From e06186309ce8fdb8614aa982ba45aaf325099f98 Mon Sep 17 00:00:00 2001
From: George Tankersley <george.tankersley@gmail.com>
Date: Thu, 21 May 2020 19:07:37 -0400
Subject: [PATCH] dnsseed: separate IPv4 and IPv6 responses

---
 dnsseed/dnsseed.go    | 11 ++++++++++-
 zcash/address_book.go | 13 ++++++++++++-
 zcash/client.go       |  9 +++++++--
 3 files changed, 29 insertions(+), 4 deletions(-)

diff --git a/dnsseed/dnsseed.go b/dnsseed/dnsseed.go
index 76da4e6..40866c5 100644
--- a/dnsseed/dnsseed.go
+++ b/dnsseed/dnsseed.go
@@ -2,6 +2,7 @@ package dnsseed
 
 import (
 	"context"
+	"net"
 
 	"github.com/coredns/coredns/plugin"
 	"github.com/coredns/coredns/request"
@@ -34,7 +35,15 @@ func (zs ZcashSeeder) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns
 		return plugin.NextOrFailure(zs.Name(), zs.Next, ctx, w, r)
 	}
 
-	peerIPs := zs.seeder.Addresses(25)
+	var peerIPs []net.IP
+	switch state.QType() {
+	case dns.TypeA:
+		peerIPs = zs.seeder.Addresses(25)
+	case dns.TypeAAAA:
+		peerIPs = zs.seeder.AddressesV6(25)
+	default:
+		return dns.RcodeNotImplemented, nil
+	}
 
 	a := new(dns.Msg)
 	a.SetReply(r)
diff --git a/zcash/address_book.go b/zcash/address_book.go
index 16e1f2a..a38b269 100644
--- a/zcash/address_book.go
+++ b/zcash/address_book.go
@@ -169,7 +169,7 @@ func (bk *AddressBook) waitForAddresses(n int, done chan struct{}) {
 
 // GetAddressList returns a slice of n valid addresses in random order.
 // If there aren't enough known addresses, it returns as many as we have.
-func (bk *AddressBook) shuffleAddressList(n int) []net.IP {
+func (bk *AddressBook) shuffleAddressList(n int, v6 bool) []net.IP {
 	bk.addrState.RLock()
 	defer bk.addrState.RUnlock()
 
@@ -177,6 +177,17 @@ func (bk *AddressBook) shuffleAddressList(n int) []net.IP {
 
 	for k, v := range bk.peers {
 		if _, blacklisted := bk.blacklist[k]; blacklisted {
+			// Check in case we've accidentally registered a bad peer
+			continue
+		}
+
+		if v6 && v.netaddr.IP.To4() != nil {
+			// skip IPv4 addresses if we're asked for v6
+			continue
+		}
+
+		if !v6 && v.netaddr.IP.To4() == nil {
+			// skip IPv6 addresses if we're asked for v4
 			continue
 		}
 
diff --git a/zcash/client.go b/zcash/client.go
index 34fd63a..8e5d27e 100644
--- a/zcash/client.go
+++ b/zcash/client.go
@@ -368,9 +368,14 @@ func (s *Seeder) Ready() bool {
 	return s.WaitForAddresses(minimumReadyAddresses, 1*time.Millisecond) == nil
 }
 
-// Addresses returns a slice of n addresses or as many as we have if it's less than that.
+// Addresses returns a slice of n IPv4 addresses or as many as we have if it's less than that.
 func (s *Seeder) Addresses(n int) []net.IP {
-	return s.addrBook.shuffleAddressList(n)
+	return s.addrBook.shuffleAddressList(n, false)
+}
+
+// AddressesV6 returns a slice of n IPv6 addresses or as many as we have if it's less than that.
+func (s *Seeder) AddressesV6(n int) []net.IP {
+	return s.addrBook.shuffleAddressList(n, true)
 }
 
 // testBlacklist adds a peer to the blacklist directly, for testing.