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/* $Id: HostDnsServiceLinux.cpp $ */
/** @file
* Linux specific DNS information fetching.
*/
/*
* Copyright (C) 2013-2020 Oracle Corporation
*
* This file is part of VirtualBox Open Source Edition (OSE), as
* available from http://www.virtualbox.org. This file is free software;
* you can redistribute it and/or modify it under the terms of the GNU
* General Public License (GPL) as published by the Free Software
* Foundation, in version 2 as it comes in the "COPYING" file of the
* VirtualBox OSE distribution. VirtualBox OSE is distributed in the
* hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
*/
#include <iprt/assert.h>
#include <iprt/errcore.h>
#include <iprt/initterm.h>
#include <iprt/file.h>
#include <iprt/log.h>
#include <iprt/stream.h>
#include <iprt/string.h>
#include <iprt/semaphore.h>
#include <iprt/thread.h>
#include <errno.h>
#include <poll.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <linux/limits.h>
/* Workaround for <sys/cdef.h> defining __flexarr to [] which beats us in
* struct inotify_event (char name __flexarr). */
#include <sys/cdefs.h>
#undef __flexarr
#define __flexarr [0]
#include <sys/inotify.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <string>
#include <vector>
#include "../HostDnsService.h"
static int g_DnsMonitorStop[2];
static const std::string g_EtcFolder = "/etc";
static const std::string g_ResolvConf = "resolv.conf";
static const std::string g_ResolvConfFullPath = "/etc/resolv.conf";
class FileDescriptor
{
public:
FileDescriptor(int d = -1):fd(d){}
virtual ~FileDescriptor() {
if (fd != -1)
close(fd);
}
int fileDescriptor() const {return fd;}
protected:
int fd;
};
class AutoNotify:public FileDescriptor
{
public:
AutoNotify()
{
FileDescriptor::fd = inotify_init();
AssertReturnVoid(FileDescriptor::fd != -1);
}
};
struct InotifyEventWithName
{
struct inotify_event e;
char name[NAME_MAX];
};
HostDnsServiceLinux::~HostDnsServiceLinux()
{
}
HRESULT HostDnsServiceLinux::init(HostDnsMonitorProxy *pProxy)
{
return HostDnsServiceResolvConf::init(pProxy, "/etc/resolv.conf");
}
int HostDnsServiceLinux::monitorThreadShutdown(RTMSINTERVAL uTimeoutMs)
{
RT_NOREF(uTimeoutMs);
send(g_DnsMonitorStop[0], "", 1, 0);
/** @todo r=andy Do we have to wait for something here? Can this fail? */
return VINF_SUCCESS;
}
int HostDnsServiceLinux::monitorThreadProc(void)
{
AutoNotify a;
int rc = socketpair(AF_LOCAL, SOCK_DGRAM, 0, g_DnsMonitorStop);
AssertMsgReturn(rc == 0, ("socketpair: failed (%d: %s)\n", errno, strerror(errno)), E_FAIL);
FileDescriptor stopper0(g_DnsMonitorStop[0]);
FileDescriptor stopper1(g_DnsMonitorStop[1]);
pollfd polls[2];
RT_ZERO(polls);
polls[0].fd = a.fileDescriptor();
polls[0].events = POLLIN;
polls[1].fd = g_DnsMonitorStop[1];
polls[1].events = POLLIN;
onMonitorThreadInitDone();
int wd[2];
wd[0] = wd[1] = -1;
/* inotify inialization */
wd[0] = inotify_add_watch(a.fileDescriptor(),
g_ResolvConfFullPath.c_str(), IN_CLOSE_WRITE|IN_DELETE_SELF);
/**
* If /etc/resolv.conf exists we want to listen for movements: because
* # mv /etc/resolv.conf ...
* won't arm IN_DELETE_SELF on wd[0] instead it will fire IN_MOVE_FROM on wd[1].
*
* Because on some distributions /etc/resolv.conf is link, wd[0] can't detect deletion,
* it's recognizible on directory level (wd[1]) only.
*/
wd[1] = inotify_add_watch(a.fileDescriptor(), g_EtcFolder.c_str(),
wd[0] == -1 ? IN_MOVED_TO|IN_CREATE : IN_MOVED_FROM|IN_DELETE);
struct InotifyEventWithName combo;
while(true)
{
rc = poll(polls, 2, -1);
if (rc == -1)
continue;
AssertMsgReturn( ((polls[0].revents & (POLLERR|POLLNVAL)) == 0)
&& ((polls[1].revents & (POLLERR|POLLNVAL)) == 0),
("Debug Me"), VERR_INTERNAL_ERROR);
if (polls[1].revents & POLLIN)
return VINF_SUCCESS; /* time to shutdown */
if (polls[0].revents & POLLIN)
{
RT_ZERO(combo);
ssize_t r = read(polls[0].fd, static_cast<void *>(&combo), sizeof(combo));
RT_NOREF(r);
if (combo.e.wd == wd[0])
{
if (combo.e.mask & IN_CLOSE_WRITE)
{
readResolvConf();
}
else if (combo.e.mask & IN_DELETE_SELF)
{
inotify_rm_watch(a.fileDescriptor(), wd[0]); /* removes file watcher */
inotify_add_watch(a.fileDescriptor(), g_EtcFolder.c_str(),
IN_MOVED_TO|IN_CREATE); /* alter folder watcher */
}
else if (combo.e.mask & IN_IGNORED)
{
wd[0] = -1; /* we want receive any events on this watch */
}
else
{
/**
* It shouldn't happen, in release we will just ignore in debug
* we will have to chance to look at into inotify_event
*/
AssertMsgFailed(("Debug Me!!!"));
}
}
else if (combo.e.wd == wd[1])
{
if ( combo.e.mask & IN_MOVED_FROM
|| combo.e.mask & IN_DELETE)
{
if (g_ResolvConf == combo.e.name)
{
/**
* Our file has been moved so we should change watching mode.
*/
inotify_rm_watch(a.fileDescriptor(), wd[0]);
wd[1] = inotify_add_watch(a.fileDescriptor(), g_EtcFolder.c_str(),
IN_MOVED_TO|IN_CREATE);
AssertMsg(wd[1] != -1,
("It shouldn't happen, further investigation is needed\n"));
}
}
else
{
AssertMsg(combo.e.mask & (IN_MOVED_TO|IN_CREATE),
("%RX32 event isn't expected, we are waiting for IN_MOVED|IN_CREATE\n",
combo.e.mask));
if (g_ResolvConf == combo.e.name)
{
AssertMsg(wd[0] == -1, ("We haven't removed file watcher first\n"));
/* alter folder watcher*/
wd[1] = inotify_add_watch(a.fileDescriptor(), g_EtcFolder.c_str(),
IN_MOVED_FROM|IN_DELETE);
AssertMsg(wd[1] != -1, ("It shouldn't happen.\n"));
wd[0] = inotify_add_watch(a.fileDescriptor(),
g_ResolvConfFullPath.c_str(),
IN_CLOSE_WRITE | IN_DELETE_SELF);
AssertMsg(wd[0] != -1, ("Adding watcher to file (%s) has been failed!\n",
g_ResolvConfFullPath.c_str()));
/* Notify our listeners */
readResolvConf();
}
}
}
else
{
/* It shouldn't happen */
AssertMsgFailed(("Shouldn't happen! Please debug me!"));
}
}
}
}
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