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Avoid locking when route doesn't require resolution 

When a route does not need to resolve a remote link address to send a
packet, avoid having to obtain the pending packets queue's lock.

PiperOrigin-RevId: 354456280
This commit is contained in:
Ghanan Gowripalan 2021-01-28 20:30:02 -08:00 committed by gVisor bot
parent ff4fc42784
commit d6a39734c4
2 changed files with 42 additions and 34 deletions
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58
pkg/tcpip/stack/nic.go
View File

@ -309,25 +309,47 @@ func (n *NIC) WritePacket(r *Route, gso *GSO, protocol tcpip.NetworkProtocolNumb
return err
}
func (n *NIC) writePacketBuffer(r RouteInfo, gso *GSO, protocol tcpip.NetworkProtocolNumber, pkt pendingPacketBuffer) (int, tcpip.Error) {
switch pkt := pkt.(type) {
case *PacketBuffer:
if err := n.writePacket(r, gso, protocol, pkt); err != nil {
return 0, err
}
return 1, nil
case *PacketBufferList:
return n.writePackets(r, gso, protocol, *pkt)
default:
panic(fmt.Sprintf("unrecognized pending packet buffer type = %T", pkt))
}
}
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.
//
// 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.
return n.linkResQueue.enqueue(r, gso, protocol, pkt)
routeInfo, _, err := r.resolvedFields(nil)
switch err.(type) {
case nil:
return n.writePacketBuffer(routeInfo, gso, protocol, pkt)
case *tcpip.ErrWouldBlock:
// 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.
return n.linkResQueue.enqueue(r, gso, protocol, pkt)
default:
return 0, err
}
}
// WritePacketToRemote implements NetworkInterface.

18
pkg/tcpip/stack/pending_packets.go
View File

@ -114,20 +114,6 @@ func (f *packetsPendingLinkResolution) dequeue(ch <-chan struct{}, linkAddr tcpi
}
}
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))
}
}
// enqueue a packet to be sent once link resolution completes.
//
// If the maximum number of pending resolutions is reached, the packets
@ -151,7 +137,7 @@ func (f *packetsPendingLinkResolution) enqueue(r *Route, gso *GSO, proto tcpip.N
// 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)
return f.nic.writePacketBuffer(routeInfo, gso, proto, pkt)
case *tcpip.ErrWouldBlock:
// We need to wait for link resolution to complete.
default:
@ -225,7 +211,7 @@ func (f *packetsPendingLinkResolution) dequeuePackets(packets []pendingPacket, l
for _, p := range packets {
if success {
p.routeInfo.RemoteLinkAddress = linkAddr
_, _ = f.writePacketBuffer(p.routeInfo, p.gso, p.proto, p.pkt)
_, _ = f.nic.writePacketBuffer(p.routeInfo, p.gso, p.proto, p.pkt)
} else {
f.incrementOutgoingPacketErrors(p.proto, p.pkt)