Protect against users deleting the filter ID's in the config file.

Incidentally, it also simplifies upgrade schema from 0 to 1.

app.go

@@ -9,6 +9,7 @@ import (
 	"os"
 	"path/filepath"
 	"strconv"
+	"time"
 
 	"github.com/gobuffalo/packr"
 	"golang.org/x/crypto/ssh/terminal"
@@ -135,6 +136,34 @@ func main() {
 		}
 	}
 
+	// Load filters from the disk
+	// And if any filter has zero ID, assign a new one
+	for i := range config.Filters {
+		filter := &config.Filters[i] // otherwise we're operating on a copy
+		if filter.ID == 0 {
+			filter.ID = assignUniqueFilterID()
+		}
+		err := filter.load()
+		if err != nil {
+			// This is okay for the first start, the filter will be loaded later
+			log.Printf("Couldn't load filter %d contents due to %s", filter.ID, err)
+			// clear LastUpdated so it gets fetched right away
+		}
+		if len(filter.Contents) == 0 {
+			filter.LastUpdated = time.Time{}
+		}
+	}
+
+	// Update filters we've just loaded right away, don't wait for periodic update timer
+	go func() {
+		checkFiltersUpdates(false)
+		// Save the updated config
+		err := writeConfig()
+		if err != nil {
+			log.Fatal(err)
+		}
+	}()
+
 	// Eat all args so that coredns can start happily
 	if len(os.Args) > 1 {
 		os.Args = os.Args[:1]
@@ -146,16 +175,6 @@ func main() {
 		log.Fatal(err)
 	}
 
-	// Load filters from the disk
-	for i := range config.Filters {
-		filter := &config.Filters[i]
-		err = filter.load()
-		if err != nil {
-			// This is okay for the first start, the filter will be loaded later
-			log.Printf("Couldn't load filter %d contents due to %s", filter.ID, err)
-		}
-	}
-
 	address := net.JoinHostPort(config.BindHost, strconv.Itoa(config.BindPort))
 
 	runFiltersUpdatesTimer()

config.go

@@ -22,7 +22,7 @@ const (
 )
 
 // Just a counter that we use for incrementing the filter ID
-var NextFilterId = time.Now().Unix()
+var nextFilterID int64 = time.Now().Unix()
 
 // configuration is loaded from YAML
 // field ordering is important -- yaml fields will mirror ordering from here
@@ -74,7 +74,7 @@ type filter struct {
 	Name        string    `json:"name" yaml:"name"`
 	RulesCount  int       `json:"rulesCount" yaml:"-"`
 	LastUpdated time.Time `json:"lastUpdated,omitempty" yaml:"last_updated,omitempty"`
-	ID          int64     // auto-assigned when filter is added (see NextFilterId)
+	ID          int64     // auto-assigned when filter is added (see nextFilterID)
 
 	Contents []byte `json:"-" yaml:"-"` // not in yaml or json
 }
@@ -165,12 +165,7 @@ func parseConfig() error {
 		config.Filters = config.Filters[:i]
 	}
 
-	// Set the next filter ID to max(filter.ID) + 1
+	updateUniqueFilterID(config.Filters)
-	for i := range config.Filters {
-		if NextFilterId < config.Filters[i].ID {
-			NextFilterId = config.Filters[i].ID + 1
-		}
-	}
 
 	return nil
 }
@@ -293,3 +288,18 @@ func generateCoreDNSConfigText() (string, error) {
 	configText = removeEmptyLines.ReplaceAllString(configText, "\n")
 	return configText, nil
 }
+
+// Set the next filter ID to max(filter.ID) + 1
+func updateUniqueFilterID(filters []filter) {
+	for _, filter := range filters {
+		if nextFilterID < filter.ID {
+			nextFilterID = filter.ID + 1
+		}
+	}
+}
+
+func assignUniqueFilterID() int64 {
+	value := nextFilterID
+	nextFilterID += 1
+	return value
+}

control.go

@@ -343,9 +343,8 @@ func handleFilteringAddURL(w http.ResponseWriter, r *http.Request) {
 	}
 
 	// Set necessary properties
-	filter.ID = NextFilterId
+	filter.ID = assignUniqueFilterID()
 	filter.Enabled = true
-	NextFilterId++
 
 	// Download the filter contents
 	ok, err := filter.update(true)
@@ -550,6 +549,11 @@ func checkFiltersUpdates(force bool) int {
 	updateCount := 0
 	for i := range config.Filters {
 		filter := &config.Filters[i] // otherwise we will be operating on a copy
+
+		if filter.ID == 0 { // protect against users modifying the yaml and removing the ID
+			filter.ID = assignUniqueFilterID()
+		}
+
 		updated, err := filter.update(force)
 		if err != nil {
 			log.Printf("Failed to update filter %s: %s\n", filter.URL, err)
@@ -601,6 +605,9 @@ func parseFilterContents(contents []byte) (int, string) {
 // If "force" is true -- does not check the filter's LastUpdated field
 // Call "save" to persist the filter contents
 func (filter *filter) update(force bool) (bool, error) {
+	if filter.ID == 0 { // protect against users deleting the ID
+		filter.ID = assignUniqueFilterID()
+	}
 	if !filter.Enabled {
 		return false, nil
 	}

upgrade.go

@@ -87,30 +87,7 @@ func upgradeSchema0to1(diskConfig *map[string]interface{}) error {
 	trace("Called")
 
 	// The first schema upgrade:
-	// Added "ID" field to "filter" -- we need to populate this field now
+	// No more "dnsfilter.txt", filters are now kept in data/filters/
-	// Added "config.ourDataDir" -- where we will now store filters contents
-	for i := range config.Filters {
-		filter := &config.Filters[i] // otherwise we will be operating on a copy
-
-		// Set the filter ID
-		log.Printf("Seting ID=%d for filter %s", NextFilterId, filter.URL)
-		filter.ID = NextFilterId
-		NextFilterId++
-
-		// Forcibly update the filter
-		_, err := filter.update(true)
-		if err != nil {
-			log.Fatal(err)
-		}
-
-		// Saving it to the filters dir now
-		err = filter.save()
-		if err != nil {
-			log.Fatal(err)
-		}
-	}
-
-	// No more "dnsfilter.txt", filters are now loaded from config.ourDataDir/filters/
 	dnsFilterPath := filepath.Join(config.ourBinaryDir, "dnsfilter.txt")
 	_, err := os.Stat(dnsFilterPath)
 	if !os.IsNotExist(err) {