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tun: add method for disabling TCP GRO on Linux

Browse source 
torvalds/linux@e269d79c7d broke virtio_net
TCP & UDP GRO causing GRO writes to return EINVAL. The bug was then
resolved later in
torvalds/linux@89add40066. The offending
commit was pulled into various LTS releases.

Updates tailscale/tailscale#13041

Signed-off-by: Jordan Whited <jordan@tailscale.com>
This commit is contained in:
Jordan Whited 2024-09-04 12:17:44 -07:00 • committed by Jordan Whited
parent 71393c576b
commit 799c1978fa
4 changed files with 114 additions and 54 deletions
Download patch file Download diff file Expand all files Collapse all files

45
tun/tun_linux.go
View file

@ -38,7 +38,6 @@ type NativeTun struct {
statusListenersShutdown chan struct{}
batchSize int
vnetHdr bool
udpGSO bool
closeOnce sync.Once
@ -53,7 +52,30 @@ type NativeTun struct {
toWrite []int
tcpGROTable *tcpGROTable
udpGROTable *udpGROTable
udpGRO bool
gro groDisablementFlags
}
type groDisablementFlags int
const (
tcpGRODisabled groDisablementFlags = 1 << iota
udpGRODisabled
)
func (g *groDisablementFlags) disableTCPGRO() {
*g |= tcpGRODisabled
}
func (g *groDisablementFlags) canTCPGRO() bool {
return (*g)&tcpGRODisabled == 0
}
func (g *groDisablementFlags) disableUDPGRO() {
*g |= udpGRODisabled
}
func (g *groDisablementFlags) canUDPGRO() bool {
return (*g)&udpGRODisabled == 0
}
func (tun *NativeTun) File() *os.File {
@ -346,7 +368,7 @@ func (tun *NativeTun) Write(bufs [][]byte, offset int) (int, error) {
)
tun.toWrite = tun.toWrite[:0]
if tun.vnetHdr {
err := handleGRO(bufs, offset, tun.tcpGROTable, tun.udpGROTable, tun.udpGRO, &tun.toWrite)
err := handleGRO(bufs, offset, tun.tcpGROTable, tun.udpGROTable, tun.gro, &tun.toWrite)
if err != nil {
return 0, err
}
@ -462,9 +484,19 @@ func (tun *NativeTun) BatchSize() int {
return tun.batchSize
}
// DisableUDPGRO disables UDP GRO if it is enabled. See the GRODevice interface
// for cases where it should be called.
func (tun *NativeTun) DisableUDPGRO() {
tun.writeOpMu.Lock()
tun.udpGRO = false
tun.gro.disableUDPGRO()
tun.writeOpMu.Unlock()
}
// DisableTCPGRO disables TCP GRO if it is enabled. See the GRODevice interface
// for cases where it should be called.
func (tun *NativeTun) DisableTCPGRO() {
tun.writeOpMu.Lock()
tun.gro.disableTCPGRO()
tun.writeOpMu.Unlock()
}
@ -503,8 +535,9 @@ func (tun *NativeTun) initFromFlags(name string) error {
tun.batchSize = conn.IdealBatchSize
// tunUDPOffloads were added in Linux v6.2. We do not return an
// error if they are unsupported at runtime.
tun.udpGSO = unix.IoctlSetInt(int(fd), unix.TUNSETOFFLOAD, tunTCPOffloads|tunUDPOffloads) == nil
tun.udpGRO = tun.udpGSO
if unix.IoctlSetInt(int(fd), unix.TUNSETOFFLOAD, tunTCPOffloads|tunUDPOffloads) != nil {
tun.gro.disableUDPGRO()
}
} else {
tun.batchSize = 1
}