Function CWallet::KeepKey requires locking as it has concurrent access to database and member nKeysLeftSinceAutoBackup.
Avoid data race when reading setInventoryTxToSend size by locking the read. If locking happens after the read, the size may change.
Lock cs_mnauth when reading verifiedProRegTxHash.
Make fRPCRunning atomic as it can be read/written from different threads simultaneously.
Make m_masternode_iqr_connection atomic as it can be read/written from different threads simultaneously.
Use a recursive mutex to synchronize concurrent access to quorumVvec.
Make m_masternode_connection atomic as it can be read/written from different threads simultaneously.
Make m_masternode_probe_connection atomic as it can be read/written from different threads simultaneously.
Use a recursive mutex in order to lock access to activeMasterNode.
Use a recursive mutex to synchronize concurrent access to skShare.
Guarded all mnauth fields of a CNode.
Co-authored-by: UdjinM6 <UdjinM6@users.noreply.github.com>
fa8ced32a60dea37ac169241cf9a1f708ef46c4b doc: Mention blocksonly in reduce-traffic.md, unhide option (MarcoFalke)
fa320de79faaca2b088fcbe7f76701faa9bff236 test: Add test for p2p_blocksonly (MarcoFalke)
fa3872e7b4540857261aed948b94b6b2bfdbc3d1 test: Format predicate source as multiline on error (MarcoFalke)
fa1dce7329d3e74d46ab98b93772b1832a3f1819 net: Rename ::fRelayTxes to ::g_relay_txes (MarcoFalke)
Pull request description:
This is de-facto no longer hidden
ACKs for commit fa8ced:
jamesob:
utACK fa8ced32a6
Tree-SHA512: 474fbdee6cbd035ed9068a066b6056c1f909ec7520be0417820fcd1672ab3069b53f55c5147968978d9258fd3a3933fe1a9ef8e4f6e14fb6ebbd79701a0a1245
a36d97d866e8a11f205d07c624ace7c3d1a2ded8 Default -whitelistforcerelay to off (Suhas Daftuar)
Pull request description:
No one seems to use this "feature", and at any rate the behavior of relaying transactions when they violate local policy is error-prone, if we ever consider changing the ban behavior of our software from one version to the next.
Defaulting this to off means that users who use -whitelist won't be unexpectedly surprised by this interaction. If anyone is still relying on this feature, it can still be explicitly turned on.
Tree-SHA512: 52650ad464a728d1648f496751e3f713077ea3a1de7278ed03531b2e8723e63cf2f6f41b56c98c0f73ffa22c36e01d9170b409ab452c737aca35b7ecd7a6b448
# Conflicts:
# doc/release-notes.md
# src/validation.h
# test/functional/p2p_segwit.py
3b05f0f70fbaee5b5eaa0d1b6f3b9d32f44410bb Reformat p2p_permissions.py (nicolas.dorier)
ce7eac3cb0e7d301db75de24e9a7b0af93c61311 [Fix] The default whitelistrelay should be true (nicolas.dorier)
Pull request description:
I thought `whitelistrelay` default was `false` when it is `true`.
The root of the issue come from the fact that all references to `DEFAULT_` are not in the scope of this file, so hard coding of default values are used everywhere in `net.cpp`. I think that in a separate PR we should fix that more fundamentally everywhere.
ACKs for top commit:
promag:
ACK 3b05f0f70fbaee5b5eaa0d1b6f3b9d32f44410bb.
Sjors:
re-ACK 3b05f0f70fbaee5b5eaa0d1b6f3b9d32f44410bb
Tree-SHA512: f4a75f986fa2adf1a5f1c91605e0d261f7ac5ac8535fb05437d83b8392dbcf5cc1a47d755adcf8ad8dc67a88de28060187200fd3ce06545261a5c7ec0fea831a
c5b404e8f1973afe071a07c63ba1038eefe13f0f Add functional tests for flexible whitebind/list (nicolas.dorier)
d541fa391844f658bd7035659b5b16695733dd56 Replace the use of fWhitelisted by permission checks (nicolas.dorier)
ecd5cf7ea4c3644a30092100ffc399e30e193275 Do not disconnect peer for asking mempool if it has NO_BAN permission (nicolas.dorier)
e5b26deaaa6842f7dd7c4537ede000f965ea0189 Make whitebind/whitelist permissions more flexible (nicolas.dorier)
Pull request description:
# Motivation
In 0.19, bloom filter will be disabled by default. I tried to make [a PR](https://github.com/bitcoin/bitcoin/pull/16176) to enable bloom filter for whitelisted peers regardless of `-peerbloomfilters`.
