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-rw-r--r--pkg/tcpip/network/fragmentation/fragmentation.go6
-rw-r--r--pkg/tcpip/network/fragmentation/reassembler.go95
-rw-r--r--pkg/tcpip/network/fragmentation/reassembler_test.go174
3 files changed, 177 insertions, 98 deletions
diff --git a/pkg/tcpip/network/fragmentation/fragmentation.go b/pkg/tcpip/network/fragmentation/fragmentation.go
index c75ca7d71..d31296a41 100644
--- a/pkg/tcpip/network/fragmentation/fragmentation.go
+++ b/pkg/tcpip/network/fragmentation/fragmentation.go
@@ -46,9 +46,13 @@ const (
)
var (
- // ErrInvalidArgs indicates to the caller that that an invalid argument was
+ // ErrInvalidArgs indicates to the caller that an invalid argument was
// provided.
ErrInvalidArgs = errors.New("invalid args")
+
+ // ErrFragmentOverlap indicates that, during reassembly, a fragment overlaps
+ // with another one.
+ ErrFragmentOverlap = errors.New("overlapping fragments")
)
// FragmentID is the identifier for a fragment.
diff --git a/pkg/tcpip/network/fragmentation/reassembler.go b/pkg/tcpip/network/fragmentation/reassembler.go
index 19f4920b3..04072d966 100644
--- a/pkg/tcpip/network/fragmentation/reassembler.go
+++ b/pkg/tcpip/network/fragmentation/reassembler.go
@@ -26,9 +26,9 @@ import (
)
type hole struct {
- first uint16
- last uint16
- deleted bool
+ first uint16
+ last uint16
+ filled bool
}
type reassembler struct {
@@ -38,7 +38,7 @@ type reassembler struct {
proto uint8
mu sync.Mutex
holes []hole
- deleted int
+ filled int
heap fragHeap
done bool
creationTime int64
@@ -53,44 +53,86 @@ func newReassembler(id FragmentID, clock tcpip.Clock) *reassembler {
creationTime: clock.NowMonotonic(),
}
r.holes = append(r.holes, hole{
- first: 0,
- last: math.MaxUint16,
- deleted: false})
+ first: 0,
+ last: math.MaxUint16,
+ filled: false,
+ })
return r
}
-// updateHoles updates the list of holes for an incoming fragment and
-// returns true iff the fragment filled at least part of an existing hole.
-func (r *reassembler) updateHoles(first, last uint16, more bool) bool {
- used := false
+// updateHoles updates the list of holes for an incoming fragment. It returns
+// true if the fragment fits, it is not a duplicate and it does not overlap with
+// another fragment.
+//
+// For IPv6, overlaps with an existing fragment are explicitly forbidden by
+// RFC 8200 section 4.5:
+// If any of the fragments being reassembled overlap with any other fragments
+// being reassembled for the same packet, reassembly of that packet must be
+// abandoned and all the fragments that have been received for that packet
+// must be discarded, and no ICMP error messages should be sent.
+//
+// It is not explicitly forbidden for IPv4, but to keep parity with Linux we
+// disallow it as well:
+// https://github.com/torvalds/linux/blob/38525c6/net/ipv4/inet_fragment.c#L349
+func (r *reassembler) updateHoles(first, last uint16, more bool) (bool, error) {
for i := range r.holes {
- if r.holes[i].deleted || first > r.holes[i].last || last < r.holes[i].first {
+ currentHole := &r.holes[i]
+
+ if currentHole.filled || last < currentHole.first || currentHole.last < first {
continue
}
- used = true
- r.deleted++
- r.holes[i].deleted = true
- if first > r.holes[i].first {
- r.holes = append(r.holes, hole{r.holes[i].first, first - 1, false})
+
+ if first < currentHole.first || currentHole.last < last {
+ // Incoming fragment only partially fits in the free hole.
+ return false, ErrFragmentOverlap
+ }
+
+ r.filled++
+ if first > currentHole.first {
+ r.holes = append(r.holes, hole{
+ first: currentHole.first,
+ last: first - 1,
+ filled: false,
+ })
+ }
+ if last < currentHole.last && more {
+ r.holes = append(r.holes, hole{
+ first: last + 1,
+ last: currentHole.last,
+ filled: false,
+ })
}
- if last < r.holes[i].last && more {
- r.holes = append(r.holes, hole{last + 1, r.holes[i].last, false})
+ // Update the current hole to precisely match the incoming fragment.
+ r.holes[i] = hole{
+ first: first,
+ last: last,
+ filled: true,
}
+ return true, nil
}
- return used
+
+ // Incoming fragment is a duplicate/subset, or its offset comes after the end
+ // of the reassembled payload.
