mirror of
https://github.com/libp2p/go-reuseport.git
synced 2025-09-28 11:42:10 +08:00
1fdf8e59b2
This ensures that, even if we can't bind to a random port on localhost for some reason, we can still correctly detect if reuse port is supported. Thanks to @Coderlane for suggesting this fix. fixes #24
48 lines
1.1 KiB
Go
48 lines
1.1 KiB
Go
// +build darwin freebsd dragonfly netbsd openbsd linux
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package reuseport
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import (
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"golang.org/x/sys/unix"
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"sync"
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"syscall"
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"time"
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sockaddrnet "github.com/libp2p/go-sockaddr/net"
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)
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var (
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hasReusePort bool
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didReusePort sync.Once
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)
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// Available returns whether or not SO_REUSEPORT is available in the OS.
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// It does so by attepting to open a tcp socket, setting the option, and
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// checking ENOPROTOOPT on error. After checking, the decision is cached
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// for the rest of the process run.
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func available() bool {
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didReusePort.Do(checkReusePort)
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return hasReusePort
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}
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func checkReusePort() {
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// there may be fluke reasons to fail to open a socket.
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// so we give it 5 shots. if not, give up and call it not avail.
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for i := 0; i < 5; i++ {
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// try to setup a TCP socket.
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fd, err := socket(sockaddrnet.AF_INET, sockaddrnet.SOCK_STREAM, sockaddrnet.IPPROTO_TCP)
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if err == nil {
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unix.Close(fd)
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hasReusePort = true
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return
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}
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if errno, ok := err.(syscall.Errno); ok && errno == unix.ENOPROTOOPT {
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return // :( that's all folks.
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}
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// not an errno? or not ENOPROTOOPT? retry.
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time.Sleep(20 * time.Millisecond) // wait a bit
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}
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}
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