v2fly/features/routing/dns/context.go

package dns

//go:generate go run github.com/v2fly/v2ray-core/v4/common/errors/errorgen

import (
	"github.com/v2fly/v2ray-core/v4/common/net"
	"github.com/v2fly/v2ray-core/v4/features/dns"
	"github.com/v2fly/v2ray-core/v4/features/routing"
)

// ResolvableContext is an implementation of routing.Context, with domain resolving capability.
type ResolvableContext struct {
	routing.Context
	dnsClient   dns.Client
	resolvedIPs []net.IP
}

// GetTargetIPs overrides original routing.Context's implementation.
func (ctx *ResolvableContext) GetTargetIPs() []net.IP {
	if ips := ctx.Context.GetTargetIPs(); len(ips) != 0 {
		return ips
	}

	if len(ctx.resolvedIPs) > 0 {
		return ctx.resolvedIPs
	}

	if domain := ctx.GetTargetDomain(); len(domain) != 0 {
		ips, err := ctx.dnsClient.LookupIP(domain)
		if err == nil {
			ctx.resolvedIPs = ips
			return ips
		}
		newError("resolve ip for ", domain).Base(err).WriteToLog()
	}

	return nil
}

// ContextWithDNSClient creates a new routing context with domain resolving capability.
// Resolved domain IPs can be retrieved by GetTargetIPs().
func ContextWithDNSClient(ctx routing.Context, client dns.Client) routing.Context {
	return &ResolvableContext{Context: ctx, dnsClient: client}
}