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-rw-r--r--pkg/tcpip/stack/linkaddrcache.go20
-rw-r--r--pkg/tcpip/stack/neighbor_entry.go8
-rw-r--r--pkg/tcpip/stack/nic.go47
-rw-r--r--pkg/tcpip/stack/pending_packets.go247
-rw-r--r--pkg/tcpip/stack/route.go67
5 files changed, 223 insertions, 166 deletions
diff --git a/pkg/tcpip/stack/linkaddrcache.go b/pkg/tcpip/stack/linkaddrcache.go
index 3c4fa341e..f116f8417 100644
--- a/pkg/tcpip/stack/linkaddrcache.go
+++ b/pkg/tcpip/stack/linkaddrcache.go
@@ -32,6 +32,8 @@ var _ LinkAddressCache = (*linkAddrCache)(nil)
//
// This struct is safe for concurrent use.
type linkAddrCache struct {
+ nic *NIC
+
// ageLimit is how long a cache entry is valid for.
ageLimit time.Duration
@@ -79,6 +81,8 @@ type linkAddrEntry struct {
// linkAddrEntryEntry access is synchronized by the linkAddrCache lock.
linkAddrEntryEntry
+ cache *linkAddrCache
+
// TODO(gvisor.dev/issue/5150): move these fields under mu.
// mu protects the fields below.
mu sync.RWMutex
@@ -104,6 +108,14 @@ func (e *linkAddrEntry) notifyCompletionLocked(linkAddr tcpip.LinkAddress) {
if ch := e.done; ch != nil {
close(ch)
e.done = nil
+ // Dequeue the pending packets in a new goroutine to not hold up the current
+ // goroutine as writing packets may be a costly operation.
+ //
+ // At the time of writing, when writing packets, a neighbor's link address
+ // is resolved (which ends up obtaining the entry's lock) while holding the
+ // link resolution queue's lock. Dequeuing packets in a new goroutine avoids
+ // a lock ordering violation.
+ go e.cache.nic.linkResQueue.dequeue(ch, linkAddr, len(linkAddr) != 0)
}
}
@@ -174,8 +186,9 @@ func (c *linkAddrCache) getOrCreateEntryLocked(k tcpip.Address) *linkAddrEntry {
}
*entry = linkAddrEntry{
- addr: k,
- s: incomplete,
+ cache: c,
+ addr: k,
+ s: incomplete,
}
c.cache.table[k] = entry
c.cache.lru.PushFront(entry)
@@ -264,8 +277,9 @@ func (c *linkAddrCache) checkLinkRequest(now time.Time, k tcpip.Address, attempt
return true
}
-func newLinkAddrCache(ageLimit, resolutionTimeout time.Duration, resolutionAttempts int) *linkAddrCache {
+func newLinkAddrCache(nic *NIC, ageLimit, resolutionTimeout time.Duration, resolutionAttempts int) *linkAddrCache {
c := &linkAddrCache{
+ nic: nic,
ageLimit: ageLimit,
resolutionTimeout: resolutionTimeout,
resolutionAttempts: resolutionAttempts,
diff --git a/pkg/tcpip/stack/neighbor_entry.go b/pkg/tcpip/stack/neighbor_entry.go
index 75afb3001..697132689 100644
--- a/pkg/tcpip/stack/neighbor_entry.go
+++ b/pkg/tcpip/stack/neighbor_entry.go
@@ -150,6 +150,14 @@ func (e *neighborEntry) notifyCompletionLocked(succeeded bool) {
if ch := e.done; ch != nil {
close(ch)
e.done = nil
+ // Dequeue the pending packets in a new goroutine to not hold up the current
+ // goroutine as writing packets may be a costly operation.
+ //
+ // At the time of writing, when writing packets, a neighbor's link address
+ // is resolved (which ends up obtaining the entry's lock) while holding the
+ // link resolution queue's lock. Dequeuing packets in a new goroutine avoids
+ // a lock ordering violation.
