From f5736fa2bf91e1bb3fd9f9625dba8c800bf2adb5 Mon Sep 17 00:00:00 2001
From: Ghanan Gowripalan <ghanan@google.com>
Date: Sun, 17 Jan 2021 18:12:47 -0800
Subject: Do not use a stack-wide queue of pending packets

Packets may be pending on link resolution to complete before being sent.
Link resolution is performed for neighbors which are unique to a NIC so
hold link resolution related state under the NIC, not the stack.

Note, this change may result in more queued packets but that is okay as
RFC 4861 section 7.2.2 recommends that the stack maintain a queue of
packets for each neighbor that is waiting for link resolution to
complete, not a fixed limit per stack.

PiperOrigin-RevId: 352322155
---
 pkg/tcpip/stack/nic.go   | 7 ++++++-
 pkg/tcpip/stack/stack.go | 5 -----
 2 files changed, 6 insertions(+), 6 deletions(-)

(limited to 'pkg')

diff --git a/pkg/tcpip/stack/nic.go b/pkg/tcpip/stack/nic.go
index 9e106a161..0f545f255 100644
--- a/pkg/tcpip/stack/nic.go
+++ b/pkg/tcpip/stack/nic.go
@@ -49,6 +49,10 @@ type NIC struct {
 	// Must be accessed using atomic operations.
 	enabled uint32
 
+	// linkResQueue holds packets that are waiting for link resolution to
+	// complete.
+	linkResQueue packetsPendingLinkResolution
+
 	mu struct {
 		sync.RWMutex
 		spoofing    bool
@@ -134,6 +138,7 @@ func newNIC(stack *Stack, id tcpip.NICID, name string, ep LinkEndpoint, ctx NICC
 		stats:            makeNICStats(),
 		networkEndpoints: make(map[tcpip.NetworkProtocolNumber]NetworkEndpoint),
 	}
+	nic.linkResQueue.init()
 	nic.mu.packetEPs = make(map[tcpip.NetworkProtocolNumber]*packetEndpointList)
 
 	// Check for Neighbor Unreachability Detection support.
@@ -315,7 +320,7 @@ func (n *NIC) WritePacket(r *Route, gso *GSO, protocol tcpip.NetworkProtocolNumb
 	if ch, err := r.Resolve(nil); err != nil {
 		if err == tcpip.ErrWouldBlock {
 			r.Acquire()
-			n.stack.linkResQueue.enqueue(ch, r, protocol, pkt)
+			n.linkResQueue.enqueue(ch, r, protocol, pkt)
 			return nil
 		}
 		return err
diff --git a/pkg/tcpip/stack/stack.go b/pkg/tcpip/stack/stack.go
index 6d761b125..c0aec61a6 100644
--- a/pkg/tcpip/stack/stack.go
+++ b/pkg/tcpip/stack/stack.go
@@ -440,10 +440,6 @@ type Stack struct {
 	// uniqueIDGenerator is a generator of unique identifiers.
 	uniqueIDGenerator UniqueID
 
-	// linkResQueue holds packets that are waiting for link resolution to
-	// complete.
-	linkResQueue packetsPendingLinkResolution
-
 	// randomGenerator is an injectable pseudo random generator that can be
 	// used when a random number is required.
 	randomGenerator *mathrand.Rand
@@ -664,7 +660,6 @@ func New(opts Options) *Stack {
 			Max:     DefaultMaxBufferSize,
 		},
 	}
-	s.linkResQueue.init()
 
 	// Add specified network protocols.
 	for _, netProtoFactory := range opts.NetworkProtocols {
-- 
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