fix: HTTP2 nil pointer panic and broken GOMEMLIMIT under hostPID

ebpftracer/l7/http2.go

@@ -263,7 +263,10 @@ func (p *Http2Parser) decodeHeaderBlock(
 		req := p.activeRequests[streamId]
 		if req == nil {
 			if len(p.activeRequests) >= maxActiveRequests {
-				// Too many active streams; skip to prevent unbounded growth
+				// Too many active streams; set no-op emit so decoder.Write still
+				// processes the HPACK block (keeps dynamic table in sync) without
+				// dereferencing a nil request.
+				decoder.SetEmitFunc(func(hf hpack.HeaderField) {})
 				break
 			}
 			req = &Http2Request{

main.go

@@ -297,8 +297,38 @@ func (o *RateLimitedLogOutput) Write(data []byte) (int, error) {
 }
 
 // readCgroupMemoryLimit reads the memory limit from cgroup v2 or v1.
+// The agent runs with hostPID, so /proc/1/cgroup points to the host root (init.scope)
+// which has no memory limit. We use /proc/self/cgroup to find the container's own
+// cgroup path where kubelet enforces the pod memory limit.
 func readCgroupMemoryLimit() (int64, error) {
-	// Try cgroup v2 first
+	// Parse /proc/self/cgroup to find the container's own cgroup path.
+	// cgroupv2: "0::/kubepods.slice/.../cri-containerd-xxx.scope"
+	// cgroupv1: "N:memory:/kubepods/burstable/pod-xxx/container-yyy"
+	if data, err := os.ReadFile("/proc/self/cgroup"); err == nil {
+		for _, line := range strings.Split(strings.TrimSpace(string(data)), "\n") {
+			parts := strings.SplitN(line, ":", 3)
+			if len(parts) < 3 {
+				continue
+			}
+			var cgPath string
+			if parts[0] == "0" { // cgroup v2
+				cgPath = "/sys/fs/cgroup" + parts[2] + "/memory.max"
+			} else if strings.Contains(parts[1], "memory") { // cgroup v1
+				cgPath = "/sys/fs/cgroup/memory" + parts[2] + "/memory.limit_in_bytes"
+			}
+			if cgPath != "" {
+				if mem, err := os.ReadFile(cgPath); err == nil {
+					s := strings.TrimSpace(string(mem))
+					if s != "max" {
+						if limit, err := strconv.ParseInt(s, 10, 64); err == nil && limit > 0 && limit < 1<<62 {
+							return limit, nil
+						}
+					}
+				}
+			}
+		}
+	}
+	// Fallback: try cgroup v2 at root (non-hostPID containers)
 	if data, err := os.ReadFile("/sys/fs/cgroup/memory.max"); err == nil {
 		s := strings.TrimSpace(string(data))
 		if s != "max" {
@@ -307,11 +337,10 @@ func readCgroupMemoryLimit() (int64, error) {
 			}
 		}
 	}
-	// Try cgroup v1
+	// Fallback: try cgroup v1 at root (non-hostPID containers)
 	if data, err := os.ReadFile("/sys/fs/cgroup/memory/memory.limit_in_bytes"); err == nil {
 		s := strings.TrimSpace(string(data))
 		if limit, err := strconv.ParseInt(s, 10, 64); err == nil {
-			// cgroup v1 reports a very large number when unlimited
 			if limit < 1<<62 {
 				return limit, nil
 			}