+ go e.nic.linkResQueue.dequeue(ch, e.neigh.LinkAddr, succeeded)
}
}
diff --git a/pkg/tcpip/stack/nic.go b/pkg/tcpip/stack/nic.go
index 447b5c99d..7592cff75 100644
--- a/pkg/tcpip/stack/nic.go
+++ b/pkg/tcpip/stack/nic.go
@@ -139,9 +139,9 @@ func newNIC(stack *Stack, id tcpip.NICID, name string, ep LinkEndpoint, ctx NICC
context: ctx,
stats: makeNICStats(),
networkEndpoints: make(map[tcpip.NetworkProtocolNumber]NetworkEndpoint),
- linkAddrCache: newLinkAddrCache(ageLimit, resolutionTimeout, resolutionAttempts),
}
- nic.linkResQueue.init()
+ nic.linkResQueue.init(nic)
+ nic.linkAddrCache = newLinkAddrCache(nic, ageLimit, resolutionTimeout, resolutionAttempts)
nic.mu.packetEPs = make(map[tcpip.NetworkProtocolNumber]*packetEndpointList)
// Check for Neighbor Unreachability Detection support.
@@ -303,6 +303,10 @@ func (n *NIC) IsLoopback() bool {
// WritePacket implements NetworkLinkEndpoint.
func (n *NIC) WritePacket(r *Route, gso *GSO, protocol tcpip.NetworkProtocolNumber, pkt *PacketBuffer) *tcpip.Error {
+ _, err := n.enqueuePacketBuffer(r, gso, protocol, pkt)
+ return err
+}
+func (n *NIC) enqueuePacketBuffer(r *Route, gso *GSO, protocol tcpip.NetworkProtocolNumber, pkt pendingPacketBuffer) (int, *tcpip.Error) {
// As per relevant RFCs, we should queue packets while we wait for link
// resolution to complete.
//
@@ -320,16 +324,7 @@ func (n *NIC) WritePacket(r *Route, gso *GSO, protocol tcpip.NetworkProtocolNumb
// be limited to some small value. When a queue overflows, the new arrival
// SHOULD replace the oldest entry. Once address resolution completes, the
// node transmits any queued packets.
- if ch, err := r.Resolve(nil); err != nil {
- if err == tcpip.ErrWouldBlock {
- r.Acquire()
- n.linkResQueue.enqueue(ch, r, protocol, pkt)
- return nil
- }
- return err
- }
-
- return n.writePacket(r.Fields(), gso, protocol, pkt)
+ return n.linkResQueue.enqueue(r, gso, protocol, pkt)
}
// WritePacketToRemote implements NetworkInterface.
@@ -358,33 +353,7 @@ func (n *NIC) writePacket(r RouteInfo, gso *GSO, protocol tcpip.NetworkProtocolN
// WritePackets implements NetworkLinkEndpoint.
func (n *NIC) WritePackets(r *Route, gso *GSO, pkts PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, *tcpip.Error) {
- // As per relevant RFCs, we should queue packets while we wait for link
- // resolution to complete.
- //
- // RFC 1122 section 2.3.2.2 (for IPv4):
- // The link layer SHOULD save (rather than discard) at least
- // one (the latest) packet of each set of packets destined to
- // the same unresolved IP address, and transmit the saved
- // packet when the address has been resolved.
- //
- // RFC 4861 section 7.2.2 (for IPv6):
- // While waiting for address resolution to complete, the sender MUST, for
- // each neighbor, retain a small queue of packets waiting for address
- // resolution to complete. The queue MUST hold at least one packet, and MAY
- // contain more. However, the number of queued packets per neighbor SHOULD
- // be limited to some small value. When a queue overflows, the new arrival
- // SHOULD replace the oldest entry. Once address resolution completes, the
- // node transmits any queued packets.
- if ch, err := r.Resolve(nil); err != nil {
- if err == tcpip.ErrWouldBlock {
- r.Acquire()
- n.linkResQueue.enqueue(ch, r, protocol, &pkts)
- return pkts.Len(), nil
- }
- return 0, err
- }
-
- return n.writePackets(r.Fields(), gso, protocol, pkts)
+ return n.enqueuePacketBuffer(r, gso, protocol, &pkts)
}
func (n *NIC) writePackets(r RouteInfo, gso *GSO, protocol tcpip.NetworkProtocolNumber, pkts PacketBufferList) (int, *tcpip.Error) {
diff --git a/pkg/tcpip/stack/pending_packets.go b/pkg/tcpip/stack/pending_packets.go
index 3ac039c7d..22dfc7960 100644
--- a/pkg/tcpip/stack/pending_packets.go
+++ b/pkg/tcpip/stack/pending_packets.go
@@ -45,135 +45,202 @@ func (p *PacketBufferList) len() int {
}
type pendingPacket struct {
- route *Route
- proto tcpip.NetworkProtocolNumber
- pkt pendingPacketBuffer
+ routeInfo RouteInfo
+ gso *GSO
+ proto tcpip.NetworkProtocolNumber
+ pkt pendingPacketBuffer
}
// packetsPendingLinkResolution is a queue of packets pending link resolution.
