public-ip-tracker/tracker/ip/ip.go

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package ip
import (
"bytes"
"context"
"fmt"
"io"
"net"
"net/http"
"time"
)
const ifconfigURL = "https://ifconfig.me"
const httpMaxRead = 100
const httpTimeout = 10 * time.Second
type IPGetter struct {
httpClt *http.Client
remoteAddress string
timeout time.Duration
}
func (c *IPGetter) GetCurrentPublicIP(ctx context.Context) (net.IP, error) {
reqCtx, cancel := context.WithTimeout(ctx, c.timeout)
defer cancel()
req, err := http.NewRequestWithContext(reqCtx, http.MethodGet, c.remoteAddress, nil)
if err != nil {
return nil, fmt.Errorf("failed to prepare public IP request: %w", err)
}
resp, err := c.httpClt.Do(req)
if err != nil {
return nil, fmt.Errorf("failed to get current IP from ifconfig: %w", err)
}
if resp.StatusCode != http.StatusOK {
return nil, fmt.Errorf("invalid returncode %d", resp.StatusCode)
}
if resp.ContentLength > httpMaxRead {
return nil, fmt.Errorf("response too big: %d/%d", resp.ContentLength, httpMaxRead)
}
buf := bytes.NewBuffer([]byte{})
if _, err := io.CopyN(buf, resp.Body, resp.ContentLength); err != nil {
return nil, fmt.Errorf("error parsing body: %w", err)
}
content := string(buf.Bytes())
res := net.ParseIP(content)
if res == nil {
return nil, fmt.Errorf("got an invalid public IP %q", content)
}
return res, nil
}
func New() *IPGetter {
return &IPGetter{
httpClt: http.DefaultClient,
remoteAddress: ifconfigURL,
timeout: httpTimeout,
}
}