diff options
Diffstat (limited to 'pkg/tcpip/network/fragmentation')
| -rw-r--r-- | pkg/tcpip/network/fragmentation/BUILD | 4 | ||||
| -rw-r--r-- | pkg/tcpip/network/fragmentation/fragmentation.go | 78 | ||||
| -rw-r--r-- | pkg/tcpip/network/fragmentation/fragmentation_test.go | 112 |
3 files changed, 193 insertions, 1 deletions
diff --git a/pkg/tcpip/network/fragmentation/BUILD b/pkg/tcpip/network/fragmentation/BUILD index e247f06a4..47fb63290 100644 --- a/pkg/tcpip/network/fragmentation/BUILD +++ b/pkg/tcpip/network/fragmentation/BUILD @@ -29,6 +29,8 @@ go_library( "//pkg/sync", "//pkg/tcpip", "//pkg/tcpip/buffer", + "//pkg/tcpip/header", + "//pkg/tcpip/stack", ], ) @@ -44,5 +46,7 @@ go_test( deps = [ "//pkg/tcpip/buffer", "//pkg/tcpip/faketime", + "//pkg/tcpip/network/testutil", + "@com_github_google_go_cmp//cmp:go_default_library", ], ) diff --git a/pkg/tcpip/network/fragmentation/fragmentation.go b/pkg/tcpip/network/fragmentation/fragmentation.go index e1909fab0..888ad62a3 100644 --- a/pkg/tcpip/network/fragmentation/fragmentation.go +++ b/pkg/tcpip/network/fragmentation/fragmentation.go @@ -13,7 +13,7 @@ // limitations under the License. // Package fragmentation contains the implementation of IP fragmentation. -// It is based on RFC 791 and RFC 815. +// It is based on RFC 791, RFC 815 and RFC 8200. package fragmentation import ( @@ -25,6 +25,7 @@ import ( "gvisor.dev/gvisor/pkg/sync" "gvisor.dev/gvisor/pkg/tcpip" "gvisor.dev/gvisor/pkg/tcpip/buffer" + "gvisor.dev/gvisor/pkg/tcpip/stack" ) const ( @@ -243,3 +244,78 @@ func (f *Fragmentation) releaseReassemblersLocked() { f.release(r) } } + +// PacketFragmenter is the book-keeping struct for packet fragmentation. +type PacketFragmenter struct { + transportHeader buffer.View + data buffer.VectorisedView + reserve int + innerMTU int + fragmentCount int + currentFragment int + fragmentOffset int +} + +// MakePacketFragmenter prepares the struct needed for packet fragmentation. +// +// pkt is the packet to be fragmented. +// +// innerMTU is the maximum number of bytes of fragmentable data a fragment can +// have. +// +// reserve is the number of bytes that should be reserved for the headers in +// each generated fragment. +func MakePacketFragmenter(pkt *stack.PacketBuffer, innerMTU int, reserve int) PacketFragmenter { + // As per RFC 8200 Section 4.5, some IPv6 extension headers should not be + // repeated in each fragment. However we do not currently support any header + // of that kind yet, so the following computation is valid for both IPv4 and + // IPv6. + // TODO(gvisor.dev/issue/3912): Once Authentication or ESP Headers are + // supported for outbound packets, the fragmentable data should not include + // these headers. + var fragmentableData buffer.VectorisedView + fragmentableData.AppendView(pkt.TransportHeader().View()) + fragmentableData.Append(pkt.Data) + fragmentCount := (fragmentableData.Size() + innerMTU - 1) / innerMTU + + return PacketFragmenter{ + data: fragmentableData, + reserve: reserve, + innerMTU: innerMTU, + fragmentCount: fragmentCount, + } +} + +// BuildNextFragment returns a packet with the payload of the next fragment, +// along with the fragment's offset, the number of bytes copied and a boolean +// indicating if there are more fragments left or not. If this function is +// called again after it indicated that no more fragments were left, it will +// panic. +// +// Note that the returned packet will not have its network and link headers +// populated, but space for them will be reserved. The transport header will be +// stored in the packet's data. +func (pf *PacketFragmenter) BuildNextFragment() (*stack.PacketBuffer, int, int, bool) { + if pf.currentFragment >= pf.fragmentCount { + panic("BuildNextFragment should not be called again after the last fragment was returned") + } + + fragPkt := stack.NewPacketBuffer(stack.PacketBufferOptions{ + ReserveHeaderBytes: pf.reserve, + }) + + // Copy data for the fragment. + copied := pf.data.ReadToVV(&fragPkt.Data, pf.innerMTU) + + offset := pf.fragmentOffset + pf.fragmentOffset += copied + pf.currentFragment++ + more := pf.currentFragment != pf.fragmentCount + + return