From 5768a147b124efbeff2800794da7ba961146af19 Mon Sep 17 00:00:00 2001 From: Ghanan Gowripalan Date: Wed, 22 Sep 2021 12:36:38 -0700 Subject: Populate forwarded packet buffer's TransportHeader Turns out certain features of iptables (e.g. NAT) will not perform any checks/work unless both the Network and Transport headers are populated. With this change, provide the packet directly to the outgoing network endpoint's `writePacket` method instead of going through `WriteHeaderIncludedPacket` which expected the headers to not be set. PiperOrigin-RevId: 398304004 --- pkg/tcpip/network/ipv4/ipv4.go | 27 +++++++++++++++++++++------ pkg/tcpip/network/ipv6/ipv6.go | 22 ++++++++++++++++------ pkg/tcpip/network/ipv6/ipv6_test.go | 5 +++-- pkg/tcpip/stack/packet_buffer.go | 31 +++++++++++++++++++++++++++++++ 4 files changed, 71 insertions(+), 14 deletions(-) diff --git a/pkg/tcpip/network/ipv4/ipv4.go b/pkg/tcpip/network/ipv4/ipv4.go index aef789b4c..63223bc92 100644 --- a/pkg/tcpip/network/ipv4/ipv4.go +++ b/pkg/tcpip/network/ipv4/ipv4.go @@ -167,6 +167,13 @@ func (p *protocol) findEndpointWithAddress(addr tcpip.Address) *endpoint { return nil } +func (p *protocol) getEndpointForNIC(id tcpip.NICID) (*endpoint, bool) { + p.mu.RLock() + defer p.mu.RUnlock() + ep, ok := p.mu.eps[id] + return ep, ok +} + func (p *protocol) forgetEndpoint(nicID tcpip.NICID) { p.mu.Lock() defer p.mu.Unlock() @@ -746,7 +753,8 @@ func (e *endpoint) forwardPacket(pkt *stack.PacketBuffer) ip.ForwardingError { // We need to do a deep copy of the IP packet because // WriteHeaderIncludedPacket takes ownership of the packet buffer, but we do // not own it. - newHdr := header.IPv4(stack.PayloadSince(pkt.NetworkHeader())) + newPkt := pkt.DeepCopyForForwarding(int(r.MaxHeaderLength())) + newHdr := header.IPv4(newPkt.NetworkHeader().View()) // As per RFC 791 page 30, Time to Live, // @@ -755,12 +763,19 @@ func (e *endpoint) forwardPacket(pkt *stack.PacketBuffer) ip.ForwardingError { // Even if no local information is available on the time actually // spent, the field must be decremented by 1. newHdr.SetTTL(ttl - 1) + // We perform a full checksum as we may have updated options above. The IP + // header is relatively small so this is not expected to be an expensive + // operation. + newHdr.SetChecksum(0) + newHdr.SetChecksum(^newHdr.CalculateChecksum()) + + forwardToEp, ok := e.protocol.getEndpointForNIC(r.NICID()) + if !ok { + // The interface was removed after we obtained the route. + return &ip.ErrOther{Err: &tcpip.ErrUnknownDevice{}} + } - switch err := r.WriteHeaderIncludedPacket(stack.NewPacketBuffer(stack.PacketBufferOptions{ - ReserveHeaderBytes: int(r.MaxHeaderLength()), - Data: buffer.View(newHdr).ToVectorisedView(), - IsForwardedPacket: true, - })); err.(type) { + switch err := forwardToEp.writePacket(r, newPkt, true /* headerIncluded */); err.(type) { case nil: return nil case *tcpip.ErrMessageTooLong: diff --git a/pkg/tcpip/network/ipv6/ipv6.go b/pkg/tcpip/network/ipv6/ipv6.go index c824e27fa..3799d8245 100644 --- a/pkg/tcpip/network/ipv6/ipv6.go +++ b/pkg/tcpip/network/ipv6/ipv6.go @@ -1024,7 +1024,8 @@ func (e *endpoint) forwardPacket(pkt *stack.PacketBuffer) ip.ForwardingError { // We need to do a deep copy of the IP packet because // WriteHeaderIncludedPacket takes ownership of the packet buffer, but we do // not own it. - newHdr := header.IPv6(stack.PayloadSince(pkt.NetworkHeader())) + newPkt := pkt.DeepCopyForForwarding(int(r.MaxHeaderLength())) + newHdr := header.IPv6(newPkt.NetworkHeader().View()) // As per RFC 8200 section 3, // @@ -1032,11 +1033,13 @@ func (e *endpoint) forwardPacket(pkt *stack.PacketBuffer) ip.ForwardingError { // each node that forwards the packet. newHdr.SetHopLimit(hopLimit - 1) - switch err := r.WriteHeaderIncludedPacket(stack.NewPacketBuffer(stack.PacketBufferOptions{ - ReserveHeaderBytes: int(r.MaxHeaderLength()), - Data: buffer.View(newHdr).ToVectorisedView(), - IsForwardedPacket: true, - })); err.