Bloom filter have non existent privacy and server can omit filter's matches. However, both problems are completely irrelevant when you connect to your own node. If you connect to your own node, bloom filters are the most bandwidth efficient way to synchronize your light client without the need of some middleware like Electrum.
It is also a superior alternative to BIP157 as it does not require to maintain an additional index and it would work well on pruned nodes.
When I attempted to allow bloom filters for whitelisted peer, my proposal has been NACKed in favor of [a more flexible approach](https://github.com/bitcoin/bitcoin/pull/16176#issuecomment-500762907) which should allow node operator to set fine grained permissions instead of a global `whitelisted` attribute.
Doing so will also make follow up idea very easy to implement in a backward compatible way.
# Implementation details
The PR propose a new format for `--white{list,bind}`. I added a way to specify permissions granted to inbound connection matching `white{list,bind}`.
The following permissions exists:
* ForceRelay
* Relay
* NoBan
* BloomFilter
* Mempool
Example:
* `-whitelist=bloomfilter@127.0.0.1/32`.
* `-whitebind=bloomfilter,relay,noban@127.0.0.1:10020`.
If no permissions are specified, `NoBan | Mempool` is assumed. (making this PR backward compatible)
When we receive an inbound connection, we calculate the effective permissions for this peer by fetching the permissions granted from `whitelist` and add to it the permissions granted from `whitebind`.
To keep backward compatibility, if no permissions are specified in `white{list,bind}` (e.g. `--whitelist=127.0.0.1`) then parameters `-whitelistforcerelay` and `-whiterelay` will add the permissions `ForceRelay` and `Relay` to the inbound node.
`-whitelistforcerelay` and `-whiterelay` are ignored if the permissions flags are explicitly set in `white{bind,list}`.
# Follow up idea
Based on this PR, other changes become quite easy to code in a trivially review-able, backward compatible way:
* Changing `connect` at rpc and config file level to understand the permissions flags.
* Changing the permissions of a peer at RPC level.
ACKs for top commit:
laanwj:
re-ACK c5b404e8f1973afe071a07c63ba1038eefe13f0f
Tree-SHA512: adfefb373d09e68cae401247c8fc64034e305694cdef104bdcdacb9f1704277bd53b18f52a2427a5cffdbc77bda410d221aed252bc2ece698ffbb9cf1b830577
eea02be70e Add locking annotation for vNodes. vNodes is guarded by cs_vNodes. (practicalswift)
Pull request description:
Add locking annotation for `vNodes`. `vNodes` is guarded by `cs_vNodes`.
Tree-SHA512: b1e18be22ba5b9dd153536380321b09b30a75a20575f975af9af94164f51982b32267ba0994e77c801513b59da05d923a974a9d2dfebdac48024c4bda98b53af
0297be61a Allow connections from misbehavior banned peers. (Gregory Maxwell)
Pull request description:
This allows incoming connections from peers which are only banned
due to an automatic misbehavior ban if doing so won't fill inbound.
These peers are preferred for eviction when inbound fills, but may
still be kept if they fall into the protected classes. This
eviction preference lasts the entire life of the connection even
if the ban expires.
If they misbehave again they'll still get disconnected.
The main purpose of banning on misbehavior is to prevent our
connections from being wasted on unhelpful peers such as ones
running incompatible consensus rules. For inbound peers this
can be better accomplished with eviction preferences.
A secondary purpose was to reduce resource waste from repeated
abuse but virtually any attacker can get a nearly unlimited
supply of addresses, so disconnection is about the best we can
do.
This can reduce the potential from negative impact due to incorrect misbehaviour bans.
