| // 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. |
| |
| // +build darwin dragonfly freebsd linux netbsd openbsd solaris |
| |
| package net |
| |
| import ( |
| "context" |
| "sync" |
| ) |
| |
| var onceReadProtocols sync.Once |
| |
| // readProtocols loads contents of /etc/protocols into protocols map |
| // for quick access. |
| func readProtocols() { |
| if file, err := open("/etc/protocols"); err == nil { |
| for line, ok := file.readLine(); ok; line, ok = file.readLine() { |
| // tcp 6 TCP # transmission control protocol |
| if i := byteIndex(line, '#'); i >= 0 { |
| line = line[0:i] |
| } |
| f := getFields(line) |
| if len(f) < 2 { |
| continue |
| } |
| if proto, _, ok := dtoi(f[1]); ok { |
| if _, ok := protocols[f[0]]; !ok { |
| protocols[f[0]] = proto |
| } |
| for _, alias := range f[2:] { |
| if _, ok := protocols[alias]; !ok { |
| protocols[alias] = proto |
| } |
| } |
| } |
| } |
| file.close() |
| } |
| } |
| |
| // lookupProtocol looks up IP protocol name in /etc/protocols and |
| // returns correspondent protocol number. |
| func lookupProtocol(_ context.Context, name string) (int, error) { |
| onceReadProtocols.Do(readProtocols) |
| proto, found := protocols[name] |
| if !found { |
| return 0, &AddrError{Err: "unknown IP protocol specified", Addr: name} |
| } |
| return proto, nil |
| } |
| |
| func lookupHost(ctx context.Context, host string) (addrs []string, err error) { |
| order := systemConf().hostLookupOrder(host) |
| if order == hostLookupCgo { |
| if addrs, err, ok := cgoLookupHost(ctx, host); ok { |
| return addrs, err |
| } |
| // cgo not available (or netgo); fall back to Go's DNS resolver |
| order = hostLookupFilesDNS |
| } |
| return goLookupHostOrder(ctx, host, order) |
| } |
| |
| func lookupIP(ctx context.Context, host string) (addrs []IPAddr, err error) { |
| order := systemConf().hostLookupOrder(host) |
| if order == hostLookupCgo { |
| if addrs, err, ok := cgoLookupIP(ctx, host); ok { |
| return addrs, err |
| } |
| // cgo not available (or netgo); fall back to Go's DNS resolver |
| order = hostLookupFilesDNS |
| } |
| return goLookupIPOrder(ctx, host, order) |
| } |
| |
| func lookupPort(ctx context.Context, network, service string) (int, error) { |
| // TODO: use the context if there ever becomes a need. Related |
| // is issue 15321. But port lookup generally just involves |
| // local files, and the os package has no context support. The |
| // files might be on a remote filesystem, though. This should |
| // probably race goroutines if ctx != context.Background(). |
| if systemConf().canUseCgo() { |
| if port, err, ok := cgoLookupPort(ctx, network, service); ok { |
| return port, err |
| } |
| } |
| return goLookupPort(network, service) |
| } |
| |
| func lookupCNAME(ctx context.Context, name string) (string, error) { |
| if systemConf().canUseCgo() { |
| if cname, err, ok := cgoLookupCNAME(ctx, name); ok { |
| return cname, err |
| } |
| } |
| return goLookupCNAME(ctx, name) |
| } |
| |
| func lookupSRV(ctx context.Context, service, proto, name string) (string, []*SRV, error) { |
| var target string |
| if service == "" && proto == "" { |
| target = name |
| } else { |
| target = "_" + service + "._" + proto + "." + name |
| } |
| cname, rrs, err := lookup(ctx, target, dnsTypeSRV) |
| if err != nil { |
| return "", nil, err |
| } |
| srvs := make([]*SRV, len(rrs)) |
| for i, rr := range rrs { |
| rr := rr.(*dnsRR_SRV) |
| srvs[i] = &SRV{Target: rr.Target, Port: rr.Port, Priority: rr.Priority, Weight: rr.Weight} |
| } |
| byPriorityWeight(srvs).sort() |
| return cname, srvs, nil |
| } |
| |
| func lookupMX(ctx context.Context, name string) ([]*MX, error) { |
| _, rrs, err := lookup(ctx, name, dnsTypeMX) |
| if err != nil { |
| return nil, err |
| } |
| mxs := make([]*MX, len(rrs)) |
| for i, rr := range rrs { |
| rr := rr.(*dnsRR_MX) |
| mxs[i] = &MX{Host: rr.Mx, Pref: rr.Pref} |
| } |
| byPref(mxs).sort() |
| return mxs, nil |
| } |
| |
| func lookupNS(ctx context.Context, name string) ([]*NS, error) { |
| _, rrs, err := lookup(ctx, name, dnsTypeNS) |
| if err != nil { |
| return nil, err |
| } |
| nss := make([]*NS, len(rrs)) |
| for i, rr := range rrs { |
| nss[i] = &NS{Host: rr.(*dnsRR_NS).Ns} |
| } |
| return nss, nil |
| } |
| |
| func lookupTXT(ctx context.Context, name string) ([]string, error) { |
| _, rrs, err := lookup(ctx, name, dnsTypeTXT) |
| if err != nil { |
| return nil, err |
| } |
| txts := make([]string, len(rrs)) |
| for i, rr := range rrs { |
| txts[i] = rr.(*dnsRR_TXT).Txt |
| } |
| return txts, nil |
| } |
| |
| func lookupAddr(ctx context.Context, addr string) ([]string, error) { |
| if systemConf().canUseCgo() { |
| if ptrs, err, ok := cgoLookupPTR(ctx, addr); ok { |
| return ptrs, err |
| } |
| } |
| return goLookupPTR(ctx, addr) |
| } |