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-rw-r--r--pkg/tcpip/buffer/view.go18
-rw-r--r--pkg/tcpip/header/ipv4.go71
-rw-r--r--pkg/tcpip/network/ipv4/icmp.go84
-rw-r--r--pkg/tcpip/network/ipv4/ipv4.go2
4 files changed, 133 insertions, 42 deletions
diff --git a/pkg/tcpip/buffer/view.go b/pkg/tcpip/buffer/view.go
index ea0c5413d..8db70a700 100644
--- a/pkg/tcpip/buffer/view.go
+++ b/pkg/tcpip/buffer/view.go
@@ -84,8 +84,8 @@ type VectorisedView struct {
size int
}
-// NewVectorisedView creates a new vectorised view from an already-allocated slice
-// of View and sets its size.
+// NewVectorisedView creates a new vectorised view from an already-allocated
+// slice of View and sets its size.
func NewVectorisedView(size int, views []View) VectorisedView {
return VectorisedView{views: views, size: size}
}
@@ -170,8 +170,9 @@ func (vv *VectorisedView) CapLength(length int) {
}
// Clone returns a clone of this VectorisedView.
-// If the buffer argument is large enough to contain all the Views of this VectorisedView,
-// the method will avoid allocations and use the buffer to store the Views of the clone.
+// If the buffer argument is large enough to contain all the Views of this
+// VectorisedView, the method will avoid allocations and use the buffer to
+// store the Views of the clone.
func (vv *VectorisedView) Clone(buffer []View) VectorisedView {
return VectorisedView{views: append(buffer[:0], vv.views...), size: vv.size}
}
@@ -209,7 +210,8 @@ func (vv *VectorisedView) PullUp(count int) (View, bool) {
return newFirst, true
}
-// Size returns the size in bytes of the entire content stored in the vectorised view.
+// Size returns the size in bytes of the entire content stored in the
+// vectorised view.
func (vv *VectorisedView) Size() int {
return vv.size
}
@@ -222,6 +224,12 @@ func (vv *VectorisedView) ToView() View {
if len(vv.views) == 1 {
return vv.views[0]
}
+ return vv.ToOwnedView()
+}
+
+// ToOwnedView returns a single view containing the content of the vectorised
+// view that vv does not own.
+func (vv *VectorisedView) ToOwnedView() View {
u := make([]byte, 0, vv.size)
for _, v := range vv.views {
u = append(u, v...)
diff --git a/pkg/tcpip/header/ipv4.go b/pkg/tcpip/header/ipv4.go
index b07d9991d..4c6e4be64 100644
--- a/pkg/tcpip/header/ipv4.go
+++ b/pkg/tcpip/header/ipv4.go
@@ -16,10 +16,29 @@ package header
import (
"encoding/binary"
+ "fmt"
"gvisor.dev/gvisor/pkg/tcpip"
)
+// RFC 971 defines the fields of the IPv4 header on page 11 using the following
+// diagram: ("Figure 4")
+// 0 1 2 3
+// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// |Version| IHL |Type of Service| Total Length |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// | Identification |Flags| Fragment Offset |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// | Time to Live | Protocol | Header Checksum |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// | Source Address |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// | Destination Address |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// | Options | Padding |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+//
const (
versIHL = 0
tos = 1
@@ -33,6 +52,7 @@ const (
checksum = 10
srcAddr = 12
dstAddr = 16
+ options = 20
)
// IPv4Fields contains the fields of an IPv4 packet. It is used to describe the
@@ -76,7 +96,8 @@ type IPv4Fields struct {
// IPv4 represents an ipv4 header stored in a byte array.
// Most of the methods of IPv4 access to the underlying slice without
// checking the boundaries and could panic because of 'index out of range'.
-// Always call IsValid() to validate an instance of IPv4 before using other methods.
+// Always call IsValid() to validate an instance of IPv4 before using other
+// methods.
type IPv4 []byte
const (
@@ -151,13 +172,44 @@ func IPVersion(b []byte) int {
if len(b) < versIHL+1 {
return -1
}
- return int(b[versIHL] >> 4)
+ return int(b[versIHL] >> ipVersionShift)
}
+// RFC 791 page 11 shows the header length (IHL) is in the lower 4 bits
+// of the first byte, and is counted in multiples of 4 bytes.
+//
+// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// |Version| IHL |Type of Service| Total Length |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// (...)
+// Version: 4 bits
+// The Version field indicates the format of the internet header. This
+// document describes version 4.
+//
+// IHL: 4 bits
+// Internet Header Length is the length of the internet header in 32
+// bit words, and thus points to the beginning of the data. Note that
+// the minimum value for a correct header is 5.
