feat(bpfsnitch): add Kprobe attacher

internal/bpf/kprobe_attacher.go

@@ -0,0 +1,79 @@
+package bpf
+
+import (
+	"fmt"
+	"log/slog"
+
+	"github.com/cilium/ebpf"
+	"github.com/cilium/ebpf/link"
+)
+
+// Struct that holds bpf kprobe required metadata
+type KProbeMeta struct {
+	function string
+	section  string
+}
+
+var kpsMeta = []KProbeMeta{
+	{
+		function: "udp_recvmsg",
+		section:  "trace_udp_recvmsg",
+	},
+	{
+		function: "udp_sendmsg",
+		section:  "trace_udp_sendmsg",
+	},
+	{
+		function: "tcp_recvmsg",
+		section:  "trace_tcp_recvmsg",
+	},
+	{
+		function: "tcp_sendmsg",
+		section:  "trace_tcp_sendmsg",
+	},
+}
+
+func attachKProbes(
+	log *slog.Logger,
+	coll *ebpf.Collection,
+) ([]link.Link, error) {
+	kps := make([]link.Link, 0, len(kpsMeta))
+	for _, kp := range kpsMeta {
+		kpLink, err := attachKProbe(coll, kp, log)
+		if err != nil {
+			return nil, fmt.Errorf(
+				"failed to attach kprobe %s: %w",
+				kp.section,
+				err,
+			)
+		}
+
+		kps = append(kps, kpLink)
+	}
+
+	return kps, nil
+}
+
+func attachKProbe(
+	coll *ebpf.Collection,
+	kp KProbeMeta,
+	log *slog.Logger,
+) (link.Link, error) {
+	prog := coll.Programs[kp.section]
+	if prog == nil {
+		return nil, fmt.Errorf("failed to find program %s", kp.section)
+	}
+
+	kpLink, err := link.Kprobe(kp.function, prog, nil)
+	if err != nil {
+		return nil, fmt.Errorf(
+			"failed to attach kprobe %s: %w",
+			kp.function,
+			err,
+		)
+	}
+
+	log.Info("Attached kprobe", "section", kp.section, "function", kp.function)
+
+	return kpLink, nil
+}