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fix(tracing): correct trace-id not-found sentinel and use Copy() for dummy BPF program specs #1986

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fix(tracing): correct trace-id not-found sentinel and use Copy() for dummy BPF program specs #1986

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6 changes: 4 additions & 2 deletions bpf/common/trace_util.h
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,8 @@ struct callback_ctx {
u8 _pad[4];
};

enum { k_tp_pos_not_found = 0xffffffffu };

static unsigned char *hex = (unsigned char *)"0123456789abcdef";
static unsigned char *reverse_hex =
(unsigned char *)"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff"
Expand Down Expand Up @@ -101,13 +103,13 @@ static __always_inline unsigned char *bpf_strstr_tp_loop(unsigned char *buf, con
return NULL;
}

struct callback_ctx data = {.buf = buf, .pos = 0};
struct callback_ctx data = {.buf = buf, .pos = k_tp_pos_not_found};

const u32 nr_loops = (u32)buf_len;

bpf_loop(nr_loops, tp_match, &data, 0);

if (data.pos) {
if (data.pos != k_tp_pos_not_found) {
return (data.pos > (TRACE_BUF_SIZE - TRACE_PARENT_HEADER_LEN)) ? NULL : &buf[data.pos];
}

Expand Down
6 changes: 4 additions & 2 deletions pkg/ebpf/common/common.go
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Original file line number Diff line number Diff line change
Expand Up @@ -521,6 +521,7 @@ func FixupSpec(spec *ebpf.CollectionSpec, overrideKernelVersion bool) {
spec.Programs["obi_continue_protocol_http"] = spec.Programs["obi_continue_protocol_http_legacy"]
spec.Programs["obi_continue_protocol_http"].Name = "obi_continue_protocol_http"
}

dummy := &ebpf.ProgramSpec{
Name: "obi_dummy",
Type: ebpf.Kprobe,
Expand All @@ -530,10 +531,11 @@ func FixupSpec(spec *ebpf.CollectionSpec, overrideKernelVersion bool) {
},
License: "MIT",
}

// Hack: insert dummy unused programs in order to be able to use bpf2go generated struct to load
// the collection.
spec.Programs["obi_protocol_http_legacy"] = dummy
spec.Programs["obi_continue_protocol_http_legacy"] = dummy
spec.Programs["obi_protocol_http_legacy"] = dummy.Copy()
spec.Programs["obi_continue_protocol_http_legacy"] = dummy.Copy()
}

// Injectable for tests
Expand Down
27 changes: 27 additions & 0 deletions pkg/ebpf/common/http_transform_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -500,3 +500,30 @@ func TestHTTPRequestResponseToSpan_OpenAIEmbeddingDetectedByOpenAISpan(t *testin
require.NotNil(t, span.GenAI.OpenAI, "span.GenAI.OpenAI should be set")
assert.Equal(t, request.EmbeddingOperationName, span.GenAI.OpenAI.OperationName)
}

func TestToRequestTraceMissingLargeBuffers(t *testing.T) {
fltr := TestPidsFilter{services: map[app.PID]svc.Attrs{}}
var record BPFHTTPInfo

record.Type = 1
record.ReqMonotimeNs = 123450
record.StartMonotimeNs = 123456
record.EndMonotimeNs = 789012
record.Status = 200
record.HasLargeBuffers = 1 // This will trigger the missing large buffers branch
record.ConnInfo.D_port = 1
record.ConnInfo.S_addr = [16]byte{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0xff, 0xff, 192, 168, 0, 1}
record.ConnInfo.D_addr = [16]byte{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0xff, 0xff, 8, 8, 8, 8}
copy(record.Buf[:], "GET /hello HTTP/1.1\r\nHost: example.com\r\n\r\n")

buf := new(bytes.Buffer)
err := binary.Write(buf, binary.LittleEndian, &record)
require.NoError(t, err)

pctx := NewEBPFParseContext(nil, nil, nil)
result, _, err := ReadHTTPInfoIntoSpan(pctx, &ringbuf.Record{RawSample: buf.Bytes()}, &fltr)
require.NoError(t, err)

require.Equal(t, "/hello", result.Path)
require.Equal(t, 200, result.Status)
}