Tree-SHA512: 03bc8ec8bae365cc437daf70000c8f2edc512e37db821bc4e0fafa6cf56cc185e9ab40453aa02445f48d6a2e3e7268767ca2017655aca5383108416f1e2cf20f
18185b57c32d0a43afeca4c125b9352c692923e9 scripted-diff: batch-recase BanMan variables (Carl Dong)
c2e04d37f3841d109c1fe60693f9622e2836cc29 banman: Add, use CBanEntry ctor that takes ban reason (Carl Dong)
1ffa4ce27d4ea6c1067d8984455df97994c7713e banman: reformulate nBanUtil calculation (Carl Dong)
daae598feb034f2f56e0b00ecfb4854d693d3641 banman: add thread annotations and mark members const where possible (Cory Fields)
84fc3fbd0304a7d6e660bf783c84bed2dd415141 scripted-diff: batch-rename BanMan members (Cory Fields)
af3503d903b1a608cd212e2d74b274103199078c net: move BanMan to its own files (Cory Fields)
d0469b2e9386a7a4b268cb9725347e7517acace6 banman: pass in default ban time as a parameter (Cory Fields)
2e56702ecedd83c4b7cb8de9de5c437c8c08e645 banman: pass the banfile path in (Cory Fields)
4c0d961eb0d7825a1e6f8389d7f5545114ee18c6 banman: create and split out banman (Cory Fields)
83c1ea2e5e66b8a83072e3d5ad6a4ced406eb1ba net: split up addresses/ban dumps in preparation for moving them (Cory Fields)
136bd7926c72659dd277a7b795ea17f72e523338 tests: remove member connman/peerLogic in TestingSetup (Cory Fields)
7cc2b9f6786f9bc33853220551eed33ca6b7b7b2 net: Break disconnecting out of Ban() (Cory Fields)
Pull request description:
**Old English à la Beowulf**
```
Banman wæs bréme --blaéd wíde sprang--
Connmanes eafera Coreum in.
aéglaéca léodum forstandan
Swá bealdode bearn Connmanes
guma gúðum cúð gódum daédum·
dréah æfter dóme· nealles druncne slóg
```
**Modern English Translation**
```
Banman was famed --his renown spread wide--
Conman's hier, in Core-land.
against the evil creature defend the people
Thus he was bold, the son of Connman
man famed in war, for good deeds;
he led his life for glory, never, having drunk, slew
```
--
With @theuni's blessing, here is Banman, rebased. Original PR: https://github.com/bitcoin/bitcoin/pull/11457
--
Followup PRs:
1. Give `CNode` a `Disconnect` method ([source](https://github.com/bitcoin/bitcoin/pull/14605#discussion_r248065847))
2. Add a comment to `std::atomic_bool fDisconnect` in `net.h` that setting this to true will cause the node to be disconnected the next time `DisconnectNodes()` runs ([source](https://github.com/bitcoin/bitcoin/pull/14605#discussion_r248384309))
Tree-SHA512: 9c207edbf577415c22c9811113e393322d936a843d4ff265186728152a67c057779ac4d4f27b895de9729f7a53e870f828b9ebc8bcdab757520c2aebe1e9be35
d6b076c17bc7d513243711563b262524ef0ba74c Drop IsLimited in favor of IsReachable (Ben Woosley)
Pull request description:
These two methods have had the same meaning, but inverted, since
110b62f069. Having one name for a single
concept simplifies the code.
This is a follow-up to #15051.
/cc #7553
Tree-SHA512: 347ceb9e2a55ea06f4c01226411c7bbcade09dd82130e4c59d0824ecefd960875938022edbe5d4bfdf12b0552c9b4cb78b09a688284d707119571daf4eb371b4
8313fa8e8112e429e104b7e7fd48e5e6e359b82e gui: Set CConnman byte counters earlier to avoid uninitialized reads (Russell Yanofsky)
Pull request description:
Initialize CConnman byte counters during construction, so GetTotalBytesRecv() and GetTotalBytesSent() methods don't return garbage before Start() is called.
Change shouldn't have any effect outside of the GUI. It just fixes a race condition during a qt test that was observed on travis: https://travis-ci.org/bitcoin/bitcoin/jobs/634989685
ACKs for top commit:
MarcoFalke:
ACK 8313fa8e8112e429e104b7e7fd48e5e6e359b82e
promag:
ACK 8313fa8e8112e429e104b7e7fd48e5e6e359b82e.
Tree-SHA512: 97c246da4e28e6e0b48f685b840f96746ad75c4b157a692201c6c4702db328a88ead8507d8e1b4e608aa1882513174ec60cf3977c31b7a9d76678cc9f49b45f8
fa8548c5d1 net: Remove unused unsanitized user agent string CNode::strSubVer (MarcoFalke)
Pull request description:
I fail to see a use case for this unsanitized byte array. In fact this can easily be confused with `cleanSubVer` and be displayed to the user (or logged) by a simple typo that is hard to find in review.