//
// Once link resolution completes successfully, the packets will be written.
type packetsPendingLinkResolution struct {
- sync.Mutex
+ nic *NIC
- // The packets to send once the resolver completes.
- packets map[<-chan struct{}][]pendingPacket
+ mu struct {
+ sync.Mutex
- // FIFO of channels used to cancel the oldest goroutine waiting for
- // link-address resolution.
- cancelChans []chan struct{}
-}
+ // The packets to send once the resolver completes.
+ //
+ // The link resolution channel is used as the key for this map.
+ packets map[<-chan struct{}][]pendingPacket
-func (f *packetsPendingLinkResolution) init() {
- f.Lock()
- defer f.Unlock()
- f.packets = make(map[<-chan struct{}][]pendingPacket)
+ // FIFO of channels used to cancel the oldest goroutine waiting for
+ // link-address resolution.
+ //
+ // cancelChans holds the same channels that are used as keys to packets.
+ cancelChans []<-chan struct{}
+ }
}
-func incrementOutgoingPacketErrors(r *Route, proto tcpip.NetworkProtocolNumber, pkt pendingPacketBuffer) {
+func (f *packetsPendingLinkResolution) incrementOutgoingPacketErrors(proto tcpip.NetworkProtocolNumber, pkt pendingPacketBuffer) {
n := uint64(pkt.len())
- r.Stats().IP.OutgoingPacketErrors.IncrementBy(n)
+ f.nic.stack.stats.IP.OutgoingPacketErrors.IncrementBy(n)
- // ok may be false if the endpoint's stats do not collect IP-related data.
- if ipEndpointStats, ok := r.outgoingNIC.getNetworkEndpoint(proto).Stats().(IPNetworkEndpointStats); ok {
+ if ipEndpointStats, ok := f.nic.getNetworkEndpoint(proto).Stats().(IPNetworkEndpointStats); ok {
ipEndpointStats.IPStats().OutgoingPacketErrors.IncrementBy(n)
}
}
-func (f *packetsPendingLinkResolution) enqueue(ch <-chan struct{}, r *Route, proto tcpip.NetworkProtocolNumber, pkt pendingPacketBuffer) {
- f.Lock()
- defer f.Unlock()
+func (f *packetsPendingLinkResolution) init(nic *NIC) {
+ f.mu.Lock()
+ defer f.mu.Unlock()
+ f.nic = nic
+ f.mu.packets = make(map[<-chan struct{}][]pendingPacket)
+}
- packets, ok := f.packets[ch]
- if len(packets) == maxPendingPacketsPerResolution {
- p := packets[0]
- packets[0] = pendingPacket{}
- packets = packets[1:]
+// dequeue any pending packets associated with ch.
+//
+// If success is true, packets will be written and sent to the given remote link
+// address.
+func (f *packetsPendingLinkResolution) dequeue(ch <-chan struct{}, linkAddr tcpip.LinkAddress, success bool) {
+ f.mu.Lock()
+ packets, ok := f.mu.packets[ch]
+ delete(f.mu.packets, ch)
+
+ if ok {
+ for i, cancelChan := range f.mu.cancelChans {
+ if cancelChan == ch {
+ f.mu.cancelChans = append(f.mu.cancelChans[:i], f.mu.cancelChans[i+1:]...)
