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wgengine/netstack: use buffer pools for UDP packet forwarding

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Use buffer pools for UDP packet forwarding to prepare for increasing the
forwarded UDP packet size for peer path MTU discovery.

Updates #311

Co-authored-by: Brad Fitzpatrick <bradfitz@tailscale.com>
Signed-off-by: Val <valerie@tailscale.com>
This commit is contained in:
Val 2023-09-19 14:55:09 +02:00 committed by valscale
parent 81e8335e23
commit fb2f3e4741
1 changed files with 17 additions and 5 deletions
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22
wgengine/netstack/netstack.go
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@ -1059,10 +1059,15 @@ func (ns *Impl) acceptUDP(r *udp.ForwarderRequest) {
go ns.forwardUDP(c, srcAddr, dstAddr)
}
// Buffer pool for forwarding UDP packets.
var udpBufPool = &sync.Pool{
New: func() any {
b := make([]byte, maxUDPPacketSize)
return &b
},
}
func (ns *Impl) handleMagicDNSUDP(srcAddr netip.AddrPort, c *gonet.UDPConn) {
// In practice, implementations are advised not to exceed 512 bytes
// due to fragmenting. Just to be sure, we bump all the way to the MTU.
var maxUDPReqSize = tstun.DefaultMTU()
// Packets are being generated by the local host, so there should be
// very, very little latency. 150ms was chosen as something of an upper
// bound on resource usage, while hopefully still being long enough for
@ -1070,7 +1075,10 @@ func (ns *Impl) handleMagicDNSUDP(srcAddr netip.AddrPort, c *gonet.UDPConn) {
const readDeadline = 150 * time.Millisecond
defer c.Close()
q := make([]byte, maxUDPReqSize)
bufp := udpBufPool.Get().(*[]byte)
defer udpBufPool.Put(bufp)
q := *bufp
// libresolv from glibc is quite adamant that transmitting multiple DNS
// requests down the same UDP socket is valid. To support this, we read
@ -1183,7 +1191,11 @@ func startPacketCopy(ctx context.Context, cancel context.CancelFunc, dst net.Pac
}
go func() {
defer cancel() // tear down the other direction's copy
pkt := make([]byte, maxUDPPacketSize)
bufp := udpBufPool.Get().(*[]byte)
defer udpBufPool.Put(bufp)
pkt := *bufp
for {
select {
case <-ctx.Done():