proposal: net: only request DNS A record when IPv6 not support, when using the net.Dial method #58995
Description
Problem:
when use net or net/http start reqeust to domain name, like this:
http.Get("https://golang.org/")
net.Dial("tcp", "golang.org:80")
net.Dial("udp", "golang.org:443")
The method DialContext of net.Dialer will resolve both A and AAAA records for a domain name, regardless of whether the machine's network supports IPv6 or not. If not support IPv6, DNS AAAA requests is unnecessary, it will cause additional cost.
Possible solution:
change file: go/src/net/dial.go
old:
func (d *Dialer) DialContext(ctx context.Context, network, address string) (Conn, error) {
...
addrs, err := d.resolver().resolveAddrList(resolveCtx, "dial", network, address, d.LocalAddr)
...
}
new:
func (d *Dialer) DialContext(ctx context.Context, network, address string) (Conn, error) {
...
networkForResolve := network
switch network {
case "tcp", "udp":
if !supportsIPv6() {
networkForResolve = network + "4"
}
}
addrs, err := d.resolver().resolveAddrList(resolveCtx, "dial", networkForResolve, address, d.LocalAddr)
...
}