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Add BPF map reuse function #346

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Add BPF map reuse function #346

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9 changes: 9 additions & 0 deletions libbpfgo.go
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Original file line number Diff line number Diff line change
Expand Up @@ -564,6 +564,15 @@ func (b *BPFMap) Type() MapType {
return MapType(C.bpf_map__type(b.bpfMap))
}

func (b *BPFMap) MapReuseFd(fd int) error {
errC := C.bpf_map__reuse_fd(b.bpfMap, C.int(fd))
if errC != 0 {
return fmt.Errorf("could not reuse bpf map fd %d: %w", fd, syscall.Errno(-errC))
}
b.fd = C.int(fd)
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The fd to be updated is an open/dupped one, not the provided. I also noticed that the map name needs to be updated.

Well, my current work is changing BPFMap to:

image

https://github.com/aquasecurity/libbpfgo/pull/356/files#diff-5ed7da7003773d8e0a4dca00d4fc08fc5582695eefe22a400db15edfd5aab840R20-R24

As I'm introducing a bunch of changes, I'm going to stop to create conflicts to you 😅, cherry-picking your contribution and doing the required adjustments.

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Thanks for taking care of this, did not know about the refactor!

return nil
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}

// SetType is used to set the type of a bpf map that isn't associated
// with a file descriptor already. If the map is already associated
// with a file descriptor the libbpf API will return error code EBUSY
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2 changes: 1 addition & 1 deletion selftest/common/common.sh
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Expand Up @@ -33,7 +33,7 @@ okcontinue() { okay "$1"; }
kern_version() {
_oper=$1; _version=$2; _notfatal=$3;
_given=$(($(echo $_version | sed 's:\.::g')))
_current=$(($(uname -r | cut -d'.' -f1,2 | sed 's:\.::g')))
_current=$(($(uname -r | cut -d'.' -f1,2,3 | sed 's:\.::g')))
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Updated this check to make it work with my release 6.3.11-200.fc38.x86_64

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echo '6.3.11-200.fc38.x86_64' | cut -d'.' -f1,2 | sed 's:\.::g'
63

It seems ok, we need to merge only the first and second field of the numeric version.

Could you please recheck this?

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On #356

[javierhonduco@fedora reuse-fd]$ ./run.sh 
[!] ERROR: kernel 64 not gt than 418

(Now with kernel 6.4.6-200.fc38.x86_64)

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Hmmm, it seems a logic issue. I'm going to take a look at this later. Thanks.


[[ "$_version" == "" ]] && errexit "no kernel version given"

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4 changes: 0 additions & 4 deletions selftest/create-map/main.go
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Expand Up @@ -36,10 +36,6 @@ func main() {
}
defer bpfModule.Close()

bpfModule.BPFLoadObject()
opts := bpf.BPFMapCreateOpts{}
opts.Size = uint64(unsafe.Sizeof(opts))
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m, err := bpf.CreateMap(bpf.MapTypeHash, "foobar", 4, 4, 420, nil)
if err != nil {
log.Fatal(err)
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7 changes: 7 additions & 0 deletions selftest/map-update/main.bpf.c
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Expand Up @@ -16,6 +16,13 @@ struct {
__uint(max_entries, 1 << 24);
} tester SEC(".maps");

struct {
__uint(type, BPF_MAP_TYPE_HASH);
__type(key, u32);
__type(value, struct value);
__uint(max_entries, 1 << 24);
} tester_reused SEC(".maps");

struct {
__uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
__uint(key_size, sizeof(u32));
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17 changes: 17 additions & 0 deletions selftest/map-update/main.go
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Expand Up @@ -87,6 +87,23 @@ func main() {
os.Exit(-1)
}

testerMap2, err := bpfModule.GetMap("tester_reused")
if err != nil {
fmt.Fprintln(os.Stderr, err)
os.Exit(-1)
}

err = testerMap2.MapReuseFd(testerMap.FileDescriptor())
if err != nil {
fmt.Fprintln(os.Stderr, err)
os.Exit(-1)
}

if err != nil {
fmt.Fprintln(os.Stderr, err)
os.Exit(-1)
}

eventsChannel := make(chan []byte)
lostChannel := make(chan uint64)
pb, err := bpfModule.InitPerfBuf("events", eventsChannel, lostChannel, 1)
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