+ break
+ }
+ }
+ }
+
+ f.mu.Unlock()
- incrementOutgoingPacketErrors(r, proto, p.pkt)
+ if ok {
+ f.dequeuePackets(packets, linkAddr, success)
+ }
+}
- p.route.Release()
+func (f *packetsPendingLinkResolution) writePacketBuffer(r RouteInfo, gso *GSO, proto tcpip.NetworkProtocolNumber, pkt pendingPacketBuffer) (int, *tcpip.Error) {
+ switch pkt := pkt.(type) {
+ case *PacketBuffer:
+ if err := f.nic.writePacket(r, gso, proto, pkt); err != nil {
+ return 0, err
+ }
+ return 1, nil
+ case *PacketBufferList:
+ return f.nic.writePackets(r, gso, proto, *pkt)
+ default:
+ panic(fmt.Sprintf("unrecognized pending packet buffer type = %T", pkt))
}
+}
- if l := len(packets); l >= maxPendingPacketsPerResolution {
- panic(fmt.Sprintf("max pending packets for resolution reached; got %d packets, max = %d", l, maxPendingPacketsPerResolution))
+// enqueue a packet to be sent once link resolution completes.
+//
+// If the maximum number of pending resolutions is reached, the packets
+// associated with the oldest link resolution will be dequeued as if they failed
+// link resolution.
+func (f *packetsPendingLinkResolution) enqueue(r *Route, gso *GSO, proto tcpip.NetworkProtocolNumber, pkt pendingPacketBuffer) (int, *tcpip.Error) {
+ f.mu.Lock()
+ // Make sure we attempt resolution while holding f's lock so that we avoid
+ // a race where link resolution completes before we enqueue the packets.
+ //
+ // A @ T1: Call ResolvedFields (get link resolution channel)
+ // B @ T2: Complete link resolution, dequeue pending packets
+ // C @ T1: Enqueue packet that already completed link resolution (which will
+ // never dequeue)
+ //
+ // To make sure B does not interleave with A and C, we make sure A and C are
+ // done while holding the lock.
+ routeInfo, ch, err := r.ResolvedFields(nil)
+ switch err {
+ case nil:
+ // The route resolved immediately, so we don't need to wait for link
+ // resolution to send the packet.
+ f.mu.Unlock()
+ return f.writePacketBuffer(routeInfo, gso, proto, pkt)
+ case tcpip.ErrWouldBlock:
+ // We need to wait for link resolution to complete.
+ default:
+ f.mu.Unlock()
+ return 0, err
}
- f.packets[ch] = append(packets, pendingPacket{
- route: r,
- proto: proto,
- pkt: pkt,
+ defer f.mu.Unlock()
+
+ packets, ok := f.mu.packets[ch]
+ packets = append(packets, pendingPacket{
+ routeInfo: routeInfo,
+ gso: gso,
+ proto: proto,
+ pkt: pkt,
})
+ if len(packets) > maxPendingPacketsPerResolution {
+ f.incrementOutgoingPacketErrors(packets[0].proto, packets[0].pkt)
+ packets[0] = pendingPacket{}
+ packets = packets[1:]
+
+ if numPackets := len(packets); numPackets != maxPendingPacketsPerResolution {
+ panic(fmt.Sprintf("holding more queued packets than expected; got = %d, want <= %d", numPackets, maxPendingPacketsPerResolution))
+ }
+ }
+
+ f.mu.packets[ch] = packets
+
if ok {
- return
+ return pkt.len(), nil
}
- // Wait for the link-address resolution to complete.
- cancel := f.newCancelChannelLocked()
- go func() {
- cancelled := false
- select {
- case <-ch:
- case <-cancel:
- cancelled = true
- }
+ cancelledPackets := f.newCancelChannelLocked(ch)
- f.Lock()
- packets, ok := f.packets[ch]
- delete(f.packets, ch)
- f.Unlock()
+ if len(cancelledPackets) != 0 {
+ // Dequeue the pending packets in a new goroutine to not hold up the current
+ // goroutine as handing link resolution failures may be a costly operation.
