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wgengine/magicsock: refactor batchingUDPConn to batchingConn interface (#13042)

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This commit adds a batchingConn interface, and renames batchingUDPConn
to linuxBatchingConn. tryUpgradeToBatchingConn() may return a platform-
specific implementation of batchingConn. So far only a Linux
implementation of this interface exists, but this refactor is being
done in anticipation of a Windows implementation.

Updates tailscale/corp#21874

Signed-off-by: Jordan Whited <jordan@tailscale.com>
This commit is contained in:
Jordan Whited
2024-08-06 09:00:28 -07:00
committed by GitHub
parent 7bac5dffcb
commit a93dc6cdb1
9 changed files with 693 additions and 655 deletions
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64
wgengine/magicsock/magicsock_linux.go
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@@ -318,70 +318,6 @@ func trySetSocketBuffer(pconn nettype.PacketConn, logf logger.Logf) {
}
}
// tryEnableUDPOffload attempts to enable the UDP_GRO socket option on pconn,
// and returns two booleans indicating TX and RX UDP offload support.
func tryEnableUDPOffload(pconn nettype.PacketConn) (hasTX bool, hasRX bool) {
if c, ok := pconn.(*net.UDPConn); ok {
rc, err := c.SyscallConn()
if err != nil {
return
}
err = rc.Control(func(fd uintptr) {
_, errSyscall := syscall.GetsockoptInt(int(fd), unix.IPPROTO_UDP, unix.UDP_SEGMENT)
hasTX = errSyscall == nil
errSyscall = syscall.SetsockoptInt(int(fd), unix.IPPROTO_UDP, unix.UDP_GRO, 1)
hasRX = errSyscall == nil
})
if err != nil {
return false, false
}
}
return hasTX, hasRX
}
// getGSOSizeFromControl returns the GSO size found in control. If no GSO size
// is found or the len(control) < unix.SizeofCmsghdr, this function returns 0.
// A non-nil error will be returned if len(control) > unix.SizeofCmsghdr but
// its contents cannot be parsed as a socket control message.
func getGSOSizeFromControl(control []byte) (int, error) {
var (
hdr unix.Cmsghdr
data []byte
rem = control
err error
)
for len(rem) > unix.SizeofCmsghdr {
hdr, data, rem, err = unix.ParseOneSocketControlMessage(control)
if err != nil {
return 0, fmt.Errorf("error parsing socket control message: %w", err)
}
if hdr.Level == unix.SOL_UDP && hdr.Type == unix.UDP_GRO && len(data) >= 2 {
return int(binary.NativeEndian.Uint16(data[:2])), nil
}
}
return 0, nil
}
// setGSOSizeInControl sets a socket control message in control containing
// gsoSize. If len(control) < controlMessageSize control's len will be set to 0.
func setGSOSizeInControl(control *[]byte, gsoSize uint16) {
*control = (*control)[:0]
if cap(*control) < int(unsafe.Sizeof(unix.Cmsghdr{})) {
return
}
if cap(*control) < controlMessageSize {
return
}
*control = (*control)[:cap(*control)]
hdr := (*unix.Cmsghdr)(unsafe.Pointer(&(*control)[0]))
hdr.Level = unix.SOL_UDP
hdr.Type = unix.UDP_SEGMENT
hdr.SetLen(unix.CmsgLen(2))
binary.NativeEndian.PutUint16((*control)[unix.SizeofCmsghdr:], gsoSize)
*control = (*control)[:unix.CmsgSpace(2)]
}
var controlMessageSize = -1 // bomb if used for allocation before init
func init() {