vendor: Add golang.org/x/net/bpf

vendor/golang.org/x/net/bpf/LICENSE

@@ -0,0 +1,27 @@
+Copyright (c) 2009 The Go Authors. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are
+met:
+
+   * Redistributions of source code must retain the above copyright
+notice, this list of conditions and the following disclaimer.
+   * Redistributions in binary form must reproduce the above
+copyright notice, this list of conditions and the following disclaimer
+in the documentation and/or other materials provided with the
+distribution.
+   * Neither the name of Google Inc. nor the names of its
+contributors may be used to endorse or promote products derived from
+this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

vendor/golang.org/x/net/bpf/asm.go

@@ -0,0 +1,41 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package bpf
+
+import "fmt"
+
+// Assemble converts insts into raw instructions suitable for loading
+// into a BPF virtual machine.
+//
+// Currently, no optimization is attempted, the assembled program flow
+// is exactly as provided.
+func Assemble(insts []Instruction) ([]RawInstruction, error) {
+	ret := make([]RawInstruction, len(insts))
+	var err error
+	for i, inst := range insts {
+		ret[i], err = inst.Assemble()
+		if err != nil {
+			return nil, fmt.Errorf("assembling instruction %d: %s", i+1, err)
+		}
+	}
+	return ret, nil
+}
+
+// Disassemble attempts to parse raw back into
+// Instructions. Unrecognized RawInstructions are assumed to be an
+// extension not implemented by this package, and are passed through
+// unchanged to the output. The allDecoded value reports whether insts
+// contains no RawInstructions.
+func Disassemble(raw []RawInstruction) (insts []Instruction, allDecoded bool) {
+	insts = make([]Instruction, len(raw))
+	allDecoded = true
+	for i, r := range raw {
+		insts[i] = r.Disassemble()
+		if _, ok := insts[i].(RawInstruction); ok {
+			allDecoded = false
+		}
+	}
+	return insts, allDecoded
+}

