listenfd/listenfd.go (view raw)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 | package listenfd // import "alin.ovh/x/listenfd"
import (
"crypto/tls"
"net"
"os"
"strconv"
"github.com/Southclaws/fault"
"github.com/Southclaws/fault/fmsg"
"alin.ovh/x/log"
)
const firstFDFallback = 3
func GetListener(i uintptr, addr string, log *log.Logger) (l net.Listener, err error) {
l, err = getFDSocket(i)
if err != nil {
log.Warn("could not create listener from listenfd", "error", err)
}
log.Debug("listener from listenfd?", "passed", l != nil)
if l == nil {
l, err = net.Listen("tcp", addr)
if err != nil {
return nil, fault.Wrap(err, fmsg.With("could not create listener"))
}
}
return
}
func GetListenerTLS(
i uintptr,
addr string,
config *tls.Config,
log *log.Logger,
) (l net.Listener, err error) {
l, err = GetListener(i, addr, log)
if err != nil {
return nil, err
}
return tls.NewListener(l, config), nil
}
func getFDSocket(i uintptr) (net.Listener, error) {
fds, present, err := lookupEnvUintptr("LISTEN_FDS")
if !present {
return nil, nil
}
if err != nil {
return nil, err
}
fdStart, present, err := lookupEnvUintptr("LISTEN_FDS_FIRST_FD")
if !present {
fdStart = firstFDFallback
}
if i >= fds {
return nil, fault.Newf("only %d fds available, requested index %d", fds, i)
}
l, err := net.FileListener(os.NewFile(uintptr(i+fdStart), ""))
if err != nil {
return nil, fault.Wrap(err, fmsg.With("could not create listener"))
}
return l, nil
}
func lookupEnvUintptr(key string) (uintptr, bool, error) {
value, present := os.LookupEnv(key)
if !present {
return 0, false, nil
}
result, err := strconv.ParseUint(value, 10, 32)
if err != nil {
return 0, true, fault.Wrap(err, fmsg.Withf("could not parse %s", key))
}
return uintptr(result), true, nil
}
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