[API CHANGE] Do not call getaddrinfo if we just want the hostname

Similiar to afc41a467fdfabb2cd0879be3e4f1879a1d1dc91 ,
don't call getaddrinfo in getLocalHostname which calls DNS.

This causes a lag when creating the lockfile on opening a document
if the network is flaky/disabled.
See tdf#97931 and tdf#47179 for some problems caused by this.

For the one case where it is expected to call DNS, add a separate function
to restore the old behavior.

The (semantic) [API CHANGE] is in osl_getLocalHostname,
it does no longer return a FQDN.

Change-Id: I43455715a474ff6770351d1ce007c28aeb08f32e
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/107554
Tested-by: Jenkins
Reviewed-by: Samuel Mehrbrodt <samuel.mehrbrodt@allotropia.de>

3 files changed, 46 insertions, 5 deletions

diff --git a/sal/inc/oslsocket.hxx b/sal/inc/oslsocket.hxx
new file mode 100644
index 000000000000..52260c263190
--- /dev/null
+++ b/sal/inc/oslsocket.hxx
@@ -0,0 +1,24 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4; fill-column: 100 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ */
+
+#pragma once
+
+#include <rtl/ustring.h>
+#include <osl/socket.h>
+
+/** Retrieve this machines hostname as fully qualified domain name (FQDN).
+    Note that this might be slower than calling osl_getLocalHostname
+    since DNS needs to be queried to determine the FQDN.
+    @param  strLocalHostname out-parameter. The string that receives the local host name.
+    @retval sal_True upon success
+    @retval sal_False
+*/
+oslSocketResult osl_getLocalHostnameFQDN(rtl_uString** strLocalHostname);
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab cinoptions=b1,g0,N-s cinkeys+=0=break: */
\ No newline at end of file
diff --git a/sal/osl/unx/file_url.cxx b/sal/osl/unx/file_url.cxx
index 54ec0c02ac46..ba5ccc766e6c 100644
--- a/sal/osl/unx/file_url.cxx
+++ b/sal/osl/unx/file_url.cxx
@@ -36,6 +36,7 @@
 #include <osl/file.hxx>
 #include <osl/security.hxx>
 #include <osl/socket.h>
+#include <oslsocket.hxx>
 #include <osl/diagnose.h>
 #include <osl/thread.h>
 #include <osl/process.h>
@@ -246,7 +247,7 @@ template<typename T> oslFileError getSystemPathFromFileUrl(
     if (url.indexOf('?', i) != -1 || url.indexOf('#', i) != -1)
         return osl_File_E_INVAL;
     // Handle authority, supporting a host of "localhost", "127.0.0.1", or the exact value (e.g.,
-    // not supporting an additional final dot, for simplicity) reported by osl_getLocalHostname
+    // not supporting an additional final dot, for simplicity) reported by osl_getLocalHostnameFQDN
     // (and, in each case, ignoring case of ASCII letters):
     if (url.getLength() - i >= 2 && url[i] == '/' && url[i + 1] == '/')
     {
@@ -265,7 +266,9 @@ template<typename T> oslFileError getSystemPathFromFileUrl(
                 != 0))
         {
             OUString hostname;
-            if (osl_getLocalHostname(&hostname.pData) != osl_Socket_Ok
+            // The 'file' URI Scheme does imply that we want a FQDN in this case
+            // See https://tools.ietf.org/html/rfc8089#section-3
+            if (osl_getLocalHostnameFQDN(&hostname.pData) != osl_Socket_Ok
                 || (rtl_ustr_compareIgnoreAsciiCase_WithLength(
                         url.pData->buffer + i, j - i, hostname.getStr(), hostname.getLength())
                     != 0))
diff --git a/sal/osl/unx/socket.cxx b/sal/osl/unx/socket.cxx
index 56a8f6cd63ac..0c93e2928500 100644
--- a/sal/osl/unx/socket.cxx
+++ b/sal/osl/unx/socket.cxx
@@ -36,6 +36,7 @@
 
 #include "sockimpl.hxx"
 #include "unixerrnostring.hxx"
+#include <oslsocket.hxx>
 
 /* defines for poll */
 #ifdef HAVE_POLL_H
@@ -865,9 +866,11 @@ void SAL_CALL osl_destroyHostAddr (oslHostAddr pAddr)
     }
 }
 
-oslSocketResult SAL_CALL osl_getLocalHostname(rtl_uString **ustrLocalHostname)
+namespace
+{
+oslSocketResult lcl_getLocalHostname(rtl_uString **ustrLocalHostname, bool bUseFQDN)
 {
-    static auto const init = []() -> std::pair<oslSocketResult, OUString> {
+    static auto const init = [bUseFQDN]() -> std::pair<oslSocketResult, OUString> {
             char LocalHostname[256] = "";
 
 #ifdef SYSV
@@ -887,7 +890,7 @@ oslSocketResult SAL_CALL osl_getLocalHostname(rtl_uString **ustrLocalHostname)
             LocalHostname[sizeof(LocalHostname)-1] = 0;
 
             /* check if we have an FQDN */
-            if (strchr(LocalHostname, '.') == nullptr)
+            if (bUseFQDN && strchr(LocalHostname, '.') == nullptr)
             {
                 oslHostAddr Addr;
 
@@ -915,6 +918,17 @@ oslSocketResult SAL_CALL osl_getLocalHostname(rtl_uString **ustrLocalHostname)
 
     return init.first;
 }
+}
+
+oslSocketResult SAL_CALL osl_getLocalHostname(rtl_uString **ustrLocalHostname)
+{
+    return lcl_getLocalHostname(ustrLocalHostname, false);
+}
+
+oslSocketResult osl_getLocalHostnameFQDN(rtl_uString **ustrLocalHostname)
+{
+    return lcl_getLocalHostname(ustrLocalHostname, true);
+}
 
 oslSocketAddr SAL_CALL osl_resolveHostname(rtl_uString *ustrHostname)
 {