needed for client channels
def __init__(self, localWindow = 0, localMaxPacket = 0,
remoteWindow = 0, remoteMaxPacket = 0,
conn = None, data=None, avatar = None):
self.localWindowSize = localWindow or 131072
self.localWindowLeft = self.localWindowSize
self.localMaxPacket = localMaxPacket or 32768
self.remoteWindowLeft = remoteWindow
self.remoteMaxPacket = remoteMaxPacket
self.areWriting = 1
self.conn = conn
self.data = data
self.avatar = avatar
self.specificData = ''
self.buf = ''
self.extBuf = []
self.closing = 0
self.localClosed = 0
self.remoteClosed = 0
self.id = None # gets set later by SSHConnection
def __str__(self):
return '<SSHChannel %s (lw %i rw %i)>' % (self.name,
self.localWindowLeft, self.remoteWindowLeft)
def logPrefix(self):
id = (self.id is not None and str(self.id)) or "unknown"
return "SSHChannel %s (%s) on %s" % (self.name, id,
self.conn.logPrefix())
def channelOpen(self, specificData):
"""
Called when the channel is opened. specificData is any data that the
other side sent us when opening the channel.
@type specificData: C{str}
"""
log.msg('channel open')
def openFailed(self, reason):
"""
Called when the the open failed for some reason.
reason.desc is a string descrption, reason.code the the SSH error code.
@type reason: L{error.ConchError}
"""
log.msg('other side refused open\nreason: %s'% reason)
def addWindowBytes(self, bytes):
"""
Called when bytes are added to the remote window. By default it clears
the data buffers.
@type bytes: C{int}
"""
self.remoteWindowLeft = self.remoteWindowLeft+bytes
if not self.areWriting and not self.closing:
self.areWriting = True
self.startWriting()
if self.buf:
b = self.buf
self.buf = ''
self.write(b)
if self.extBuf:
b = self.extBuf
self.extBuf = []
for (type, data) in b:
self.writeExtended(type, data)
def requestReceived(self, requestType, data):
"""
Called when a request is sent to this channel. By default it delegates
to self.request_<requestType>.
If this function returns true, the request succeeded, otherwise it
failed.
@type requestType: C{str}
@type data: C{str}
@rtype: C{bool}
"""
foo = requestType.replace('-', '_')
f = getattr(self, 'request_%s'%foo, None)
if f:
return f(data)
log.msg('unhandled request for %s'%requestType)
return 0
def dataReceived(self, data):
"""
Called when we receive data.
@type data: C{str}
"""
log.msg('got data %s'%repr(data))
def extReceived(self, dataType, data):
"""
Called when we receive extended data (usually standard error).
@type dataType: C{int}
@type data: C{str}
"""
log.msg('got extended data %s %s'%(dataType, repr(data)))
def eofReceived(self):
"""
Called when the other side will send no more data.
"""
log.msg('remote eof')
def closeReceived(self):
"""
Called when the other side has closed the channel.
"""
log.msg('remote close')
self.loseConnection()
def closed(self):
"""
Called when the channel is closed. This means that both our side and
the remote side have closed the channel.
"""
log.msg('closed')
# transport stuff
def write(self, data):
"""
Write some data to the channel. If there is not enough remote window
available, buffer until it is. Otherwise, split the data into
packets of length remoteMaxPacket and send them.
@type data: C{str}
"""
if self.buf:
self.buf += data
return
top = len(data)
if top > self.remoteWindowLeft:
data, self.buf = (data[:self.remoteWindowLeft],
data[self.remoteWindowLeft:])
self.areWriting = 0
self.stopWriting()
top = self.remoteWindowLeft
rmp = self.remoteMaxPacket
write = self.conn.sendData
r = range(0, top, rmp)
for offset in r:
write(self, data[offset: offset+rmp])
self.remoteWindowLeft -= top
if self.closing and not self.buf:
self.loseConnection() # try again
def writeExtended(self, dataType, data):
"""
Send extended data to this channel. If there is not enough remote
window available, buffer until there is. Otherwise, split the data
into packets of length remoteMaxPacket and send them.
@type dataType: C{int}
@type data: C{str}
"""
if self.extBuf:
if self.extBuf[-1][0] == dataType:
self.extBuf[-1][1] += data
else:
self.extBuf.append([dataType, data])
return
if len(data) > self.remoteWindowLeft:
data, self.extBuf = (data[:self.remoteWindowLeft],
[[dataType, data[self.remoteWindowLeft:]]])
self.areWriting = 0
self.stopWriting()
while len(data) > self.remoteMaxPacket:
self.conn.sendExtendedData(self, dataType,
data[:self.remoteMaxPacket])
data = data[self.remoteMaxPacket:]
self.remoteWindowLeft -= self.remoteMaxPacket
if data:
self.conn.sendExtendedData(self, dataType, data)
self.remoteWindowLeft -= len(data)
if self.closing:
self.loseConnection() # try again
def writeSequence(self, data):
"""
Part of the Transport interface. Write a list of strings to the
channel.
@type data: C{list} of C{str}
"""
self.write(''.join(data))
def loseConnection(self):
"""
Close the channel if there is no buferred data. Otherwise, note the
request and return.
"""
self.closing = 1
if not self.buf and not self.extBuf:
self.conn.sendClose(self)
def getPeer(self):
"""
Return a tuple describing the other side of the connection.
@rtype: C{tuple}
"""
return('SSH', )+self.conn.transport.getPeer()
def getHost(self):
"""
Return a tuple describing our side of the connection.
@rtype: C{tuple}
"""
return('SSH', )+self.conn.transport.getHost()
def stopWriting(self):
"""
Called when the remote buffer is full, as a hint to stop writing.
This can be ignored, but it can be helpful.
"""
def startWriting(self):
"""
Called when the remote buffer has more room, as a hint to continue
writing.
"""
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