From a155a23480abfafe096ff50f2c4aaf2c215b6c44 Mon Sep 17 00:00:00 2001
From: Ghanan Gowripalan <ghanan@google.com>
Date: Fri, 21 Feb 2020 11:20:15 -0800
Subject: Attach LinkEndpoint to NetworkDispatcher immediately

Tests: stack_test.TestAttachToLinkEndpointImmediately
PiperOrigin-RevId: 296474068
---
 pkg/tcpip/stack/nic.go | 25 +++++++++----------------
 1 file changed, 9 insertions(+), 16 deletions(-)

(limited to 'pkg/tcpip/stack/nic.go')

diff --git a/pkg/tcpip/stack/nic.go b/pkg/tcpip/stack/nic.go
index b2be18e47..862954ab2 100644
--- a/pkg/tcpip/stack/nic.go
+++ b/pkg/tcpip/stack/nic.go
@@ -44,8 +44,7 @@ type NIC struct {
 	linkEP  LinkEndpoint
 	context NICContext
 
-	stats  NICStats
-	attach sync.Once
+	stats NICStats
 
 	mu struct {
 		sync.RWMutex
@@ -141,6 +140,8 @@ func newNIC(stack *Stack, id tcpip.NICID, name string, ep LinkEndpoint, ctx NICC
 		nic.mu.packetEPs[netProto.Number()] = []PacketEndpoint{}
 	}
 
+	nic.linkEP.Attach(nic)
+
 	return nic
 }
 
@@ -200,14 +201,16 @@ func (n *NIC) disable() *tcpip.Error {
 		}
 	}
 
-	// TODO(b/147015577): Should n detach from its LinkEndpoint?
-
 	n.mu.enabled = false
 	return nil
 }
 
-// enable enables n. enable will attach the nic to its LinkEndpoint and
-// join the IPv6 All-Nodes Multicast address (ff02::1).
+// enable enables n.
+//
+// If the stack has IPv6 enabled, enable will join the IPv6 All-Nodes Multicast
+// address (ff02::1), start DAD for permanent addresses, and start soliciting
+// routers if the stack is not operating as a router. If the stack is also
+// configured to auto-generate a link-local address, one will be generated.
 func (n *NIC) enable() *tcpip.Error {
 	n.mu.RLock()
 	enabled := n.mu.enabled
@@ -225,8 +228,6 @@ func (n *NIC) enable() *tcpip.Error {
 
 	n.mu.enabled = true
 
-	n.attachLinkEndpoint()
-
 	// Create an endpoint to receive broadcast packets on this interface.
 	if _, ok := n.stack.networkProtocols[header.IPv4ProtocolNumber]; ok {
 		if _, err := n.addAddressLocked(ipv4BroadcastAddr, NeverPrimaryEndpoint, permanent, static, false /* deprecated */); err != nil {
@@ -321,14 +322,6 @@ func (n *NIC) becomeIPv6Host() {
 	n.mu.ndp.startSolicitingRouters()
 }
 
-// attachLinkEndpoint attaches the NIC to the endpoint, which will enable it
-// to start delivering packets.
-func (n *NIC) attachLinkEndpoint() {
-	n.attach.Do(func() {
-		n.linkEP.Attach(n)
-	})
-}
-
 // setPromiscuousMode enables or disables promiscuous mode.
 func (n *NIC) setPromiscuousMode(enable bool) {
 	n.mu.Lock()
-- 
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