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network/iptables: Add iptables rules to FORWARD chain
To work around the Docker change from v1.13 which changed the default FORWARD policy to DROP. The change has bitten many many users. The troubleshooting documentation is also updated talk about the issue. Replaces PR flannel-io#862 Fixes flannel-io#834 Fixes flannel-io#823 Fixes flannel-io#609 Fixes flannel-io#799
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,141 @@ | ||
| // Copyright 2015 flannel authors | ||
| // | ||
| // 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. | ||
|
|
||
| package network | ||
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||
| import ( | ||
| "fmt" | ||
| "strings" | ||
|
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| log "github.com/golang/glog" | ||
|
|
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| "time" | ||
|
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| "github.com/coreos/flannel/pkg/ip" | ||
| "github.com/coreos/flannel/subnet" | ||
| "github.com/coreos/go-iptables/iptables" | ||
| ) | ||
|
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| type IPTables interface { | ||
| AppendUnique(table string, chain string, rulespec ...string) error | ||
| Delete(table string, chain string, rulespec ...string) error | ||
| Exists(table string, chain string, rulespec ...string) (bool, error) | ||
| } | ||
|
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| type IPTablesRule struct { | ||
| table string | ||
| chain string | ||
| rulespec []string | ||
| } | ||
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| func MasqRules(ipn ip.IP4Net, lease *subnet.Lease) []IPTablesRule { | ||
| n := ipn.String() | ||
| sn := lease.Subnet.String() | ||
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| return []IPTablesRule{ | ||
| // This rule makes sure we don't NAT traffic within overlay network (e.g. coming out of docker0) | ||
| {"nat", "POSTROUTING", []string{"-s", n, "-d", n, "-j", "RETURN"}}, | ||
| // NAT if it's not multicast traffic | ||
| {"nat", "POSTROUTING", []string{"-s", n, "!", "-d", "224.0.0.0/4", "-j", "MASQUERADE"}}, | ||
| // Prevent performing Masquerade on external traffic which arrives from a Node that owns the container/pod IP address | ||
| {"nat", "POSTROUTING", []string{"!", "-s", n, "-d", sn, "-j", "RETURN"}}, | ||
| // Masquerade anything headed towards flannel from the host | ||
| {"nat", "POSTROUTING", []string{"!", "-s", n, "-d", n, "-j", "MASQUERADE"}}, | ||
| } | ||
| } | ||
|
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| func ForwardRules(flannelNetwork string) []IPTablesRule { | ||
| return []IPTablesRule{ | ||
| // These rules allow traffic to be forwarded if it is to or from the flannel network range. | ||
| {"filter", "FORWARD", []string{"-s", flannelNetwork, "-j", "ACCEPT"}}, | ||
| {"filter", "FORWARD", []string{"-d", flannelNetwork, "-j", "ACCEPT"}}, | ||
| } | ||
| } | ||
|
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| func ipTablesRulesExist(ipt IPTables, rules []IPTablesRule) (bool, error) { | ||
| for _, rule := range rules { | ||
| exists, err := ipt.Exists(rule.table, rule.chain, rule.rulespec...) | ||
| if err != nil { | ||
| // this shouldn't ever happen | ||
| return false, fmt.Errorf("failed to check rule existence", err) | ||
| } | ||
| if !exists { | ||
| return false, nil | ||
| } | ||
| } | ||
|
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| return true, nil | ||
| } | ||
|
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| func SetupAndEnsureIPTables(rules []IPTablesRule) { | ||
| ipt, err := iptables.New() | ||
| if err != nil { | ||
| // if we can't find iptables, give up and return | ||
| log.Errorf("Failed to setup IPTables. iptables binary was not found: %v", err) | ||
| return | ||
| } | ||
|
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| defer func() { | ||
| teardownIPTables(ipt, rules) | ||
| }() | ||
|
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| for { | ||
| // Ensure that all the iptables rules exist every 5 seconds | ||
| if err := ensureIPTables(ipt, rules); err != nil { | ||
| log.Errorf("Failed to ensure iptables rules: %v", err) | ||
| } | ||
|
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| time.Sleep(5 * time.Second) | ||
| } | ||
| } | ||
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| func ensureIPTables(ipt IPTables, rules []IPTablesRule) error { | ||
| exists, err := ipTablesRulesExist(ipt, rules) | ||
| if err != nil { | ||
| return fmt.Errorf("Error checking rule existence: %v", err) | ||
| } | ||
| if exists { | ||
| // if all the rules already exist, no need to do anything | ||
| return nil | ||
| } | ||
| // Otherwise, teardown all the rules and set them up again | ||
| // We do this because the order of the rules is important | ||
| log.Info("Some iptables rules are missing; deleting and recreating rules") | ||
| teardownIPTables(ipt, rules) | ||
| if err = setupIPTables(ipt, rules); err != nil { | ||
| return fmt.Errorf("Error setting up rules: %v", err) | ||
| } | ||
| return nil | ||
| } | ||
|
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| func setupIPTables(ipt IPTables, rules []IPTablesRule) error { | ||
| for _, rule := range rules { | ||
| log.Info("Adding iptables rule: ", strings.Join(rule.rulespec, " ")) | ||
| err := ipt.AppendUnique(rule.table, rule.chain, rule.rulespec...) | ||
| if err != nil { | ||
| return fmt.Errorf("failed to insert IPTables rule: %v", err) | ||
| } | ||
| } | ||
|
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| return nil | ||
| } | ||
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| func teardownIPTables(ipt IPTables, rules []IPTablesRule) { | ||
| for _, rule := range rules { | ||
| log.Info("Deleting iptables rule: ", strings.Join(rule.rulespec, " ")) | ||
| // We ignore errors here because if there's an error it's almost certainly because the rule | ||
| // doesn't exist, which is fine (we don't need to delete rules that don't exist) | ||
| ipt.Delete(rule.table, rule.chain, rule.rulespec...) | ||
| } | ||
| } |
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