Further reading: https://btcinformation.org/en/developer-reference#version
ACKs for commit fa8548:
promag:
utACK fa8548c, good catch.
practicalswift:
utACK fa8548c5d13957f57f9b1e20e03002600962f7f0
sipa:
utACK fa8548c5d13957f57f9b1e20e03002600962f7f0
Tree-SHA512: 3c3ff1504d1583ad099df9a6aa761458a82ec48a58ef7aaa9b5679a5281dd1b59036ba2932ed708488951a565b669a3083ef70be5a58472ff8677b971162ae2f
* partial backport 18544: net: limit BIP37 filter lifespan (active between 'filterload'..'filterclear')
Previously, a default match-everything bloom filter was set for every peer,
i.e. even before receiving a 'filterload' message and after receiving a
'filterclear' message code branches checking for the existence of the filter
by testing the pointer "pfilter" were _always_ executed.
* net: Match the backport PR a bit more
Co-authored-by: xdustinface <xdustinfacex@gmail.com>
2b3ea39 Polish interfaces around PeerLogicValidation (Vasil Dimov)
Pull request description:
Silence the following compiler warning:
/usr/include/c++/v1/memory:2285:5: error: delete called on non-final 'PeerLogicValidation' that has
virtual functions but non-virtual destructor [-Werror,-Wdelete-non-virtual-dtor]
delete __ptr;
^
/usr/include/c++/v1/memory:2598:7: note: in instantiation of member function
'std::__1::default_delete<PeerLogicValidation>::operator()' requested here
__ptr_.second()(__tmp);
^
init.cpp:201:15: note: in instantiation of member function 'std::__1::unique_ptr<PeerLogicValidation,
std::__1::default_delete<PeerLogicValidation> >::reset' requested here
peerLogic.reset();
^
Tree-SHA512: 0e5ead0da2da76a5276cd45e28ddfa4b92cc7225fa154a2662aad88e7210acd17b81431c98e90a2c7be08d39f8689f1d9982cdb18297d4bb0b6195ae40c7ec17
* Backport Statoshi
This backports some of https://github.com/jlopp/statoshi.
Missing stuff: README.md and client name changes, segwit and fee estimation stats.
Fix RejectCodeToString
Fix copy-paste mistake s/InvalidBlockFound/InvalidChainFound/
* Merge #16728: move-only: move coins statistics utils out of RPC
8a3b2eb17572ca2131778d52cc25ec359470a90f move-only: move coins statistics utils out of RPC (James O'Beirne)
Pull request description:
This is part of the [assumeutxo project](https://github.com/bitcoin/bitcoin/projects/11):
Parent PR: #15606
Issue: #15605
Specification: https://github.com/jamesob/assumeutxo-docs/tree/master/proposal
---
In the short-term, this move-only commit will help with fuzzing (https://github.com/bitcoin/bitcoin/pull/15606#issuecomment-524482297). Later, these procedures will be used to compute statistics (particularly a content hash) for UTXO sets coming in from snapshots.
Most easily reviewed with `git ... --color-moved=dimmed_zebra`. A nice follow-up would be adding unittests, which I'll do if nobody else gets around to it.
ACKs for top commit:
MarcoFalke:
ACK 8a3b2eb17572ca2131778d52cc25ec359470a90f, checked --color-moved=dimmed-zebra
Tree-SHA512: a187d2f7590ad2450b8e8fa3d038c80a04fc3d903618c24222d7e3172250ce51badea35860c86101f2ba266eb4354e6efb8d7d508b353f29276e4665a1efdf74
* Fix 16728
* Modernize StatsdClient
- Reuse some functionality from netbase
- Switch from GetRand to FastRandomContext
- Drop `using namespace std` and add `// namespace statsd`
* Introduce PeriodicStats and make StatsdClient configurable via -stats<smth> (enabled/host/port/ns/period)
* Move/rename tip stats from CheckBlock to ConnectBlock
* Add new false positives to lint-format-strings.py
* Add snprintf in statsd_client to the list of known violations in lint-locale-dependence.sh
* Fix incorrect include guard
* Use bracket syntax includes
* Replace magic numbers with defaults
* Move connection stats calculation into its own function
And bail out early if stats are disabled
* assert in PeriodicStats
Co-authored-by: PastaPastaPasta <6443210+PastaPastaPasta@users.noreply.github.com>
Co-authored-by: MarcoFalke <falke.marco@gmail.com>
Co-authored-by: PastaPastaPasta <6443210+PastaPastaPasta@users.noreply.github.com>
4b6ab02122d225818f6c6a4b4ef343d2c90e6d55 Remove unused argument to ProcessGetBlockData(...) (practicalswift)
c469ecf22e8ab55acf2cf8fc6fcf34415b541f76 net: Remove unused interrupt from SendMessages (fanquake)
Pull request description:
Discussed very briefly with cfields.
