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Only block resolution when NUD is incomplete

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When a completed entry exists for a neighbor, there is no need to block
while reachability is (re)confirmed. The stack should continue to use
the neighbor's link address while NUD is performed.

Test: stack_test.TestNeighborCacheReplace
PiperOrigin-RevId: 336199043
This commit is contained in:
Ghanan Gowripalan
2020-10-08 17:34:28 -07:00
committed by gVisor bot
parent 6bad4851d4
commit 07b1d7413e
2 changed files with 47 additions and 34 deletions
Download Patch File Download Diff File Expand all files Collapse all files
pkg/tcpip/stack/neighbor_cache.go
+10 -5
View File
@@ -131,10 +131,17 @@ func (n *neighborCache) entry(remoteAddr, localAddr tcpip.Address, linkRes LinkA
defer entry.mu.Unlock()
switch s := entry.neigh.State; s {
case Reachable, Static:
case Stale:
entry.handlePacketQueuedLocked()
fallthrough
case Reachable, Static, Delay, Probe:
// As per RFC 4861 section 7.3.3:
// "Neighbor Unreachability Detection operates in parallel with the sending
// of packets to a neighbor. While reasserting a neighbor's reachability,
// a node continues sending packets to that neighbor using the cached
// link-layer address."
return entry.neigh, nil, nil
case Unknown, Incomplete, Stale, Delay, Probe:
case Unknown, Incomplete:
entry.addWakerLocked(w)
if entry.done == nil {
@@ -147,10 +154,8 @@ func (n *neighborCache) entry(remoteAddr, localAddr tcpip.Address, linkRes LinkA
entry.handlePacketQueuedLocked()
return entry.neigh, entry.done, tcpip.ErrWouldBlock
case Failed:
return entry.neigh, nil, tcpip.ErrNoLinkAddress
default:
panic(fmt.Sprintf("Invalid cache entry state: %s", s))
}
pkg/tcpip/stack/neighbor_cache_test.go
+37 -29
View File
@@ -1500,24 +1500,26 @@ func TestNeighborCacheReplace(t *testing.T) {
}
// Verify the entry exists
e, doneCh, err := neigh.entry(entry.Addr, entry.LocalAddr, linkRes, nil)
if err != nil {
t.Errorf("unexpected error from neigh.entry(%s, %s, _, nil): %s", entry.Addr, entry.LocalAddr, err)
}
if doneCh != nil {
t.Errorf("unexpected done channel from neigh.entry(%s, %s, _, nil): %v", entry.Addr, entry.LocalAddr, doneCh)
}
if t.Failed() {
t.FailNow()
}
want := NeighborEntry{
Addr: entry.Addr,
LocalAddr: entry.LocalAddr,
LinkAddr: entry.LinkAddr,
State: Reachable,
}
if diff := cmp.Diff(e, want, entryDiffOpts()...); diff != "" {
t.Errorf("neigh.entry(%s, %s, _, nil) mismatch (-got, +want):\n%s", entry.Addr, entry.LinkAddr, diff)
{
e, doneCh, err := neigh.entry(entry.Addr, entry.LocalAddr, linkRes, nil)
if err != nil {
t.Errorf("unexpected error from neigh.entry(%s, %s, _, nil): %s", entry.Addr, entry.LocalAddr, err)
}
if doneCh != nil {
t.Errorf("unexpected done channel from neigh.entry(%s, %s, _, nil): %v", entry.Addr, entry.LocalAddr, doneCh)
}
if t.Failed() {
t.FailNow()
}
want := NeighborEntry{
Addr: entry.Addr,
LocalAddr: entry.LocalAddr,
LinkAddr: entry.LinkAddr,
State: Reachable,
}
if diff := cmp.Diff(e, want, entryDiffOpts()...); diff != "" {
t.Errorf("neigh.entry(%s, %s, _, nil) mismatch (-got, +want):\n%s", entry.Addr, entry.LinkAddr, diff)
}
}
// Notify of a link address change
@@ -1536,28 +1538,34 @@ func TestNeighborCacheReplace(t *testing.T) {
IsRouter: false,
})
// Requesting the entry again should start address resolution
// Requesting the entry again should start neighbor reachability confirmation.
//
// Verify the entry's new link address and the new state.
{
_, doneCh, err := neigh.entry(entry.Addr, entry.LocalAddr, linkRes, nil)
if err != tcpip.ErrWouldBlock {
t.Fatalf("got neigh.entry(%s, %s, _, nil) = %v, want = %s", entry.Addr, entry.LocalAddr, err, tcpip.ErrWouldBlock)
e, _, err := neigh.entry(entry.Addr, entry.LocalAddr, linkRes, nil)
if err != nil {
t.Fatalf("neigh.entry(%s, %s, _, nil): %s", entry.Addr, entry.LocalAddr, err)
}
want := NeighborEntry{
Addr: entry.Addr,
LocalAddr: entry.LocalAddr,
LinkAddr: updatedLinkAddr,
State: Delay,
}
if diff := cmp.Diff(e, want, entryDiffOpts()...); diff != "" {
t.Errorf("neigh.entry(%s, %s, _, nil) mismatch (-got, +want):\n%s", entry.Addr, entry.LocalAddr, diff)
}
clock.Advance(config.DelayFirstProbeTime + typicalLatency)
select {
case <-doneCh:
default:
t.Fatalf("expected notification from done channel returned by neigh.entry(%s, %s, _, nil)", entry.Addr, entry.LocalAddr)
}
}
// Verify the entry's new link address
// Verify that the neighbor is now reachable.
{
e, _, err := neigh.entry(entry.Addr, entry.LocalAddr, linkRes, nil)
clock.Advance(typicalLatency)
if err != nil {
t.Errorf("unexpected error from neigh.entry(%s, %s, _, nil): %s", entry.Addr, entry.LocalAddr, err)
}
want = NeighborEntry{
want := NeighborEntry{
Addr: entry.Addr,
LocalAddr: entry.LocalAddr,
LinkAddr: updatedLinkAddr,