+ go f.dequeuePackets(cancelledPackets, "" /* linkAddr */, false /* success */)
+ }
- if !ok {
- panic(fmt.Sprintf("link-resolution goroutine woke up but no entry exists in the queue of packets"))
- }
+ return pkt.len(), nil
+}
- for _, p := range packets {
- if cancelled || p.route.IsResolutionRequired() {
- incrementOutgoingPacketErrors(r, proto, p.pkt)
-
- if linkResolvableEP, ok := p.route.outgoingNIC.getNetworkEndpoint(p.route.NetProto).(LinkResolvableNetworkEndpoint); ok {
- switch pkt := p.pkt.(type) {
- case *PacketBuffer:
- linkResolvableEP.HandleLinkResolutionFailure(pkt)
- case *PacketBufferList:
- for pb := pkt.Front(); pb != nil; pb = pb.Next() {
- linkResolvableEP.HandleLinkResolutionFailure(pb)
- }
- default:
- panic(fmt.Sprintf("unrecognized pending packet buffer type = %T", p.pkt))
- }
- }
- } else {
+// newCancelChannelLocked appends the link resolution channel to a FIFO. If the
+// maximum number of pending resolutions is reached, the oldest channel will be
+// removed and its associated pending packets will be returned.
+func (f *packetsPendingLinkResolution) newCancelChannelLocked(newCH <-chan struct{}) []pendingPacket {
+ f.mu.cancelChans = append(f.mu.cancelChans, newCH)
+ if len(f.mu.cancelChans) <= maxPendingResolutions {
+ return nil
+ }
+
+ ch := f.mu.cancelChans[0]
+ f.mu.cancelChans[0] = nil
+ f.mu.cancelChans = f.mu.cancelChans[1:]
+ if l := len(f.mu.cancelChans); l > maxPendingResolutions {
+ panic(fmt.Sprintf("max pending resolutions reached; got %d active resolutions, max = %d", l, maxPendingResolutions))
+ }
+
+ packets, ok := f.mu.packets[ch]
+ if !ok {
+ panic("must have a packet queue for an uncancelled channel")
+ }
+ delete(f.mu.packets, ch)
+
+ return packets
+}
+
+func (f *packetsPendingLinkResolution) dequeuePackets(packets []pendingPacket, linkAddr tcpip.LinkAddress, success bool) {
+ for _, p := range packets {
+ if success {
+ p.routeInfo.RemoteLinkAddress = linkAddr
+ _, _ = f.writePacketBuffer(p.routeInfo, p.gso, p.proto, p.pkt)
+ } else {
+ f.incrementOutgoingPacketErrors(p.proto, p.pkt)
+
+ if linkResolvableEP, ok := f.nic.getNetworkEndpoint(p.proto).(LinkResolvableNetworkEndpoint); ok {
switch pkt := p.pkt.(type) {
case *PacketBuffer:
- p.route.outgoingNIC.writePacket(p.route.Fields(), nil /* gso */, p.proto, pkt)
+ linkResolvableEP.HandleLinkResolutionFailure(pkt)
case *PacketBufferList:
- p.route.outgoingNIC.writePackets(p.route.Fields(), nil /* gso */, p.proto, *pkt)
+ for pb := pkt.Front(); pb != nil; pb = pb.Next() {
+ linkResolvableEP.HandleLinkResolutionFailure(pb)
+ }
default:
panic(fmt.Sprintf("unrecognized pending packet buffer type = %T", p.pkt))
}
}
- p.route.Release()
}
- }()
-}
-
-// newCancelChannel creates a channel that can cancel a pending forwarding
-// activity. The oldest channel is closed if the number of open channels would
-// exceed maxPendingResolutions.
-func (f *packetsPendingLinkResolution) newCancelChannelLocked() chan struct{} {
- if len(f.cancelChans) == maxPendingResolutions {
- ch := f.cancelChans[0]
- f.cancelChans[0] = nil
- f.cancelChans = f.cancelChans[1:]
- close(ch)
}
- if l := len(f.cancelChans); l >= maxPendingResolutions {
- panic(fmt.Sprintf("max pending resolutions reached; got %d active resolutions, max = %d", l, maxPendingResolutions))
- }
-
- ch := make(chan struct{})
- f.cancelChans = append(f.cancelChans, ch)
- return ch
}
diff --git a/pkg/tcpip/stack/route.go b/pkg/tcpip/stack/route.go
index 1ff7b3a37..093b676aa 100644
--- a/pkg/tcpip/stack/route.go
+++ b/pkg/tcpip/stack/route.go
@@ -86,12 +86,21 @@ type RouteInfo struct {
RemoteLinkAddress tcpip.LinkAddress
}
-// Fields returns a RouteInfo with all of r's exported fields. This allows
-// callers to store the route's fields without retaining a reference to it.
