// Copyright 2019 The gVisor 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 iptables import ( "context" "encoding/binary" "errors" "fmt" "net" "os/exec" "strings" "time" "gvisor.dev/gvisor/pkg/test/testutil" ) // filterTable calls `ip{6}tables -t filter` with the given args. func filterTable(ipv6 bool, args ...string) error { return tableCmd(ipv6, "filter", args) } // natTable calls `ip{6}tables -t nat` with the given args. func natTable(ipv6 bool, args ...string) error { return tableCmd(ipv6, "nat", args) } func tableCmd(ipv6 bool, table string, args []string) error { args = append([]string{"-t", table}, args...) binary := "iptables" if ipv6 { binary = "ip6tables" } cmd := exec.Command(binary, args...) if out, err := cmd.CombinedOutput(); err != nil { return fmt.Errorf("error running iptables with args %v\nerror: %v\noutput: %s", args, err, string(out)) } return nil } // filterTableRules is like filterTable, but runs multiple iptables commands. func filterTableRules(ipv6 bool, argsList [][]string) error { return tableRules(ipv6, "filter", argsList) } // natTableRules is like natTable, but runs multiple iptables commands. func natTableRules(ipv6 bool, argsList [][]string) error { return tableRules(ipv6, "nat", argsList) } func tableRules(ipv6 bool, table string, argsList [][]string) error { for _, args := range argsList { if err := tableCmd(ipv6, table, args); err != nil { return err } } return nil } // listenUDP listens on a UDP port and returns nil if the first read from that // port is successful. func listenUDP(ctx context.Context, port int, ipv6 bool) error { _, err := listenUDPFrom(ctx, port, ipv6) return err } // listenUDPFrom listens on a UDP port and returns the sender's UDP address if // the first read from that port is successful. func listenUDPFrom(ctx context.Context, port int, ipv6 bool) (*net.UDPAddr, error) { localAddr := net.UDPAddr{ Port: port, } conn, err := net.ListenUDP(udpNetwork(ipv6), &localAddr) if err != nil { return nil, err } defer conn.Close() type result struct { remoteAddr *net.UDPAddr err error } ch := make(chan result) go func() { _, remoteAddr, err := conn.ReadFromUDP([]byte{0}) ch <- result{remoteAddr, err} }() select { case res := <-ch: return res.remoteAddr, res.err case <-ctx.Done(): return nil, fmt.Errorf("timed out reading from %s: %w", &localAddr, ctx.Err()) } } // sendUDPLoop sends 1 byte UDP packets repeatedly to the IP and port specified // over a duration. func sendUDPLoop(ctx context.Context, ip net.IP, port int, ipv6 bool) error { remote := net.UDPAddr{ IP: ip, Port: port, } conn, err := net.DialUDP(udpNetwork(ipv6), nil, &remote) if err != nil { return err } defer conn.Close() for { // This may return an error (connection refused) if the remote // hasn't started listening yet or they're dropping our // packets. So we ignore Write errors and depend on the remote // to report a failure if it doesn't get a packet it needs. conn.Write([]byte{0}) select { case <-ctx.Done(): // Being cancelled or timing out isn't an error, as we // cannot tell with UDP whether we succeeded. return nil // Continue looping. case <-time.After(200 * time.Millisecond): } } } // listenTCP listens for connections on a TCP port, and returns nil if a // connection is established. func listenTCP(ctx context.Context, port int, ipv6 bool) error { _, err := listenTCPFrom(ctx, port, ipv6) return err } // listenTCP listens for connections on a TCP port, and returns the remote // TCP address if a connection is established. func listenTCPFrom(ctx context.Context, port int, ipv6 bool) (net.Addr, error) { localAddr := net.TCPAddr{ Port: port, } // Starts listening on port. lConn, err := net.ListenTCP(tcpNetwork(ipv6), &localAddr) if err != nil { return nil, err } defer lConn.Close() type result struct { remoteAddr net.Addr err error } // Accept connections on port. ch := make(chan result) go func() { conn, err := lConn.AcceptTCP() var remoteAddr net.Addr if err == nil { remoteAddr = conn.RemoteAddr() } ch <- result{remoteAddr, err} conn.Close() }() select { case res := <-ch: return res.remoteAddr, res.err case <-ctx.Done(): return nil, fmt.Errorf("timed out waiting for a connection at %s: %w", &localAddr, ctx.Err()) } } // connectTCP connects to the given IP and port from an ephemeral local address. func connectTCP(ctx context.Context, ip net.IP, port int, ipv6 bool) error { contAddr := net.TCPAddr{ IP: ip, Port: port, } // The container may not be listening when we first connect, so retry // upon error. callback := func() error { var d net.Dialer conn, err := d.DialContext(ctx, tcpNetwork(ipv6), contAddr.String()) if conn != nil { conn.Close() } return err } if err := testutil.PollContext(ctx, callback); err != nil { return fmt.Errorf("timed out waiting to connect IP on port %v, most recent error: %w", port, err) } return nil } // localAddrs returns a list of local network interface addresses. When ipv6 is // true, only IPv6 addresses are returned. Otherwise only IPv4 addresses are // returned. func localAddrs(ipv6 bool) ([]string, error) { addrs, err := net.InterfaceAddrs() if err != nil { return nil, err } addrStrs := make([]string, 0, len(addrs)) for _, addr := range addrs { // Add only IPv4 or only IPv6 addresses. parts := strings.Split(addr.String(), "/") if len(parts) != 2 { return nil, fmt.Errorf("bad interface address: %q", addr.String()) } if isIPv6 := net.ParseIP(parts[0]).To4() == nil; isIPv6 == ipv6 { addrStrs = append(addrStrs, addr.String()) } } return filterAddrs(addrStrs, ipv6), nil } func filterAddrs(addrs []string, ipv6 bool) []string { addrStrs := make([]string, 0, len(addrs)) for _, addr := range addrs { // Add only IPv4 or only IPv6 addresses. parts := strings.Split(addr, "/") if isIPv6 := net.ParseIP(parts[0]).To4() == nil; isIPv6 == ipv6 { addrStrs = append(addrStrs, parts[0]) } } return addrStrs } // getInterfaceName returns the name of the interface other than loopback. func getInterfaceName() (string, bool) { iface, ok := getNonLoopbackInterface() if !ok { return "", false } return iface.Name, true } func getInterfaceAddrs(ipv6 bool) ([]net.IP, error) { iface, ok := getNonLoopbackInterface() if !ok { return nil, errors.New("no non-loopback interface found") } addrs, err := iface.Addrs() if err != nil { return nil, err } // Get only IPv4 or IPv6 addresses. ips := make([]net.IP, 0, len(addrs)) for _, addr := range addrs { parts := strings.Split(addr.String(), "/") var ip net.IP // To16() returns IPv4 addresses as IPv4-mapped IPv6 addresses. // So we check whether To4() returns nil to test whether the // address is v4 or v6. if v4 := net.ParseIP(parts[0]).To4(); ipv6 && v4 == nil { ip = net.ParseIP(parts[0]).To16() } else { ip = v4 } if ip != nil { ips = append(ips, ip) } } return ips, nil } func getNonLoopbackInterface() (net.Interface, bool) { if interfaces, err := net.Interfaces(); err == nil { for _, intf := range interfaces { if intf.Name != "lo" { return intf, true } } } return net.Interface{}, false } func htons(x uint16) uint16 { buf := make([]byte, 2) binary.BigEndian.PutUint16(buf, x) return binary.LittleEndian.Uint16(buf) } func localIP(ipv6 bool) string { if ipv6 { return "::1" } return "127.0.0.1" } func nowhereIP(ipv6 bool) string { if ipv6 { return "2001:db8::1" } return "192.0.2.1" } // udpNetwork returns an IPv6 or IPv6 UDP network argument to net.Dial. func udpNetwork(ipv6 bool) string { if ipv6 { return "udp6" } return "udp4" } // tcpNetwork returns an IPv6 or IPv6 TCP network argument to net.Dial. func tcpNetwork(ipv6 bool) string { if ipv6 { return "tcp6" } return "tcp4" }