Added documentation to ebpf.go

GetRuntimeAddresses/ebpf/ebpf.go

@@ -69,6 +69,7 @@ import (
 	"unsafe"
 )
 
+// MapFD is a file descriptor representing a eBPF map
 type MapFD int
 
 // CreateMap creates an eBPF map from int->uint64. The file descriptor of the
@@ -113,18 +114,26 @@ func (mfd MapFD) GetMap() (map[int]uint64, error) {
 	}
 }
 
+// Add puts the (key, value) into the eBPF map, only if the key does not exist
+// yet in the map. It returns an error otherwise.
 func (mfd MapFD) Add(key int, value uint64) error {
 	return mfd.updateElement(key, value, C.BPF_NOEXIST)
 }
 
+// Change changes the value to an existing key in the eBPF map.  It returns an
+// error otherwise.
 func (mfd MapFD) Change(key int, value uint64) error {
 	return mfd.updateElement(key, value, C.BPF_EXIST)
 }
 
+// Set puts the (key, value) into the eBPF map.  It will create or overwrite an
+// existing entry for that key.
 func (mfd MapFD) Set(key int, value uint64) error {
 	return mfd.updateElement(key, value, C.BPF_ANY)
 }
 
+// updateElement is the low level wrapper to bpf_update_elem, used from Add(),
+// Set() and Change().
 func (mfd MapFD) updateElement(key int, value uint64, flag C.uint64_t) error {
 
 	r, errno := C.bpf_update_elem(C.int(mfd),