vendor/golang.org/x/net/bpf/constants.go

@@ -0,0 +1,215 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package bpf
+
+// A Register is a register of the BPF virtual machine.
+type Register uint16
+
+const (
+	// RegA is the accumulator register. RegA is always the
+	// destination register of ALU operations.
+	RegA Register = iota
+	// RegX is the indirection register, used by LoadIndirect
+	// operations.
+	RegX
+)
+
+// An ALUOp is an arithmetic or logic operation.
+type ALUOp uint16
+
+// ALU binary operation types.
+const (
+	ALUOpAdd ALUOp = iota << 4
+	ALUOpSub
+	ALUOpMul
+	ALUOpDiv
+	ALUOpOr
+	ALUOpAnd
+	ALUOpShiftLeft
+	ALUOpShiftRight
+	aluOpNeg // Not exported because it's the only unary ALU operation, and gets its own instruction type.
+	ALUOpMod
+	ALUOpXor
+)
+
+// A JumpTest is a comparison operator used in conditional jumps.
+type JumpTest uint16
+
+// Supported operators for conditional jumps.
+const (
+	// K == A
+	JumpEqual JumpTest = iota
+	// K != A
+	JumpNotEqual
+	// K > A
+	JumpGreaterThan
+	// K < A
+	JumpLessThan
+	// K >= A
+	JumpGreaterOrEqual
+	// K <= A
+	JumpLessOrEqual
+	// K & A != 0
+	JumpBitsSet
+	// K & A == 0
+	JumpBitsNotSet
+)
+
+// An Extension is a function call provided by the kernel that
+// performs advanced operations that are expensive or impossible
+// within the BPF virtual machine.
+//
+// Extensions are only implemented by the Linux kernel.
+//
+// TODO: should we prune this list? Some of these extensions seem
+// either broken or near-impossible to use correctly, whereas other
+// (len, random, ifindex) are quite useful.
+type Extension int
+
+// Extension functions available in the Linux kernel.
+const (
+	// ExtLen returns the length of the packet.
+	ExtLen Extension = 1
+	// ExtProto returns the packet's L3 protocol type.
+	ExtProto = 0
+	// ExtType returns the packet's type (skb->pkt_type in the kernel)
+	//
+	// TODO: better documentation. How nice an API do we want to
+	// provide for these esoteric extensions?
+	ExtType = 4
+	// ExtPayloadOffset returns the offset of the packet payload, or
+	// the first protocol header that the kernel does not know how to
+	// parse.
+	ExtPayloadOffset = 52
+	// ExtInterfaceIndex returns the index of the interface on which
+	// the packet was received.
+	ExtInterfaceIndex = 8
+	// ExtNetlinkAttr returns the netlink attribute of type X at
+	// offset A.
+	ExtNetlinkAttr = 12
+	// ExtNetlinkAttrNested returns the nested netlink attribute of
+	// type X at offset A.
+	ExtNetlinkAttrNested = 16
+	// ExtMark returns the packet's mark value.
+	ExtMark = 20
+	// ExtQueue returns the packet's assigned hardware queue.
+	ExtQueue = 24
+	// ExtLinkLayerType returns the packet's hardware address type
+	// (e.g. Ethernet, Infiniband).
+	ExtLinkLayerType = 28
+	// ExtRXHash returns the packets receive hash.
+	//
+	// TODO: figure out what this rxhash actually is.
+	ExtRXHash = 32
+	// ExtCPUID returns the ID of the CPU processing the current
+	// packet.
+	ExtCPUID = 36
+	// ExtVLANTag returns the packet's VLAN tag.
+	ExtVLANTag = 44
+	// ExtVLANTagPresent returns non-zero if the packet has a VLAN
+	// tag.
+	//
+	// TODO: I think this might be a lie: it reads bit 0x1000 of the
+	// VLAN header, which changed meaning in recent revisions of the
+	// spec - this extension may now return meaningless information.
+	ExtVLANTagPresent = 48
+	// ExtVLANProto returns 0x8100 if the frame has a VLAN header,
+	// 0x88a8 if the frame has a "Q-in-Q" double VLAN header, or some
+	// other value if no VLAN information is present.
+	ExtVLANProto = 60
+	// ExtRand returns a uniformly random uint32.
+	ExtRand = 56
+)
+
+// The following gives names to various bit patterns used in opcode construction.
+
+const (
+	opMaskCls uint16 = 0x7
+	// opClsLoad masks
+	opMaskLoadDest  = 0x01
+	opMaskLoadWidth = 0x18
+	opMaskLoadMode  = 0xe0
+	// opClsALU
+	opMaskOperandSrc = 0x08
+	opMaskOperator   = 0xf0
+	// opClsJump
+	opMaskJumpConst = 0x0f
+	opMaskJumpCond  = 0xf0
+)
+
+const (
+	// +---------------+-----------------+---+---+---+
+	// | AddrMode (3b) | LoadWidth (2b)  | 0 | 0 | 0 |
+	// +---------------+-----------------+---+---+---+
+	opClsLoadA uint16 = iota
+	// +---------------+-----------------+---+---+---+
+	// | AddrMode (3b) | LoadWidth (2b)  | 0 | 0 | 1 |
+	// +---------------+-----------------+---+---+---+
+	opClsLoadX
+	// +---+---+---+---+---+---+---+---+
+	// | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 |
+	// +---+---+---+---+---+---+---+---+
+	opClsStoreA
+	// +---+---+---+---+---+---+---+---+
+	// | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 1 |
+	// +---+---+---+---+---+---+---+---+
+	opClsStoreX
+	// +---------------+-----------------+---+---+---+
+	// | Operator (4b) | OperandSrc (1b) | 1 | 0 | 0 |
+	// +---------------+-----------------+---+---+---+
+	opClsALU
+	// +-----------------------------+---+---+---+---+
+	// |      TestOperator (4b)      | 0 | 1 | 0 | 1 |
+	// +-----------------------------+---+---+---+---+
+	opClsJump
+	// +---+-------------------------+---+---+---+---+
+	// | 0 | 0 | 0 |   RetSrc (1b)   | 0 | 1 | 1 | 0 |
+	// +---+-------------------------+---+---+---+---+
+	opClsReturn
+	// +---+-------------------------+---+---+---+---+
+	// | 0 | 0 | 0 |  TXAorTAX (1b)  | 0 | 1 | 1 | 1 |
+	// +---+-------------------------+---+---+---+---+
+	opClsMisc
+)
+
+const (
+	opAddrModeImmediate uint16 = iota << 5
+	opAddrModeAbsolute
+	opAddrModeIndirect
+	opAddrModeScratch
+	opAddrModePacketLen // actually an extension, not an addressing mode.
+	opAddrModeMemShift
+)
+
+const (
+	opLoadWidth4 uint16 = iota << 3
+	opLoadWidth2
+	opLoadWidth1
+)
+
+// Operator defined by ALUOp*
+
+const (
+	opALUSrcConstant uint16 = iota << 3
+	opALUSrcX
+)
+
+const (
+	opJumpAlways = iota << 4
+	opJumpEqual
+	opJumpGT
+	opJumpGE
+	opJumpSet
+)
+
+const (
+	opRetSrcConstant uint16 = iota << 4
+	opRetSrcA
+)
+
+const (
+	opMiscTAX = 0x00
+	opMiscTXA = 0x80
+)

