From fee2cd640fc3929586bbf44d5e5e597dd389bcf6 Mon Sep 17 00:00:00 2001 From: Peter Johnston Date: Tue, 22 Dec 2020 01:34:41 -0800 Subject: Invoke address resolution upon subsequent traffic to Failed neighbor MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Removes the period of time in which subseqeuent traffic to a Failed neighbor immediately fails with ErrNoLinkAddress. A Failed neighbor is one in which address resolution fails; or in other words, the neighbor's IP address cannot be translated to a MAC address. This means removing the Failed state for linkAddrCache and allowing transitiong out of Failed into Incomplete for neighborCache. Previously, both caches would transition entries to Failed after address resolution fails. In this state, any subsequent traffic requested within an unreachable time would immediately fail with ErrNoLinkAddress. This does not follow RFC 4861 section 7.3.3: If address resolution fails, the entry SHOULD be deleted, so that subsequent traffic to that neighbor invokes the next-hop determination procedure again. Invoking next-hop determination at this point ensures that alternate default routers are tried. The API for getting a link address for a given address, whether through the link address cache or the neighbor table, is updated to optionally take a callback which will be called when address resolution completes. This allows `Route` to handle completing link resolution internally, so callers of (*Route).Resolve (e.g. endpoints) don’t have to keep track of when it completes and update the Route accordingly. This change also removes the wakers from LinkAddressCache, NeighborCache, and Route in favor of the callbacks, and callers that previously used a waker can now just pass a callback to (*Route).Resolve that will notify the waker on resolution completion. Fixes #4796 Startblock: has LGTM from sbalana and then add reviewer ghanan PiperOrigin-RevId: 348597478 --- pkg/tcpip/transport/tcp/accept.go | 2 +- pkg/tcpip/transport/tcp/connect.go | 21 ++++++++++++--------- pkg/tcpip/transport/tcp/endpoint.go | 3 ++- 3 files changed, 15 insertions(+), 11 deletions(-) (limited to 'pkg/tcpip/transport/tcp') diff --git a/pkg/tcpip/transport/tcp/accept.go b/pkg/tcpip/transport/tcp/accept.go index 3e1041cbe..2d96a65bd 100644 --- a/pkg/tcpip/transport/tcp/accept.go +++ b/pkg/tcpip/transport/tcp/accept.go @@ -778,7 +778,7 @@ func (e *endpoint) protocolListenLoop(rcvWnd seqnum.Size) { e.waiterQueue.Notify(waiter.EventIn | waiter.EventOut | waiter.EventHUp | waiter.EventErr) }() - s := sleep.Sleeper{} + var s sleep.Sleeper s.AddWaker(&e.notificationWaker, wakerForNotification) s.AddWaker(&e.newSegmentWaker, wakerForNewSegment) for { diff --git a/pkg/tcpip/transport/tcp/connect.go b/pkg/tcpip/transport/tcp/connect.go index c944dccc0..0dc710276 100644 --- a/pkg/tcpip/transport/tcp/connect.go +++ b/pkg/tcpip/transport/tcp/connect.go @@ -462,7 +462,7 @@ func (h *handshake) processSegments() *tcpip.Error { func (h *handshake) resolveRoute() *tcpip.Error { // Set up the wakers. - s := sleep.Sleeper{} + var s sleep.Sleeper resolutionWaker := &sleep.Waker{} s.AddWaker(resolutionWaker, wakerForResolution) s.AddWaker(&h.ep.notificationWaker, wakerForNotification) @@ -470,24 +470,27 @@ func (h *handshake) resolveRoute() *tcpip.Error { // Initial action is to resolve route. index := wakerForResolution + attemptedResolution := false for { switch index { case wakerForResolution: - if _, err := h.ep.route.Resolve(resolutionWaker); err != tcpip.ErrWouldBlock { - if err == tcpip.ErrNoLinkAddress { - h.ep.stats.SendErrors.NoLinkAddr.Increment() - } else if err != nil { + if _, err := h.ep.route.Resolve(resolutionWaker.Assert); err != tcpip.ErrWouldBlock { + if err != nil { h.ep.stats.SendErrors.NoRoute.Increment() } // Either success (err == nil) or failure. return err } + if attemptedResolution { + h.ep.stats.SendErrors.NoLinkAddr.Increment() + return tcpip.ErrNoLinkAddress + } + attemptedResolution = true // Resolution not completed. Keep trying... case wakerForNotification: n := h.ep.fetchNotifications() if n¬ifyClose != 0 { - h.ep.route.RemoveWaker(resolutionWaker) return tcpip.ErrAborted } if n¬ifyDrain != 0 { @@ -563,7 +566,7 @@ func (h *handshake) start() *tcpip.Error { // complete completes the TCP 3-way handshake initiated by h.start(). func (h *handshake) complete() *tcpip.Error { // Set up the wakers. - s := sleep.Sleeper{} + var s sleep.Sleeper resendWaker := sleep.Waker{} s.AddWaker(&resendWaker, wakerForResend) s.AddWaker(&h.ep.notificationWaker, wakerForNotification) @@ -1512,7 +1515,7 @@ func (e *endpoint) protocolMainLoop(handshake bool, wakerInitDone chan<- struct{ } // Initialize the sleeper based on the wakers in funcs. - s := sleep.Sleeper{} + var s sleep.Sleeper for i := range funcs { s.AddWaker(funcs[i].w, i) } @@ -1699,7 +1702,7 @@ func (e *endpoint) doTimeWait() (twReuse func()) { const notification = 2 const timeWaitDone = 3 - s := sleep.Sleeper{} + var s sleep.Sleeper defer s.Done() s.AddWaker(&e.newSegmentWaker, newSegment) s.AddWaker(&e.notificationWaker, notification) diff --git a/pkg/tcpip/transport/tcp/endpoint.go b/pkg/tcpip/transport/tcp/endpoint.go index 2128206d7..c88e74bec 100644 --- a/pkg/tcpip/transport/tcp/endpoint.go +++ b/pkg/tcpip/transport/tcp/endpoint.go @@ -2292,7 +2292,8 @@ func (e *endpoint) connect(addr tcpip.FullAddress, handshake bool, run bool) *tc e.isRegistered = true e.setEndpointState(StateConnecting) - e.route = r.Clone() + r.Acquire() + e.route = r e.boundNICID = nicID e.effectiveNetProtos = netProtos e.connectingAddress = connectingAddr -- cgit v1.2.3