package dhcpd import ( "encoding/json" "errors" "fmt" "io/ioutil" "net" "net/http" "os" "os/exec" "runtime" "strings" "time" "github.com/AdguardTeam/golibs/file" "github.com/AdguardTeam/golibs/log" ) func httpError(r *http.Request, w http.ResponseWriter, code int, format string, args ...interface{}) { text := fmt.Sprintf(format, args...) log.Info("DHCP: %s %s: %s", r.Method, r.URL, text) http.Error(w, text, code) } // []Lease -> JSON func convertLeases(inputLeases []Lease, includeExpires bool) []map[string]string { leases := []map[string]string{} for _, l := range inputLeases { lease := map[string]string{ "mac": l.HWAddr.String(), "ip": l.IP.String(), "hostname": l.Hostname, } if includeExpires { lease["expires"] = l.Expiry.Format(time.RFC3339) } leases = append(leases, lease) } return leases } func (s *Server) handleDHCPStatus(w http.ResponseWriter, r *http.Request) { leases := convertLeases(s.Leases(), true) staticLeases := convertLeases(s.StaticLeases(), false) status := map[string]interface{}{ "config": s.conf, "leases": leases, "static_leases": staticLeases, } w.Header().Set("Content-Type", "application/json") err := json.NewEncoder(w).Encode(status) if err != nil { httpError(r, w, http.StatusInternalServerError, "Unable to marshal DHCP status json: %s", err) return } } type staticLeaseJSON struct { HWAddr string `json:"mac"` IP string `json:"ip"` Hostname string `json:"hostname"` } type dhcpServerConfigJSON struct { ServerConfig `json:",inline"` StaticLeases []staticLeaseJSON `json:"static_leases"` } func (s *Server) handleDHCPSetConfig(w http.ResponseWriter, r *http.Request) { newconfig := dhcpServerConfigJSON{} err := json.NewDecoder(r.Body).Decode(&newconfig) if err != nil { httpError(r, w, http.StatusBadRequest, "Failed to parse new DHCP config json: %s", err) return } err = s.CheckConfig(newconfig.ServerConfig) if err != nil { httpError(r, w, http.StatusBadRequest, "Invalid DHCP configuration: %s", err) return } err = s.Stop() if err != nil { log.Error("failed to stop the DHCP server: %s", err) } err = s.Init(newconfig.ServerConfig) if err != nil { httpError(r, w, http.StatusBadRequest, "Invalid DHCP configuration: %s", err) return } s.conf.ConfigModified() if newconfig.Enabled { staticIP, err := hasStaticIP(newconfig.InterfaceName) if !staticIP && err == nil { err = setStaticIP(newconfig.InterfaceName) if err != nil { httpError(r, w, http.StatusInternalServerError, "Failed to configure static IP: %s", err) return } } err = s.Start() if err != nil { httpError(r, w, http.StatusBadRequest, "Failed to start DHCP server: %s", err) return } } } type netInterface struct { Name string `json:"name"` MTU int `json:"mtu"` HardwareAddr string `json:"hardware_address"` Addresses []string `json:"ip_addresses"` Flags string `json:"flags"` } // getValidNetInterfaces returns interfaces that are eligible for DNS and/or DHCP // invalid interface is a ppp interface or the one that doesn't allow broadcasts func getValidNetInterfaces() ([]net.Interface, error) { ifaces, err := net.Interfaces() if err != nil { return nil, fmt.Errorf("Couldn't get list of interfaces: %s", err) } netIfaces := []net.Interface{} for i := range ifaces { if ifaces[i].Flags&net.FlagPointToPoint != 0 { // this interface is ppp, we're not interested in this one continue } iface := ifaces[i] netIfaces = append(netIfaces, iface) } return netIfaces, nil } func (s *Server) handleDHCPInterfaces(w http.ResponseWriter, r *http.Request) { response := map[string]interface{}{} ifaces, err := getValidNetInterfaces() if err != nil { httpError(r, w, http.StatusInternalServerError, "Couldn't get interfaces: %s", err) return } for _, iface := range ifaces { if iface.Flags&net.FlagLoopback != 0 { // it's a loopback, skip it continue } if iface.Flags&net.FlagBroadcast == 0 { // this interface doesn't support broadcast, skip it continue } addrs, err := iface.Addrs() if err != nil { httpError(r, w, http.StatusInternalServerError, "Failed to get addresses for interface %s: %s", iface.Name, err) return } jsonIface := netInterface{ Name: iface.Name, MTU: iface.MTU, HardwareAddr: iface.HardwareAddr.String(), } if iface.Flags != 0 { jsonIface.Flags = iface.Flags.String() } // we don't want link-local addresses in json, so skip them for _, addr := range addrs { ipnet, ok := addr.