(type) { + forwardToEp, ok := e.protocol.getEndpointForNIC(r.NICID()) + if !ok { + // The interface was removed after we obtained the route. + return &ip.ErrOther{Err: &tcpip.ErrUnknownDevice{}} + } + + switch err := forwardToEp.writePacket(r, newPkt, newPkt.TransportProtocolNumber, true /* headerIncluded */); err.(type) { case nil: return nil case *tcpip.ErrMessageTooLong: @@ -2082,6 +2085,13 @@ func (p *protocol) findEndpointWithAddress(addr tcpip.Address) *endpoint { return nil } +func (p *protocol) getEndpointForNIC(id tcpip.NICID) (*endpoint, bool) { + p.mu.RLock() + defer p.mu.RUnlock() + ep, ok := p.mu.eps[id] + return ep, ok +} + func (p *protocol) forgetEndpoint(nicID tcpip.NICID) { p.mu.Lock() defer p.mu.Unlock() diff --git a/pkg/tcpip/network/ipv6/ipv6_test.go b/pkg/tcpip/network/ipv6/ipv6_test.go index 0735ebb23..74f19900c 100644 --- a/pkg/tcpip/network/ipv6/ipv6_test.go +++ b/pkg/tcpip/network/ipv6/ipv6_test.go @@ -3373,7 +3373,8 @@ func TestForwarding(t *testing.T) { ipHeaderLength := header.IPv6MinimumSize icmpHeaderLength := header.ICMPv6MinimumSize - totalLength := ipHeaderLength + icmpHeaderLength + test.payloadLength + extHdrLen + payloadLength := icmpHeaderLength + test.payloadLength + extHdrLen + totalLength := ipHeaderLength + payloadLength hdr := buffer.NewPrependable(totalLength) hdr.Prepend(test.payloadLength) icmpH := header.ICMPv6(hdr.Prepend(icmpHeaderLength)) @@ -3391,7 +3392,7 @@ func TestForwarding(t *testing.T) { copy(hdr.Prepend(extHdrLen), extHdrBytes) ip := header.IPv6(hdr.Prepend(ipHeaderLength)) ip.Encode(&header.IPv6Fields{ - PayloadLength: uint16(header.ICMPv6MinimumSize + test.payloadLength), + PayloadLength: uint16(payloadLength), TransportProtocol: transportProtocol, HopLimit: test.TTL, SrcAddr: test.sourceAddr, diff --git a/pkg/tcpip/stack/packet_buffer.go b/pkg/tcpip/stack/packet_buffer.go index 29c22bfd4..b9280c2de 100644 --- a/pkg/tcpip/stack/packet_buffer.go +++ b/pkg/tcpip/stack/packet_buffer.go @@ -341,6 +341,37 @@ func (pk *PacketBuffer) CloneToInbound() *PacketBuffer { return newPk } +// DeepCopyForForwarding creates a deep copy of the packet buffer for +// forwarding. +// +// The returned packet buffer will have the network and transport headers +// set if the original packet buffer did. +func (pk *PacketBuffer) DeepCopyForForwarding(reservedHeaderBytes int) *PacketBuffer { + newPkt := NewPacketBuffer(PacketBufferOptions{ + ReserveHeaderBytes: reservedHeaderBytes, + Data: PayloadSince(pk.NetworkHeader()).ToVectorisedView(), + IsForwardedPacket: true, + }) + + { + consumeBytes := pk.NetworkHeader().View().Size() + if _, consumed := newPkt.NetworkHeader().Consume(consumeBytes); !consumed { + panic(fmt.Sprintf("expected to consume network header %d bytes from new packet", consumeBytes)) + } + newPkt.NetworkProtocolNumber = pk.NetworkProtocolNumber + } + + { + consumeBytes := pk.TransportHeader().View().Size() + if _, consumed := newPkt.TransportHeader().Consume(consumeBytes); !consumed { + panic(fmt.Sprintf("expected to consume transport header %d bytes from new packet", consumeBytes)) + } + newPkt.TransportProtocolNumber = pk.TransportProtocolNumber + } + + return newPkt +} + // headerInfo stores metadata about a header in a packet. type headerInfo struct { // offset is the offset of the header in pk.buf relative to -- cgit v1.2.3