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tun: export GSOSplit() for external Device implementers

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External implementers of tun.Device may support GSO, and may also be
platform-agnostic, e.g. gVisor.

Signed-off-by: Jordan Whited <jordan@tailscale.com>
This commit is contained in:
Jordan Whited 2024-07-16 15:36:20 -07:00 • committed by Jordan Whited
parent 2f5d148bcf
commit 60eeedfd62
4 changed files with 354 additions and 162 deletions
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67
tun/tun_linux.go
View file

@ -380,73 +380,32 @@ func handleVirtioRead(in []byte, bufs [][]byte, sizes []int, offset int) (int, e
return 0, err
}
in = in[virtioNetHdrLen:]
if hdr.gsoType == unix.VIRTIO_NET_HDR_GSO_NONE {
if hdr.flags&unix.VIRTIO_NET_HDR_F_NEEDS_CSUM != 0 {
// This means CHECKSUM_PARTIAL in skb context. We are responsible
// for computing the checksum starting at hdr.csumStart and placing
// at hdr.csumOffset.
err = gsoNoneChecksum(in, hdr.csumStart, hdr.csumOffset)
if err != nil {
return 0, err
}
}
if len(in) > len(bufs[0][offset:]) {
return 0, fmt.Errorf("read len %d overflows bufs element len %d", len(in), len(bufs[0][offset:]))
}
n := copy(bufs[0][offset:], in)
sizes[0] = n
return 1, nil
}
if hdr.gsoType != unix.VIRTIO_NET_HDR_GSO_TCPV4 && hdr.gsoType != unix.VIRTIO_NET_HDR_GSO_TCPV6 && hdr.gsoType != unix.VIRTIO_NET_HDR_GSO_UDP_L4 {
return 0, fmt.Errorf("unsupported virtio GSO type: %d", hdr.gsoType)
options, err := hdr.toGSOOptions()
if err != nil {
return 0, err
}
ipVersion := in[0] >> 4
switch ipVersion {
case 4:
if hdr.gsoType != unix.VIRTIO_NET_HDR_GSO_TCPV4 && hdr.gsoType != unix.VIRTIO_NET_HDR_GSO_UDP_L4 {
return 0, fmt.Errorf("ip header version: %d, GSO type: %d", ipVersion, hdr.gsoType)
}
case 6:
if hdr.gsoType != unix.VIRTIO_NET_HDR_GSO_TCPV6 && hdr.gsoType != unix.VIRTIO_NET_HDR_GSO_UDP_L4 {
return 0, fmt.Errorf("ip header version: %d, GSO type: %d", ipVersion, hdr.gsoType)
}
default:
return 0, fmt.Errorf("invalid ip header version: %d", ipVersion)
}
// Don't trust hdr.hdrLen from the kernel as it can be equal to the length
// Don't trust HdrLen from the kernel as it can be equal to the length
// of the entire first packet when the kernel is handling it as part of a
// FORWARD path. Instead, parse the transport header length and add it onto
// csumStart, which is synonymous for IP header length.
if hdr.gsoType == unix.VIRTIO_NET_HDR_GSO_UDP_L4 {
hdr.hdrLen = hdr.csumStart + 8
} else {
if len(in) <= int(hdr.csumStart+12) {
// CsumStart, which is synonymous for IP header length.
if options.GSOType == GSOUDPL4 {
options.HdrLen = options.CsumStart + 8
} else if options.GSOType != GSONone {
if len(in) <= int(options.CsumStart+12) {
return 0, errors.New("packet is too short")
}
tcpHLen := uint16(in[hdr.csumStart+12] >> 4 * 4)
tcpHLen := uint16(in[options.CsumStart+12] >> 4 * 4)
if tcpHLen < 20 || tcpHLen > 60 {
// A TCP header must be between 20 and 60 bytes in length.
return 0, fmt.Errorf("tcp header len is invalid: %d", tcpHLen)
}
hdr.hdrLen = hdr.csumStart + tcpHLen
options.HdrLen = options.CsumStart + tcpHLen
}
if len(in) < int(hdr.hdrLen) {
return 0, fmt.Errorf("length of packet (%d) < virtioNetHdr.hdrLen (%d)", len(in), hdr.hdrLen)
}
if hdr.hdrLen < hdr.csumStart {
return 0, fmt.Errorf("virtioNetHdr.hdrLen (%d) < virtioNetHdr.csumStart (%d)", hdr.hdrLen, hdr.csumStart)
}
cSumAt := int(hdr.csumStart + hdr.csumOffset)
if cSumAt+1 >= len(in) {
return 0, fmt.Errorf("end of checksum offset (%d) exceeds packet length (%d)", cSumAt+1, len(in))
}
return gsoSplit(in, hdr, bufs, sizes, offset, ipVersion == 6)
return GSOSplit(in, options, bufs, sizes, offset)
}
func (tun *NativeTun) Read(bufs [][]byte, sizes []int, offset int) (int, error) {