(*net.IPNet) if !ok { // not an IPNet, should not happen httpError(r, w, http.StatusInternalServerError, "SHOULD NOT HAPPEN: got iface.Addrs() element %s that is not net.IPNet, it is %T", addr, addr) return } // ignore link-local if ipnet.IP.IsLinkLocalUnicast() { continue } jsonIface.Addresses = append(jsonIface.Addresses, ipnet.IP.String()) } if len(jsonIface.Addresses) != 0 { response[iface.Name] = jsonIface } } err = json.NewEncoder(w).Encode(response) if err != nil { httpError(r, w, http.StatusInternalServerError, "Failed to marshal json with available interfaces: %s", err) return } } // Perform the following tasks: // . Search for another DHCP server running // . Check if a static IP is configured for the network interface // Respond with results func (s *Server) handleDHCPFindActiveServer(w http.ResponseWriter, r *http.Request) { body, err := ioutil.ReadAll(r.Body) if err != nil { errorText := fmt.Sprintf("failed to read request body: %s", err) log.Error(errorText) http.Error(w, errorText, http.StatusBadRequest) return } interfaceName := strings.TrimSpace(string(body)) if interfaceName == "" { errorText := fmt.Sprintf("empty interface name specified") log.Error(errorText) http.Error(w, errorText, http.StatusBadRequest) return } found, err := CheckIfOtherDHCPServersPresent(interfaceName) othSrv := map[string]interface{}{} foundVal := "no" if found { foundVal = "yes" } else if err != nil { foundVal = "error" othSrv["error"] = err.Error() } othSrv["found"] = foundVal staticIP := map[string]interface{}{} isStaticIP, err := hasStaticIP(interfaceName) staticIPStatus := "yes" if err != nil { staticIPStatus = "error" staticIP["error"] = err.Error() } else if !isStaticIP { staticIPStatus = "no" staticIP["ip"] = getFullIP(interfaceName) } staticIP["static"] = staticIPStatus result := map[string]interface{}{} result["other_server"] = othSrv result["static_ip"] = staticIP w.Header().Set("Content-Type", "application/json") err = json.NewEncoder(w).Encode(result) if err != nil { httpError(r, w, http.StatusInternalServerError, "Failed to marshal DHCP found json: %s", err) return } } // Check if network interface has a static IP configured func hasStaticIP(ifaceName string) (bool, error) { if runtime.GOOS == "windows" { return false, errors.New("Can't detect static IP: not supported on Windows") } body, err := ioutil.ReadFile("/etc/dhcpcd.conf") if err != nil { return false, err } lines := strings.Split(string(body), "\n") nameLine := fmt.Sprintf("interface %s", ifaceName) withinInterfaceCtx := false for _, line := range lines { line = strings.TrimSpace(line) if withinInterfaceCtx && len(line) == 0 { // an empty line resets our state withinInterfaceCtx = false } if len(line) == 0 || line[0] == '#' { continue } line = strings.TrimSpace(line) if !withinInterfaceCtx { if line == nameLine { // we found our interface withinInterfaceCtx = true } } else { if strings.HasPrefix(line, "interface ") { // we found another interface - reset our state withinInterfaceCtx = false continue } if strings.HasPrefix(line, "static ip_address=") { return true, nil } } } return false, nil } // Get IP address with netmask func getFullIP(ifaceName string) string { cmd := exec.Command("ip", "-oneline", "-family", "inet", "address", "show", ifaceName) log.Tracef("executing %s %v", cmd.Path, cmd.Args) d, err := cmd.Output() if err != nil || cmd.ProcessState.ExitCode() != 0 { return "" } fields := strings.Fields(string(d)) if len(fields) < 4 { return "" } _, _, err = net.ParseCIDR(fields[3]) if err != nil { return "" } return fields[3] } // Get gateway IP address func getGatewayIP(ifaceName string) string { cmd := exec.Command("ip", "route", "show", "dev", ifaceName) log.Tracef("executing %s %v", cmd.Path, cmd.Args) d, err := cmd.Output() if err != nil || cmd.ProcessState.ExitCode() != 0 { return "" } fields := strings.Fields(string(d)) if len(fields) < 3 || fields[0] != "default" { return "" } ip := net.ParseIP(fields[2]) if ip == nil { return "" } return fields[2] } // Set a static IP for network interface func setStaticIP(ifaceName string) error { ip := getFullIP(ifaceName) if len(ip) == 0 { return errors.New("Can't get IP address") } body, err := ioutil.ReadFile("/etc/dhcpcd.conf") if err != nil { return err } ip4, _, err := net.ParseCIDR(ip) if err != nil { return err } add := fmt.Sprintf("\ninterface %s\nstatic ip_address=%s\n", ifaceName, ip) body = append(body, []byte(add)...) gatewayIP := getGatewayIP(ifaceName) if len(gatewayIP) != 0 { add = fmt.Sprintf("static routers=%s\n", gatewayIP) body = append(body, []byte(add)...) } add = fmt.Sprintf("static domain_name_servers=%s\n\n", ip4) body = append(body, []byte(add)...) err = file.SafeWrite("/etc/dhcpcd.conf", body) if err != nil { return err } return nil } func (s *Server) handleDHCPAddStaticLease(w http.ResponseWriter, r *http.Request) { lj := staticLeaseJSON{} err := json.NewDecoder(r.Body).Decode(&lj) if err != nil { httpError(r, w, http.StatusBadRequest, "json.Decode: %s", err) return } ip, _ := parseIPv4(lj.IP) if ip == nil { httpError(r, w, http.StatusBadRequest, "invalid IP") return } mac, _ := net.ParseMAC(lj.HWAddr) lease := Lease{ IP: ip, HWAddr: mac, Hostname: lj.Hostname, } err = s.AddStaticLease(lease) if err != nil { httpError(r, w, http.StatusBadRequest, "%s", err) return } } func (s *Server) handleDHCPRemoveStaticLease(w http.ResponseWriter, r *http.Request) { lj := staticLeaseJSON{} err := json.NewDecoder(r.Body).Decode(&lj) if err != nil { httpError(r, w, http.StatusBadRequest, "json.Decode: %s", err) return } ip, _ := parseIPv4(lj.IP) if ip == nil { httpError(r, w, http.StatusBadRequest, "invalid IP") return } mac, _ := net.ParseMAC(lj.HWAddr) lease := Lease{ IP: ip, HWAddr: mac, Hostname: lj.Hostname, } err = s.RemoveStaticLease(lease) if err != nil { httpError(r, w, http.StatusBadRequest, "%s", err) return } } func (s *Server) handleReset(w http.ResponseWriter, r *http.Request) { err := s.Stop() if err != nil { log.Error("DHCP: Stop: %s", err) } err = os.Remove(s.conf.DBFilePath) if err != nil && !os.IsNotExist(err) { log.Error("DHCP: os.Remove: %s: %s", s.conf.DBFilePath, err) } oldconf := s.conf s.conf = ServerConfig{} s.conf.LeaseDuration = 86400 s.conf.ICMPTimeout = 1000 s.conf.WorkDir = oldconf.WorkDir s.conf.HTTPRegister = oldconf.HTTPRegister s.conf.ConfigModified = oldconf.ConfigModified s.conf.DBFilePath = oldconf.DBFilePath s.conf.ConfigModified() } func (s *Server) registerHandlers() { s.conf.HTTPRegister("GET", "/control/dhcp/status", s.handleDHCPStatus) s.conf.HTTPRegister("GET", "/control/dhcp/interfaces", s.handleDHCPInterfaces) s.conf.HTTPRegister("POST", "/control/dhcp/set_config", s.handleDHCPSetConfig) s.conf.HTTPRegister("POST", "/control/dhcp/find_active_dhcp", s.handleDHCPFindActiveServer) s.conf.HTTPRegister("POST", "/control/dhcp/add_static_lease", s.handleDHCPAddStaticLease) s.conf.HTTPRegister("POST", "/control/dhcp/remove_static_lease", s.handleDHCPRemoveStaticLease) s.conf.HTTPRegister("POST", "/control/dhcp/reset", s.handleReset) }