diff options
Diffstat (limited to 'src/pkg/net/dnsclient.go')
| -rw-r--r-- | src/pkg/net/dnsclient.go | 109 |
1 files changed, 93 insertions, 16 deletions
diff --git a/src/pkg/net/dnsclient.go b/src/pkg/net/dnsclient.go index 3252dd454..c3e727bce 100644 --- a/src/pkg/net/dnsclient.go +++ b/src/pkg/net/dnsclient.go @@ -21,6 +21,7 @@ import ( "rand" "sync" "time" + "sort" ) // DNSError represents a DNS lookup error. @@ -159,7 +160,7 @@ func tryOneName(cfg *dnsConfig, name string, qtype uint16) (cname string, addrs // all the cfg.servers[i] are IP addresses, which // Dial will use without a DNS lookup. server := cfg.servers[i] + ":53" - c, cerr := Dial("udp", "", server) + c, cerr := Dial("udp", server) if cerr != nil { err = cerr continue @@ -178,12 +179,23 @@ func tryOneName(cfg *dnsConfig, name string, qtype uint16) (cname string, addrs return } -func convertRR_A(records []dnsRR) []string { - addrs := make([]string, len(records)) +func convertRR_A(records []dnsRR) []IP { + addrs := make([]IP, len(records)) for i := 0; i < len(records); i++ { rr := records[i] a := rr.(*dnsRR_A).A - addrs[i] = IPv4(byte(a>>24), byte(a>>16), byte(a>>8), byte(a)).String() + addrs[i] = IPv4(byte(a>>24), byte(a>>16), byte(a>>8), byte(a)) + } + return addrs +} + +func convertRR_AAAA(records []dnsRR) []IP { + addrs := make([]IP, len(records)) + for i := 0; i < len(records); i++ { + rr := records[i] + a := make(IP, 16) + copy(a, rr.(*dnsRR_AAAA).AAAA[:]) + addrs[i] = a } return addrs } @@ -294,10 +306,8 @@ func lookup(name string, qtype uint16) (cname string, addrs []dnsRR, err os.Erro return } -// LookupHost looks for name using the local hosts file and DNS resolver. -// It returns the canonical name for the host and an array of that -// host's addresses. -func LookupHost(name string) (cname string, addrs []string, err os.Error) { +// goLookupHost is the native Go implementation of LookupHost. +func goLookupHost(name string) (addrs []string, err os.Error) { onceLoadConfig.Do(loadConfig) if dnserr != nil || cfg == nil { err = dnserr @@ -306,18 +316,69 @@ func LookupHost(name string) (cname string, addrs []string, err os.Error) { // Use entries from /etc/hosts if they match. addrs = lookupStaticHost(name) if len(addrs) > 0 { - cname = name + return + } + ips, err := goLookupIP(name) + if err != nil { + return + } + addrs = make([]string, 0, len(ips)) + for _, ip := range ips { + addrs = append(addrs, ip.String()) + } + return +} + +// goLookupIP is the native Go implementation of LookupIP. +func goLookupIP(name string) (addrs []IP, err os.Error) { + onceLoadConfig.Do(loadConfig) + if dnserr != nil || cfg == nil { + err = dnserr return } var records []dnsRR + var cname string cname, records, err = lookup(name, dnsTypeA) if err != nil { return } addrs = convertRR_A(records) + if cname != "" { + name = cname + } + _, records, err = lookup(name, dnsTypeAAAA) + if err != nil && len(addrs) > 0 { + // Ignore error because A lookup succeeded. + err = nil + } + if err != nil { + return + } + addrs = append(addrs, convertRR_AAAA(records)...) return } +// LookupCNAME returns the canonical DNS host for the given name. +// Callers that do not care about the canonical name can call +// LookupHost or LookupIP directly; both take care of resolving +// the canonical name as part of the lookup. +func LookupCNAME(name string) (cname string, err os.Error) { + onceLoadConfig.Do(loadConfig) + if dnserr != nil || cfg == nil { + err = dnserr + return + } + _, rr, err := lookup(name, dnsTypeCNAME) + if err != nil { + return + } + if len(rr) >= 0 { + cname = rr[0].(*dnsRR_CNAME).Cname + } + return +} + +// An SRV represents a single DNS SRV record. type SRV struct { Target string Port uint16 @@ -344,22 +405,38 @@ func LookupSRV(service, proto, name string) (cname string, addrs []*SRV, err os. return } +// An MX represents a single DNS MX record. type MX struct { Host string Pref uint16 } -func LookupMX(name string) (entries []*MX, err os.Error) { - var records []dnsRR - _, records, err = lookup(name, dnsTypeMX) +// byPref implements sort.Interface to sort MX records by preference +type byPref []*MX + +func (s byPref) Len() int { return len(s) } + +func (s byPref) Less(i, j int) bool { return s[i].Pref < s[j].Pref } + +func (s byPref) Swap(i, j int) { s[i], s[j] = s[j], s[i] } + +// LookupMX returns the DNS MX records for the given domain name sorted by preference. +func LookupMX(name string) (mx []*MX, err os.Error) { + _, rr, err := lookup(name, dnsTypeMX) if err != nil { return } - entries = make([]*MX, len(records)) - for i := range records { - r := records[i].(*dnsRR_MX) - entries[i] = &MX{r.Mx, r.Pref} + mx = make([]*MX, len(rr)) + for i := range rr { + r := rr[i].(*dnsRR_MX) + mx[i] = &MX{r.Mx, r.Pref} + } + // Shuffle the records to match RFC 5321 when sorted + for i := range mx { + j := rand.Intn(i + 1) + mx[i], mx[j] = mx[j], mx[i] } + sort.Sort(byPref(mx)) return } |