plugin/log - Support for Metadata (#2251)

* - add metadata support to Log

* - adapt ctx after rebase

5 files changed, 123 insertions, 19 deletions

diff --git a/plugin/log/README.md b/plugin/log/README.md
index 48e5acb6c..f2d89741c 100644
--- a/plugin/log/README.md
+++ b/plugin/log/README.md
@@ -61,6 +61,7 @@ The following place holders are supported:
 * `{class}`: qclass of the request
 * `{proto}`: protocol used (tcp or udp)
 * `{remote}`: client's IP address, for IPv6 addresses these are enclosed in brackets: `[::1]`
+* `{local}`: server's IP address, for IPv6 addresses these are enclosed in brackets: `[::1]`
 * `{size}`: request size in bytes
 * `{port}`: client's port
 * `{duration}`: response duration
@@ -72,6 +73,10 @@ The following place holders are supported:
 * `{>do}`: is the EDNS0 DO (DNSSEC OK) bit set in the query
 * `{>id}`: query ID
 * `{>opcode}`: query OPCODE
+* `{/[LABEL]}`: any metadata label is accepted as a place holder if it is enclosed between `{/` and  `}`.
+the place holder will be replaced by the corresponding metadata value or the default value `-` if label is not defined.
+
+
 
 The default Common Log Format is:
 
diff --git a/plugin/log/log.go b/plugin/log/log.go
index 685c55191..98f00d762 100644
--- a/plugin/log/log.go
+++ b/plugin/log/log.go
@@ -57,7 +57,7 @@ func (l Logger) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg)
 		// If we don't set up a class in config, the default "all" will be added
 		// and we shouldn't have an empty rule.Class.
 		if rule.Class[response.All] || rule.Class[class] {
-			rep := replacer.New(r, rrw, CommonLogEmptyValue)
+			rep := replacer.New(ctx, r, rrw, CommonLogEmptyValue)
 			clog.Infof(rep.Replace(rule.Format))
 		}
 
diff --git a/plugin/pkg/replacer/replacer.go b/plugin/pkg/replacer/replacer.go
index 695e9e392..8c8032c76 100644
--- a/plugin/pkg/replacer/replacer.go
+++ b/plugin/pkg/replacer/replacer.go
@@ -1,10 +1,12 @@
 package replacer
 
 import (
+	"context"
 	"strconv"
 	"strings"
 	"time"
 
+	"github.com/coredns/coredns/plugin/metadata"
 	"github.com/coredns/coredns/plugin/pkg/dnstest"
 	"github.com/coredns/coredns/request"
 
@@ -21,6 +23,7 @@ type Replacer interface {
 }
 
 type replacer struct {
+	ctx          context.Context
 	replacements map[string]string
 	emptyValue   string
 }
@@ -31,9 +34,10 @@ type replacer struct {
 // values into the replacer. rr may be nil if it is not
 // available. emptyValue should be the string that is used
 // in place of empty string (can still be empty string).
-func New(r *dns.Msg, rr *dnstest.Recorder, emptyValue string) Replacer {
+func New(ctx context.Context, r *dns.Msg, rr *dnstest.Recorder, emptyValue string) Replacer {
 	req := request.Request{W: rr, Req: r}
 	rep := replacer{
+		ctx: ctx,
 		replacements: map[string]string{
 			"{type}":   req.Type(),
 			"{name}":   req.Name(),
@@ -43,6 +47,7 @@ func New(r *dns.Msg, rr *dnstest.Recorder, emptyValue string) Replacer {
 			"{size}":   strconv.Itoa(req.Len()),
 			"{remote}": addrToRFC3986(req.IP()),
 			"{port}":   req.Port(),
+			"{local}":  addrToRFC3986(req.LocalIP()),
 		},
 		emptyValue: emptyValue,
 	}
@@ -71,23 +76,36 @@ func New(r *dns.Msg, rr *dnstest.Recorder, emptyValue string) Replacer {
 // Replace performs a replacement of values on s and returns
 // the string with the replaced values.
 func (r replacer) Replace(s string) string {
-	// Header replacements - these are case-insensitive, so we can't just use strings.Replace()
-	for strings.Contains(s, headerReplacer) {
-		idxStart := strings.Index(s, headerReplacer)
-		endOffset := idxStart + len(headerReplacer)
-		idxEnd := strings.Index(s[endOffset:], "}")
-		if idxEnd > -1 {
-			placeholder := strings.ToLower(s[idxStart : endOffset+idxEnd+1])
-			replacement := r.replacements[placeholder]
-			if replacement == "" {
-				replacement = r.emptyValue
+
+	// declare a function that replace based on header matching
+	fscanAndReplace := func(s string, header string, replace func(string) string) string {
+		b := strings.Builder{}
+		for strings.Contains(s, header) {
+			idxStart := strings.Index(s, header)
+			endOffset := idxStart + len(header)
+			idxEnd := strings.Index(s[endOffset:], "}")
+			if idxEnd > -1 {
+				placeholder := strings.ToLower(s[idxStart : endOffset+idxEnd+1])
+				replacement := replace(placeholder)
+				if replacement == "" {
+					replacement = r.emptyValue
+				}
+				b.WriteString(s[:idxStart])
+				b.WriteString(replacement)
+				s = s[endOffset+idxEnd+1:]
+			} else {
+				break
 			}
-			s = s[:idxStart] + replacement + s[endOffset+idxEnd+1:]
-		} else {
-			break
 		}
+		b.WriteString(s)
+		return b.String()
 	}
 
