Add mmdbquery util

.gitignore

@@ -1,6 +1,7 @@
 # Binaries
 cmd/mmdbmeld/mmdbmeld
 cmd/mmdbcheck/mmdbcheck
+cmd/mmdbquery/mmdbquery
 
 # Input
 input/**.csv
@@ -10,3 +11,6 @@ input/**.etag
 
 # Output
 output/*
+
+# Dev files
+config.yml

README.md

@@ -8,6 +8,7 @@ __Step 1: Compile__
 
     $ go build -C cmd/mmdbmeld
     $ go build -C cmd/mmdbcheck
+    $ go build -C cmd/mmdbquery
 
 __Step 2: Download geoip data sources__
 
@@ -107,6 +108,16 @@ This check queries the following fields:
 - SP: `is_satellite_provider`
 - AP: `is_anonymous_proxy`
 
+__Step 5: Query your MMDBs__
+
+    $ ./cmd/mmdbquery/mmdbquery output/geoip-v4.mmdb 1.1.1.1
+
+    1.1.1.0/24:
+      autonomous_system_number: 13335
+      autonomous_system_organization: Cloudflare, Inc.
+      country:
+        iso_code: AU
+
 ### Customize your MMDBs.
 
 Take a look at the <config-example.yml> to get an idea how to customize your MMDB.

cmd/mmdbquery/main.go

@@ -0,0 +1,86 @@
+package main
+
+import (
+	"fmt"
+	"net"
+	"os"
+	"slices"
+	"strings"
+
+	reader "github.com/oschwald/maxminddb-golang"
+)
+
+func main() {
+	if len(os.Args) < 3 {
+		fmt.Printf("usage: %s <mmdb> <IPs>\n", os.Args[0])
+		os.Exit(1)
+	}
+
+	r, err := reader.Open(os.Args[1])
+	if err != nil {
+		fmt.Printf("error:  failed to open mmdb file: %s\n", err)
+		os.Exit(2)
+	}
+
+	for i, ipArg := range os.Args[2:] {
+		// Add a space after first result.
+		if i > 0 {
+			fmt.Println()
+		}
+
+		// Parse IP.
+		ip := net.ParseIP(ipArg)
+		if ip == nil {
+			fmt.Printf("error: invalid IP: %s\n", ipArg)
+			os.Exit(2)
+		}
+
+		// Get data of IP.
+		anyData := make(map[string]any)
+		recordNet, ok, err := r.LookupNetwork(ip, &anyData)
+		if err != nil {
+			fmt.Printf("error: failed to lookup IP: %s\n", err)
+			os.Exit(4)
+		}
+		if !ok {
+			fmt.Printf("error: database does not have a record for %s\n", ip)
+		}
+
+		// Print result.
+		fmt.Printf("%s:\n", recordNet)
+		printData(anyData, "  ")
+	}
+}
+
+type keyValue struct {
+	key   string
+	value any
+}
+
+func printData(m map[string]any, indent string) {
+	// Order data.
+	ordered := make([]keyValue, 0, len(m))
+	for k, v := range m {
+		ordered = append(ordered, keyValue{
+			key:   k,
+			value: v,
+		})
+	}
+	slices.SortFunc[[]keyValue, keyValue](
+		ordered,
+		func(a, b keyValue) int {
+			return strings.Compare(a.key, b.key)
+		},
+	)
+
+	// Print ordered data.
+	for _, e := range ordered {
+		subMap, ok := e.value.(map[string]any)
+		if ok {
+			fmt.Printf("%s%s:\n", indent, e.key)
+			printData(subMap, indent+"  ")
+		} else {
+			fmt.Printf("%s%s: %v\n", indent, e.key, e.value)
+		}
+	}
+}