vendor/golang.org/x/net/bpf/doc.go

@@ -0,0 +1,82 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+/*
+
+Package bpf implements marshaling and unmarshaling of programs for the
+Berkeley Packet Filter virtual machine, and provides a Go implementation
+of the virtual machine.
+
+BPF's main use is to specify a packet filter for network taps, so that
+the kernel doesn't have to expensively copy every packet it sees to
+userspace. However, it's been repurposed to other areas where running
+user code in-kernel is needed. For example, Linux's seccomp uses BPF
+to apply security policies to system calls. For simplicity, this
+documentation refers only to packets, but other uses of BPF have their
+own data payloads.
+
+BPF programs run in a restricted virtual machine. It has almost no
+access to kernel functions, and while conditional branches are
+allowed, they can only jump forwards, to guarantee that there are no
+infinite loops.
+
+The virtual machine
+
+The BPF VM is an accumulator machine. Its main register, called
+register A, is an implicit source and destination in all arithmetic
+and logic operations. The machine also has 16 scratch registers for
+temporary storage, and an indirection register (register X) for
+indirect memory access. All registers are 32 bits wide.
+
+Each run of a BPF program is given one packet, which is placed in the
+VM's read-only "main memory". LoadAbsolute and LoadIndirect
+instructions can fetch up to 32 bits at a time into register A for
+examination.
+
+The goal of a BPF program is to produce and return a verdict (uint32),
+which tells the kernel what to do with the packet. In the context of
+packet filtering, the returned value is the number of bytes of the
+packet to forward to userspace, or 0 to ignore the packet. Other
+contexts like seccomp define their own return values.
+
+In order to simplify programs, attempts to read past the end of the
+packet terminate the program execution with a verdict of 0 (ignore
+packet). This means that the vast majority of BPF programs don't need
+to do any explicit bounds checking.
+
+In addition to the bytes of the packet, some BPF programs have access
+to extensions, which are essentially calls to kernel utility
+functions. Currently, the only extensions supported by this package
+are the Linux packet filter extensions.
+
+Examples
+
+This packet filter selects all ARP packets.
+
+	bpf.Assemble([]bpf.Instruction{
+		// Load "EtherType" field from the ethernet header.
+		bpf.LoadAbsolute{Off: 12, Size: 2},
+		// Skip over the next instruction if EtherType is not ARP.
+		bpf.JumpIf{Cond: bpf.JumpNotEqual, Val: 0x0806, SkipTrue: 1},
+		// Verdict is "send up to 4k of the packet to userspace."
+		bpf.RetConstant{Val: 4096},
+		// Verdict is "ignore packet."
+		bpf.RetConstant{Val: 0},
+	})
+
+This packet filter captures a random 1% sample of traffic.
+
+	bpf.Assemble([]bpf.Instruction{
+		// Get a 32-bit random number from the Linux kernel.
+		bpf.LoadExtension{Num: bpf.ExtRand},
+		// 1% dice roll?
+		bpf.JumpIf{Cond: bpf.JumpLessThan, Val: 2^32/100, SkipFalse: 1},
+		// Capture.
+		bpf.RetConstant{Val: 4096},
+		// Ignore.
+		bpf.RetConstant{Val: 0},
+	})
+
+*/
+package bpf // import "golang.org/x/net/bpf"

