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net/batching: eliminate gso helper func indirection

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These were previously swappable for historical reasons that are no
longer relevant.

Removing the indirection enables future inlining optimizations if we
simplify further.

Updates tailscale/corp#38703

Signed-off-by: Jordan Whited <jordan@tailscale.com>
This commit is contained in:
Jordan Whited
2026-03-17 15:12:57 -07:00
committed by Jordan Whited
parent 26ba71d23f
commit 31d65a909d
2 changed files with 34 additions and 45 deletions
Download Patch File Download Diff File Expand all files Collapse all files
net/batching/conn_linux.go
+17 -18
View File
@@ -52,14 +52,12 @@ var (
// linuxBatchingConn is a UDP socket that provides batched i/o. It implements
// [Conn].
type linuxBatchingConn struct {
pc *net.UDPConn
xpc xnetBatchReaderWriter
rxOffload bool // supports UDP GRO or similar
txOffload atomic.Bool // supports UDP GSO or similar
setGSOSizeInControl func(control *[]byte, gsoSize uint16) // typically setGSOSizeInControl(); swappable for testing
getGSOSizeFromControl func(control []byte) (int, error) // typically getGSOSizeFromControl(); swappable for testing
sendBatchPool sync.Pool
rxqOverflowsMetric *clientmetric.Metric
pc *net.UDPConn
xpc xnetBatchReaderWriter
rxOffload bool // supports UDP GRO or similar
txOffload atomic.Bool // supports UDP GSO or similar
sendBatchPool sync.Pool
rxqOverflowsMetric *clientmetric.Metric
// readOpMu guards read operations that must perform accounting against
// rxqOverflows in single-threaded fashion. There are no concurrent usages
@@ -134,7 +132,7 @@ func (c *linuxBatchingConn) coalesceMessages(addr *net.UDPAddr, geneve packet.Ge
msgs[base].Buffers[0] = append(msgs[base].Buffers[0], make([]byte, msgLen)...)
copy(msgs[base].Buffers[0][baseLenBefore:], buff)
if i == len(buffs)-1 {
c.setGSOSizeInControl(&msgs[base].OOB, uint16(gsoSize))
setGSOSizeInControl(&msgs[base].OOB, uint16(gsoSize))
}
dgramCnt++
if msgLen < gsoSize {
@@ -146,7 +144,7 @@ func (c *linuxBatchingConn) coalesceMessages(addr *net.UDPAddr, geneve packet.Ge
}
}
if dgramCnt > 1 {
c.setGSOSizeInControl(&msgs[base].OOB, uint16(gsoSize))
setGSOSizeInControl(&msgs[base].OOB, uint16(gsoSize))
}
// Reset prior to incrementing base since we are preparing to start a
// new potential batch.
@@ -262,7 +260,7 @@ func (c *linuxBatchingConn) splitCoalescedMessages(msgs []ipv6.Message, firstMsg
end = msg.N
numToSplit = 1
)
gsoSize, err = c.getGSOSizeFromControl(msg.OOB[:msg.NN])
gsoSize, err = getGSOSizeFromControl(msg.OOB[:msg.NN])
if err != nil {
return n, err
}
@@ -426,9 +424,10 @@ func tryEnableUDPOffload(pconn nettype.PacketConn) (hasTX bool, hasRX bool) {
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 control is malformed.
// getGSOSizeFromControl returns the GSO size found in control associated with a
// cmsg type of UDP_GRO, which the kernel populates in the read direction. If no
// GSO size is found or the len(control) < unix.SizeofCmsghdr, this function
// returns 0. A non-nil error will be returned if control is malformed.
func getGSOSizeFromControl(control []byte) (int, error) {
data, err := getDataFromControl(control, unix.SOL_UDP, unix.UDP_GRO, 2)
if err != nil {