+ return false, nil
}
func (r *reassembler) process(first, last uint16, more bool, proto uint8, pkt *stack.PacketBuffer) (buffer.VectorisedView, uint8, bool, int, error) {
r.mu.Lock()
defer r.mu.Unlock()
- consumed := 0
if r.done {
// A concurrent goroutine might have already reassembled
// the packet and emptied the heap while this goroutine
// was waiting on the mutex. We don't have to do anything in this case.
- return buffer.VectorisedView{}, 0, false, consumed, nil
+ return buffer.VectorisedView{}, 0, false, 0, nil
}
- if r.updateHoles(first, last, more) {
+
+ used, err := r.updateHoles(first, last, more)
+ if err != nil {
+ return buffer.VectorisedView{}, 0, false, 0, fmt.Errorf("fragment reassembly failed: %w", err)
+ }
+
+ var consumed int
+ if used {
// For IPv6, it is possible to have different Protocol values between
// fragments of a packet (because, unlike IPv4, the Protocol is not used to
// identify a fragment). In this case, only the Protocol of the first
@@ -109,13 +151,14 @@ func (r *reassembler) process(first, last uint16, more bool, proto uint8, pkt *s
consumed = vv.Size()
r.size += consumed
}
- // Check if all the holes have been deleted and we are ready to reassamble.
- if r.deleted < len(r.holes) {
+
+ // Check if all the holes have been filled and we are ready to reassemble.
+ if r.filled < len(r.holes) {
return buffer.VectorisedView{}, 0, false, consumed, nil
}
res, err := r.heap.reassemble()
if err != nil {
- return buffer.VectorisedView{}, 0, false, consumed, fmt.Errorf("fragment reassembly failed: %w", err)
+ return buffer.VectorisedView{}, 0, false, 0, fmt.Errorf("fragment reassembly failed: %w", err)
}
return res, r.proto, true, consumed, nil
}
diff --git a/pkg/tcpip/network/fragmentation/reassembler_test.go b/pkg/tcpip/network/fragmentation/reassembler_test.go
index a0a04a027..cee3063b1 100644
--- a/pkg/tcpip/network/fragmentation/reassembler_test.go
+++ b/pkg/tcpip/network/fragmentation/reassembler_test.go
@@ -16,92 +16,124 @@ package fragmentation
import (
"math"
- "reflect"
"testing"
+ "github.com/google/go-cmp/cmp"
"gvisor.dev/gvisor/pkg/tcpip/faketime"
)
-type updateHolesInput struct {
- first uint16
- last uint16
- more bool
+type updateHolesParams struct {
+ first uint16
+ last uint16
+ more bool
+ wantUsed bool
+ wantError error
}
-var holesTestCases = []struct {
- comment string
- in []updateHolesInput
- want []hole
-}{
- {
- comment: "No fragments. Expected holes: {[0 -> inf]}.",
- in: []updateHolesInput{},
- want: []hole{{first: 0, last: math.MaxUint16, deleted: false}},
- },
- {
- comment: "One fragment at beginning. Expected holes: {[2, inf]}.",
- in: []updateHolesInput{{first: 0, last: 1, more: true}},
- want: []hole{
- {first: 0, last: math.MaxUint16, deleted: true},
- {first: 2, last: math.MaxUint16, deleted: false},
+func TestUpdateHoles(t *testing.T) {
+ var tests = []struct {
+ name string
+ params []updateHolesParams
+ want []hole
+ }{
+ {
+ name: "No fragments",
+ params: nil,
+ want: []hole{{first: 0, last: math.MaxUint16, filled: false}},
},
- },
- {
- comment: "One fragment in the middle. Expected holes: {[0, 0], [3, inf]}.",
- in: []updateHolesInput{{first: 1, last: 2, more: true}},
- want: []hole{
- {first: 0, last: math.MaxUint16, deleted: true},
- {first: 0, last: 0, deleted: false},
- {first: 3, last: math.MaxUint16, deleted: false},
+ {
+ name: "One fragment at beginning",
+ params: []updateHolesParams{{first: 0, last: 1, more: true, wantUsed: true, wantError: nil}},
+ want: []hole{
+ {first: 0, last: 1, filled: true},
+ {first: 2, last: math.MaxUint16, filled: false},
+ },
},
- },
- {
- comment: "One fragment at the end. Expected holes: {[0, 0]}.",
- in: []updateHolesInput{{first: 1, last: 2, more: false}},
- want: []hole{
- {first: 0, last: math.MaxUint16, deleted: true},
- {first: 0, last: 0, deleted: false},
+ {
+ name: "One fragment in the middle",
+ params: []updateHolesParams{{first: 1, last: 2, more: true, wantUsed: true, wantError: nil}},
