Enhance DNS and Dialer (#341)

common/log/dns.go

@@ -0,0 +1,59 @@
+package log
+
+import (
+	"net"
+	"strings"
+	"time"
+)
+
+type DNSLog struct {
+	Server  string
+	Domain  string
+	Result  []net.IP
+	Status  dnsStatus
+	Elapsed time.Duration
+	Error   error
+}
+
+func (l *DNSLog) String() string {
+	builder := &strings.Builder{}
+
+	// Server got answer: domain -> [ip1, ip2] 23ms
+	builder.WriteString(l.Server)
+	builder.WriteString(" ")
+	builder.WriteString(string(l.Status))
+	builder.WriteString(" ")
+	builder.WriteString(l.Domain)
+	builder.WriteString(" -> [")
+	builder.WriteString(joinNetIP(l.Result))
+	builder.WriteString("]")
+
+	if l.Elapsed > 0 {
+		builder.WriteString(" ")
+		builder.WriteString(l.Elapsed.String())
+	}
+	if l.Error != nil {
+		builder.WriteString(" <")
+		builder.WriteString(l.Error.Error())
+		builder.WriteString(">")
+	}
+	return builder.String()
+}
+
+type dnsStatus string
+
+var (
+	DNSQueried  = dnsStatus("got answer:")
+	DNSCacheHit = dnsStatus("cache HIT:")
+)
+
+func joinNetIP(ips []net.IP) string {
+	if len(ips) == 0 {
+		return ""
+	}
+	sips := make([]string, 0, len(ips))
+	for _, ip := range ips {
+		sips = append(sips, ip.String())
+	}
+	return strings.Join(sips, ", ")
+}