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ipchecker.go
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/
ipchecker.go
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package ipchecker
import (
"errors"
"github.com/miekg/dns"
"github.com/sirupsen/logrus"
)
type IPChecker struct {
serverAddr string
client DNSClient
log *logrus.Entry
}
type Option func(*IPChecker)
func WithServerAddr(serverAddr string) Option {
return func(c *IPChecker) {
c.serverAddr = serverAddr
}
}
func WithLogger(logger *logrus.Entry) Option {
return func(c *IPChecker) {
c.log = logger
}
}
func WithDNSClient(dns DNSClient) Option {
return func(c *IPChecker) {
c.client = dns
}
}
func New(opts ...Option) *IPChecker {
c := &IPChecker{
log: logrus.NewEntry(logrus.New()),
client: &dns.Client{},
}
for _, apply := range opts {
apply(c)
}
c.log = c.log.WithFields(logrus.Fields{
"service": "ip_checker",
"server": c.serverAddr,
})
return c
}
func (c *IPChecker) CheckIP(domain string) (ip string, ttl uint32, err error) {
log := c.log.WithFields(logrus.Fields{
"method": "check_ip",
"domain": domain,
})
log.Debug("querying dns records for domain")
message := new(dns.Msg).SetQuestion(domain+".", dns.TypeA)
r, _, err := c.client.Exchange(message, c.serverAddr+":53")
if err != nil {
return "", 0, err
}
if len(r.Answer) == 0 {
return "", 0, errors.New("no answers returned")
}
for _, ans := range r.Answer {
if a, ok := ans.(*dns.A); ok {
ip = a.A.String()
ttl = ans.Header().Ttl
}
}
log.Debug("received dns answer record for domain")
return ip, ttl, nil
}