@@ -441,7 +440,9 @@ func getGSOSizeFromControl(control []byte) (int, error) {
}
// setGSOSizeInControl sets a socket control message in control containing
// gsoSize. If len(control) < controlMessageSize control's len will be set to 0.
// gsoSize with an associated cmsg type of UDP_SEGMENT, which we are responsible
// for populating prior to writing towards the kernel. 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{})) {
@@ -513,9 +514,7 @@ func TryUpgradeToConn(pconn nettype.PacketConn, network string, batchSize int, r
return pconn
}
b := &linuxBatchingConn{
pc: uc,
getGSOSizeFromControl: getGSOSizeFromControl,
setGSOSizeInControl: setGSOSizeInControl,
pc: uc,
sendBatchPool: sync.Pool{
New: func() any {
ua := &net.UDPAddr{
net/batching/conn_linux_test.go
+17 -27
View File
@@ -18,33 +18,17 @@ import (
"tailscale.com/net/packet"
)
func setGSOSize(control *[]byte, gsoSize uint16) {
*control = (*control)[:cap(*control)]
binary.LittleEndian.PutUint16(*control, gsoSize)
}
func getGSOSize(control []byte) (int, error) {
if len(control) < 2 {
return 0, nil
}
return int(binary.LittleEndian.Uint16(control)), nil
}
func Test_linuxBatchingConn_splitCoalescedMessages(t *testing.T) {
c := &linuxBatchingConn{
setGSOSizeInControl: setGSOSize,
getGSOSizeFromControl: getGSOSize,
}
c := &linuxBatchingConn{}
newMsg := func(n, gso int) ipv6.Message {
newMsg := func(n int, gso uint16) ipv6.Message {
msg := ipv6.Message{
Buffers: [][]byte{make([]byte, 1024)},
N: n,
OOB: make([]byte, 2),
OOB: gsoControl(gso),
}
binary.LittleEndian.PutUint16(msg.OOB, uint16(gso))
if gso > 0 {
msg.NN = 2
msg.NN = len(msg.OOB)
}
return msg
}
@@ -156,10 +140,7 @@ func Test_linuxBatchingConn_splitCoalescedMessages(t *testing.T) {
}
func Test_linuxBatchingConn_coalesceMessages(t *testing.T) {
c := &linuxBatchingConn{
setGSOSizeInControl: setGSOSize,
getGSOSizeFromControl: getGSOSize,
}
c := &linuxBatchingConn{}
withGeneveSpace := func(len, cap int) []byte {
return make([]byte, len+packet.GeneveFixedHeaderLength, cap+packet.GeneveFixedHeaderLength)
@@ -285,7 +266,7 @@ func Test_linuxBatchingConn_coalesceMessages(t *testing.T) {
msgs := make([]ipv6.Message, len(tt.buffs))
for i := range msgs {
msgs[i].Buffers = make([][]byte, 1)
msgs[i].OOB = make([]byte, 0, 2)
msgs[i].OOB = make([]byte, controlMessageSize)
}
got := c.coalesceMessages(addr, tt.geneve, tt.buffs, msgs, packet.GeneveFixedHeaderLength)
if got != len(tt.wantLens) {
@@ -299,9 +280,18 @@ func Test_linuxBatchingConn_coalesceMessages(t *testing.T) {
if gotLen != tt.wantLens[i] {
t.Errorf("len(msgs[%d].Buffers[0]) %d != %d", i, gotLen, tt.wantLens[i])
}
gotGSO, err := getGSOSize(msgs[i].OOB)
// coalesceMessages calls setGSOSizeInControl, which uses a cmsg
// type of UDP_SEGMENT, and getGSOSizeInControl scans for a cmsg
// type of UDP_GRO. Therefore, we have to use the lower-level
// getDataFromControl in order to specify the cmsg type of
// interest for this test.
data, err := getDataFromControl(msgs[i].OOB, unix.SOL_UDP, unix.UDP_SEGMENT, 2)
if err != nil {
t.Fatalf("msgs[%d] getGSOSize err: %v", i, err)
t.Fatalf("msgs[%d] getDataFromControl err: %v", i, err)
}
var gotGSO int
if len(data) >= 2 {
gotGSO = int(binary.NativeEndian.Uint16(data))
}
if gotGSO != tt.wantGSO[i] {
t.Errorf("msgs[%d] gsoSize %d != %d", i, gotGSO, tt.wantGSO[i])