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OpenStack Study: iptables_manager.py**** CubicPower OpenStack Study ****
# vim: tabstop=4 shiftwidth=4 softtabstop=4 # Copyright 2012 Locaweb. # All Rights Reserved. # # Licensed under the Apache License, Version 2.0 (the "License"); # you may not use this file except in compliance with the License. # You may obtain a copy of the License at # # http://www.apache.org/licenses/LICENSE-2.0 # # Unless required by applicable law or agreed to in writing, software # distributed under the License is distributed on an "AS IS" BASIS, # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. # See the License for the specific language governing permissions and # limitations under the License. # # @author: Juliano Martinez, Locaweb. # based on # https://github.com/openstack/nova/blob/master/nova/network/linux_net.py """Implements iptables rules using linux utilities.""" import inspect import os from neutron.agent.linux import utils as linux_utils from neutron.common import utils from neutron.openstack.common import lockutils from neutron.openstack.common import log as logging LOG = logging.getLogger(__name__) # NOTE(vish): Iptables supports chain names of up to 28 characters, and we # add up to 12 characters to binary_name which is used as a prefix, # so we limit it to 16 characters. # (max_chain_name_length - len('-POSTROUTING') == 16)
**** CubicPower OpenStack Study **** def get_binary_name(): """Grab the name of the binary we're running in.""" return os.path.basename(inspect.stack()[-1][1])[:16] binary_name = get_binary_name() # A length of a chain name must be less than or equal to 11 characters. # MAX_CHAIN_LEN_WRAP = 11 MAX_CHAIN_LEN_NOWRAP = 28
**** CubicPower OpenStack Study **** def get_chain_name(chain_name, wrap=True): if wrap: return chain_name[:MAX_CHAIN_LEN_WRAP] else: return chain_name[:MAX_CHAIN_LEN_NOWRAP]
**** CubicPower OpenStack Study **** class IptablesRule(object): """An iptables rule. You shouldn't need to use this class directly, it's only used by IptablesManager. """
**** CubicPower OpenStack Study **** def __init__(self, chain, rule, wrap=True, top=False, binary_name=binary_name, tag=None): self.chain = get_chain_name(chain, wrap) self.rule = rule self.wrap = wrap self.top = top self.wrap_name = binary_name[:16] self.tag = tag
**** CubicPower OpenStack Study **** def __eq__(self, other): return ((self.chain == other.chain) and (self.rule == other.rule) and (self.top == other.top) and (self.wrap == other.wrap))
**** CubicPower OpenStack Study **** def __ne__(self, other): return not self == other
**** CubicPower OpenStack Study **** def __str__(self): if self.wrap: chain = '%s-%s' % (self.wrap_name, self.chain) else: chain = self.chain return '-A %s %s' % (chain, self.rule)
**** CubicPower OpenStack Study **** class IptablesTable(object): """An iptables table."""
**** CubicPower OpenStack Study **** def __init__(self, binary_name=binary_name): self.rules = [] self.remove_rules = [] self.chains = set() self.unwrapped_chains = set() self.remove_chains = set() self.wrap_name = binary_name[:16]
**** CubicPower OpenStack Study **** def add_chain(self, name, wrap=True): """Adds a named chain to the table. The chain name is wrapped to be unique for the component creating it, so different components of Nova can safely create identically named chains without interfering with one another. At the moment, its wrapped name is so if nova-compute creates a chain named 'OUTPUT', it'll actually end up named 'nova-compute-OUTPUT'. """ name = get_chain_name(name, wrap) if wrap: self.chains.add(name) else: self.unwrapped_chains.add(name)
**** CubicPower OpenStack Study **** def _select_chain_set(self, wrap): if wrap: return self.chains else: return self.unwrapped_chains
**** CubicPower OpenStack Study **** def ensure_remove_chain(self, name, wrap=True): """Ensure the chain is removed. This removal "cascades". All rule in the chain are removed, as are all rules in other chains that jump to it. """ name = get_chain_name(name, wrap) chain_set = self._select_chain_set(wrap) if name not in chain_set: return self.remove_chain(name, wrap)
**** CubicPower OpenStack Study **** def