Includes 65b4400 from #13554 as it's a similar refactor.
Tree-SHA512: 45cd64208a5c8164242db74e6687e9344ea592bab5e7f9ba8e1bb449057fc908ec9d8b8523748a68426e4a4304e3388a138cd834698b39837b2149b72beefdc9
* Revert "Only call SendMessages when ProcessMessages did some work or when some time passed"
This reverts commit 24ead62905.
* Only skip SendMessages() for fMasternode connections
* Merge #12381: Remove more boost threads
004f999 boost: drop boost threads for [alert|block|wallet]notify (Cory Fields)
0827267 boost: drop boost threads from torcontrol (Cory Fields)
ba91724 boost: remove useless threadGroup parameter from Discover (Cory Fields)
f26866b boost: drop boost threads for upnp (Cory Fields)
Pull request description:
This doesn't completely get rid of boost::thread, but this batch should be easy to review, and leaves us with only threadGroup (scheduler + scriptcheck) remaining.
Note to reviewers: The upnp diff changes a bunch of whitespace, it's much more clear with 'git diff -w'
Tree-SHA512: 5a356798d0785f93ed143d1f0afafe890bc82f0d470bc969473da2d2aa78bcb9b096f7ba11b92564d546fb447d4bd0d347e7842994ea0170aafd53fda7e0a66e
* fix using std::thread
Signed-off-by: pasta <pasta@dashboost.org>
* Switch to std::thread in NotifyTransactionLock
* Move StopTorControl call from Shutdown to PrepareShutdown
Co-authored-by: Wladimir J. van der Laan <laanwj@gmail.com>
Co-authored-by: UdjinM6 <UdjinM6@users.noreply.github.com>
48b37db50 make peertimeout a debug argument, remove error message translation (Zain Iqbal Allarakhia)
8042bbfbf p2p: allow p2ptimeout to be configurable, speed up slow test (Zain Iqbal Allarakhia)
Pull request description:
**Summary:**
1. _Primary_: Adds a `debug_only=true` flag for peertimeout, defaults to 60 sec., the current hard-coded setting.
2. _Secondary_: Drastically speeds up `p2p_timeout.py` test.
3. _Secondary_: Tests that the correct code path is being tested by adding log assertions to the test.
**Rationale:**
- P2P timeout was hard-coded: make it explicitly specified and configurable, instead of a magic number.
- Addresses #13518; `p2p_timeout.py` takes 4 sec. to run instead of 61 sec.
- Makes `p2p_timeout.py` more explicit. Previously, we relied on a comment to inform us of the timeout amount being tested. Now it is specified directly in the test via passing in the new arg; `-peertimeout=3`.
- Opens us up to testing more P2P scenarios; oftentimes slow tests are the reason we don't test.
**Locally verified changes:**
_With Proposed Change (4.7 sec.):_
```
$ time ./test/functional/p2p_timeouts.py
2018-11-19T00:04:19.077000Z TestFramework (INFO): Initializing test directory /tmp/testhja7g2n7
2018-11-19T00:04:23.479000Z TestFramework (INFO): Stopping nodes
2018-11-19T00:04:23.683000Z TestFramework (INFO): Cleaning up /tmp/testhja7g2n7 on exit
2018-11-19T00:04:23.683000Z TestFramework (INFO): Tests successful
real 0m4.743s
```
_Currently on master (62.8 sec.):_
```
$ time ./test/functional/p2p_timeouts.py
2018-11-19T00:06:10.948000Z TestFramework (INFO): Initializing test directory /tmp/test6mo6k21h
2018-11-19T00:07:13.376000Z TestFramework (INFO): Stopping nodes
2018-11-19T00:07:13.631000Z TestFramework (INFO): Cleaning up /tmp/test6mo6k21h on exit
2018-11-19T00:07:13.631000Z TestFramework (INFO): Tests successful
real 1m2.836s
```
_Error message demonstrated for new argument `-peertimeout`:_
```
$ ./bitcoind -peertimeout=-5
...
