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caddyhttp: Fix listener overlap detection on Linux

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Sigh, apparently Linux is incapable of distinguishing host interfaces
in socket addresses, even though it works fine on Mac. I suppose we just
have to assume that any listeners with the same port are the same
address, completely ignoring the host interface on Linux... oh well.
This commit is contained in:
Matthew Holt 2020-04-26 22:28:49 -06:00
parent 768383a610
commit 83c85c53f5
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GPG key ID: 2A349DD577D586A5
1 changed files with 25 additions and 2 deletions
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27
modules/caddyhttp/server.go
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@ -21,6 +21,7 @@ import (
"net"
"net/http"
"net/url"
"runtime"
"strings"
"time"
@ -307,8 +308,30 @@ func (s *Server) hasListenerAddress(fullAddr string) bool {
continue
}
// host must be the same and port must fall within port range
if (thisAddrs.Host == laddrs.Host) &&
// Apparently, Linux requires all bound ports to be distinct
// *regardless of host interface* even if the addresses are
// in fact different; binding "192.168.0.1:9000" and then
// ":9000" will fail for ":9000" because "address is already
// in use" even though it's not, and the same bindings work
// fine on macOS. I also found on Linux that listening on
// "[::]:9000" would fail with a similar error, except with
// the address "0.0.0.0:9000", as if deliberately ignoring
// that I specified the IPv6 interface explicitly. This seems
// to be a major bug in the Linux network stack and I don't
// know why it hasn't been fixed yet, so for now we have to
// special-case ourselves around Linux like a doting parent.
// The second issue seems very similar to a discussion here:
// https://github.com/nodejs/node/issues/9390
//
// This is very easy to reproduce by creating an HTTP server
// that listens to both addresses or just one with a host
// interface; or for a more confusing reproduction, try
// listening on "127.0.0.1:80" and ":443" and you'll see
// the error, if you take away the GOOS condition below.
//
// So, an address is equivalent if the port is in the port
// range, and if not on Linux, the host is the same... sigh.
if (runtime.GOOS == "linux" || thisAddrs.Host == laddrs.Host) &&
(laddrs.StartPort <= thisAddrs.EndPort) &&
(laddrs.StartPort >= thisAddrs.StartPort) {
return true