remove_chain(self, name, wrap=True): """Remove named chain. This removal "cascades". All rule in the chain are removed, as are all rules in other chains that jump to it. If the chain is not found, this is merely logged. """ name = get_chain_name(name, wrap) chain_set = self._select_chain_set(wrap) if name not in chain_set: LOG.warn(_('Attempted to remove chain %s which does not exist'), name) return chain_set.remove(name) if not wrap: # non-wrapped chains and rules need to be dealt with specially, # so we keep a list of them to be iterated over in apply() self.remove_chains.add(name) # first, add rules to remove that have a matching chain name self.remove_rules += [r for r in self.rules if r.chain == name] # next, remove rules from list that have a matching chain name self.rules = [r for r in self.rules if r.chain != name] if not wrap: jump_snippet = '-j %s' % name # next, add rules to remove that have a matching jump chain self.remove_rules += [r for r in self.rules if jump_snippet in r.rule] else: jump_snippet = '-j %s-%s' % (self.wrap_name, name) # finally, remove rules from list that have a matching jump chain self.rules = [r for r in self.rules if jump_snippet not in r.rule]
**** CubicPower OpenStack Study **** def add_rule(self, chain, rule, wrap=True, top=False, tag=None): """Add a rule to the table. This is just like what you'd feed to iptables, just without the '-A However, if you need to jump to one of your wrapped chains, prepend its name with a '$' which will ensure the wrapping is applied correctly. """ chain = get_chain_name(chain, wrap) if wrap and chain not in self.chains: raise LookupError(_('Unknown chain: %r') % chain) if '$' in rule: rule = ' '.join( self._wrap_target_chain(e, wrap) for e in rule.split(' ')) self.rules.append(IptablesRule(chain, rule, wrap, top, self.wrap_name, tag))
**** CubicPower OpenStack Study **** def _wrap_target_chain(self, s, wrap): if s.startswith('$'): s = ('%s-%s' % (self.wrap_name, get_chain_name(s[1:], wrap))) return s
**** CubicPower OpenStack Study **** def remove_rule(self, chain, rule, wrap=True, top=False): """Remove a rule from a chain. Note: The rule must be exactly identical to the one that was added. You cannot switch arguments around like you can with the iptables CLI tool. """ chain = get_chain_name(chain, wrap) try: if '$' in rule: rule = ' '.join( self._wrap_target_chain(e, wrap) for e in rule.split(' ')) self.rules.remove(IptablesRule(chain, rule, wrap, top, self.wrap_name)) if not wrap: self.remove_rules.append(IptablesRule(chain, rule, wrap, top, self.wrap_name)) except ValueError: LOG.warn(_('Tried to remove rule that was not there:' ' %(chain)r %(rule)r %(wrap)r %(top)r'), {'chain': chain, 'rule': rule, 'top': top, 'wrap': wrap})
**** CubicPower OpenStack Study **** def empty_chain(self, chain, wrap=True): """Remove all rules from a chain.""" chain = get_chain_name(chain, wrap) chained_rules = [rule for rule in self.rules if rule.chain == chain and rule.wrap == wrap] for rule in chained_rules: self.rules.remove(rule)
**** CubicPower OpenStack Study **** def clear_rules_by_tag(self, tag): if not tag: return rules = [rule for rule in self.rules if rule.tag == tag] for rule in rules: self.rules.remove(rule)
**** CubicPower OpenStack Study **** class IptablesManager(object): """Wrapper for iptables. See IptablesTable for some usage docs A number of chains are set up to begin with. First, neutron-filter-top. It's added at the top of FORWARD and OUTPUT. Its name is not wrapped, so it's shared between the various nova workers. It's intended for rules that need to live at the top of the FORWARD and OUTPUT chains. It's in both the ipv4 and ipv6 set of tables. For ipv4 and ipv6, the built-in INPUT, OUTPUT, and FORWARD filter chains are wrapped, meaning that the "real" INPUT chain has a rule that jumps to the wrapped INPUT chain, etc. Additionally, there's a wrapped chain named "local" which is jumped to from neutron-filter-top. For ipv4, the built-in PREROUTING, OUTPUT, and POSTROUTING nat chains are wrapped in the same was as the built-in filter chains. Additionally, there's a snat chain that is applied after the POSTROUTING chain. """
**** CubicPower OpenStack Study **** def __init__(self, _execute=None, state_less=False, root_helper=None, use_ipv6=False, namespace=None, binary_name=binary_name): if _execute: self.execute = _execute else: self.execute = linux_utils.execute self.use_ipv6 = use_ipv6 self.root_helper = root_helper self.namespace = namespace self.iptables_apply_deferred = False self.wrap_name = binary_name[:16] self.ipv4 = {'filter': IptablesTable(binary_name=self.wrap_name)} self.ipv6 = {'filter': IptablesTable(binary_name=self.wrap_name)} # Add a neutron-filter-top chain. It's intended to be shared # among the various nova components. It sits at the very top # of FORWARD and OUTPUT. for tables in [self.ipv4, self.ipv6]: tables['filter'].add_chain('neutron-filter-top', wrap=False) tables['filter'].add_rule('FORWARD', '-j neutron-filter-top', wrap=False, top=True) tables['filter'].add_rule('OUTPUT', '-j neutron-filter-top', wrap=False, top=True) tables['filter'].add_chain('local') tables['filter'].add_rule('neutron-filter-top', '-j $local', wrap=False) # Wrap the built-in chains builtin_chains = {4: {'filter': ['INPUT', 'OUTPUT', 'FORWARD']}, 6: {'filter': ['INPUT', 'OUTPUT', 'FORWARD']}} if not state_less: self.ipv4.update( {'nat': IptablesTable(binary_name=self.wrap_name)}) builtin_chains[4].update({'nat': ['PREROUTING', 'OUTPUT', 'POSTROUTING']}) for ip_version in builtin_chains: if ip_version == 4: tables = self.ipv4 elif ip_version == 6: tables = self.ipv6 for table, chains in builtin_chains[ip_version].iteritems(): for chain in chains: tables[table].add_chain(chain) tables[table].add_rule(chain, '-j $%s' % (chain), wrap=False) if not state_less: # Add a neutron-postrouting-bottom chain. It's intended to be # shared among the various nova components. We set it as the last # chain of POSTROUTING chain. self.ipv4['nat'].add_chain('neutron-postrouting-bottom', wrap=False) self.ipv4['nat'].add_rule('POSTROUTING', '-j neutron-postrouting-bottom', wrap=False) # We add a snat chain to the shared neutron-postrouting-bottom # chain so that it's applied last. self.ipv4['nat'].add_chain('snat') self.ipv4['nat'].add_rule('neutron-postrouting-bottom', '-j $snat', wrap=False) # And then we add a float-snat chain and jump to first thing in # the snat chain. self.ipv4['nat'].add_chain('float-snat') self.ipv4['nat'].add_rule('snat', '-j $float-snat')
**** CubicPower OpenStack Study **** def defer_apply_on(self): self.iptables_apply_deferred = True
**** CubicPower OpenStack Study **** def defer_apply_off(self): self.iptables_apply_deferred = False self._apply()
**** CubicPower OpenStack Study **** def apply(self): if self.iptables_apply_deferred: return self._apply()
**** CubicPower OpenStack Study **** def _apply(self): lock_name = 'iptables' if self.namespace: lock_name += '-' + self.namespace try: with lockutils.lock(lock_name, utils.SYNCHRONIZED_PREFIX, True): LOG.debug(_('Got semaphore / lock "%s"'), lock_name) return self._apply_synchronized() finally: LOG.debug(_('Semaphore / lock released "%s"'), lock_name)
**** CubicPower OpenStack Study **** def _apply_synchronized(self): """Apply the current in-memory set of iptables rules. This will blow away any rules left over from previous runs of the same component of Nova, and replace them with our current set of rules. This happens atomically, thanks to iptables-restore. """ s = [('iptables', self.ipv4)] if self.use_ipv6: s += [('ip6tables', self.ipv6)] for cmd, tables in s: args = ['%s-save' % (cmd,), '-c'] if self.namespace: args = ['ip', 'netns', 'exec', self.namespace] + args all_tables = self.execute(args, root_helper=self.root_helper) all_lines = all_tables.split('\n') for table_name, table in tables.iteritems(): start, end = self._find_table(all_lines, table_name) all_lines[start:end] = self._modify_rules( all_lines[start:end], table, table_name) args = ['%s-restore' % (cmd,), '-c'] if self.namespace: args = ['ip', 'netns', 'exec', self.namespace] + args self.execute(args, process_input='\n'.join(all_lines), root_helper=self.root_helper) LOG.debug(_("IPTablesManager.apply completed with success"))
**** CubicPower OpenStack Study **** def _find_table(self, lines, table_name): if len(lines) < 3: # length only <2 when fake iptables