4bca3e76bf
Because these package names are short and they are unique, it can not conflict. So the import aliases that can be omitted and we should remove them.
134 lines
3.6 KiB
Go
134 lines
3.6 KiB
Go
// Copyright 2017 CNI authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package main
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import (
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"fmt"
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"strings"
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"github.com/coreos/go-iptables/iptables"
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"github.com/mattn/go-shellwords"
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)
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type chain struct {
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table string
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name string
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entryChains []string // the chains to add the entry rule
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entryRules [][]string // the rules that "point" to this chain
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rules [][]string // the rules this chain contains
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}
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// setup idempotently creates the chain. It will not error if the chain exists.
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func (c *chain) setup(ipt *iptables.IPTables) error {
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// create the chain
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exists, err := chainExists(ipt, c.table, c.name)
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if err != nil {
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return err
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}
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if !exists {
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if err := ipt.NewChain(c.table, c.name); err != nil {
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return err
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}
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}
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// Add the rules to the chain
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for i := len(c.rules) - 1; i >= 0; i-- {
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if err := prependUnique(ipt, c.table, c.name, c.rules[i]); err != nil {
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return err
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}
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}
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// Add the entry rules to the entry chains
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for _, entryChain := range c.entryChains {
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for i := len(c.entryRules) - 1; i >= 0; i-- {
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r := []string{}
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r = append(r, c.entryRules[i]...)
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r = append(r, "-j", c.name)
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if err := prependUnique(ipt, c.table, entryChain, r); err != nil {
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return err
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}
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}
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}
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return nil
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}
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// teardown idempotently deletes a chain. It will not error if the chain doesn't exist.
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// It will first delete all references to this chain in the entryChains.
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func (c *chain) teardown(ipt *iptables.IPTables) error {
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// flush the chain
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// This will succeed *and create the chain* if it does not exist.
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// If the chain doesn't exist, the next checks will fail.
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if err := ipt.ClearChain(c.table, c.name); err != nil {
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return err
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}
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for _, entryChain := range c.entryChains {
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entryChainRules, err := ipt.List(c.table, entryChain)
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if err != nil || len(entryChainRules) < 1 {
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// Swallow error here - probably the chain doesn't exist.
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// If we miss something the deletion will fail
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continue
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}
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for _, entryChainRule := range entryChainRules[1:] {
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if strings.HasSuffix(entryChainRule, "-j "+c.name) {
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chainParts, err := shellwords.Parse(entryChainRule)
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if err != nil {
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return fmt.Errorf("error parsing iptables rule: %s: %v", entryChainRule, err)
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}
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chainParts = chainParts[2:] // List results always include an -A CHAINNAME
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if err := ipt.Delete(c.table, entryChain, chainParts...); err != nil {
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return fmt.Errorf("Failed to delete referring rule %s %s: %v", c.table, entryChainRule, err)
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}
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}
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}
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}
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if err := ipt.DeleteChain(c.table, c.name); err != nil {
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return err
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}
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return nil
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}
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// prependUnique will prepend a rule to a chain, if it does not already exist
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func prependUnique(ipt *iptables.IPTables, table, chain string, rule []string) error {
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exists, err := ipt.Exists(table, chain, rule...)
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if err != nil {
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return err
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}
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if exists {
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return nil
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}
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return ipt.Insert(table, chain, 1, rule...)
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}
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func chainExists(ipt *iptables.IPTables, tableName, chainName string) (bool, error) {
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chains, err := ipt.ListChains(tableName)
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if err != nil {
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return false, err
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}
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for _, ch := range chains {
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if ch == chainName {
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return true, nil
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}
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}
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return false, nil
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}
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