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init: fixes file descriptor accounting #30065

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init: fixes file descriptor accounting #30065

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e09dded
init: fixes fd accounting regarding poll/select
sr-gi May 8, 2024
0a7030d
init: improves file descriptors accounting and docs
sr-gi May 8, 2024
fe76929
init: error out if -maxconnections is negative
sr-gi May 24, 2024
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41 changes: 24 additions & 17 deletions src/init.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -142,11 +142,12 @@ static constexpr bool DEFAULT_STOPAFTERBLOCKIMPORT{false};
// Win32 LevelDB doesn't use filedescriptors, and the ones used for
// accessing block files don't count towards the fd_set size limit
// anyway.
#define MIN_CORE_FILEDESCRIPTORS 0
#define MIN_LEVELDB_FDS 0
#else
#define MIN_CORE_FILEDESCRIPTORS 150
#define MIN_LEVELDB_FDS 150
#endif

static const int MIN_CORE_FDS = MIN_LEVELDB_FDS + NUM_FDS_MESSAGE_CAPTURE;
static const char* DEFAULT_ASMAP_FILENAME="ip_asn.map";

/**
Expand Down Expand Up @@ -820,7 +821,7 @@ namespace { // Variables internal to initialization process only

int nMaxConnections;
int nUserMaxConnections;
int nFD;
int available_fds;
ServiceFlags nLocalServices = ServiceFlags(NODE_NETWORK_LIMITED | NODE_WITNESS);
int64_t peer_connect_timeout;
std::set<BlockFilterType> g_enabled_filter_types;
Expand Down Expand Up @@ -967,24 +968,30 @@ bool AppInitParameterInteraction(const ArgsManager& args)
return InitError(Untranslated("Cannot set -listen=0 together with -listenonion=1"));
}

// Make sure enough file descriptors are available
// Make sure enough file descriptors are available. We need to reserve enough FDs to account for the bare minimum,
// plus all manual connections and all bound interfaces. Any remainder will be available for connection sockets

// Number of bound interfaces (we have at least one)
int nBind = std::max(nUserBind, size_t(1));
// Maximum number of connections with other nodes, this accounts for all types of outbounds and inbounds except for manual
nUserMaxConnections = args.GetIntArg("-maxconnections", DEFAULT_MAX_PEER_CONNECTIONS);
nMaxConnections = std::max(nUserMaxConnections, 0);

nFD = RaiseFileDescriptorLimit(nMaxConnections + MIN_CORE_FILEDESCRIPTORS + MAX_ADDNODE_CONNECTIONS + nBind + NUM_FDS_MESSAGE_CAPTURE);
if (nUserMaxConnections < 0){
return InitError(Untranslated("-maxconnections must be greater or equal than zero"));
}
// Reserve enough FDs to account for the bare minimum, plus any manual connections, plus the bound interfaces
int min_required_fds = MIN_CORE_FDS + MAX_ADDNODE_CONNECTIONS + nBind;

#ifdef USE_POLL
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int fd_max = nFD;
#else
int fd_max = FD_SETSIZE;
// Try raising the FD limit to what we need (available_fds may be smaller than the requested amount if this fails)
available_fds = RaiseFileDescriptorLimit(nUserMaxConnections + min_required_fds);
// If we are using select instead of poll, our actual limit may be even smaller
#ifndef USE_POLL
available_fds = std::min(FD_SETSIZE, available_fds);
#endif
if (available_fds < min_required_fds)
return InitError(strprintf(_("Not enough file descriptors available. %d available, %d required."), available_fds, min_required_fds));

// Trim requested connection counts, to fit into system limitations
// <int> in std::min<int>(...) to work around FreeBSD compilation issue described in #2695
nMaxConnections = std::max(std::min<int>(nMaxConnections, fd_max - nBind - MIN_CORE_FILEDESCRIPTORS - MAX_ADDNODE_CONNECTIONS - NUM_FDS_MESSAGE_CAPTURE), 0);
if (nFD < MIN_CORE_FILEDESCRIPTORS)
return InitError(_("Not enough file descriptors available."));
nMaxConnections = std::min(nFD - MIN_CORE_FILEDESCRIPTORS - MAX_ADDNODE_CONNECTIONS - NUM_FDS_MESSAGE_CAPTURE, nMaxConnections);
nMaxConnections = std::min(available_fds - min_required_fds, nUserMaxConnections);

if (nMaxConnections < nUserMaxConnections)
InitWarning(strprintf(_("Reducing -maxconnections from %d to %d, because of system limitations."), nUserMaxConnections, nMaxConnections));
Expand Down Expand Up @@ -1130,7 +1137,7 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
return false;
}

LogPrintf("Using at most %i automatic connections (%i file descriptors available)\n", nMaxConnections, nFD);
LogPrintf("Using at most %i automatic connections (%i file descriptors available)\n", nMaxConnections, available_fds);

// Warn about relative -datadir path.
if (args.IsArgSet("-datadir") && !args.GetPathArg("-datadir").is_absolute()) {
Expand Down