vendor/golang.org/x/net/bpf/instructions.go

@@ -0,0 +1,434 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package bpf
+
+import "fmt"
+
+// An Instruction is one instruction executed by the BPF virtual
+// machine.
+type Instruction interface {
+	// Assemble assembles the Instruction into a RawInstruction.
+	Assemble() (RawInstruction, error)
+}
+
+// A RawInstruction is a raw BPF virtual machine instruction.
+type RawInstruction struct {
+	// Operation to execute.
+	Op uint16
+	// For conditional jump instructions, the number of instructions
+	// to skip if the condition is true/false.
+	Jt uint8
+	Jf uint8
+	// Constant parameter. The meaning depends on the Op.
+	K uint32
+}
+
+// Assemble implements the Instruction Assemble method.
+func (ri RawInstruction) Assemble() (RawInstruction, error) { return ri, nil }
+
+// Disassemble parses ri into an Instruction and returns it. If ri is
+// not recognized by this package, ri itself is returned.
+func (ri RawInstruction) Disassemble() Instruction {
+	switch ri.Op & opMaskCls {
+	case opClsLoadA, opClsLoadX:
+		reg := Register(ri.Op & opMaskLoadDest)
+		sz := 0
+		switch ri.Op & opMaskLoadWidth {
+		case opLoadWidth4:
+			sz = 4
+		case opLoadWidth2:
+			sz = 2
+		case opLoadWidth1:
+			sz = 1
+		default:
+			return ri
+		}
+		switch ri.Op & opMaskLoadMode {
+		case opAddrModeImmediate:
+			if sz != 4 {
+				return ri
+			}
+			return LoadConstant{Dst: reg, Val: ri.K}
+		case opAddrModeScratch:
+			if sz != 4 || ri.K > 15 {
+				return ri
+			}
+			return LoadScratch{Dst: reg, N: int(ri.K)}
+		case opAddrModeAbsolute:
+			return LoadAbsolute{Size: sz, Off: ri.K}
+		case opAddrModeIndirect:
+			return LoadIndirect{Size: sz, Off: ri.K}
+		case opAddrModePacketLen:
+			if sz != 4 {
+				return ri
+			}
+			return LoadExtension{Num: ExtLen}
+		case opAddrModeMemShift:
+			return LoadMemShift{Off: ri.K}
+		default:
+			return ri
+		}
+
+	case opClsStoreA:
+		if ri.Op != opClsStoreA || ri.K > 15 {
+			return ri
+		}
+		return StoreScratch{Src: RegA, N: int(ri.K)}
+
+	case opClsStoreX:
+		if ri.Op != opClsStoreX || ri.K > 15 {
+			return ri
+		}
+		return StoreScratch{Src: RegX, N: int(ri.K)}
+
+	case opClsALU:
+		switch op := ALUOp(ri.Op & opMaskOperator); op {
+		case ALUOpAdd, ALUOpSub, ALUOpMul, ALUOpDiv, ALUOpOr, ALUOpAnd, ALUOpShiftLeft, ALUOpShiftRight, ALUOpMod, ALUOpXor:
+			if ri.Op&opMaskOperandSrc != 0 {
+				return ALUOpX{Op: op}
+			}
+			return ALUOpConstant{Op: op, Val: ri.K}
+		case aluOpNeg:
+			return NegateA{}
+		default:
+			return ri
+		}
+
+	case opClsJump:
+		if ri.Op&opMaskJumpConst != opClsJump {
+			return ri
+		}
+		switch ri.Op & opMaskJumpCond {
+		case opJumpAlways:
+			return Jump{Skip: ri.K}
+		case opJumpEqual:
+			return JumpIf{
+				Cond:      JumpEqual,
+				Val:       ri.K,
+				SkipTrue:  ri.Jt,
+				SkipFalse: ri.Jf,
+			}
+		case opJumpGT:
+			return JumpIf{
+				Cond:      JumpGreaterThan,
+				Val:       ri.K,
+				SkipTrue:  ri.Jt,
+				SkipFalse: ri.Jf,
+			}
+		case opJumpGE:
+			return JumpIf{
+				Cond:      JumpGreaterOrEqual,
+				Val:       ri.K,
+				SkipTrue:  ri.Jt,
+				SkipFalse: ri.Jf,
+			}
+		case opJumpSet:
+			return JumpIf{
+				Cond:      JumpBitsSet,
+				Val:       ri.K,
+				SkipTrue:  ri.Jt,
+				SkipFalse: ri.Jf,
+			}
+		default:
+			return ri
+		}
+
+	case opClsReturn:
+		switch ri.Op {
+		case opClsReturn | opRetSrcA:
+			return RetA{}
+		case opClsReturn | opRetSrcConstant:
+			return RetConstant{Val: ri.K}
+		default:
+			return ri
