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//go:build !windows
package libnetwork
import (
"fmt"
"net"
"github.com/docker/docker/libnetwork/iptables"
)
const (
// output chain used for docker embedded DNS resolver
outputChain = "DOCKER_OUTPUT"
// postrouting chain used for docker embedded DNS resolver
postroutingChain = "DOCKER_POSTROUTING"
)
func (r *Resolver) setupIPTable() error {
if r.err != nil {
return r.err
}
laddr := r.conn.LocalAddr().String()
ltcpaddr := r.tcpListen.Addr().String()
resolverIP, ipPort, _ := net.SplitHostPort(laddr)
_, tcpPort, _ := net.SplitHostPort(ltcpaddr)
rules := [][]string{
{"-t", "nat", "-I", outputChain, "-d", resolverIP, "-p", "udp", "--dport", dnsPort, "-j", "DNAT", "--to-destination", laddr},
{"-t", "nat", "-I", postroutingChain, "-s", resolverIP, "-p", "udp", "--sport", ipPort, "-j", "SNAT", "--to-source", ":" + dnsPort},
{"-t", "nat", "-I", outputChain, "-d", resolverIP, "-p", "tcp", "--dport", dnsPort, "-j", "DNAT", "--to-destination", ltcpaddr},
{"-t", "nat", "-I", postroutingChain, "-s", resolverIP, "-p", "tcp", "--sport", tcpPort, "-j", "SNAT", "--to-source", ":" + dnsPort},
}
var setupErr error
err := r.backend.ExecFunc(func() {
// TODO IPv6 support
iptable := iptables.GetIptable(iptables.IPv4)
// insert outputChain and postroutingchain
if iptable.ExistsNative("nat", "OUTPUT", "-d", resolverIP, "-j", outputChain) {
if err := iptable.RawCombinedOutputNative("-t", "nat", "-F", outputChain); err != nil {
setupErr = err
return
}
} else {
if err := iptable.RawCombinedOutputNative("-t", "nat", "-N", outputChain); err != nil {
setupErr = err
return
}
if err := iptable.RawCombinedOutputNative("-t", "nat", "-I", "OUTPUT", "-d", resolverIP, "-j", outputChain); err != nil {
setupErr = err
return
}
}
if iptable.ExistsNative("nat", "POSTROUTING", "-d", resolverIP, "-j", postroutingChain) {
if err := iptable.RawCombinedOutputNative("-t", "nat", "-F", postroutingChain); err != nil {
setupErr = err
return
}
} else {
if err := iptable.RawCombinedOutputNative("-t", "nat", "-N", postroutingChain); err != nil {
setupErr = err
return
}
if err := iptable.RawCombinedOutputNative("-t", "nat", "-I", "POSTROUTING", "-d", resolverIP, "-j", postroutingChain); err != nil {
setupErr = err
return
}
}
for _, rule := range rules {
if iptable.RawCombinedOutputNative(rule...) != nil {
setupErr = fmt.Errorf("set up rule failed, %v", rule)
return
}
}
})
if err != nil {
return err
}
return setupErr
}
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