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overlay/tio: error on multi-segment WriteGSO with a bogus IP version

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gsoTypeFromProto returns GSO_NONE when the IP version nibble is
neither 4 nor 6, so a multi-fragment superpacket went out as one
silent jumbo GSO_NONE packet -- exactly the silent mis-emission the
geometry checks promise not to allow.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014ugV2edVqoz3tBvq9J6yWp
This commit is contained in:
JackDoan
2026-07-29 17:14:04 -05:00
parent 9ce0596f5c
commit e9870686c8
2 changed files with 8 additions and 0 deletions
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overlay/tio/tio_gso_linux.go
+6
View File
@@ -358,6 +358,12 @@ func (r *Offload) WriteGSO(hdr []byte, transportHdr []byte, pays [][]byte, proto
gsoType := uint8(unix.VIRTIO_NET_HDR_GSO_NONE)
if len(pays) > 1 {
gsoType = gsoTypeFromProto(proto, hdr[0]>>4)
if gsoType == unix.VIRTIO_NET_HDR_GSO_NONE {
// gsoTypeFromProto only yields GSO_NONE for a bogus IP version
// nibble. A multi-segment superpacket must carry a real GSO type,
// or the kernel would deliver it as a single jumbo packet.
return fmt.Errorf("tio: WriteGSO IP version %d is not GSO-capable", hdr[0]>>4)
}
}
var gsoSize uint16
if gsoType != unix.VIRTIO_NET_HDR_GSO_NONE {
overlay/tio/tun_linux_offload_test.go
+2
View File
@@ -997,6 +997,8 @@ func TestWriteGSORejectsBadGeometry(t *testing.T) {
{"undersize-middle-fragment", ipHdr, udpHdr, [][]byte{seg, make([]byte, 100), seg}, GSOProtoUDP, true},
{"oversize-last-fragment", ipHdr, tcpHdr, [][]byte{seg, make([]byte, 1201)}, GSOProtoTCP, true},
{"short-last-fragment-ok", ipHdr, udpHdr, [][]byte{seg, seg, make([]byte, 100)}, GSOProtoUDP, false},
{"multi-segment-bad-ip-version", []byte{0x05}, udpHdr, [][]byte{seg, seg}, GSOProtoUDP, true},
{"single-segment-bad-ip-version-ok", []byte{0x05}, udpHdr, [][]byte{seg}, GSOProtoUDP, false},
{"no-pays-noop", ipHdr, udpHdr, nil, GSOProtoUDP, false},
{"valid-udp", ipHdr, udpHdr, [][]byte{seg, seg}, GSOProtoUDP, false},
{"valid-tcp", ipHdr, tcpHdr, [][]byte{seg, seg}, GSOProtoTCP, false},