+	// Header replacements - these are case-insensitive, so we can't just use strings.Replace()
+	s = fscanAndReplace(s, headerReplacer, func(placeholder string) string {
+		return r.replacements[placeholder]
+	})
+
 	// Regular replacements - these are easier because they're case-sensitive
 	for placeholder, replacement := range r.replacements {
 		if replacement == "" {
@@ -96,6 +114,16 @@ func (r replacer) Replace(s string) string {
 		s = strings.Replace(s, placeholder, replacement, -1)
 	}
 
+	// Metadata label replacements
+	s = fscanAndReplace(s, headerLabelReplacer, func(placeholder string) string {
+		// label place holder has the format {/<label>}
+		fm := metadata.ValueFunc(r.ctx, placeholder[len(headerLabelReplacer):len(placeholder)-1])
+		if fm != nil {
+			return fm()
+		}
+		return ""
+	})
+
 	return s
 }
 
@@ -161,4 +189,7 @@ func addrToRFC3986(addr string) string {
 	return addr
 }
 
-const headerReplacer = "{>"
+const (
+	headerReplacer      = "{>"
+	headerLabelReplacer = "{/"
+)
diff --git a/plugin/pkg/replacer/replacer_test.go b/plugin/pkg/replacer/replacer_test.go
index 2fcaafc92..a813057d8 100644
--- a/plugin/pkg/replacer/replacer_test.go
+++ b/plugin/pkg/replacer/replacer_test.go
@@ -1,9 +1,13 @@
 package replacer
 
 import (
+	"context"
 	"strings"
 	"testing"
 
+	"github.com/coredns/coredns/plugin/metadata"
+	"github.com/coredns/coredns/request"
+
 	"github.com/coredns/coredns/plugin/pkg/dnstest"
 	"github.com/coredns/coredns/plugin/test"
 
@@ -17,7 +21,7 @@ func TestNewReplacer(t *testing.T) {
 	r.SetQuestion("example.org.", dns.TypeHINFO)
 	r.MsgHdr.AuthenticatedData = true
 
-	replaceValues := New(r, w, "")
+	replaceValues := New(context.TODO(), r, w, "")
 
 	switch v := replaceValues.(type) {
 	case replacer:
@@ -47,7 +51,7 @@ func TestSet(t *testing.T) {
 	r.SetQuestion("example.org.", dns.TypeHINFO)
 	r.MsgHdr.AuthenticatedData = true
 
-	repl := New(r, w, "")
+	repl := New(context.TODO(), r, w, "")
 
 	repl.Set("name", "coredns.io.")
 	repl.Set("type", "A")
@@ -63,3 +67,66 @@ func TestSet(t *testing.T) {
 		t.Error("Expected size replacement failed")
 	}
 }
+
+type testProvider map[string]metadata.Func
+
+func (tp testProvider) Metadata(ctx context.Context, state request.Request) context.Context {
+	for k, v := range tp {
+		metadata.SetValueFunc(ctx, k, v)
+	}
+	return ctx
+}
+
+type testHandler struct{ ctx context.Context }
+
+func (m *testHandler) Name() string { return "test" }
+
+func (m *testHandler) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
+	m.ctx = ctx
+	return 0, nil
+}
+
+func TestMetadataReplacement(t *testing.T) {
+
+	mdata := testProvider{
+		"test/key2": func() string { return "two" },
+	}
+
+	tests := []struct {
+		expr   string
+		result string
+	}{
+		{"{name}", "example.org."},
+		{"{/test/key2}", "two"},
+		{"TYPE={type}, NAME={name}, BUFSIZE={>bufsize}, WHAT={/test/key2} .. and more", "TYPE=HINFO, NAME=example.org., BUFSIZE=512, WHAT=two .. and more"},
+		{"{/test/key2}{/test/key4}", "two-"},
+		{"{test/key2", "{test/key2"}, // if last } is missing, the end of format is considered static text
+		{"{/test-key2}", "-"},        // everything that is not a placeholder for log or a metadata label is invalid
+	}
+
+	next := &testHandler{} // fake handler which stores the resulting context
+	m := metadata.Metadata{
+		Zones:     []string{"."},
+		Providers: []metadata.Provider{mdata},
+		Next:      next,
+	}
+
+	ctx := context.TODO()
+	m.ServeDNS(ctx, &test.ResponseWriter{}, new(dns.Msg))
+	nctx := next.ctx
+
+	w := dnstest.NewRecorder(&test.ResponseWriter{})
+
+	r := new(dns.Msg)
+	r.SetQuestion("example.org.", dns.TypeHINFO)
+	r.MsgHdr.AuthenticatedData = true
+
+	repl := New(nctx, r, w, "-")
+
+	for i, ts := range tests {
+		r := repl.Replace(ts.expr)
+		if r != ts.result {
+			t.Errorf("Test %d - expr : %s, expected replacement being %s, and got %s", i, ts.expr, ts.result, r)
+		}
+	}
+}
diff --git a/plugin/rewrite/condition.go b/plugin/rewrite/condition.go
index f8d2a9f08..97ca99753 100644
--- a/plugin/rewrite/condition.go
+++ b/plugin/rewrite/condition.go
@@ -1,6 +1,7 @@
 package rewrite
 
 import (
+	"context"
 	"fmt"
 	"regexp"
 	"strings"
@@ -22,7 +23,7 @@ const (
 	NotMatch   = "not_match"
 )
 
-func newReplacer(r *dns.Msg) replacer.Replacer { return replacer.New(r, nil, "") }
+func newReplacer(r *dns.Msg) replacer.Replacer { return replacer.New(context.TODO(), r, nil, "") }
 
 // condition is a rewrite condition.
 type condition func(string, string) bool