+		}
+
+	case opClsMisc:
+		switch ri.Op {
+		case opClsMisc | opMiscTAX:
+			return TAX{}
+		case opClsMisc | opMiscTXA:
+			return TXA{}
+		default:
+			return ri
+		}
+
+	default:
+		panic("unreachable") // switch is exhaustive on the bit pattern
+	}
+}
+
+// LoadConstant loads Val into register Dst.
+type LoadConstant struct {
+	Dst Register
+	Val uint32
+}
+
+// Assemble implements the Instruction Assemble method.
+func (a LoadConstant) Assemble() (RawInstruction, error) {
+	return assembleLoad(a.Dst, 4, opAddrModeImmediate, a.Val)
+}
+
+// LoadScratch loads scratch[N] into register Dst.
+type LoadScratch struct {
+	Dst Register
+	N   int // 0-15
+}
+
+// Assemble implements the Instruction Assemble method.
+func (a LoadScratch) Assemble() (RawInstruction, error) {
+	if a.N < 0 || a.N > 15 {
+		return RawInstruction{}, fmt.Errorf("invalid scratch slot %d", a.N)
+	}
+	return assembleLoad(a.Dst, 4, opAddrModeScratch, uint32(a.N))
+}
+
+// LoadAbsolute loads packet[Off:Off+Size] as an integer value into
+// register A.
+type LoadAbsolute struct {
+	Off  uint32
+	Size int // 1, 2 or 4
+}
+
+// Assemble implements the Instruction Assemble method.
+func (a LoadAbsolute) Assemble() (RawInstruction, error) {
+	return assembleLoad(RegA, a.Size, opAddrModeAbsolute, a.Off)
+}
+
+// LoadIndirect loads packet[X+Off:X+Off+Size] as an integer value
+// into register A.
+type LoadIndirect struct {
+	Off  uint32
+	Size int // 1, 2 or 4
+}
+
+// Assemble implements the Instruction Assemble method.
+func (a LoadIndirect) Assemble() (RawInstruction, error) {
+	return assembleLoad(RegA, a.Size, opAddrModeIndirect, a.Off)
+}
+
+// LoadMemShift multiplies the first 4 bits of the byte at packet[Off]
+// by 4 and stores the result in register X.
+//
+// This instruction is mainly useful to load into X the length of an
+// IPv4 packet header in a single instruction, rather than have to do
+// the arithmetic on the header's first byte by hand.
+type LoadMemShift struct {
+	Off uint32
+}
+
+// Assemble implements the Instruction Assemble method.
+func (a LoadMemShift) Assemble() (RawInstruction, error) {
+	return assembleLoad(RegX, 1, opAddrModeMemShift, a.Off)
+}
+
+// LoadExtension invokes a linux-specific extension and stores the
+// result in register A.
+type LoadExtension struct {
+	Num Extension
+}
+
+// Assemble implements the Instruction Assemble method.
+func (a LoadExtension) Assemble() (RawInstruction, error) {
+	if a.Num == ExtLen {
+		return assembleLoad(RegA, 4, opAddrModePacketLen, 0)
+	}
+	return assembleLoad(RegA, 4, opAddrModeAbsolute, uint32(-0x1000+a.Num))
+}
+
+// StoreScratch stores register Src into scratch[N].
+type StoreScratch struct {
+	Src Register
+	N   int // 0-15
+}
+
+// Assemble implements the Instruction Assemble method.
+func (a StoreScratch) Assemble() (RawInstruction, error) {
+	if a.N < 0 || a.N > 15 {
+		return RawInstruction{}, fmt.Errorf("invalid scratch slot %d", a.N)
+	}
+	var op uint16
+	switch a.Src {
+	case RegA:
+		op = opClsStoreA
+	case RegX:
+		op = opClsStoreX
+	default:
+		return RawInstruction{}, fmt.Errorf("invalid source register %v", a.Src)
+	}
+
+	return RawInstruction{
+		Op: op,
+		K:  uint32(a.N),
+	}, nil
+}
+
+// ALUOpConstant executes A = A <Op> Val.
+type ALUOpConstant struct {
+	Op  ALUOp
+	Val uint32
+}
+
+// Assemble implements the Instruction Assemble method.
+func (a ALUOpConstant) Assemble() (RawInstruction, error) {
+	return RawInstruction{
+		Op: opClsALU | opALUSrcConstant | uint16(a.Op),