Error: peertimeout cannot be configured with a negative value.
```
Tree-SHA512: ff7a244ebea54c4059407bf4fb86465714e6a79cef5d2bcaa22cfe831a81761aaf597ba4d5172fc2ec12266f54712216fc41b5d24849e5d9dab39ba6f09e3a2a
66b3fc5437 Skip stale tip checking if outbound connections are off or if reindexing. (Gregory Maxwell)
Pull request description:
I got tired of the pointless stale tip notices in reindex and on nodes with connections disabled.
Tree-SHA512: eb07d9c5c787ae6dea02cdd1d67a48a36a30adc5ccc74d6f1c0c7364d404dc8848b35d2b8daf5283f7c8f36f1a3c463aacb190d70a22d1fe796a301bb1f03228
e254ff5d53b79bee29203b965fca572f218bff54 Introduce a maximum size for locators. (Gregory Maxwell)
Pull request description:
The largest sensible size for a locator is log in the number of blocks.
But, as noted by Coinr8d on BCT a maximum size message could encode a
hundred thousand locators. If height were used to limit the messages
that could open new attacks where peers on long low diff forks would
get disconnected and end up stuck.
Ideally, nodes first first learn to limit the size of locators they
send before limiting what would be processed, but common implementations
back off with an exponent of 2 and have an implicit limit of 2^32
blocks, so they already cannot produce locators over some size.
Locators are cheap to process so allowing a few more is harmless,
so this sets the maximum to 64-- which is enough for blockchains
with 2^64 blocks before the get overhead starts increasing.
Tree-SHA512: da28df9c46c988980da861046c62e6e7f93d0eaab3083d32e408d1062f45c00316d5e1754127e808c1feb424fa8e00e5a91aea2cc3b80326b71c148696f7cdb3
FindNode is only interested in active connections, especially when called
from OpenNetworkConnection. Connections which are about to get disconnected
and removed should be treated as if they are not existent anymore, as
otherwise there is a small race between disconnecting and reconnecting
nodes, causing OpenNetworkConnection to return early.
* Merge #10387: Eventually connect to NODE_NETWORK_LIMITED peers
eb91835 Add setter for g_initial_block_download_completed (Jonas Schnelli)
3f56df5 [QA] add NODE_NETWORK_LIMITED address relay and sync test (Jonas Schnelli)
158e1a6 [QA] fix mininode CAddress ser/deser (Jonas Schnelli)
fa999af [QA] Allow addrman loopback tests (add debug option -addrmantest) (Jonas Schnelli)
6fe57bd Connect to peers signaling NODE_NETWORK_LIMITED when out-of-IBD (Jonas Schnelli)
31c45a9 Accept addresses with NODE_NETWORK_LIMITED flag (Jonas Schnelli)
Pull request description:
Eventually connect to peers signalling NODE_NETWORK_LIMITED if we are out of IBD.
Accept and relay NODE_NETWORK_LIMITED peers in addrman.
Tree-SHA512: 8a238fc97f767f81cae1866d6cc061390f23a72af4a711d2f7158c77f876017986abb371d213d1c84019eef7be4ca951e8e6f83fda36769c4e1a1d763f787037
Signed-off-by: Pasta <pasta@dashboost.org>
# Conflicts:
# src/init.cpp
# src/protocol.h
# test/functional/node_network_limited.py
* remove witness
Signed-off-by: Pasta <pasta@dashboost.org>
* fix test expecting witness flag
Signed-off-by: Pasta <pasta@dashboost.org>
Co-authored-by: Wladimir J. van der Laan <laanwj@gmail.com>
Instead of selecting every socket in every SocketHandler iteration, we will
now track which nodes are known to have pending receivable data and/or
have empty send buffers.
Each time recv fails to fill a whole receive buffer, fHasRecvData is
set to false so that the socket is added to the receive select set
in the next iteration. When that socket is signalled through select/poll,
fHasRecvData is set to true again and remains true until a future recv
fails.
Each time send fails to send a full message, fCanSendData is set to false
so that the socket is added to the send select set in the next iteration.
At the same time, nodes which have pending messages to send are tracked
in mapNodesWithDataToSend, so that SocketHandler knows for which nodes
SocketSendData must be invoked.