+//
+const (
+ ipVersionShift = 4
+ ipIHLMask = 0x0f
+ IPv4IHLStride = 4
+)
+
// HeaderLength returns the value of the "header length" field of the ipv4
// header. The length returned is in bytes.
func (b IPv4) HeaderLength() uint8 {
- return (b[versIHL] & 0xf) * 4
+ return (b[versIHL] & ipIHLMask) * IPv4IHLStride
+}
+
+// SetHeaderLength sets the value of the "Internet Header Length" field.
+func (b IPv4) SetHeaderLength(hdrLen uint8) {
+ if hdrLen > IPv4MaximumHeaderSize {
+ panic(fmt.Sprintf("got IPv4 Header size = %d, want <= %d", hdrLen, IPv4MaximumHeaderSize))
+ }
+ b[versIHL] = (IPv4Version << ipVersionShift) | ((hdrLen / IPv4IHLStride) & ipIHLMask)
}
// ID returns the value of the identifier field of the ipv4 header.
@@ -211,6 +263,12 @@ func (b IPv4) DestinationAddress() tcpip.Address {
return tcpip.Address(b[dstAddr : dstAddr+IPv4AddressSize])
}
+// Options returns a a buffer holding the options.
+func (b IPv4) Options() []byte {
+ hdrLen := b.HeaderLength()
+ return b[options:hdrLen:hdrLen]
+}
+
// TransportProtocol implements Network.TransportProtocol.
func (b IPv4) TransportProtocol() tcpip.TransportProtocolNumber {
return tcpip.TransportProtocolNumber(b.Protocol())
@@ -236,6 +294,11 @@ func (b IPv4) SetTOS(v uint8, _ uint32) {
b[tos] = v
}
+// SetTTL sets the "Time to Live" field of the IPv4 header.
+func (b IPv4) SetTTL(v byte) {
+ b[ttl] = v
+}
+
// SetTotalLength sets the "total length" field of the ipv4 header.
func (b IPv4) SetTotalLength(totalLength uint16) {
binary.BigEndian.PutUint16(b[IPv4TotalLenOffset:], totalLength)
@@ -276,7 +339,7 @@ func (b IPv4) CalculateChecksum() uint16 {
// Encode encodes all the fields of the ipv4 header.
func (b IPv4) Encode(i *IPv4Fields) {
- b[versIHL] = (4 << 4) | ((i.IHL / 4) & 0xf)
+ b.SetHeaderLength(i.IHL)
b[tos] = i.TOS
b.SetTotalLength(i.TotalLength)
binary.BigEndian.PutUint16(b[id:], i.ID)
diff --git a/pkg/tcpip/network/ipv4/icmp.go b/pkg/tcpip/network/ipv4/icmp.go
index a8985ff5d..eab9a530c 100644
--- a/pkg/tcpip/network/ipv4/icmp.go
+++ b/pkg/tcpip/network/ipv4/icmp.go
@@ -79,27 +79,27 @@ func (e *endpoint) handleICMP(r *stack.Route, pkt *stack.PacketBuffer) {
received.Echo.Increment()
// Only send a reply if the checksum is valid.
- wantChecksum := h.Checksum()
- // Reset the checksum field to 0 to can calculate the proper
- // checksum. We'll have to reset this before we hand the packet
- // off.
+ headerChecksum := h.Checksum()
h.SetChecksum(0)
- gotChecksum := ^header.ChecksumVV(pkt.Data, 0 /* initial */)
- if gotChecksum != wantChecksum {
- // It's possible that a raw socket expects to receive this.
- h.SetChecksum(wantChecksum)
+ calculatedChecksum := ^header.ChecksumVV(pkt.Data, 0 /* initial */)
+ h.SetChecksum(headerChecksum)
+ if calculatedChecksum != headerChecksum {
+ // It's possible that a raw socket still expects to receive this.
e.dispatcher.DeliverTransportPacket(r, header.ICMPv4ProtocolNumber, pkt)
received.Invalid.Increment()
return
}
- // Make a copy of data before pkt gets sent to raw socket.
- // DeliverTransportPacket will take ownership of pkt.
- replyData := pkt.Data.Clone(nil)
- replyData.TrimFront(header.ICMPv4MinimumSize)
+ // DeliverTransportPacket will take ownership of pkt so don't use it beyond
+ // this point. Make a deep copy of the data before pkt gets sent as we will
+ // be modifying fields.
+ //
+ // TODO(gvisor.dev/issue/4399): The copy may not be needed if there are no
+ // waiting endpoints. Consider moving responsibility for doing the copy to
+ // DeliverTransportPacket so that is is only done when needed.