return (0, 0) try: start = lines.index('*%s' % table_name) - 1 except ValueError: # Couldn't find table_name LOG.debug(_('Unable to find table %s'), table_name) return (0, 0) end = lines[start:].index('COMMIT') + start + 2 return (start, end)
**** CubicPower OpenStack Study **** def _find_rules_index(self, lines): seen_chains = False rules_index = 0 for rules_index, rule in enumerate(lines): if not seen_chains: if rule.startswith(':'): seen_chains = True else: if not rule.startswith(':'): break if not seen_chains: rules_index = 2 return rules_index
**** CubicPower OpenStack Study **** def _modify_rules(self, current_lines, table, table_name): unwrapped_chains = table.unwrapped_chains chains = table.chains remove_chains = table.remove_chains rules = table.rules remove_rules = table.remove_rules if not current_lines: fake_table = ['# Generated by iptables_manager', '*' + table_name, 'COMMIT', '# Completed by iptables_manager'] current_lines = fake_table # Fill old_filter with any chains or rules we might have added, # they could have a [packet:byte] count we want to preserve. # Fill new_filter with any chains or rules without our name in them. old_filter, new_filter = [], [] for line in current_lines: (old_filter if self.wrap_name in line else new_filter).append(line.strip()) rules_index = self._find_rules_index(new_filter) all_chains = [':%s' % name for name in unwrapped_chains] all_chains += [':%s-%s' % (self.wrap_name, name) for name in chains] # Iterate through all the chains, trying to find an existing # match. our_chains = [] for chain in all_chains: chain_str = str(chain).strip() orig_filter = [s for s in old_filter if chain_str in s.strip()] dup_filter = [s for s in new_filter if chain_str in s.strip()] new_filter = [s for s in new_filter if chain_str not in s.strip()] # if no old or duplicates, use original chain if orig_filter: # grab the last entry, if there is one old = orig_filter[-1] chain_str = str(old).strip() elif dup_filter: # grab the last entry, if there is one dup = dup_filter[-1] chain_str = str(dup).strip() else: # add-on the [packet:bytes] chain_str += ' - [0:0]' our_chains += [chain_str] # Iterate through all the rules, trying to find an existing # match. our_rules = [] bot_rules = [] for rule in rules: rule_str = str(rule).strip() # Further down, we weed out duplicates from the bottom of the # list, so here we remove the dupes ahead of time. orig_filter = [s for s in old_filter if rule_str in s.strip()] dup_filter = [s for s in new_filter if rule_str in s.strip()] new_filter = [s for s in new_filter if rule_str not in s.strip()] # if no old or duplicates, use original rule if orig_filter: # grab the last entry, if there is one old = orig_filter[-1] rule_str = str(old).strip() elif dup_filter: # grab the last entry, if there is one dup = dup_filter[-1] rule_str = str(dup).strip() # backup one index so we write the array correctly rules_index -= 1 else: # add-on the [packet:bytes] rule_str = '[0:0] ' + rule_str if rule.top: # rule.top == True means we want this rule to be at the top. our_rules += [rule_str] else: bot_rules += [rule_str] our_rules += bot_rules new_filter[rules_index:rules_index] = our_rules new_filter[rules_index:rules_index] = our_chains def _strip_packets_bytes(line): # strip any [packet:byte] counts at start or end of lines if line.startswith(':'): # it's a chain, for example, ":neutron-billing - [0:0]" line = line.split(':')[1] line = line.split(' - [', 1)[0] elif line.startswith('['): # it's a rule, for example, "[0:0] -A neutron-billing..." line = line.split('] ', 1)[1] line = line.strip() return line seen_chains = set() def _weed_out_duplicate_chains(line): # ignore [packet:byte] counts at end of lines if line.startswith(':'): line = _strip_packets_bytes(line) if line in seen_chains: return False else: seen_chains.add(line) # Leave it alone return True seen_rules = set() def _weed_out_duplicate_rules(line): if line.startswith('['): line = _strip_packets_bytes(line) if line in seen_rules: return False else: seen_rules.add(line) # Leave it alone return True def _weed_out_removes(line): # We need to find exact matches here if line.startswith(':'): line = _strip_packets_bytes(line) for