net: require P2P binds to succeed

In the Tor case, this prevents us from telling the Tor daemon to send
our incoming connections from the Tor network to an address where we
do not listen (we tried to listen but failed probably because another
application is already listening).

In the other cases (IPv4/IPv6 binds) this also prevents unpleasant
surprises caused by continuing operations even on bind failure. For
example, another application may be listening on portX, bitcoind tries
to bind on portX and portY, only succeeds with portY and continues
operation leaving the user thinking that his bitcoind is listening on
portX whereas another application is listening (the error message in
the log could easily be missed).

Avoid having the functional testing framework start multiple `bitcoind`s
that try to listen on the same `127.0.0.1:18445` (Tor listen for
regtest) if `bind_to_localhost_only` is set to `False`.

Also fix a typo in `test-shell.md` related to `bind_to_localhost_only`.

Fixes bitcoin/bitcoin#22727

Author: vasild

src/net.cpp

@@ -3198,24 +3198,36 @@ bool CConnman::Bind(const CService& addr_, unsigned int flags, NetPermissionFlag
 
 bool CConnman::InitBinds(const Options& options)
 {
-    bool fBound = false;
     for (const auto& addrBind : options.vBinds) {
-        fBound |= Bind(addrBind, BF_REPORT_ERROR, NetPermissionFlags::None);
+        if (!Bind(addrBind, BF_REPORT_ERROR, NetPermissionFlags::None)) {
+            return false;
+        }
     }
     for (const auto& addrBind : options.vWhiteBinds) {
-        fBound |= Bind(addrBind.m_service, BF_REPORT_ERROR, addrBind.m_flags);
+        if (!Bind(addrBind.m_service, BF_REPORT_ERROR, addrBind.m_flags)) {
+            return false;
+        }
     }
     for (const auto& addr_bind : options.onion_binds) {
-        fBound |= Bind(addr_bind, BF_REPORT_ERROR | BF_DONT_ADVERTISE, NetPermissionFlags::None);
+        if (!Bind(addr_bind, BF_REPORT_ERROR | BF_DONT_ADVERTISE, NetPermissionFlags::None)) {
+            return false;
+        }
     }
     if (options.bind_on_any) {
+        // Don't consider errors to bind on IPv6 "::" fatal because the host OS
+        // may not have IPv6 support and the user did not explicitly ask us to
+        // bind on that.
+        const CService ipv6_any{in6_addr(IN6ADDR_ANY_INIT), GetListenPort()}; // ::
+        Bind(ipv6_any, BF_NONE, NetPermissionFlags::None);
+
         struct in_addr inaddr_any;
         inaddr_any.s_addr = htonl(INADDR_ANY);
-        struct in6_addr inaddr6_any = IN6ADDR_ANY_INIT;
-        fBound |= Bind(CService(inaddr6_any, GetListenPort()), BF_NONE, NetPermissionFlags::None);
-        fBound |= Bind(CService(inaddr_any, GetListenPort()), !fBound ? BF_REPORT_ERROR : BF_NONE, NetPermissionFlags::None);
+        const CService ipv4_any{inaddr_any, GetListenPort()}; // 0.0.0.0
+        if (!Bind(ipv4_any, BF_REPORT_ERROR, NetPermissionFlags::None)) {
+            return false;
+        }
     }
-    return fBound;
+    return true;
 }
 
 bool CConnman::Start(CScheduler& scheduler, const Options& connOptions)

test/functional/test-shell.md

@@ -169,7 +169,7 @@ can be called after the TestShell is shut down.
 
 | Test parameter key | Default Value | Description |
 |---|---|---|
-| `bind_to_localhost_only` | `True` | Binds bitcoind RPC services to `127.0.0.1` if set to `True`.|
+| `bind_to_localhost_only` | `True` | Binds bitcoind P2P services to `127.0.0.1` if set to `True`.|
 | `cachedir` | `"/path/to/bitcoin/test/cache"` | Sets the bitcoind datadir directory. |
 | `chain`  | `"regtest"` | Sets the chain-type for the underlying test bitcoind processes. |
 | `configfile` | `"/path/to/bitcoin/test/config.ini"` | Sets the location of the test framework config file. |

test/functional/test_framework/test_node.py

@@ -39,6 +39,7 @@
     rpc_url,
     wait_until_helper_internal,
     p2p_port,
+    tor_port,
 )
 
 BITCOIND_PROC_WAIT_TIMEOUT = 60
@@ -88,8 +89,11 @@ def __init__(self, i, datadir_path, *, chain, rpchost, timewait, timeout_factor,
         self.coverage_dir = coverage_dir
         self.cwd = cwd
         self.descriptors = descriptors
+        self.has_explicit_bind = False
         if extra_conf is not None:
             append_config(self.datadir_path, extra_conf)
+            # Remember if there is bind=... in the config file.
+            self.has_explicit_bind = any(e.startswith("bind=") for e in extra_conf)
         # Most callers will just need to add extra args to the standard list below.
         # For those callers that need more flexibility, they can just set the args property directly.
         # Note that common args are set in the config file (see initialize_datadir)
@@ -210,6 +214,17 @@ def start(self, extra_args=None, *, cwd=None, stdout=None, stderr=None, env=None
         if extra_args is None:
             extra_args = self.extra_args
 
+        # If listening and no -bind is given, then bitcoind would bind P2P ports on
+        # 0.0.0.0:P and 127.0.0.1:18445 (for incoming Tor connections), where P is
+        # a unique port chosen by the test framework and configured as port=P in
+        # bitcoin.conf. To avoid collisions on 127.0.0.1:18445, change it to
+        # 127.0.0.1:tor_port().
+        will_listen = all(e != "-nolisten" and e != "-listen=0" for e in extra_args)
+        has_explicit_bind = self.has_explicit_bind or any(e.startswith("-bind=") for e in extra_args)
+        if will_listen and not has_explicit_bind:
+            extra_args.append(f"-bind=0.0.0.0:{p2p_port(self.index)}")
+            extra_args.append(f"-bind=127.0.0.1:{tor_port(self.index)}=onion")
+
         self.use_v2transport = "-v2transport=1" in extra_args or (self.default_to_v2 and "-v2transport=0" not in extra_args)
 
         # Add a new stdout and stderr file each time bitcoind is started

test/functional/test_framework/util.py

@@ -309,9 +309,9 @@ def sha256sum_file(filename):
 
 # The maximum number of nodes a single test can spawn
 MAX_NODES = 12
-# Don't assign rpc or p2p ports lower than this
+# Don't assign p2p, rpc or tor ports lower than this
 PORT_MIN = int(os.getenv('TEST_RUNNER_PORT_MIN', default=11000))
-# The number of ports to "reserve" for p2p and rpc, each
+# The number of ports to "reserve" for p2p, rpc and tor, each
 PORT_RANGE = 5000
 
 
@@ -351,7 +351,11 @@ def p2p_port(n):
 
 
 def rpc_port(n):
-    return PORT_MIN + PORT_RANGE + n + (MAX_NODES * PortSeed.n) % (PORT_RANGE - 1 - MAX_NODES)
+    return p2p_port(n) + PORT_RANGE
+
+
+def tor_port(n):
+    return p2p_port(n) + PORT_RANGE * 2
 
 
 def rpc_url(datadir, i, chain, rpchost):