AF_PACKET support for netstack (aka epsocket).

Like (AF_INET, SOCK_RAW) sockets, AF_PACKET sockets require CAP_NET_RAW. With
runsc, you'll need to pass `--net-raw=true` to enable them.

Binding isn't supported yet.

PiperOrigin-RevId: 275909366

3 files changed, 481 insertions, 0 deletions

diff --git a/pkg/tcpip/transport/packet/BUILD b/pkg/tcpip/transport/packet/BUILD
new file mode 100644
index 000000000..8ea2e6ee5
--- /dev/null
+++ b/pkg/tcpip/transport/packet/BUILD
@@ -0,0 +1,46 @@
+load("//tools/go_generics:defs.bzl", "go_template_instance")
+load("//tools/go_stateify:defs.bzl", "go_library")
+
+package(licenses = ["notice"])
+
+go_template_instance(
+    name = "packet_list",
+    out = "packet_list.go",
+    package = "packet",
+    prefix = "packet",
+    template = "//pkg/ilist:generic_list",
+    types = {
+        "Element": "*packet",
+        "Linker": "*packet",
+    },
+)
+
+go_library(
+    name = "packet",
+    srcs = [
+        "endpoint.go",
+        "endpoint_state.go",
+        "packet_list.go",
+    ],
+    importpath = "gvisor.dev/gvisor/pkg/tcpip/transport/packet",
+    imports = ["gvisor.dev/gvisor/pkg/tcpip/buffer"],
+    visibility = ["//visibility:public"],
+    deps = [
+        "//pkg/log",
+        "//pkg/sleep",
+        "//pkg/tcpip",
+        "//pkg/tcpip/buffer",
+        "//pkg/tcpip/header",
+        "//pkg/tcpip/iptables",
+        "//pkg/tcpip/stack",
+        "//pkg/waiter",
+    ],
+)
+
+filegroup(
+    name = "autogen",
+    srcs = [
+        "packet_list.go",
+    ],
+    visibility = ["//:sandbox"],
+)
diff --git a/pkg/tcpip/transport/packet/endpoint.go b/pkg/tcpip/transport/packet/endpoint.go
new file mode 100644
index 000000000..73cdaa265
--- /dev/null
+++ b/pkg/tcpip/transport/packet/endpoint.go
@@ -0,0 +1,363 @@
+// Copyright 2019 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package packet provides the implementation of packet sockets (see
+// packet(7)). Packet sockets allow applications to:
+//
+//   * manually write and inspect link, network, and transport headers
+//   * receive all traffic of a given network protocol, or all protocols
+//
+// Packet sockets are similar to raw sockets, but provide even more power to
+// users, letting them effectively talk directly to the network device.
+//
+// Packet sockets skip the input and output iptables chains.
+package packet
+
+import (
+	"sync"
+
+	"gvisor.dev/gvisor/pkg/tcpip"
+	"gvisor.dev/gvisor/pkg/tcpip/buffer"
+	"gvisor.dev/gvisor/pkg/tcpip/header"
+	"gvisor.dev/gvisor/pkg/tcpip/iptables"
+	"gvisor.dev/gvisor/pkg/tcpip/stack"
+	"gvisor.dev/gvisor/pkg/waiter"
+)
+
+// +stateify savable
+type packet struct {
+	packetEntry
+	// data holds the actual packet data, including any headers and
+	// payload.
+	data buffer.VectorisedView `state:".(buffer.VectorisedView)"`
+	// views is pre-allocated space to back data. As long as the packet is
+	// made up of fewer than 8 buffer.Views, no extra allocation is
+	// necessary to store packet data.
+	views [8]buffer.View `state:"nosave"`
+	// timestampNS is the unix time at which the packet was received.
+	timestampNS int64
+	// senderAddr is the network address of the sender.
+	senderAddr tcpip.FullAddress
+}
+
+// endpoint is the packet socket implementation of tcpip.Endpoint. It is legal
+// to have goroutines make concurrent calls into the endpoint.
+//
+// Lock order:
+//   endpoint.mu
+//     endpoint.rcvMu
+//
+// +stateify savable
+type endpoint struct {
+	stack.TransportEndpointInfo
+	// The following fields are initialized at creation time and are
+	// immutable.
+	stack       *stack.Stack `state:"manual"`
+	netProto    tcpip.NetworkProtocolNumber
+	waiterQueue *waiter.Queue
+	cooked      bool
+
+	// The following fields are used to manage the receive queue and are
+	// protected by rcvMu.
+	rcvMu         sync.Mutex `state:"nosave"`
+	rcvList       packetList
+	rcvBufSizeMax int `state:".(int)"`
+	rcvBufSize    int
+	rcvClosed     bool
+
+	// The following fields are protected by mu.
