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net/sockopts,wgengine/magicsock: export socket buffer sizing logic (#16909)

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For eventual use by net/udprelay.Server

Updates tailscale/corp#31164

Signed-off-by: Jordan Whited <jordan@tailscale.com>
This commit is contained in:
Jordan Whited
2025-08-20 16:24:00 -07:00
committed by GitHub
parent b48d2de6ab
commit 641a90ea33
11 changed files with 119 additions and 52 deletions
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wgengine/magicsock/magicsock.go
+13 -13
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@@ -45,6 +45,7 @@ import (
"tailscale.com/net/packet"
"tailscale.com/net/ping"
"tailscale.com/net/portmapper"
"tailscale.com/net/sockopts"
"tailscale.com/net/sockstats"
"tailscale.com/net/stun"
"tailscale.com/net/tstun"
@@ -3857,20 +3858,19 @@ func (c *Conn) DebugForcePreferDERP(n int) {
c.netChecker.SetForcePreferredDERP(n)
}
// portableTrySetSocketBuffer sets SO_SNDBUF and SO_RECVBUF on pconn to socketBufferSize,
// logging an error if it occurs.
func portableTrySetSocketBuffer(pconn nettype.PacketConn, logf logger.Logf) {
if runtime.GOOS == "plan9" {
// Not supported. Don't try. Avoid logspam.
return
}
if c, ok := pconn.(*net.UDPConn); ok {
// Attempt to increase the buffer size, and allow failures.
if err := c.SetReadBuffer(socketBufferSize); err != nil {
logf("magicsock: failed to set UDP read buffer size to %d: %v", socketBufferSize, err)
// trySetSocketBuffer attempts to set SO_SNDBUFFORCE and SO_RECVBUFFORCE which
// can overcome the limit of net.core.{r,w}mem_max, but require CAP_NET_ADMIN.
// It falls back to the portable implementation if that fails, which may be
// silently capped to net.core.{r,w}mem_max.
func trySetSocketBuffer(pconn nettype.PacketConn, logf logger.Logf) {
directions := []sockopts.BufferDirection{sockopts.ReadDirection, sockopts.WriteDirection}
for _, direction := range directions {
forceErr, portableErr := sockopts.SetBufferSize(pconn, direction, socketBufferSize)
if forceErr != nil {
logf("magicsock: [warning] failed to force-set UDP %v buffer size to %d: %v; using kernel default values (impacts throughput only)", direction, socketBufferSize, forceErr)
}
if err := c.SetWriteBuffer(socketBufferSize); err != nil {
logf("magicsock: failed to set UDP write buffer size to %d: %v", socketBufferSize, err)
if portableErr != nil {
logf("magicsock: failed to set UDP %v buffer size to %d: %v", direction, socketBufferSize, portableErr)
}
}
}