// Copyright 2011 The Go Authors. All rights reserved. // Use of this source code is governed by a BSD-style // license that can be found in the LICENSE file. package net import ( "errors" "os" ) func query(filename, query string, bufSize int) (res []string, err error) { file, err := os.OpenFile(filename, os.O_RDWR, 0) if err != nil { return } defer file.Close() _, err = file.Seek(0, 0) if err != nil { return } _, err = file.WriteString(query) if err != nil { return } _, err = file.Seek(0, 0) if err != nil { return } buf := make([]byte, bufSize) for { n, _ := file.Read(buf) if n <= 0 { break } res = append(res, string(buf[:n])) } return } func queryCS(net, host, service string) (res []string, err error) { switch net { case "tcp4", "tcp6": net = "tcp" case "udp4", "udp6": net = "udp" } if host == "" { host = "*" } return query(netdir+"/cs", net+"!"+host+"!"+service, 128) } func queryCS1(net string, ip IP, port int) (clone, dest string, err error) { ips := "*" if len(ip) != 0 && !ip.IsUnspecified() { ips = ip.String() } lines, err := queryCS(net, ips, itoa(port)) if err != nil { return } f := getFields(lines[0]) if len(f) < 2 { return "", "", errors.New("bad response from ndb/cs") } clone, dest = f[0], f[1] return } func queryDNS(addr string, typ string) (res []string, err error) { return query(netdir+"/dns", addr+" "+typ, 1024) } // toLower returns a lower-case version of in. Restricting us to // ASCII is sufficient to handle the IP protocol names and allow // us to not depend on the strings and unicode packages. func toLower(in string) string { for _, c := range in { if 'A' <= c && c <= 'Z' { // Has upper case; need to fix. out := []byte(in) for i := 0; i < len(in); i++ { c := in[i] if 'A' <= c && c <= 'Z' { c += 'a' - 'A' } out[i] = c } return string(out) } } return in } // lookupProtocol looks up IP protocol name and returns // the corresponding protocol number. func lookupProtocol(name string) (proto int, err error) { lines, err := query(netdir+"/cs", "!protocol="+toLower(name), 128) if err != nil { return 0, err } unknownProtoError := errors.New("unknown IP protocol specified: " + name) if len(lines) == 0 { return 0, unknownProtoError } f := getFields(lines[0]) if len(f) < 2 { return 0, unknownProtoError } s := f[1] if n, _, ok := dtoi(s, byteIndex(s, '=')+1); ok { return n, nil } return 0, unknownProtoError } func lookupHost(host string) (addrs []string, err error) { // Use netdir/cs instead of netdir/dns because cs knows about // host names in local network (e.g. from /lib/ndb/local) lines, err := queryCS("net", host, "1") if err != nil { return } loop: for _, line := range lines { f := getFields(line) if len(f) < 2 { continue } addr := f[1] if i := byteIndex(addr, '!'); i >= 0 { addr = addr[:i] // remove port } if ParseIP(addr) == nil { continue } // only return unique addresses for _, a := range addrs { if a == addr { continue loop } } addrs = append(addrs, addr) } return } func lookupIP(host string) (ips []IP, err error) { addrs, err := LookupHost(host) if err != nil { return } for _, addr := range addrs { if ip := ParseIP(addr); ip != nil { ips = append(ips, ip) } } return } func lookupPort(network, service string) (port int, err error) { switch network { case "tcp4", "tcp6": network = "tcp" case "udp4", "udp6": network = "udp" } lines, err := queryCS(network, "127.0.0.1", service) if err != nil { return } unknownPortError := &AddrError{"unknown port", network + "/" + service} if len(lines) == 0 { return 0, unknownPortError } f := getFields(lines[0]) if len(f) < 2 { return 0, unknownPortError } s := f[1] if i := byteIndex(s, '!'); i >= 0 { s = s[i+1:] // remove address } if n, _, ok := dtoi(s, 0); ok { return n, nil } return 0, unknownPortError } func lookupCNAME(name string) (cname string, err error) { lines, err := queryDNS(name, "cname") if err != nil { return } if len(lines) > 0 { if f := getFields(lines[0]); len(f) >= 3 { return f[2] + ".", nil } } return "", errors.New("bad response from ndb/dns") } func lookupSRV(service, proto, name string) (cname string, addrs []*SRV, err error) { var target string if service == "" && proto == "" { target = name } else { target = "_" + service + "._" + proto + "." + name } lines, err := queryDNS(target, "srv") if err != nil { return } for _, line := range lines { f := getFields(line) if len(f) < 6 { continue } port, _, portOk := dtoi(f[4], 0) priority, _, priorityOk := dtoi(f[3], 0) weight, _, weightOk := dtoi(f[2], 0) if !(portOk && priorityOk && weightOk) { continue } addrs = append(addrs, &SRV{f[5], uint16(port), uint16(priority), uint16(weight)}) cname = f[0] } byPriorityWeight(addrs).sort() return } func lookupMX(name string) (mx []*MX, err error) { lines, err := queryDNS(name, "mx") if err != nil { return } for _, line := range lines { f := getFields(line) if len(f) < 4 { continue } if pref, _, ok := dtoi(f[2], 0); ok { mx = append(mx, &MX{f[3], uint16(pref)}) } } byPref(mx).sort() return } func lookupNS(name string) (ns []*NS, err error) { lines, err := queryDNS(name, "ns") if err != nil { return } for _, line := range lines { f := getFields(line) if len(f) < 3 { continue } ns = append(ns, &NS{f[2]}) } return } func lookupTXT(name string) (txt []string, err error) { lines, err := queryDNS(name, "txt") if err != nil { return } for _, line := range lines { if i := byteIndex(line, '\t'); i >= 0 { txt = append(txt, line[i+1:]) } } return } func lookupAddr(addr string) (name []string, err error) { arpa, err := reverseaddr(addr) if err != nil { return } lines, err := queryDNS(arpa, "ptr") if err != nil { return } for _, line := range lines { f := getFields(line) if len(f) < 3 { continue } name = append(name, f[2]) } return }