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/* SPDX-License-Identifier: MIT
*
* Copyright (C) 2017-2025 WireGuard LLC. All Rights Reserved.
*/
package conn
import (
"fmt"
"runtime"
"syscall"
"golang.org/x/sys/unix"
)
// Taken from go/src/internal/syscall/unix/kernel_version_linux.go
func kernelVersion() (major, minor int) {
var uname unix.Utsname
if err := unix.Uname(&uname); err != nil {
return
}
var (
values [2]int
value, vi int
)
for _, c := range uname.Release {
if '0' <= c && c <= '9' {
value = (value * 10) + int(c-'0')
} else {
// Note that we're assuming N.N.N here.
// If we see anything else, we are likely to mis-parse it.
values[vi] = value
vi++
if vi >= len(values) {
break
}
value = 0
}
}
return values[0], values[1]
}
func init() {
controlFns = append(controlFns,
// Attempt to set the socket buffer size beyond net.core.{r,w}mem_max by
// using SO_*BUFFORCE. This requires CAP_NET_ADMIN, and is allowed here to
// fail silently - the result of failure is lower performance on very fast
// links or high latency links.
func(network, address string, c syscall.RawConn) error {
return c.Control(func(fd uintptr) {
// Set up to *mem_max
_ = unix.SetsockoptInt(int(fd), unix.SOL_SOCKET, unix.SO_RCVBUF, socketBufferSize)
_ = unix.SetsockoptInt(int(fd), unix.SOL_SOCKET, unix.SO_SNDBUF, socketBufferSize)
// Set beyond *mem_max if CAP_NET_ADMIN
_ = unix.SetsockoptInt(int(fd), unix.SOL_SOCKET, unix.SO_RCVBUFFORCE, socketBufferSize)
_ = unix.SetsockoptInt(int(fd), unix.SOL_SOCKET, unix.SO_SNDBUFFORCE, socketBufferSize)
})
},
// Enable receiving of the packet information (IP_PKTINFO for IPv4,
// IPV6_PKTINFO for IPv6) that is used to implement sticky socket support.
func(network, address string, c syscall.RawConn) error {
var err error
switch network {
case "udp4":
if runtime.GOOS != "android" {
c.Control(func(fd uintptr) {
err = unix.SetsockoptInt(int(fd), unix.IPPROTO_IP, unix.IP_PKTINFO, 1)
})
}
case "udp6":
c.Control(func(fd uintptr) {
if runtime.GOOS != "android" {
err = unix.SetsockoptInt(int(fd), unix.IPPROTO_IPV6, unix.IPV6_RECVPKTINFO, 1)
if err != nil {
return
}
}
err = unix.SetsockoptInt(int(fd), unix.IPPROTO_IPV6, unix.IPV6_V6ONLY, 1)
})
default:
err = fmt.Errorf("unhandled network: %s: %w", network, unix.EINVAL)
}
return err
},
// Attempt to enable UDP_GRO
func(network, address string, c syscall.RawConn) error {
// Kernels below 5.12 are missing 98184612aca0 ("net:
// udp: Add support for getsockopt(..., ..., UDP_GRO,
// ..., ...);"), which means we can't read this back
// later. We could pipe the return value through to
// the rest of the code, but UDP_GRO is kind of buggy
// anyway, so just gate this here.
major, minor := kernelVersion()
if major < 5 || (major == 5 && minor < 12) {
return nil
}
c.Control(func(fd uintptr) {
_ = unix.SetsockoptInt(int(fd), unix.IPPROTO_UDP, unix.UDP_GRO, 1)
})
return nil
},
)
}
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