+		K:  a.Val,
+	}, nil
+}
+
+// ALUOpX executes A = A <Op> X
+type ALUOpX struct {
+	Op ALUOp
+}
+
+// Assemble implements the Instruction Assemble method.
+func (a ALUOpX) Assemble() (RawInstruction, error) {
+	return RawInstruction{
+		Op: opClsALU | opALUSrcX | uint16(a.Op),
+	}, nil
+}
+
+// NegateA executes A = -A.
+type NegateA struct{}
+
+// Assemble implements the Instruction Assemble method.
+func (a NegateA) Assemble() (RawInstruction, error) {
+	return RawInstruction{
+		Op: opClsALU | uint16(aluOpNeg),
+	}, nil
+}
+
+// Jump skips the following Skip instructions in the program.
+type Jump struct {
+	Skip uint32
+}
+
+// Assemble implements the Instruction Assemble method.
+func (a Jump) Assemble() (RawInstruction, error) {
+	return RawInstruction{
+		Op: opClsJump | opJumpAlways,
+		K:  a.Skip,
+	}, nil
+}
+
+// JumpIf skips the following Skip instructions in the program if A
+// <Cond> Val is true.
+type JumpIf struct {
+	Cond      JumpTest
+	Val       uint32
+	SkipTrue  uint8
+	SkipFalse uint8
+}
+
+// Assemble implements the Instruction Assemble method.
+func (a JumpIf) Assemble() (RawInstruction, error) {
+	var (
+		cond uint16
+		flip bool
+	)
+	switch a.Cond {
+	case JumpEqual:
+		cond = opJumpEqual
+	case JumpNotEqual:
+		cond, flip = opJumpEqual, true
+	case JumpGreaterThan:
+		cond = opJumpGT
+	case JumpLessThan:
+		cond, flip = opJumpGE, true
+	case JumpGreaterOrEqual:
+		cond = opJumpGE
+	case JumpLessOrEqual:
+		cond, flip = opJumpGT, true
+	case JumpBitsSet:
+		cond = opJumpSet
+	case JumpBitsNotSet:
+		cond, flip = opJumpSet, true
+	default:
+		return RawInstruction{}, fmt.Errorf("unknown JumpTest %v", a.Cond)
+	}
+	jt, jf := a.SkipTrue, a.SkipFalse
+	if flip {
+		jt, jf = jf, jt
+	}
+	return RawInstruction{
+		Op: opClsJump | cond,
+		Jt: jt,
+		Jf: jf,
+		K:  a.Val,
+	}, nil
+}
+
+// RetA exits the BPF program, returning the value of register A.
+type RetA struct{}
+
+// Assemble implements the Instruction Assemble method.
+func (a RetA) Assemble() (RawInstruction, error) {
+	return RawInstruction{
+		Op: opClsReturn | opRetSrcA,
+	}, nil
+}
+
+// RetConstant exits the BPF program, returning a constant value.
+type RetConstant struct {
+	Val uint32
+}
+
+// Assemble implements the Instruction Assemble method.
+func (a RetConstant) Assemble() (RawInstruction, error) {
+	return RawInstruction{
+		Op: opClsReturn | opRetSrcConstant,
+		K:  a.Val,
+	}, nil
+}
+
+// TXA copies the value of register X to register A.
+type TXA struct{}
+
+// Assemble implements the Instruction Assemble method.
+func (a TXA) Assemble() (RawInstruction, error) {
+	return RawInstruction{
+		Op: opClsMisc | opMiscTXA,
+	}, nil
+}
+
+// TAX copies the value of register A to register X.
+type TAX struct{}
+
+// Assemble implements the Instruction Assemble method.
+func (a TAX) Assemble() (RawInstruction, error) {
+	return RawInstruction{
+		Op: opClsMisc | opMiscTAX,
+	}, nil
+}
+
+func assembleLoad(dst Register, loadSize int, mode uint16, k uint32) (RawInstruction, error) {
+	var (
+		cls uint16
+		sz  uint16
+	)
+	switch dst {
+	case RegA:
+		cls = opClsLoadA
+	case RegX:
+		cls = opClsLoadX
+	default:
+		return RawInstruction{}, fmt.Errorf("invalid target register %v", dst)
+	}
+	switch loadSize {
+	case 1:
+		sz = opLoadWidth1
+	case 2:
+		sz = opLoadWidth2
+	case 4:
+		sz = opLoadWidth4
+	default:
+		return RawInstruction{}, fmt.Errorf("invalid load byte length %d", sz)
+	}
+	return RawInstruction{
+		Op: cls | sz | mode,
+		K:  k,
+	}, nil
+}