fragPkt, offset, copied, more +} + +// RemainingFragmentCount returns the number of fragments left to be built. +func (pf *PacketFragmenter) RemainingFragmentCount() int { + return pf.fragmentCount - pf.currentFragment +} diff --git a/pkg/tcpip/network/fragmentation/fragmentation_test.go b/pkg/tcpip/network/fragmentation/fragmentation_test.go index 189b223c5..31a1eb862 100644 --- a/pkg/tcpip/network/fragmentation/fragmentation_test.go +++ b/pkg/tcpip/network/fragmentation/fragmentation_test.go @@ -20,8 +20,10 @@ import ( "testing" "time" + "github.com/google/go-cmp/cmp" "gvisor.dev/gvisor/pkg/tcpip/buffer" "gvisor.dev/gvisor/pkg/tcpip/faketime" + "gvisor.dev/gvisor/pkg/tcpip/network/testutil" ) // vv is a helper to build VectorisedView from different strings. @@ -381,3 +383,113 @@ func TestErrors(t *testing.T) { }) } } + +type fragmentInfo struct { + remaining int + copied int + offset int + more bool +} + +func TestPacketFragmenter(t *testing.T) { + const ( + reserve = 60 + proto = 0 + ) + + tests := []struct { + name string + innerMTU int + transportHeaderLen int + payloadSize int + wantFragments []fragmentInfo + }{ + { + name: "Packet exactly fits in MTU", + innerMTU: 1280, + transportHeaderLen: 0, + payloadSize: 1280, + wantFragments: []fragmentInfo{ + {remaining: 0, copied: 1280, offset: 0, more: false}, + }, + }, + { + name: "Packet exactly does not fit in MTU", + innerMTU: 1000, + transportHeaderLen: 0, + payloadSize: 1001, + wantFragments: []fragmentInfo{ + {remaining: 1, copied: 1000, offset: 0, more: true}, + {remaining: 0, copied: 1, offset: 1000, more: false}, + }, + }, + { + name: "Packet has a transport header", + innerMTU: 560, + transportHeaderLen: 40, + payloadSize: 560, + wantFragments: []fragmentInfo{ + {remaining: 1, copied: 560, offset: 0, more: true}, + {remaining: 0, copied: 40, offset: 560, more: false}, + }, + }, + { + name: "Packet has a huge transport header", + innerMTU: 500, + transportHeaderLen: 1300, + payloadSize: 500, + wantFragments: []fragmentInfo{ + {remaining: 3, copied: 500, offset: 0, more: true}, + {remaining: 2, copied: 500, offset: 500, more: true}, + {remaining: 1, copied: 500, offset: 1000, more: true}, + {remaining: 0, copied: 300, offset: 1500, more: false}, + }, + }, + } + + for _, test := range tests { + t.Run(test.name, func(t *testing.T) { + pkt := testutil.MakeRandPkt(test.transportHeaderLen, reserve, []int{test.payloadSize}, proto) + var originalPayload buffer.VectorisedView + originalPayload.AppendView(pkt.TransportHeader().View()) + originalPayload.Append(pkt.Data) + var reassembledPayload buffer.VectorisedView + pf := MakePacketFragmenter(pkt, test.innerMTU, reserve) + for i := 0; ; i++ { + fragPkt, offset, copied, more := pf.BuildNextFragment() + wantFragment := test.wantFragments[i] + if got := pf.RemainingFragmentCount(); got != wantFragment.remaining { + t.Errorf("(fragment #%d) got pf.RemainingFragmentCount() = %d, want = %d", i, got, wantFragment.remaining) + } + if copied != wantFragment.copied { + t.Errorf("(fragment #%d) got copied = %d, want = %d", i, copied, wantFragment.copied) + } + if offset != wantFragment.offset { + t.Errorf("(fragment #%d) got offset = %d, want = %d", i, offset, wantFragment.offset) + } + if more != wantFragment.more { + t.Errorf("(fragment #%d) got more = %t, want = %t", i, more, wantFragment.more) + } + if got := fragPkt.Size(); got > test.innerMTU { + t.Errorf("(fragment #%d) got fragPkt.Size() = %d, want <= %d", i, got, test.innerMTU) + } + if got := fragPkt.AvailableHeaderBytes(); got != reserve { + t.Errorf("(fragment #%d) got fragPkt.AvailableHeaderBytes() = %d, want = %d", i, got, reserve) + } + if got := fragPkt.TransportHeader().View().Size(); got != 0 { + t.Errorf("(fragment #%d) got fragPkt.TransportHeader().View().Size() = %d, want = 0", i, got) + } + reassembledPayload.Append(fragPkt.Data) + if !more { + if i != len(test.wantFragments)-1 { + t.Errorf("got fragment count = %d, want = %d", i, len(test.wantFragments)-1) + } + break + } + } + if diff := cmp.Diff(reassembledPayload.ToView(), originalPayload.ToView()); diff != "" { + t.Errorf("reassembledPayload mismatch (-want +got):\n%s", diff) + } + }) + } +} |