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package main
import (
"context"
"fmt"
"net"
"os"
"time"
)
const (
ipv6TestHost = "ipv6.google.com"
testPort = "443" // HTTPS port
)
func main() {
// --- Step 1: Fast DNS Lookup ---
// We'll use a separate, short timeout just for the DNS resolution.
// If DNS is broken, we'll know in a second or two.
dnsTimeout := 2 * time.Second
ctx, cancel := context.WithTimeout(context.Background(), dnsTimeout)
defer cancel()
// net.DefaultResolver.LookupIPAddr forces the resolver to look up the host.
// We specify "ip6" to ensure we only get AAAA records.
addrs, err := net.DefaultResolver.LookupIPAddr(ctx, "ip6", ipv6TestHost)
if err != nil {
fmt.Printf("IPv6 DNS resolution failed: %v\n", err)
fmt.Println("This likely means your network cannot resolve IPv6 addresses.")
os.Exit(1)
}
if len(addrs) == 0 {
fmt.Printf("No IPv6 addresses found for %s\n", ipv6TestHost)
os.Exit(1)
}
// If we get here, DNS is working. Let's use the first address we found.
targetIP := addrs[0].IP.String()
fmt.Printf("Successfully resolved %s to IPv6 address: %s\n", ipv6TestHost, targetIP)
// --- Step 2: Connection Attempt ---
// Now we try to connect to the IP we found. This tests routing and firewalls.
connectionTimeout := 3 * time.Second
conn, err := net.DialTimeout("tcp6", net.JoinHostPort(targetIP, testPort), connectionTimeout)
if err != nil {
fmt.Printf("IPv6 connection to %s failed: %v\n", targetIP, err)
fmt.Println("This likely means your network has an IPv6 routing or firewall issue.")
os.Exit(1)
}
defer conn.Close()
fmt.Println("IPv6 connectivity test successful.")
os.Exit(0)
}
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