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//go:build linux
package http
import (
"fmt"
"net"
"os"
"strconv"
)
func getSystemdListeners() (Listeners, error) {
pidStr := os.Getenv("LISTEN_PID")
fdStr := os.Getenv("LISTEN_FDS")
if pidStr == "" || fdStr == "" {
return nil, nil // Not running under systemd
}
pid, err := strconv.Atoi(pidStr)
if err != nil {
// Not our activation — another process might have inherited the env.
return nil, nil
}
if pid != os.Getpid() {
return nil, fmt.Errorf("LISTEN_PID %d does not match current PID %d", pid, os.Getpid())
}
defer func() {
_ = os.Unsetenv("LISTEN_PID")
_ = os.Unsetenv("LISTEN_FDS")
}()
nfds, err := strconv.ParseUint(fdStr, 10, 64)
if err != nil {
return nil, fmt.Errorf("invalid LISTEN_FDS: %w", err)
}
if nfds == 0 {
return nil, nil // Nothing to do
}
lns := make(Listeners, 0, nfds)
for i := range nfds {
fd := i + 3
file := os.NewFile(uintptr(fd), fmt.Sprintf("fd_%d", fd))
if file == nil {
return nil, fmt.Errorf("fd %d was nil", fd)
}
ln, err := net.FileListener(file)
if err != nil {
file.Close()
return nil, fmt.Errorf("failed to create listener from fd %d: %w", fd, err)
}
lns = append(lns, ln)
}
return lns, nil
}
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