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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_linux.go
-29
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@@ -13,7 +13,6 @@ import (
"net"
"net/netip"
"strings"
"syscall"
"time"
"github.com/mdlayher/socket"
@@ -28,7 +27,6 @@ import (
"tailscale.com/types/ipproto"
"tailscale.com/types/key"
"tailscale.com/types/logger"
"tailscale.com/types/nettype"
)
const (
@@ -489,30 +487,3 @@ func printSockaddr(sa unix.Sockaddr) string {
return fmt.Sprintf("unknown(%T)", sa)
}
}
// 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) {
if c, ok := pconn.(*net.UDPConn); ok {
var errRcv, errSnd error
rc, err := c.SyscallConn()
if err == nil {
rc.Control(func(fd uintptr) {
errRcv = syscall.SetsockoptInt(int(fd), syscall.SOL_SOCKET, syscall.SO_RCVBUFFORCE, socketBufferSize)
if errRcv != nil {
logf("magicsock: [warning] failed to force-set UDP read buffer size to %d: %v; using kernel default values (impacts throughput only)", socketBufferSize, errRcv)
}
errSnd = syscall.SetsockoptInt(int(fd), syscall.SOL_SOCKET, syscall.SO_SNDBUFFORCE, socketBufferSize)
if errSnd != nil {
logf("magicsock: [warning] failed to force-set UDP write buffer size to %d: %v; using kernel default values (impacts throughput only)", socketBufferSize, errSnd)
}
})
}
if err != nil || errRcv != nil || errSnd != nil {
portableTrySetSocketBuffer(pconn, logf)
}
}
}