+	mu         sync.RWMutex `state:"nosave"`
+	sndBufSize int
+	closed     bool
+	stats      tcpip.TransportEndpointStats `state:"nosave"`
+}
+
+// NewEndpoint returns a new packet endpoint.
+func NewEndpoint(s *stack.Stack, cooked bool, netProto tcpip.NetworkProtocolNumber, waiterQueue *waiter.Queue) (tcpip.Endpoint, *tcpip.Error) {
+	ep := &endpoint{
+		stack: s,
+		TransportEndpointInfo: stack.TransportEndpointInfo{
+			NetProto: netProto,
+		},
+		cooked:        cooked,
+		netProto:      netProto,
+		waiterQueue:   waiterQueue,
+		rcvBufSizeMax: 32 * 1024,
+		sndBufSize:    32 * 1024,
+	}
+
+	if err := s.RegisterPacketEndpoint(0, netProto, ep); err != nil {
+		return nil, err
+	}
+	return ep, nil
+}
+
+// Close implements tcpip.Endpoint.Close.
+func (ep *endpoint) Close() {
+	ep.mu.Lock()
+	defer ep.mu.Unlock()
+
+	if ep.closed {
+		return
+	}
+
+	ep.stack.UnregisterPacketEndpoint(0, ep.netProto, ep)
+
+	ep.rcvMu.Lock()
+	defer ep.rcvMu.Unlock()
+
+	// Clear the receive list.
+	ep.rcvClosed = true
+	ep.rcvBufSize = 0
+	for !ep.rcvList.Empty() {
+		ep.rcvList.Remove(ep.rcvList.Front())
+	}
+
+	ep.closed = true
+	ep.waiterQueue.Notify(waiter.EventHUp | waiter.EventErr | waiter.EventIn | waiter.EventOut)
+}
+
+// ModerateRecvBuf implements tcpip.Endpoint.ModerateRecvBuf.
+func (ep *endpoint) ModerateRecvBuf(copied int) {}
+
+// IPTables implements tcpip.Endpoint.IPTables.
+func (ep *endpoint) IPTables() (iptables.IPTables, error) {
+	return ep.stack.IPTables(), nil
+}
+
+// Read implements tcpip.Endpoint.Read.
+func (ep *endpoint) Read(addr *tcpip.FullAddress) (buffer.View, tcpip.ControlMessages, *tcpip.Error) {
+	ep.rcvMu.Lock()
+
+	// If there's no data to read, return that read would block or that the
+	// endpoint is closed.
+	if ep.rcvList.Empty() {
+		err := tcpip.ErrWouldBlock
+		if ep.rcvClosed {
+			ep.stats.ReadErrors.ReadClosed.Increment()
+			err = tcpip.ErrClosedForReceive
+		}
+		ep.rcvMu.Unlock()
+		return buffer.View{}, tcpip.ControlMessages{}, err
+	}
+
+	packet := ep.rcvList.Front()
+	ep.rcvList.Remove(packet)
+	ep.rcvBufSize -= packet.data.Size()
+
+	ep.rcvMu.Unlock()
+
+	if addr != nil {
+		*addr = packet.senderAddr
+	}
+
+	return packet.data.ToView(), tcpip.ControlMessages{HasTimestamp: true, Timestamp: packet.timestampNS}, nil
+}
+
+func (ep *endpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, <-chan struct{}, *tcpip.Error) {
+	// TODO(b/129292371): Implement.
+	return 0, nil, tcpip.ErrInvalidOptionValue
+}
+
+// Peek implements tcpip.Endpoint.Peek.
+func (ep *endpoint) Peek([][]byte) (int64, tcpip.ControlMessages, *tcpip.Error) {
+	return 0, tcpip.ControlMessages{}, nil
+}
+
+// Disconnect implements tcpip.Endpoint.Disconnect. Packet sockets cannot be
+// disconnected, and this function always returns tpcip.ErrNotSupported.
+func (*endpoint) Disconnect() *tcpip.Error {
+	return tcpip.ErrNotSupported
+}
+
+// Connect implements tcpip.Endpoint.Connect. Packet sockets cannot be
+// connected, and this function always returnes tcpip.ErrNotSupported.
+func (ep *endpoint) Connect(addr tcpip.FullAddress) *tcpip.Error {
+	return tcpip.ErrNotSupported
+}
+
+// Shutdown implements tcpip.Endpoint.Shutdown. Packet sockets cannot be used
+// with Shutdown, and this function always returns tcpip.ErrNotSupported.
+func (ep *endpoint) Shutdown(flags tcpip.ShutdownFlags) *tcpip.Error {
+	return tcpip.ErrNotSupported
+}
+
+// Listen implements tcpip.Endpoint.Listen. Packet sockets cannot be used with
+// Listen, and this function always returns tcpip.ErrNotSupported.
