feat(map): Introduce GetMapsIDsByName

Allow a user to get a list of maps IDs filtered by map name.

Co-authored-by: Geyslan Gregório <geyslan@gmail.com>

map-low.go

@@ -99,6 +99,45 @@ func GetMapByID(id uint32) (*BPFMapLow, error) {
 	}, nil
 }
 
+// GetMapsIDsByName searches for maps with a given name.
+// It returns a slice of unsigned 32-bit integers representing the IDs of matching maps.
+// If no maps are found, it returns an empty slice and no error.
+func GetMapsIDsByName(name string) ([]uint32, error) {
+	bpfMapsIds := []uint32{}
+
+	startId := C.uint(0)
+	nextId := C.uint(0)
+
+	for {
+		retC := C.bpf_map_get_next_id(startId, &nextId)
+		errno := syscall.Errno(-retC)
+		if retC < 0 {
+			if errno == syscall.ENOENT {
+				return bpfMapsIds, nil
+			}
+
+			return bpfMapsIds, fmt.Errorf("failed to get next map id: %w", errno)
+		}
+
+		startId = nextId + 1
+
+		bpfMapLow, err := GetMapByID(uint32(nextId))
+		if err != nil {
+			return bpfMapsIds, err
+		}
+
+		if err := syscall.Close(bpfMapLow.FileDescriptor()); err != nil {
+			return bpfMapsIds, err
+		}
+
+		if bpfMapLow.Name() != name {
+			continue
+		}
+
+		bpfMapsIds = append(bpfMapsIds, bpfMapLow.info.ID)
+	}
+}
+
 //
 // BPFMapLow Specs
 //

selftest/map-getmapsbyname/Makefile

@@ -0,0 +1 @@
+../common/Makefile

selftest/map-getmapsbyname/go.mod

@@ -0,0 +1,7 @@
+module github.com/aquasecurity/libbpfgo/selftest/map-update
+
+go 1.18
+
+require github.com/aquasecurity/libbpfgo v0.4.7-libbpf-1.2.0-b2e29a1
+
+replace github.com/aquasecurity/libbpfgo => ../../

selftest/map-getmapsbyname/go.sum

@@ -0,0 +1,4 @@
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/stretchr/testify v1.8.2 h1:+h33VjcLVPDHtOdpUCuF+7gSuG3yGIftsP1YvFihtJ8=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=

selftest/map-getmapsbyname/main.bpf.c

@@ -0,0 +1,14 @@
+//+build ignore
+
+#include <vmlinux.h>
+
+#include <bpf/bpf_helpers.h>
+
+struct {
+    __uint(type, BPF_MAP_TYPE_ARRAY);
+    __uint(max_entries, 1);
+    __uint(key_size, sizeof(u32));
+    __uint(value_size, sizeof(u32));
+} test_name SEC(".maps");
+
+char LICENSE[] SEC("license") = "Dual BSD/GPL";

selftest/map-getmapsbyname/main.go

@@ -0,0 +1,84 @@
+package main
+
+import "C"
+
+import (
+	"log"
+	"syscall"
+	"unsafe"
+
+	bpf "github.com/aquasecurity/libbpfgo"
+)
+
+const (
+	BPFMapNameToNotFind = "not_found"
+	// The following properties are used to identify the map
+	BPFMapNameToFind       = "test_name"
+	BPFMapTypeToFind       = bpf.MapTypeArray
+	BPFMapMaxEntriesToFind = 1
+	BPFMapKeySizeToFind    = 4
+	BPFMapValSizeToFind    = 4
+)
+
+func main() {
+	bpfModule, err := bpf.NewModuleFromFile("main.bpf.o")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer bpfModule.Close()
+
+	bpfModule.BPFLoadObject()
+
+	notFoundMapsIDs, err := bpf.GetMapsIDsByName(BPFMapNameToNotFind)
+	if len(notFoundMapsIDs) != 0 {
+		log.Fatalf("the %s map should not be found, but it was found with ids: %v", BPFMapNameToNotFind, notFoundMapsIDs)
+	}
+
+	mapsIDs, err := bpf.GetMapsIDsByName(BPFMapNameToFind)
+	if err != nil {
+		log.Fatal(err)
+	}
+	if len(mapsIDs) == 0 {
+		log.Fatalf("the %s map was not found", BPFMapNameToFind)
+	}
+
+	// try to identify the map by its properties
+	similarMaps := []*bpf.BPFMapLow{}
+	for _, id := range mapsIDs {
+		bpfMap, err := bpf.GetMapByID(id)
+		if err != nil {
+			log.Fatalf("the %s map with %d id was not found: %v", BPFMapNameToFind, id, err)
+		}
+
+		if bpfMap.Type() == BPFMapTypeToFind &&
+			bpfMap.MaxEntries() == BPFMapMaxEntriesToFind &&
+			bpfMap.KeySize() == BPFMapKeySizeToFind &&
+			bpfMap.ValueSize() == BPFMapValSizeToFind {
+			// found a map with the same properties
+			similarMaps = append(similarMaps, bpfMap)
+		} else {
+			if err := syscall.Close(bpfMap.FileDescriptor()); err != nil {
+				log.Fatalf("failed to close the file descriptor of the %s map with %d id: %v", BPFMapNameToFind, id, err)
+			}
+		}
+	}
+
+	if len(similarMaps) == 0 {
+		log.Fatalf("no %s maps with the same properties found", BPFMapNameToFind)
+	}
+	if len(similarMaps) > 1 {
+		// This is a conundrum for the user, as they cannot decide which map to use
+		// automatically. Perhaps they should change the name of the map to make it
+		// unique.
+		_ = 0
+	}
+
+	// use the first map of the similar ones
+	bpfMap := similarMaps[0]
+
+	key1 := uint32(0)
+	value1 := uint32(55)
+	if err := bpfMap.Update(unsafe.Pointer(&key1), unsafe.Pointer(&value1)); err != nil {
+		log.Fatal(err)
+	}
+}

selftest/map-getmapsbyname/run.sh

@@ -0,0 +1 @@
+../common/run.sh