chain in remove_chains: if chain == line: remove_chains.remove(chain) return False elif line.startswith('['): line = _strip_packets_bytes(line) for rule in remove_rules: rule_str = _strip_packets_bytes(str(rule)) if rule_str == line: remove_rules.remove(rule) return False # Leave it alone return True # We filter duplicates. Go through the chains and rules, letting # the *last* occurrence take precendence since it could have a # non-zero [packet:byte] count we want to preserve. We also filter # out anything in the "remove" list. new_filter.reverse() new_filter = [line for line in new_filter if _weed_out_duplicate_chains(line) and _weed_out_duplicate_rules(line) and _weed_out_removes(line)] new_filter.reverse() # flush lists, just in case we didn't find something remove_chains.clear() for rule in remove_rules: remove_rules.remove(rule) return new_filter
**** CubicPower OpenStack Study **** def _strip_packets_bytes(line): # strip any [packet:byte] counts at start or end of lines if line.startswith(':'): # it's a chain, for example, ":neutron-billing - [0:0]" line = line.split(':')[1] line = line.split(' - [', 1)[0] elif line.startswith('['): # it's a rule, for example, "[0:0] -A neutron-billing..." line = line.split('] ', 1)[1] line = line.strip() return line seen_chains = set()
**** CubicPower OpenStack Study **** def _weed_out_duplicate_chains(line): # ignore [packet:byte] counts at end of lines if line.startswith(':'): line = _strip_packets_bytes(line) if line in seen_chains: return False else: seen_chains.add(line) # Leave it alone return True seen_rules = set()
**** CubicPower OpenStack Study **** def _weed_out_duplicate_rules(line): if line.startswith('['): line = _strip_packets_bytes(line) if line in seen_rules: return False else: seen_rules.add(line) # Leave it alone return True
**** CubicPower OpenStack Study **** def _weed_out_removes(line): # We need to find exact matches here if line.startswith(':'): line = _strip_packets_bytes(line) for chain in remove_chains: if chain == line: remove_chains.remove(chain) return False elif line.startswith('['): line = _strip_packets_bytes(line) for rule in remove_rules: rule_str = _strip_packets_bytes(str(rule)) if rule_str == line: remove_rules.remove(rule) return False # Leave it alone return True # We filter duplicates. Go through the chains and rules, letting # the *last* occurrence take precendence since it could have a # non-zero [packet:byte] count we want to preserve. We also filter # out anything in the "remove" list. new_filter.reverse() new_filter = [line for line in new_filter if _weed_out_duplicate_chains(line) and _weed_out_duplicate_rules(line) and _weed_out_removes(line)] new_filter.reverse() # flush lists, just in case we didn't find something remove_chains.clear() for rule in remove_rules: remove_rules.remove(rule) return new_filter
**** CubicPower OpenStack Study **** def _get_traffic_counters_cmd_tables(self, chain, wrap=True): name = get_chain_name(chain, wrap) cmd_tables = [('iptables', key) for key, table in self.ipv4.items() if name in table._select_chain_set(wrap)] cmd_tables += [('ip6tables', key) for key, table in self.ipv6.items() if name in table._select_chain_set(wrap)] return cmd_tables
**** CubicPower OpenStack Study **** def get_traffic_counters(self, chain, wrap=True, zero=False): """Return the sum of the traffic counters of all rules of a chain.""" cmd_tables = self._get_traffic_counters_cmd_tables(chain, wrap) if not cmd_tables: LOG.warn(_('Attempted to get traffic counters of chain %s which ' 'does not exist'), chain) return name = get_chain_name(chain, wrap) acc = {'pkts': 0, 'bytes': 0} for cmd, table in cmd_tables: args = [cmd, '-t', table, '-L', name, '-n', '-v', '-x'] if zero: args.append('-Z') if self.namespace: args = ['ip', 'netns', 'exec', self.namespace] + args current_table = (self.execute(args, root_helper=self.root_helper)) current_lines = current_table.split('\n') for line in current_lines[2:]: if not line: break data = line.split() if (len(data) < 2 or not data[0].isdigit() or not data[1].isdigit()): break acc['pkts'] += int(data[0]) acc['bytes'] += int(data[1]) return acc
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