diff options
Diffstat (limited to 'pkg/tcpip/network')
| -rw-r--r-- | pkg/tcpip/network/ipv4/icmp.go | 84 | ||||
| -rw-r--r-- | pkg/tcpip/network/ipv4/ipv4.go | 2 |
2 files changed, 53 insertions, 33 deletions
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. |