// Copyright (c) 2012 The Chromium Authors. All rights reserved. // Use of this source code is governed by a BSD-style license that can be // found in the LICENSE file. #include "net/dns/host_resolver_proc.h" #include "build/build_config.h" #include "base/logging.h" #include "base/sys_byteorder.h" #include "base/threading/scoped_blocking_call.h" #include "net/base/address_list.h" #include "net/base/net_errors.h" #include "net/base/sys_addrinfo.h" #include "net/dns/dns_reloader.h" #include "net/dns/dns_util.h" #if defined(OS_OPENBSD) #define AI_ADDRCONFIG 0 #endif namespace net { namespace { bool IsAllLocalhostOfOneFamily(const struct addrinfo* ai) { bool saw_v4_localhost = false; bool saw_v6_localhost = false; for (; ai != NULL; ai = ai->ai_next) { switch (ai->ai_family) { case AF_INET: { const struct sockaddr_in* addr_in = reinterpret_cast(ai->ai_addr); if ((base::NetToHost32(addr_in->sin_addr.s_addr) & 0xff000000) == 0x7f000000) saw_v4_localhost = true; else return false; break; } case AF_INET6: { const struct sockaddr_in6* addr_in6 = reinterpret_cast(ai->ai_addr); if (IN6_IS_ADDR_LOOPBACK(&addr_in6->sin6_addr)) saw_v6_localhost = true; else return false; break; } default: NOTREACHED(); return false; } } return saw_v4_localhost != saw_v6_localhost; } } // namespace HostResolverProc* HostResolverProc::default_proc_ = NULL; HostResolverProc::HostResolverProc(HostResolverProc* previous) { SetPreviousProc(previous); // Implicitly fall-back to the global default procedure. if (!previous) SetPreviousProc(default_proc_); } HostResolverProc::~HostResolverProc() { } int HostResolverProc::ResolveUsingPrevious( const std::string& host, AddressFamily address_family, HostResolverFlags host_resolver_flags, AddressList* addrlist, int* os_error) { if (previous_proc_.get()) { return previous_proc_->Resolve( host, address_family, host_resolver_flags, addrlist, os_error); } // Final fallback is the system resolver. return SystemHostResolverCall(host, address_family, host_resolver_flags, addrlist, os_error); } void HostResolverProc::SetPreviousProc(HostResolverProc* proc) { HostResolverProc* current_previous = previous_proc_.get(); previous_proc_ = NULL; // Now that we've guaranteed |this| is the last proc in a chain, we can // detect potential cycles using GetLastProc(). previous_proc_ = (GetLastProc(proc) == this) ? current_previous : proc; } void HostResolverProc::SetLastProc(HostResolverProc* proc) { GetLastProc(this)->SetPreviousProc(proc); } // static HostResolverProc* HostResolverProc::GetLastProc(HostResolverProc* proc) { if (proc == NULL) return NULL; HostResolverProc* last_proc = proc; while (last_proc->previous_proc_.get() != NULL) last_proc = last_proc->previous_proc_.get(); return last_proc; } // static HostResolverProc* HostResolverProc::SetDefault(HostResolverProc* proc) { HostResolverProc* old = default_proc_; default_proc_ = proc; return old; } // static HostResolverProc* HostResolverProc::GetDefault() { return default_proc_; } int SystemHostResolverCall(const std::string& host, AddressFamily address_family, HostResolverFlags host_resolver_flags, AddressList* addrlist, int* os_error) { // |host| should be a valid domain name. HostResolverImpl::Resolve has checks // to fail early if this is not the case. DCHECK(IsValidDNSDomain(host)); if (os_error) *os_error = 0; struct addrinfo* ai = NULL; struct addrinfo hints = {0}; switch (address_family) { case ADDRESS_FAMILY_IPV4: hints.ai_family = AF_INET; break; case ADDRESS_FAMILY_IPV6: hints.ai_family = AF_INET6; break; case ADDRESS_FAMILY_UNSPECIFIED: hints.ai_family = AF_UNSPEC; break; default: NOTREACHED(); hints.ai_family = AF_UNSPEC; } #if defined(OS_WIN) // DO NOT USE AI_ADDRCONFIG ON WINDOWS. // // The following comment in is the best documentation I found // on AI_ADDRCONFIG for Windows: // Flags used in "hints" argument to getaddrinfo() // - AI_ADDRCONFIG is supported starting with Vista // - default is AI_ADDRCONFIG ON whether the flag is set or not // because the performance penalty in not having ADDRCONFIG in // the multi-protocol stack environment is severe; // this defaulting may be disabled by specifying the AI_ALL flag, // in that case AI_ADDRCONFIG must be EXPLICITLY specified to // enable ADDRCONFIG behavior // // Not only is AI_ADDRCONFIG unnecessary, but it can be harmful. If the // computer is not connected to a network, AI_ADDRCONFIG causes getaddrinfo // to fail with WSANO_DATA (11004) for "localhost", probably because of the // following note on AI_ADDRCONFIG in the MSDN getaddrinfo page: // The IPv4 or IPv6 loopback address is not considered a valid global // address. // See http://crbug.com/5234. // // OpenBSD does not support it, either. hints.ai_flags = 0; #else hints.ai_flags = AI_ADDRCONFIG; #endif // On Linux AI_ADDRCONFIG doesn't consider loopback addreses, even if only // loopback addresses are configured. So don't use it when there are only // loopback addresses. if (host_resolver_flags & HOST_RESOLVER_LOOPBACK_ONLY) hints.ai_flags &= ~AI_ADDRCONFIG; if (host_resolver_flags & HOST_RESOLVER_CANONNAME) hints.ai_flags |= AI_CANONNAME; // Restrict result set to only this socket type to avoid duplicates. hints.ai_socktype = SOCK_STREAM; // This function can block for a long time. Use ScopedBlockingCall to increase // the current thread pool's capacity and thus avoid reducing CPU usage by the // current process during that time. base::ScopedBlockingCall scoped_blocking_call(base::BlockingType::WILL_BLOCK); #if defined(OS_POSIX) && !defined(OS_MACOSX) && !defined(OS_OPENBSD) && \ !defined(OS_ANDROID) && !defined(OS_FUCHSIA) DnsReloaderMaybeReload(); #endif int err = getaddrinfo(host.c_str(), NULL, &hints, &ai); bool should_retry = false; // If the lookup was restricted (either by address family, or address // detection), and the results where all localhost of a single family, // maybe we should retry. There were several bugs related to these // issues, for example http://crbug.com/42058 and http://crbug.com/49024 if ((hints.ai_family != AF_UNSPEC || hints.ai_flags & AI_ADDRCONFIG) && err == 0 && IsAllLocalhostOfOneFamily(ai)) { if (host_resolver_flags & HOST_RESOLVER_DEFAULT_FAMILY_SET_DUE_TO_NO_IPV6) { hints.ai_family = AF_UNSPEC; should_retry = true; } if (hints.ai_flags & AI_ADDRCONFIG) { hints.ai_flags &= ~AI_ADDRCONFIG; should_retry = true; } } if (should_retry) { if (ai != NULL) { freeaddrinfo(ai); ai = NULL; } err = getaddrinfo(host.c_str(), NULL, &hints, &ai); } if (err) { #if defined(OS_WIN) err = WSAGetLastError(); #endif // Return the OS error to the caller. if (os_error) *os_error = err; // If the call to getaddrinfo() failed because of a system error, report // it separately from ERR_NAME_NOT_RESOLVED. #if defined(OS_WIN) if (err != WSAHOST_NOT_FOUND && err != WSANO_DATA) return ERR_NAME_RESOLUTION_FAILED; #elif defined(OS_POSIX) && !defined(OS_FREEBSD) if (err != EAI_NONAME && err != EAI_NODATA) return ERR_NAME_RESOLUTION_FAILED; #endif return ERR_NAME_NOT_RESOLVED; } #if defined(OS_ANDROID) // Workaround for Android's getaddrinfo leaving ai==NULL without an error. // http://crbug.com/134142 if (ai == NULL) return ERR_NAME_NOT_RESOLVED; #endif *addrlist = AddressList::CreateFromAddrinfo(ai); freeaddrinfo(ai); return OK; } SystemHostResolverProc::SystemHostResolverProc() : HostResolverProc(NULL) {} int SystemHostResolverProc::Resolve(const std::string& hostname, AddressFamily address_family, HostResolverFlags host_resolver_flags, AddressList* addr_list, int* os_error) { return SystemHostResolverCall(hostname, address_family, host_resolver_flags, addr_list, os_error); } SystemHostResolverProc::~SystemHostResolverProc() {} } // namespace net