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// +build linux darwin dragonfly freebsd netbsd openbsd rumprun
// Package reuseport provides TCP net.Listener with SO_REUSEPORT support.
//
// SO_REUSEPORT allows linear scaling server performance on multi-CPU servers.
// See https://www.nginx.com/blog/socket-sharding-nginx-release-1-9-1/ for more details :)
//
// The package is based on https://github.com/kavu/go_reuseport .
package reuseport
import (
"errors"
"fmt"
"net"
"os"
"syscall"
)
func getSockaddr(network, addr string) (sa syscall.Sockaddr, soType int, err error) {
// TODO: add support for tcp and tcp6 networks.
if network != "tcp4" {
return nil, -1, errors.New("only tcp4 network is supported")
}
tcpAddr, err := net.ResolveTCPAddr(network, addr)
if err != nil {
return nil, -1, err
}
var sa4 syscall.SockaddrInet4
sa4.Port = tcpAddr.Port
copy(sa4.Addr[:], tcpAddr.IP.To4())
return &sa4, syscall.AF_INET, nil
}
// ErrNoReusePort is returned if the OS doesn't support SO_REUSEPORT.
type ErrNoReusePort struct {
err error
}
// Error implements error interface.
func (e *ErrNoReusePort) Error() string {
return fmt.Sprintf("The OS doesn't support SO_REUSEPORT: %s", e.err)
}
// Listen returns TCP listener with SO_REUSEPORT option set.
//
// Only tcp4 network is supported.
//
// ErrNoReusePort error is returned if the system doesn't support SO_REUSEPORT.
func Listen(network, addr string) (l net.Listener, err error) {
var (
soType, fd int
file *os.File
sockaddr syscall.Sockaddr
)
if sockaddr, soType, err = getSockaddr(network, addr); err != nil {
return nil, err
}
syscall.ForkLock.RLock()
fd, err = syscall.Socket(soType, syscall.SOCK_STREAM, syscall.IPPROTO_TCP)
if err == nil {
syscall.CloseOnExec(fd)
}
syscall.ForkLock.RUnlock()
if err != nil {
return nil, err
}
if err = syscall.SetsockoptInt(fd, syscall.SOL_SOCKET, syscall.SO_REUSEADDR, 1); err != nil {
syscall.Close(fd)
return nil, err
}
if err = syscall.SetsockoptInt(fd, syscall.SOL_SOCKET, soReusePort, 1); err != nil {
syscall.Close(fd)
return nil, &ErrNoReusePort{err}
}
if err = syscall.Bind(fd, sockaddr); err != nil {
syscall.Close(fd)
return nil, err
}
if err = syscall.Listen(fd, syscall.SOMAXCONN); err != nil {
syscall.Close(fd)
return nil, err
}
name := fmt.Sprintf("reuseport.%d.%s.%s", os.Getpid(), network, addr)
file = os.NewFile(uintptr(fd), name)
if l, err = net.FileListener(file); err != nil {
file.Close()
return nil, err
}
if err = file.Close(); err != nil {
l.Close()
return nil, err
}
return l, err
}
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