From 118b170210962da5d088d196feccc6e14ba5a132 Mon Sep 17 00:00:00 2001
From: Simon Zolin <s.zolin@adguard.com>
Date: Tue, 26 May 2020 11:42:42 +0300
Subject: [PATCH] + rewrites: support exceptions:
*.host -> IP
my.host -> my.host
*.my.host -> *.my.host
Requests for my.host and *.my.host will be passed to upstream servers,
while all other requests for *.host will be answered with a rewritten IP
---
dnsfilter/dnsfilter.go | 7 +++++++
dnsfilter/rewrites.go | 10 +++++-----
dnsfilter/rewrites_test.go | 40 ++++++++++++++++++++++++++++++++++++++
3 files changed, 52 insertions(+), 5 deletions(-)
diff --git a/dnsfilter/dnsfilter.go b/dnsfilter/dnsfilter.go
index 6a79b79a..bcd597d8 100644
--- a/dnsfilter/dnsfilter.go
+++ b/dnsfilter/dnsfilter.go
@@ -390,6 +390,7 @@ func (d *Dnsfilter) CheckHost(host string, qtype uint16, setts *RequestFiltering
// Process rewrites table
// . Find CNAME for a domain name (exact match or by wildcard)
+// . if found and CNAME equals to domain name - this is an exception; exit
// . if found, set domain name to canonical name
// . repeat for the new domain name (Note: we return only the last CNAME)
// . Find A or AAAA record for a domain name (exact match or by wildcard)
@@ -409,6 +410,12 @@ func (d *Dnsfilter) processRewrites(host string) Result {
origHost := host
for len(rr) != 0 && rr[0].Type == dns.TypeCNAME {
log.Debug("Rewrite: CNAME for %s is %s", host, rr[0].Answer)
+
+ if host == rr[0].Answer { // "host == CNAME" is an exception
+ res.Reason = 0
+ return res
+ }
+
host = rr[0].Answer
_, ok := cnames[host]
if ok {
diff --git a/dnsfilter/rewrites.go b/dnsfilter/rewrites.go
index cbc02a16..166ff0bb 100644
--- a/dnsfilter/rewrites.go
+++ b/dnsfilter/rewrites.go
@@ -43,14 +43,14 @@ func (a rewritesArray) Len() int { return len(a) }
func (a rewritesArray) Swap(i, j int) { a[i], a[j] = a[j], a[i] }
// Priority:
-// . CNAME > A/AAAA;
-// . exact > wildcard;
-// . higher level wildcard > lower level wildcard
+// . CNAME < A/AAAA;
+// . exact < wildcard;
+// . higher level wildcard < lower level wildcard
func (a rewritesArray) Less(i, j int) bool {
if a[i].Type == dns.TypeCNAME && a[j].Type != dns.TypeCNAME {
- return false
- } else if a[i].Type != dns.TypeCNAME && a[j].Type == dns.TypeCNAME {
return true
+ } else if a[i].Type != dns.TypeCNAME && a[j].Type == dns.TypeCNAME {
+ return false
}
if isWildcard(a[i].Domain) {
diff --git a/dnsfilter/rewrites_test.go b/dnsfilter/rewrites_test.go
index 6da3e0f9..aac9cedd 100644
--- a/dnsfilter/rewrites_test.go
+++ b/dnsfilter/rewrites_test.go
@@ -125,3 +125,43 @@ func TestRewritesLevels(t *testing.T) {
assert.Equal(t, 1, len(r.IPList))
assert.Equal(t, "3.3.3.3", r.IPList[0].String())
}
+
+func TestRewritesException(t *testing.T) {
+ d := Dnsfilter{}
+ // wildcard; exception for a sub-domain
+ d.Rewrites = []RewriteEntry{
+ RewriteEntry{"*.host.com", "2.2.2.2", 0, nil},
+ RewriteEntry{"sub.host.com", "sub.host.com", 0, nil},
+ }
+ d.prepareRewrites()
+
+ // match sub-domain
+ r := d.processRewrites("my.host.com")
+ assert.Equal(t, ReasonRewrite, r.Reason)
+ assert.Equal(t, 1, len(r.IPList))
+ assert.Equal(t, "2.2.2.2", r.IPList[0].String())
+
+ // match sub-domain, but handle exception
+ r = d.processRewrites("sub.host.com")
+ assert.Equal(t, NotFilteredNotFound, r.Reason)
+}
+
+func TestRewritesExceptionWC(t *testing.T) {
+ d := Dnsfilter{}
+ // wildcard; exception for a sub-wildcard
+ d.Rewrites = []RewriteEntry{
+ RewriteEntry{"*.host.com", "2.2.2.2", 0, nil},
+ RewriteEntry{"*.sub.host.com", "*.sub.host.com", 0, nil},
+ }
+ d.prepareRewrites()
+
+ // match sub-domain
+ r := d.processRewrites("my.host.com")
+ assert.Equal(t, ReasonRewrite, r.Reason)
+ assert.Equal(t, 1, len(r.IPList))
+ assert.Equal(t, "2.2.2.2", r.IPList[0].String())
+
+ // match sub-domain, but handle exception
+ r = d.processRewrites("my.sub.host.com")
+ assert.Equal(t, NotFilteredNotFound, r.Reason)
+}