+ replyData := pkt.Data.ToOwnedView()
+ replyIPHdr := header.IPv4(append(buffer.View(nil), pkt.NetworkHeader().View()...))
- // It's possible that a raw socket expects to receive this.
- h.SetChecksum(wantChecksum)
e.dispatcher.DeliverTransportPacket(r, header.ICMPv4ProtocolNumber, pkt)
remoteLinkAddr := r.RemoteLinkAddress
@@ -122,29 +122,49 @@ func (e *endpoint) handleICMP(r *stack.Route, pkt *stack.PacketBuffer) {
// Use the remote link address from the incoming packet.
r.ResolveWith(remoteLinkAddr)
- // Prepare a reply packet.
- icmpHdr := make(header.ICMPv4, header.ICMPv4MinimumSize)
- copy(icmpHdr, h)
- icmpHdr.SetType(header.ICMPv4EchoReply)
- icmpHdr.SetChecksum(0)
- icmpHdr.SetChecksum(^header.Checksum(icmpHdr, header.ChecksumVV(replyData, 0)))
- dataVV := buffer.View(icmpHdr).ToVectorisedView()
- dataVV.Append(replyData)
+ // TODO(gvisor.dev/issue/3810:) When adding protocol numbers into the
+ // header information, we may have to change this code to handle the
+ // ICMP header no longer being in the data buffer.
+
+ // Because IP and ICMP are so closely intertwined, we need to handcraft our
+ // IP header to be able to follow RFC 792. The wording on page 13 is as
+ // follows:
+ // IP Fields:
+ // Addresses
+ // The address of the source in an echo message will be the
+ // destination of the echo reply message. To form an echo reply
+ // message, the source and destination addresses are simply reversed,
+ // the type code changed to 0, and the checksum recomputed.
+ //
+ // This was interpreted by early implementors to mean that all options must
+ // be copied from the echo request IP header to the echo reply IP header
+ // and this behaviour is still relied upon by some applications.
+ //
+ // Create a copy of the IP header we received, options and all, and change
+ // The fields we need to alter.
+ //
+ // We need to produce the entire packet in the data segment in order to
+ // use WriteHeaderIncludedPacket().
+ replyIPHdr.SetSourceAddress(r.LocalAddress)
+ replyIPHdr.SetDestinationAddress(r.RemoteAddress)
+ replyIPHdr.SetTTL(r.DefaultTTL())
+
+ replyICMPHdr := header.ICMPv4(replyData)
+ replyICMPHdr.SetType(header.ICMPv4EchoReply)
+ replyICMPHdr.SetChecksum(0)
+ replyICMPHdr.SetChecksum(^header.Checksum(replyData, 0))
+
+ replyVV := buffer.View(replyIPHdr).ToVectorisedView()
+ replyVV.AppendView(replyData)
replyPkt := stack.NewPacketBuffer(stack.PacketBufferOptions{
ReserveHeaderBytes: int(r.MaxHeaderLength()),
- Data: dataVV,
+ Data: replyVV,
})
- // TODO(gvisor.dev/issue/3810): When adding protocol numbers into the header
- // information we will have to change this code to handle the ICMP header
- // no longer being in the data buffer.
replyPkt.TransportProtocolNumber = header.ICMPv4ProtocolNumber
- // Send out the reply packet.
+
+ // The checksum will be calculated so we don't need to do it here.
sent := stats.ICMP.V4PacketsSent
- if err := r.WritePacket(nil /* gso */, stack.NetworkHeaderParams{
- Protocol: header.ICMPv4ProtocolNumber,
- TTL: r.DefaultTTL(),
- TOS: stack.DefaultTOS,
- }, replyPkt); err != nil {
+ if err := r.WriteHeaderIncludedPacket(replyPkt); err != nil {
sent.Dropped.Increment()
return
}
diff --git a/pkg/tcpip/network/ipv4/ipv4.go b/pkg/tcpip/network/ipv4/ipv4.go
index 1f6e14c3f..a2be64fb8 100644
--- a/pkg/tcpip/network/ipv4/ipv4.go
+++ b/pkg/tcpip/network/ipv4/ipv4.go
@@ -174,7 +174,7 @@ func (e *endpoint) MTU() uint32 {
// MaxHeaderLength returns the maximum length needed by ipv4 headers (and
// underlying protocols).
func (e *endpoint) MaxHeaderLength() uint16 {
- return e.linkEP.MaxHeaderLength() + header.IPv4MinimumSize
+ return e.linkEP.MaxHeaderLength() + header.IPv4MaximumHeaderSize
}
// GSOMaxSize returns the maximum GSO packet size.
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-19 04:52:23 +0000