+func (ep *endpoint) Listen(backlog int) *tcpip.Error {
+	return tcpip.ErrNotSupported
+}
+
+// Accept implements tcpip.Endpoint.Accept. Packet sockets cannot be used with
+// Accept, and this function always returns tcpip.ErrNotSupported.
+func (ep *endpoint) Accept() (tcpip.Endpoint, *waiter.Queue, *tcpip.Error) {
+	return nil, nil, tcpip.ErrNotSupported
+}
+
+// Bind implements tcpip.Endpoint.Bind.
+func (ep *endpoint) Bind(addr tcpip.FullAddress) *tcpip.Error {
+	// TODO(gvisor.dev/issue/173): Add Bind support.
+
+	// "By default, all packets of the specified protocol type are passed
+	// to a packet socket.  To get packets only from a specific interface
+	// use bind(2) specifying an address in a struct sockaddr_ll to bind
+	// the packet socket  to  an interface.  Fields used for binding are
+	// sll_family (should be AF_PACKET), sll_protocol, and sll_ifindex."
+	// - packet(7).
+
+	return tcpip.ErrNotSupported
+}
+
+// GetLocalAddress implements tcpip.Endpoint.GetLocalAddress.
+func (ep *endpoint) GetLocalAddress() (tcpip.FullAddress, *tcpip.Error) {
+	return tcpip.FullAddress{}, tcpip.ErrNotSupported
+}
+
+// GetRemoteAddress implements tcpip.Endpoint.GetRemoteAddress.
+func (ep *endpoint) GetRemoteAddress() (tcpip.FullAddress, *tcpip.Error) {
+	// Even a connected socket doesn't return a remote address.
+	return tcpip.FullAddress{}, tcpip.ErrNotConnected
+}
+
+// Readiness implements tcpip.Endpoint.Readiness.
+func (ep *endpoint) Readiness(mask waiter.EventMask) waiter.EventMask {
+	// The endpoint is always writable.
+	result := waiter.EventOut & mask
+
+	// Determine whether the endpoint is readable.
+	if (mask & waiter.EventIn) != 0 {
+		ep.rcvMu.Lock()
+		if !ep.rcvList.Empty() || ep.rcvClosed {
+			result |= waiter.EventIn
+		}
+		ep.rcvMu.Unlock()
+	}
+
+	return result
+}
+
+// SetSockOpt implements tcpip.Endpoint.SetSockOpt. Packet sockets cannot be
+// used with SetSockOpt, and this function always returns
+// tcpip.ErrNotSupported.
+func (ep *endpoint) SetSockOpt(opt interface{}) *tcpip.Error {
+	return tcpip.ErrNotSupported
+}
+
+// SetSockOptInt implements tcpip.Endpoint.SetSockOptInt.
+func (ep *endpoint) SetSockOptInt(opt tcpip.SockOpt, v int) *tcpip.Error {
+	return tcpip.ErrUnknownProtocolOption
+}
+
+// GetSockOptInt implements tcpip.Endpoint.GetSockOptInt.
+func (ep *endpoint) GetSockOptInt(opt tcpip.SockOpt) (int, *tcpip.Error) {
+	return 0, tcpip.ErrNotSupported
+}
+
+// GetSockOpt implements tcpip.Endpoint.GetSockOpt.
+func (ep *endpoint) GetSockOpt(opt interface{}) *tcpip.Error {
+	return tcpip.ErrNotSupported
+}
+
+// HandlePacket implements stack.PacketEndpoint.HandlePacket.
+func (ep *endpoint) HandlePacket(nicid tcpip.NICID, localAddr tcpip.LinkAddress, netProto tcpip.NetworkProtocolNumber, vv buffer.VectorisedView, ethHeader buffer.View) {
+	ep.rcvMu.Lock()
+
+	// Drop the packet if our buffer is currently full.
+	if ep.rcvClosed {
+		ep.rcvMu.Unlock()
+		ep.stack.Stats().DroppedPackets.Increment()
+		ep.stats.ReceiveErrors.ClosedReceiver.Increment()
+		return
+	}
+
+	if ep.rcvBufSize >= ep.rcvBufSizeMax {
+		ep.rcvMu.Unlock()
+		ep.stack.Stats().DroppedPackets.Increment()
+		ep.stats.ReceiveErrors.ReceiveBufferOverflow.Increment()
+		return
+	}
+
+	wasEmpty := ep.rcvBufSize == 0
+
+	// Push new packet into receive list and increment the buffer size.
+	var packet packet
+	// TODO(b/129292371): Return network protocol.
+	if len(ethHeader) > 0 {
+		// Get info directly from the ethernet header.
+		hdr := header.Ethernet(ethHeader)
+		packet.senderAddr = tcpip.FullAddress{
+			NIC:  nicid,
+			Addr: tcpip.Address(hdr.SourceAddress()),
+		}
+	} else {
+		// Guess the would-be ethernet header.
