From e66649a45f0fc024381e600541ce82712580e752 Mon Sep 17 00:00:00 2001
From: Shawn Carey <shawn.carey@netfoundry.io>
Date: Thu, 1 Aug 2024 15:28:43 -0400
Subject: [PATCH] check for existing hostname/IP when applying intercept
 address

---
 tunnel/dns/dummy.go         | 5 +++++
 tunnel/dns/file.go          | 4 ++++
 tunnel/dns/refcount.go      | 4 ++++
 tunnel/dns/resolver.go      | 1 +
 tunnel/dns/server.go        | 6 ++++--
 tunnel/intercept/iputils.go | 5 +++++
 6 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/tunnel/dns/dummy.go b/tunnel/dns/dummy.go
index e109ab1ae..f3fd42b04 100644
--- a/tunnel/dns/dummy.go
+++ b/tunnel/dns/dummy.go
@@ -22,6 +22,11 @@ func (d dummy) Lookup(_ net.IP) (string, error) {
 	return "", nil
 }
 
+func (d dummy) LookupIP(_ string) (net.IP, bool) {
+	pfxlog.Logger().Warnf("dummy resolver does not store hostname/ip mappings")
+	return nil, false
+}
+
 func (d dummy) RemoveHostname(_ string) net.IP {
 	return nil
 }
diff --git a/tunnel/dns/file.go b/tunnel/dns/file.go
index 6e09cc214..161858665 100644
--- a/tunnel/dns/file.go
+++ b/tunnel/dns/file.go
@@ -60,6 +60,10 @@ func (h *hostFile) Lookup(_ net.IP) (string, error) {
 	return "", fmt.Errorf("not implemented")
 }
 
+func (h *hostFile) LookupIP(_ string) (net.IP, bool) {
+	return nil, false
+}
+
 func (h *hostFile) AddHostname(hostname string, ip net.IP) error {
 	h.mutex.Lock()
 	defer h.mutex.Unlock()
diff --git a/tunnel/dns/refcount.go b/tunnel/dns/refcount.go
index 55b67b4b9..68f085b3d 100644
--- a/tunnel/dns/refcount.go
+++ b/tunnel/dns/refcount.go
@@ -21,6 +21,10 @@ func (self *RefCountingResolver) Lookup(ip net.IP) (string, error) {
 	return self.wrapped.Lookup(ip)
 }
 
+func (self *RefCountingResolver) LookupIP(hostname string) (net.IP, bool) {
+	return self.wrapped.LookupIP(hostname)
+}
+
 func (self *RefCountingResolver) AddDomain(name string, cb func(string) (net.IP, error)) error {
 	return self.wrapped.AddDomain(name, cb)
 }
diff --git a/tunnel/dns/resolver.go b/tunnel/dns/resolver.go
index d8279b632..0722b7228 100644
--- a/tunnel/dns/resolver.go
+++ b/tunnel/dns/resolver.go
@@ -22,6 +22,7 @@ type Resolver interface {
 	AddHostname(string, net.IP) error
 	AddDomain(string, func(string) (net.IP, error)) error
 	Lookup(net.IP) (string, error)
+	LookupIP(string) (net.IP, bool)
 	RemoveHostname(string) net.IP
 	RemoveDomain(string)
 	Cleanup() error
diff --git a/tunnel/dns/server.go b/tunnel/dns/server.go
index 07c782834..e728d6e07 100644
--- a/tunnel/dns/server.go
+++ b/tunnel/dns/server.go
@@ -157,7 +157,7 @@ func (r *resolver) testSystemResolver() error {
 	return nil
 }
 
-func (r *resolver) getHostnameIp(name string) (net.IP, bool) {
+func (r *resolver) LookupIP(name string) (net.IP, bool) {
 	r.namesMtx.Lock()
 	defer r.namesMtx.Unlock()
 	canonical := strings.ToLower(name)
@@ -166,7 +166,7 @@ func (r *resolver) getHostnameIp(name string) (net.IP, bool) {
 }
 
 func (r *resolver) getAddress(name string) (net.IP, error) {
-	a, ok := r.getHostnameIp(name)
+	a, ok := r.LookupIP(name)
 	if ok {
 		return a, nil
 	}
@@ -271,6 +271,8 @@ func (r *resolver) AddHostname(hostname string, ip net.IP) error {
 		log.Infof("adding %s = %s to resolver", hostname, ip.String())
 		r.names[canonical] = ip
 		r.ips[ip.String()] = canonical[0 : len(canonical)-1] // drop the dot
+	} else {
+		log.Infof("hostname %s already assigned (%s)", hostname, r.names[canonical])
 	}
 
 	return nil
diff --git a/tunnel/intercept/iputils.go b/tunnel/intercept/iputils.go
index 74888475c..e3f3a1e84 100644
--- a/tunnel/intercept/iputils.go
+++ b/tunnel/intercept/iputils.go
@@ -82,6 +82,11 @@ func getDnsIp(host string, addrCB func(*net.IPNet, bool), svc *entities.Service,
 	defer dnsCurrentIpMtx.Unlock()
 	var ip netip.Addr
 
+	foundIP, found := resolver.LookupIP(host + ".")
+	if found {
+		return foundIP, nil
+	}
+
 	// look for returned IPs first
 	if dnsRecycledIps.Len() > 0 {
 		e := dnsRecycledIps.Front()