vendor/golang.org/x/net/bpf/vm.go

@@ -0,0 +1,140 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package bpf
+
+import (
+	"errors"
+	"fmt"
+)
+
+// A VM is an emulated BPF virtual machine.
+type VM struct {
+	filter []Instruction
+}
+
+// NewVM returns a new VM using the input BPF program.
+func NewVM(filter []Instruction) (*VM, error) {
+	if len(filter) == 0 {
+		return nil, errors.New("one or more Instructions must be specified")
+	}
+
+	for i, ins := range filter {
+		check := len(filter) - (i + 1)
+		switch ins := ins.(type) {
+		// Check for out-of-bounds jumps in instructions
+		case Jump:
+			if check <= int(ins.Skip) {
+				return nil, fmt.Errorf("cannot jump %d instructions; jumping past program bounds", ins.Skip)
+			}
+		case JumpIf:
+			if check <= int(ins.SkipTrue) {
+				return nil, fmt.Errorf("cannot jump %d instructions in true case; jumping past program bounds", ins.SkipTrue)
+			}
+			if check <= int(ins.SkipFalse) {
+				return nil, fmt.Errorf("cannot jump %d instructions in false case; jumping past program bounds", ins.SkipFalse)
+			}
+		// Check for division or modulus by zero
+		case ALUOpConstant:
+			if ins.Val != 0 {
+				break
+			}
+
+			switch ins.Op {
+			case ALUOpDiv, ALUOpMod:
+				return nil, errors.New("cannot divide by zero using ALUOpConstant")
+			}
+		// Check for unknown extensions
+		case LoadExtension:
+			switch ins.Num {
+			case ExtLen:
+			default:
+				return nil, fmt.Errorf("extension %d not implemented", ins.Num)
+			}
+		}
+	}
+
+	// Make sure last instruction is a return instruction
+	switch filter[len(filter)-1].(type) {
+	case RetA, RetConstant:
+	default:
+		return nil, errors.New("BPF program must end with RetA or RetConstant")
+	}
+
+	// Though our VM works using disassembled instructions, we
+	// attempt to assemble the input filter anyway to ensure it is compatible
+	// with an operating system VM.
+	_, err := Assemble(filter)
+
+	return &VM{
+		filter: filter,
+	}, err
+}
+
+// Run runs the VM's BPF program against the input bytes.
+// Run returns the number of bytes accepted by the BPF program, and any errors
+// which occurred while processing the program.
+func (v *VM) Run(in []byte) (int, error) {
+	var (
+		// Registers of the virtual machine
+		regA       uint32
+		regX       uint32
+		regScratch [16]uint32
+
+		// OK is true if the program should continue processing the next
+		// instruction, or false if not, causing the loop to break
+		ok = true
+	)
+
+	// TODO(mdlayher): implement:
+	// - NegateA:
+	//   - would require a change from uint32 registers to int32
+	//     registers
+
+	// TODO(mdlayher): add interop tests that check signedness of ALU
+	// operations against kernel implementation, and make sure Go
+	// implementation matches behavior
+
+	for i := 0; i < len(v.filter) && ok; i++ {
+		ins := v.filter[i]
+
+		switch ins := ins.(type) {
+		case ALUOpConstant:
+			regA = aluOpConstant(ins, regA)
+		case ALUOpX:
+			regA, ok = aluOpX(ins, regA, regX)
+		case Jump:
+			i += int(ins.Skip)
+		case JumpIf:
+			jump := jumpIf(ins, regA)
+			i += jump
+		case LoadAbsolute:
+			regA, ok = loadAbsolute(ins, in)
+		case LoadConstant:
+			regA, regX = loadConstant(ins, regA, regX)
+		case LoadExtension:
+			regA = loadExtension(ins, in)
+		case LoadIndirect:
+			regA, ok = loadIndirect(ins, in, regX)
+		case LoadMemShift:
+			regX, ok = loadMemShift(ins, in)
+		case LoadScratch:
+			regA, regX = loadScratch(ins, regScratch, regA, regX)
+		case RetA:
+			return int(regA), nil
+		case RetConstant:
+			return int(ins.Val), nil
+		case StoreScratch:
+			regScratch = storeScratch(ins, regScratch, regA, regX)
+		case TAX:
+			regX = regA
+		case TXA:
+			regA = regX
+		default:
+			return 0, fmt.Errorf("unknown Instruction at index %d: %T", i, ins)
+		}
+	}
+
+	return 0, nil
+}

