/
dns_query.go
55 lines (48 loc) · 1.37 KB
/
dns_query.go
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package main
import (
"context"
"net"
)
// force Dialer to connect via IPv4/v6 and a specific server
// code from https://github.com/Jamesits/myip/blob/master/src/opendns-dns.go
func dialContextFactory(mode Mode, server string) func(context.Context, string, string) (net.Conn, error) {
var ret func(context.Context, string, string) (net.Conn, error)
switch mode {
case MODE_IPv4:
ret = func(ctx context.Context, network, address string) (net.Conn, error) {
switch network {
case "tcp", "tcp4", "tcp6":
network = "tcp4"
case "udp", "udp4", "udp6":
network = "udp4"
}
return (&net.Dialer{}).DialContext(ctx, network, server)
}
case MODE_IPv6:
ret = func(ctx context.Context, network, address string) (net.Conn, error) {
switch network {
case "tcp", "tcp4", "tcp6":
network = "tcp6"
case "udp", "udp4", "udp6":
network = "udp6"
}
return (&net.Dialer{}).DialContext(ctx, network, server)
}
default:
ret = func(ctx context.Context, network, address string) (net.Conn, error) {
return (&net.Dialer{DualStack: true}).DialContext(ctx, network, server)
}
}
return ret
}
func newResolver() *net.Resolver {
resolver := &net.Resolver{
PreferGo: true,
}
return resolver
}
func newCustomResolver(mode Mode, server string) *net.Resolver {
resolver := newResolver()
resolver.Dial = dialContextFactory(mode, server)
return resolver
}