feat: replace *log.Logger with interface for tc

[nddq]

Replace the default logger used in tc with an interface instead. Add some tests to verify that other loggers such as zap and logrus are able to satisfy the interface.

Addressed #143

[florianl]

Thanks for taking on #143. When creating the issue, the idea was to introduce logging with various levels. But in the current code base logging is hardly used and there is also no request or need to add more logging. On the contrary, there are more requests for lightweight dependencies.

Therefore, would you mind updating the PR in a way, that it removes logging instead of replacing it with a interface?

For the existing log messages in the code, it could look something like this:

@@ -108,8 +108,7 @@ func (tc *Tc) action(action int, flags netlink.HeaderFlags, msg interface{}, opt
 
        for _, msg := range msgs {
                if msg.Header.Type == netlink.Error {
-                       // see https://www.infradead.org/~tgr/libnl/doc/core.html#core_errmsg
-                       tc.logger.Printf("received netlink.Error in action()\n")
+                       return fmt.Errorf("received netlink Error: %#v", msg)
                }
        }
 
@@ -294,7 +293,6 @@ func (tc *Tc) Monitor(ctx context.Context, deadline time.Duration, fn HookFunc)
                                return 0
                        }
                }
-               tc.logger.Printf("Could not receive message: %v\n", err)
                return 1
        })
 }
@@ -362,12 +360,10 @@ func (tc *Tc) monitor(ctx context.Context, deadline time.Duration,
                        for _, msg := range msgs {
                                var monitored Object
                                if err := unmarshalStruct(msg.Data[:20], &monitored.Msg); err != nil {
-                                       tc.logger.Printf("could not extract tc.Msg from %v\n", msg.Data[:20])
                                        continue
                                }
                                if err := extractTcmsgAttributes(int(msg.Header.Type), msg.Data[20:],
                                        &monitored.Attribute); err != nil {
-                                       tc.logger.Printf("could not extract attributes from %v\n", msg.Data[20:36])
                                        continue
                                }
                                if fn(uint16(msg.Header.Type), monitored) != 0 {

[florianl]

Resolved with #190