+ want: []hole{
+ {first: 1, last: 2, filled: true},
+ {first: 0, last: 0, filled: false},
+ {first: 3, last: math.MaxUint16, filled: false},
+ },
},
- },
- {
- comment: "One fragment completing a packet. Expected holes: {}.",
- in: []updateHolesInput{{first: 0, last: 1, more: false}},
- want: []hole{
- {first: 0, last: math.MaxUint16, deleted: true},
+ {
+ name: "One fragment at the end",
+ params: []updateHolesParams{{first: 1, last: 2, more: false, wantUsed: true, wantError: nil}},
+ want: []hole{
+ {first: 1, last: 2, filled: true},
+ {first: 0, last: 0, filled: false},
+ },
},
- },
- {
- comment: "Two non-overlapping fragments completing a packet. Expected holes: {}.",
- in: []updateHolesInput{
- {first: 0, last: 1, more: true},
- {first: 2, last: 3, more: false},
+ {
+ name: "One fragment completing a packet",
+ params: []updateHolesParams{{first: 0, last: 1, more: false, wantUsed: true, wantError: nil}},
+ want: []hole{
+ {first: 0, last: 1, filled: true},
+ },
},
- want: []hole{
- {first: 0, last: math.MaxUint16, deleted: true},
- {first: 2, last: math.MaxUint16, deleted: true},
+ {
+ name: "Two fragments completing a packet",
+ params: []updateHolesParams{
+ {first: 0, last: 1, more: true, wantUsed: true, wantError: nil},
+ {first: 2, last: 3, more: false, wantUsed: true, wantError: nil},
+ },
+ want: []hole{
+ {first: 0, last: 1, filled: true},
+ {first: 2, last: 3, filled: true},
+ },
},
- },
- {
- comment: "Two overlapping fragments completing a packet. Expected holes: {}.",
- in: []updateHolesInput{
- {first: 0, last: 2, more: true},
- {first: 2, last: 3, more: false},
+ {
+ name: "Two fragments completing a packet with a duplicate",
+ params: []updateHolesParams{
+ {first: 0, last: 1, more: true, wantUsed: true, wantError: nil},
+ {first: 0, last: 1, more: true, wantUsed: false, wantError: nil},
+ {first: 2, last: 3, more: false, wantUsed: true, wantError: nil},
+ },
+ want: []hole{
+ {first: 0, last: 1, filled: true},
+ {first: 2, last: 3, filled: true},
+ },
},
- want: []hole{
- {first: 0, last: math.MaxUint16, deleted: true},
- {first: 3, last: math.MaxUint16, deleted: true},
+ {
+ name: "Two overlapping fragments",
+ params: []updateHolesParams{
+ {first: 0, last: 10, more: true, wantUsed: true, wantError: nil},
+ {first: 5, last: 15, more: false, wantUsed: false, wantError: ErrFragmentOverlap},
+ {first: 11, last: 15, more: false, wantUsed: true, wantError: nil},
+ },
+ want: []hole{
+ {first: 0, last: 10, filled: true},
+ {first: 11, last: 15, filled: true},
+ },
},
- },
-}
+ {
+ name: "Out of bounds fragment",
+ params: []updateHolesParams{
+ {first: 0, last: 10, more: true, wantUsed: true, wantError: nil},
+ {first: 11, last: 15, more: false, wantUsed: true, wantError: nil},
+ {first: 16, last: 20, more: false, wantUsed: false, wantError: nil},
+ },
+ want: []hole{
+ {first: 0, last: 10, filled: true},
+ {first: 11, last: 15, filled: true},
+ },
+ },
+ }
-func TestUpdateHoles(t *testing.T) {
- for _, c := range holesTestCases {
- r := newReassembler(FragmentID{}, &faketime.NullClock{})
- for _, i := range c.in {
- r.updateHoles(i.first, i.last, i.more)
- }
- if !reflect.DeepEqual(r.holes, c.want) {
- t.Errorf("Test \"%s\" produced unexepetced holes. Got %v. Want %v", c.comment, r.holes, c.want)
- }
+ for _, test := range tests {
+ t.Run(test.name, func(t *testing.T) {
+ r := newReassembler(FragmentID{}, &faketime.NullClock{})
+ for _, param := range test.params {
+ used, err := r.updateHoles(param.first, param.last, param.more)
+ if used != param.wantUsed || err != param.wantError {
+ t.Errorf("got r.updateHoles(%d, %d, %t) = (%t, %v), want = (%t, %v)", param.first, param.last, param.more, used, err, param.wantUsed, param.wantError)
+ }
+ }
+ if diff := cmp.Diff(test.want, r.holes, cmp.AllowUnexported(hole{})); diff != "" {
+ t.Errorf("r.holes mismatch (-want +got):\n%s", diff)
+ }
+ })
}
}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-01 20:41:13 +0000