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NetworkAddressResolver: cache needs to be locked

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It is not a good idea to have a thread get an address from the request
cache, while another thread is deleting said address as the cache has
grown too large. Add a lock around the cache access to make it safe.
This commit is contained in:
Adrien Destugues 2017-11-21 22:11:03 +01:00
parent 4c99992724
commit b140a1c340
2 changed files with 16 additions and 4 deletions
headers/os/net
NetworkAddressResolver.h
src/kits/network/libnetapi
NetworkAddressResolver.cpp

4
headers/os/net/NetworkAddressResolver.h

@ -1,11 +1,12 @@
/*
* Copyright 2010, Haiku, Inc. All Rights Reserved.
* Copyright 2010-2017, Haiku, Inc. All Rights Reserved.
* Distributed under the terms of the MIT License.
*/
#ifndef _NETWORK_ADDRESS_RESOLVER_H
#define _NETWORK_ADDRESS_RESOLVER_H
#include <Locker.h>
#include <ObjectList.h>
#include <Referenceable.h>
#include <String.h>
@ -103,6 +104,7 @@ private:
BReference<const BNetworkAddressResolver> fResolver;
};
static BLocker sCacheLock;
static BObjectList<CacheEntry> sCacheMap;
};

16
src/kits/network/libnetapi/NetworkAddressResolver.cpp

@ -1,5 +1,6 @@
/*
* Copyright 2010-2011, Axel Dörfler, axeld@pinc-software.de.
* Copyright 2015-2017, Adrien Destugues, pulkomandy@pulkomandy.tk.
* Distributed under the terms of the MIT License.
*/
@ -9,6 +10,7 @@
#include <errno.h>
#include <netdb.h>
#include <Autolock.h>
#include <NetworkAddress.h>
@ -296,6 +298,8 @@ BNetworkAddressResolver::Resolve(int family, const char* address,
BNetworkAddressResolver::Resolve(int family, const char* address,
const char* service, uint32 flags)
{
BAutolock locker(&sCacheLock);
// TODO it may be faster to use an hash map to have faster lookup of the
// cache. However, we also need to access the cache by LRU, and for that
// a doubly-linked list is better. We should have these two share the same
@ -312,17 +316,23 @@ BNetworkAddressResolver::Resolve(int family, const char* address,
}
}
// Cache miss! Unlock the cache while we perform the costly address
// resolution
locker.Unlock();
BNetworkAddressResolver* resolver = new(std::nothrow)
BNetworkAddressResolver(family, address, service, flags);
if (resolver != NULL && resolver->InitCheck() == B_OK) {
CacheEntry* entry = new(std::nothrow) CacheEntry(family, address,
service, flags, resolver);
locker.Lock();
// TODO adjust capacity. Chrome uses 256 entries with a timeout of
// 1 minute, IE uses 1000 entries with a timeout of 30 seconds.
if (sCacheMap.CountItems() > 255)
delete sCacheMap.RemoveItemAt(0);
CacheEntry* entry = new(std::nothrow) CacheEntry(family, address,
service, flags, resolver);
if (entry)
sCacheMap.AddItem(entry, sCacheMap.CountItems());
}
@ -330,6 +340,6 @@ BNetworkAddressResolver::Resolve(int family, const char* address,
return BReference<const BNetworkAddressResolver>(resolver, true);
}
BLocker BNetworkAddressResolver::sCacheLock("DNS cache");
BObjectList<BNetworkAddressResolver::CacheEntry>
BNetworkAddressResolver::sCacheMap;