[#1422] multinet: Add metrics

Signed-off-by: Dmitrii Stepanov <d.stepanov@yadro.com>

internal/net/event_handler.go

@@ -0,0 +1,29 @@
+package net
+
+import (
+	"net"
+
+	"git.frostfs.info/TrueCloudLab/frostfs-node/internal/metrics"
+	"git.frostfs.info/TrueCloudLab/multinet"
+)
+
+var _ multinet.EventHandler = (*metricsEventHandler)(nil)
+
+type metricsEventHandler struct {
+	m metrics.MultinetMetrics
+}
+
+func (m *metricsEventHandler) DialPerformed(sourceIP net.Addr, _ string, _ string, err error) {
+	sourceIPString := "undefined"
+	if sourceIP != nil {
+		sourceIPString = sourceIP.Network() + "://" + sourceIP.String()
+	}
+	m.m.Dial(sourceIPString, err == nil)
+}
+
+func newEventHandler(m metrics.MultinetMetrics) multinet.EventHandler {
+	if m == nil {
+		return nil
+	}
+	return &metricsEventHandler{m: m}
+}