vendor/golang.org/x/net/bpf/vm_instructions.go

@@ -0,0 +1,174 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package bpf
+
+import (
+	"encoding/binary"
+	"fmt"
+)
+
+func aluOpConstant(ins ALUOpConstant, regA uint32) uint32 {
+	return aluOpCommon(ins.Op, regA, ins.Val)
+}
+
+func aluOpX(ins ALUOpX, regA uint32, regX uint32) (uint32, bool) {
+	// Guard against division or modulus by zero by terminating
+	// the program, as the OS BPF VM does
+	if regX == 0 {
+		switch ins.Op {
+		case ALUOpDiv, ALUOpMod:
+			return 0, false
+		}
+	}
+
+	return aluOpCommon(ins.Op, regA, regX), true
+}
+
+func aluOpCommon(op ALUOp, regA uint32, value uint32) uint32 {
+	switch op {
+	case ALUOpAdd:
+		return regA + value
+	case ALUOpSub:
+		return regA - value
+	case ALUOpMul:
+		return regA * value
+	case ALUOpDiv:
+		// Division by zero not permitted by NewVM and aluOpX checks
+		return regA / value
+	case ALUOpOr:
+		return regA | value
+	case ALUOpAnd:
+		return regA & value
+	case ALUOpShiftLeft:
+		return regA << value
+	case ALUOpShiftRight:
+		return regA >> value
+	case ALUOpMod:
+		// Modulus by zero not permitted by NewVM and aluOpX checks
+		return regA % value
+	case ALUOpXor:
+		return regA ^ value
+	default:
+		return regA
+	}
+}
+
+func jumpIf(ins JumpIf, value uint32) int {
+	var ok bool
+	inV := uint32(ins.Val)
+
+	switch ins.Cond {
+	case JumpEqual:
+		ok = value == inV
+	case JumpNotEqual:
+		ok = value != inV
+	case JumpGreaterThan:
+		ok = value > inV
+	case JumpLessThan:
+		ok = value < inV
+	case JumpGreaterOrEqual:
+		ok = value >= inV
+	case JumpLessOrEqual:
+		ok = value <= inV
+	case JumpBitsSet:
+		ok = (value & inV) != 0
+	case JumpBitsNotSet:
+		ok = (value & inV) == 0
+	}
+
+	if ok {
+		return int(ins.SkipTrue)
+	}
+
+	return int(ins.SkipFalse)
+}
+
+func loadAbsolute(ins LoadAbsolute, in []byte) (uint32, bool) {
+	offset := int(ins.Off)
+	size := int(ins.Size)
+
+	return loadCommon(in, offset, size)
+}
+
+func loadConstant(ins LoadConstant, regA uint32, regX uint32) (uint32, uint32) {
+	switch ins.Dst {
+	case RegA:
+		regA = ins.Val
+	case RegX:
+		regX = ins.Val
+	}
+
+	return regA, regX
+}
+
+func loadExtension(ins LoadExtension, in []byte) uint32 {
+	switch ins.Num {
+	case ExtLen:
+		return uint32(len(in))
+	default:
+		panic(fmt.Sprintf("unimplemented extension: %d", ins.Num))
+	}
+}
+
+func loadIndirect(ins LoadIndirect, in []byte, regX uint32) (uint32, bool) {
+	offset := int(ins.Off) + int(regX)
+	size := int(ins.Size)
+
+	return loadCommon(in, offset, size)
+}
+
+func loadMemShift(ins LoadMemShift, in []byte) (uint32, bool) {
+	offset := int(ins.Off)
+
+	if !inBounds(len(in), offset, 0) {
+		return 0, false
+	}
+
+	// Mask off high 4 bits and multiply low 4 bits by 4
+	return uint32(in[offset]&0x0f) * 4, true
+}
+
+func inBounds(inLen int, offset int, size int) bool {
+	return offset+size <= inLen
+}
+
+func loadCommon(in []byte, offset int, size int) (uint32, bool) {
+	if !inBounds(len(in), offset, size) {
+		return 0, false
+	}
+
+	switch size {
+	case 1:
+		return uint32(in[offset]), true
+	case 2:
+		return uint32(binary.BigEndian.Uint16(in[offset : offset+size])), true
+	case 4:
+		return uint32(binary.BigEndian.Uint32(in[offset : offset+size])), true
+	default:
+		panic(fmt.Sprintf("invalid load size: %d", size))
+	}
+}
+
+func loadScratch(ins LoadScratch, regScratch [16]uint32, regA uint32, regX uint32) (uint32, uint32) {
+	switch ins.Dst {
+	case RegA:
+		regA = regScratch[ins.N]
+	case RegX:
+		regX = regScratch[ins.N]
+	}
+
+	return regA, regX
+}
+
+func storeScratch(ins StoreScratch, regScratch [16]uint32, regA uint32, regX uint32) [16]uint32 {
+	switch ins.Src {
+	case RegA:
+		regScratch[ins.N] = regA
+	case RegX:
+		regScratch[ins.N] = regX
+	}
+
+	return regScratch
+}

vendor/manifest

@@ -239,6 +239,14 @@
 			"branch": "master",
 			"path": "/blowfish"
 		},
+		{
+			"importpath": "golang.org/x/net/bpf",
+			"repository": "https://go.googlesource.com/net",
+			"revision": "749a502dd1eaf3e5bfd4f8956748c502357c0bbe",
+			"branch": "master",
+			"path": "/bpf",
+			"notests": true
+		},
 		{
 			"importpath": "golang.org/x/net/context",
 			"repository": "https://go.googlesource.com/net",