+// Fields returns a RouteInfo with all of the known values for the route's
+// fields.
+//
+// If any fields are unknown (e.g. remote link address when it is waiting for
+// link address resolution), they will be unset.
func (r *Route) Fields() RouteInfo {
+ r.mu.RLock()
+ defer r.mu.RUnlock()
+ return r.fieldsLocked()
+}
+
+func (r *Route) fieldsLocked() RouteInfo {
return RouteInfo{
routeInfo: r.routeInfo,
- RemoteLinkAddress: r.RemoteLinkAddress(),
+ RemoteLinkAddress: r.mu.remoteLinkAddress,
}
}
@@ -306,29 +315,26 @@ func (r *Route) ResolveWith(addr tcpip.LinkAddress) {
r.mu.remoteLinkAddress = addr
}
-// Resolve attempts to resolve the link address if necessary.
+// ResolvedFields is like Fields but also attempts to resolve the remote link
+// address if it is not yet known.
//
-// Returns tcpip.ErrWouldBlock if address resolution requires blocking (e.g.
-// waiting for ARP reply). If address resolution is required, a notification
-// channel is also returned for the caller to block on. The channel is closed
+// If address resolution is required, returns tcpip.ErrWouldBlock and a
+// notification channel for the caller to block on. The channel will be readable
// once address resolution is complete (successful or not). If a callback is
// provided, it will be called when address resolution is complete, regardless
-// of success or failure.
-func (r *Route) Resolve(afterResolve func()) (<-chan struct{}, *tcpip.Error) {
- r.mu.Lock()
-
- if !r.isResolutionRequiredRLocked() {
- // Nothing to do if there is no cache (which does the resolution on cache miss) or
- // link address is already known.
- r.mu.Unlock()
- return nil, nil
+// of success or failure before the notification channel is readable.
+//
+// Note, the route will not cache the remote link address when address
+// resolution completes.
+func (r *Route) ResolvedFields(afterResolve func()) (RouteInfo, <-chan struct{}, *tcpip.Error) {
+ r.mu.RLock()
+ fields := r.fieldsLocked()
+ resolutionRequired := r.isResolutionRequiredRLocked()
+ r.mu.RUnlock()
+ if !resolutionRequired {
+ return fields, nil, nil
}
- // Increment the route's reference count because finishResolution retains a
- // reference to the route and releases it when called.
- r.acquireLocked()
- r.mu.Unlock()
-
nextAddr := r.NextHop
if nextAddr == "" {
nextAddr = r.RemoteAddress
@@ -341,18 +347,15 @@ func (r *Route) Resolve(afterResolve func()) (<-chan struct{}, *tcpip.Error) {
linkAddressResolutionRequestLocalAddr = r.LocalAddress
}
- finishResolution := func(linkAddress tcpip.LinkAddress, ok bool) {
- if ok {
- r.ResolveWith(linkAddress)
- }
+ linkAddr, ch, err := r.outgoingNIC.getNeighborLinkAddress(nextAddr, linkAddressResolutionRequestLocalAddr, r.linkRes, func(tcpip.LinkAddress, bool) {
if afterResolve != nil {
afterResolve()
}
- r.Release()
+ })
+ if err == nil {
+ fields.RemoteLinkAddress = linkAddr
}
-
- _, ch, err := r.outgoingNIC.getNeighborLinkAddress(nextAddr, linkAddressResolutionRequestLocalAddr, r.linkRes, finishResolution)
- return ch, err
+ return fields, ch, err
}
// local returns true if the route is a local route.
@@ -371,11 +374,7 @@ func (r *Route) IsResolutionRequired() bool {
}
func (r *Route) isResolutionRequiredRLocked() bool {
- if !r.isValidForOutgoingRLocked() || r.mu.remoteLinkAddress != "" || r.local() {
- return false
- }
-
- return r.linkRes != nil
+ return len(r.mu.remoteLinkAddress) == 0 && r.linkRes != nil && r.isValidForOutgoingRLocked() && !r.local()
}
func (r *Route) isValidForOutgoing() bool {
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-14 03:28:36 +0000