+		packet.senderAddr = tcpip.FullAddress{
+			NIC:  nicid,
+			Addr: tcpip.Address(localAddr),
+		}
+	}
+
+	if ep.cooked {
+		// Cooked packets can simply be queued.
+		packet.data = vv.Clone(packet.views[:])
+	} else {
+		// Raw packets need their ethernet headers prepended before
+		// queueing.
+		if len(ethHeader) == 0 {
+			// We weren't provided with an actual ethernet header,
+			// so fake one.
+			ethFields := header.EthernetFields{
+				SrcAddr: tcpip.LinkAddress([]byte{0x00, 0x00, 0x00, 0x00, 0x00, 0x00}),
+				DstAddr: localAddr,
+				Type:    netProto,
+			}
+			fakeHeader := make(header.Ethernet, header.EthernetMinimumSize)
+			fakeHeader.Encode(&ethFields)
+			ethHeader = buffer.View(fakeHeader)
+		}
+		combinedVV := buffer.View(ethHeader).ToVectorisedView()
+		combinedVV.Append(vv)
+		packet.data = combinedVV.Clone(packet.views[:])
+	}
+	packet.timestampNS = ep.stack.NowNanoseconds()
+
+	ep.rcvList.PushBack(&packet)
+	ep.rcvBufSize += packet.data.Size()
+
+	ep.rcvMu.Unlock()
+	ep.stats.PacketsReceived.Increment()
+	// Notify waiters that there's data to be read.
+	if wasEmpty {
+		ep.waiterQueue.Notify(waiter.EventIn)
+	}
+}
+
+// State implements socket.Socket.State.
+func (ep *endpoint) State() uint32 {
+	return 0
+}
+
+// Info returns a copy of the endpoint info.
+func (ep *endpoint) Info() tcpip.EndpointInfo {
+	ep.mu.RLock()
+	// Make a copy of the endpoint info.
+	ret := ep.TransportEndpointInfo
+	ep.mu.RUnlock()
+	return &ret
+}
+
+// Stats returns a pointer to the endpoint stats.
+func (ep *endpoint) Stats() tcpip.EndpointStats {
+	return &ep.stats
+}
diff --git a/pkg/tcpip/transport/packet/endpoint_state.go b/pkg/tcpip/transport/packet/endpoint_state.go
new file mode 100644
index 000000000..9b88f17e4
--- /dev/null
+++ b/pkg/tcpip/transport/packet/endpoint_state.go
@@ -0,0 +1,72 @@
+// Copyright 2018 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package packet
+
+import (
+	"gvisor.dev/gvisor/pkg/tcpip/buffer"
+	"gvisor.dev/gvisor/pkg/tcpip/stack"
+)
+
+// saveData saves packet.data field.
+func (p *packet) saveData() buffer.VectorisedView {
+	// We cannot save p.data directly as p.data.views may alias to p.views,
+	// which is not allowed by state framework (in-struct pointer).
+	return p.data.Clone(nil)
+}
+
+// loadData loads packet.data field.
+func (p *packet) loadData(data buffer.VectorisedView) {
+	// NOTE: We cannot do the p.data = data.Clone(p.views[:]) optimization
+	// here because data.views is not guaranteed to be loaded by now. Plus,
+	// data.views will be allocated anyway so there really is little point
+	// of utilizing p.views for data.views.
+	p.data = data
+}
+
+// beforeSave is invoked by stateify.
+func (ep *endpoint) beforeSave() {
+	// Stop incoming packets from being handled (and mutate endpoint state).
+	// The lock will be released after saveRcvBufSizeMax(), which would have
+	// saved ep.rcvBufSizeMax and set it to 0 to continue blocking incoming
+	// packets.
+	ep.rcvMu.Lock()
+}
+
+// saveRcvBufSizeMax is invoked by stateify.
+func (ep *endpoint) saveRcvBufSizeMax() int {
+	max := ep.rcvBufSizeMax
+	// Make sure no new packets will be handled regardless of the lock.
+	ep.rcvBufSizeMax = 0
+	// Release the lock acquired in beforeSave() so regular endpoint closing
+	// logic can proceed after save.
+	ep.rcvMu.Unlock()
+	return max
+}
+
+// loadRcvBufSizeMax is invoked by stateify.
+func (ep *endpoint) loadRcvBufSizeMax(max int) {
+	ep.rcvBufSizeMax = max
+}
+
+// afterLoad is invoked by stateify.
+func (ep *endpoint) afterLoad() {
+	// StackFromEnv is a stack used specifically for save/restore.
+	ep.stack = stack.StackFromEnv
+
+	// TODO(gvisor.dev/173): Once bind is supported, choose the right NIC.
+	if err := ep.stack.RegisterPacketEndpoint(0, ep.netProto, ep); err != nil {
+		panic(*err)
+	}
+}