Create geoip plugin (#4688)

* Create geoip plugin

Signed-off-by: Sven Nebel <nebel.sven@gmail.com>

* Update plugin/geoip/README.md

Co-authored-by: Miek Gieben <miek@miek.nl>
Signed-off-by: Sven Nebel <nebel.sven@gmail.com>

* Update plugin/geoip/README.md

Co-authored-by: Miek Gieben <miek@miek.nl>
Signed-off-by: Sven Nebel <nebel.sven@gmail.com>

* Update plugin/geoip/README.md

Co-authored-by: Miek Gieben <miek@miek.nl>
Signed-off-by: Sven Nebel <nebel.sven@gmail.com>

* Move DBFILE bullet below example

Signed-off-by: Sven Nebel <nebel.sven@gmail.com>

* Update plugin/geoip/README.md

Co-authored-by: Miek Gieben <miek@miek.nl>
Signed-off-by: Sven Nebel <nebel.sven@gmail.com>

* Remove plugin name test case

Signed-off-by: Sven Nebel <nebel.sven@gmail.com>

* Remove languages option

Signed-off-by: Sven Nebel <nebel.sven@gmail.com>

* Update free database link

Signed-off-by: Sven Nebel <nebel.sven@gmail.com>

* Remove last language bits

Signed-off-by: Sven Nebel <nebel.sven@gmail.com>

* Use 127.0.0.1 as probing IP

Signed-off-by: Sven Nebel <nebel.sven@gmail.com>

* Update plugin/geoip/geoip.go

Co-authored-by: Miek Gieben <miek@miek.nl>
Signed-off-by: Sven Nebel <nebel.sven@gmail.com>

* Update plugin/geoip/geoip.go

Co-authored-by: Miek Gieben <miek@miek.nl>
Signed-off-by: Sven Nebel <nebel.sven@gmail.com>

* Use relative path for fixtures dir

Signed-off-by: Sven Nebel <nebel.sven@gmail.com>

* Set names with default string zero value

Signed-off-by: Sven Nebel <nebel.sven@gmail.com>

* Remove unused db types

Signed-off-by: Sven Nebel <nebel.sven@gmail.com>

* Remove non city databases in testdata

Signed-off-by: Sven Nebel <nebel.sven@gmail.com>

* Remove create databases main

Signed-off-by: Sven Nebel <nebel.sven@gmail.com>

* Fix metadata label format test case

Signed-off-by: Sven Nebel <nebel.sven@gmail.com>

* Fix import path block

Signed-off-by: Sven Nebel <nebel.sven@gmail.com>

* go fmt after changes

Signed-off-by: Sven Nebel <nebel.sven@gmail.com>

* Tidy up go.mod and go.sum

Signed-off-by: Sven Nebel <nebel.sven@gmail.com>

* Add plugin to CODEOWNERS

Signed-off-by: Sven Nebel <nebel.sven@gmail.com>

Co-authored-by: Miek Gieben <miek@miek.nl>

1 files changed, 95 insertions, 0 deletions

diff --git a/plugin/geoip/geoip.go b/plugin/geoip/geoip.go
new file mode 100644
index 000000000..674157716
--- /dev/null
+++ b/plugin/geoip/geoip.go
@@ -0,0 +1,95 @@
+// Package geoip implements a max mind database plugin.
+package geoip
+
+import (
+	"context"
+	"fmt"
+	"net"
+	"path/filepath"
+
+	"github.com/coredns/coredns/plugin"
+	clog "github.com/coredns/coredns/plugin/pkg/log"
+	"github.com/coredns/coredns/request"
+
+	"github.com/miekg/dns"
+	"github.com/oschwald/geoip2-golang"
+)
+
+var log = clog.NewWithPlugin(pluginName)
+
+// GeoIP is a plugin that add geo location data to the request context by looking up a maxmind
+// geoIP2 database, and which data can be later consumed by other middlewares.
+type GeoIP struct {
+	Next plugin.Handler
+	db   db
+}
+
+type db struct {
+	*geoip2.Reader
+	// provides defines the schemas that can be obtained by querying this database, by using
+	// bitwise operations.
+	provides int
+}
+
+const (
+	city = 1 << iota
+)
+
+var probingIP = net.ParseIP("127.0.0.1")
+
+func newGeoIP(dbPath string) (*GeoIP, error) {
+	reader, err := geoip2.Open(dbPath)
+	if err != nil {
+		return nil, fmt.Errorf("failed to open database file: %v", err)
+	}
+	db := db{Reader: reader}
+	schemas := []struct {
+		provides int
+		name     string
+		validate func() error
+	}{
+		{name: "city", provides: city, validate: func() error { _, err := reader.City(probingIP); return err }},
+	}
+	// Query the database to figure out the database type.
+	for _, schema := range schemas {
+		if err := schema.validate(); err != nil {
+			// If we get an InvalidMethodError then we know this database does not provide that schema.
+			if _, ok := err.(geoip2.InvalidMethodError); !ok {
+				return nil, fmt.Errorf("unexpected failure looking up database %q schema %q: %v", filepath.Base(dbPath), schema.name, err)
+			}
+		} else {
+			db.provides = db.provides | schema.provides
+		}
+	}
+
+	if db.provides&city == 0 {
+		return nil, fmt.Errorf("database does not provide city schema")
+	}
+
+	return &GeoIP{db: db}, nil
+}
+
+// ServeDNS implements the plugin.Handler interface.
+func (g GeoIP) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
+	return plugin.NextOrFailure(pluginName, g.Next, ctx, w, r)
+}
+
+// Metadata implements the metadata.Provider Interface in the metadata plugin, and is used to store
+// the data associated with the source IP of every request.
+func (g GeoIP) Metadata(ctx context.Context, state request.Request) context.Context {
+	srcIP := net.ParseIP(state.IP())
+
+	switch {
+	case g.db.provides&city == city:
+		data, err := g.db.City(srcIP)
+		if err != nil {
+			log.Debugf("Setting up metadata failed due to database lookup error: %v", err)
+			return ctx
+		}
+		g.setCityMetadata(ctx, data)
+	}
+	return ctx
+}
+
+// Name implements the Handler interface.
+func (g GeoIP) Name() string { return pluginName }