config: enable passing -asmap an absolute file path

- allow passing an absolute file path to the -asmap config arg

- update the -asmap config help

- add a functional test in feature_asmap.py

src/init.cpp

@@ -475,7 +475,7 @@ std::string HelpMessage(HelpMessageMode mode)
 
     strUsage += HelpMessageGroup(_("Connection options:"));
     strUsage += HelpMessageOpt("-addnode=<ip>", _("Add a node to connect to and attempt to keep the connection open"));
-    strUsage += HelpMessageOpt("-asmap=<file>", strprintf("Specify asn mapping used for bucketing of the peers (default: %s). Path should be relative to the -datadir path.", DEFAULT_ASMAP_FILENAME);
+    strUsage += HelpMessageOpt("-asmap=<file>", strprintf("Specify asn mapping used for bucketing of the peers (default: %s). Relative paths will be prefixed by the net-specific datadir location.", DEFAULT_ASMAP_FILENAME));
     strUsage += HelpMessageOpt("-banscore=<n>", strprintf(_("Threshold for disconnecting misbehaving peers (default: %u)"), DEFAULT_BANSCORE_THRESHOLD));
     strUsage += HelpMessageOpt("-bantime=<n>", strprintf(_("Number of seconds to keep misbehaving peers from reconnecting (default: %u)"), DEFAULT_MISBEHAVING_BANTIME));
     strUsage += HelpMessageOpt("-bind=<addr>", _("Bind to given address and always listen on it. Use [host]:port notation for IPv6"));
@@ -1969,11 +1969,13 @@ bool AppInitMain()
 
     // Read asmap file if configured
     if (gArgs.IsArgSet("-asmap")) {
-        std::string asmap_file = gArgs.GetArg("-asmap", "");
-        if (asmap_file.empty()) {
-            asmap_file = DEFAULT_ASMAP_FILENAME;
+        fs::path asmap_path = fs::path(gArgs.GetArg("-asmap", ""));
+        if (asmap_path.empty()) {
+            asmap_path = DEFAULT_ASMAP_FILENAME;
+        }
+        if (!asmap_path.is_absolute()) {
+            asmap_path = GetDataDir() / asmap_path;
         }
-        const fs::path asmap_path = GetDataDir() / asmap_file;
         std::vector<bool> asmap = CAddrMan::DecodeAsmap(asmap_path);
         if (asmap.size() == 0) {
             UIError(strprintf(_("Could not find or parse specified asmap: '%s'"), asmap_path));

test/functional/feature_asmap.py

@@ -8,11 +8,13 @@
 
 1. `bitcoind` with no -asmap arg, using /16 prefix for IP bucketing
 
-2. `bitcoind -asmap=<relative path>`, using the unit test skeleton asmap
+2. `bitcoind -asmap=<absolute path>`, using the unit test skeleton asmap
 
-3. `bitcoind -asmap/-asmap=` with no file specified, using the default asmap
+3. `bitcoind -asmap=<relative path>`, using the unit test skeleton asmap
 
-4. `bitcoind -asmap` with no file specified, and a missing default asmap file
+4. `bitcoind -asmap/-asmap=` with no file specified, using the default asmap
+
+5. `bitcoind -asmap` with no file specified and a missing default asmap file
 
 The tests are order-independent. The slowest test (missing default asmap file)
 is placed last.
@@ -42,6 +44,15 @@ def test_without_asmap_arg(self):
         with self.node.assert_debug_log(['Using /16 prefix for IP bucketing']):
             self.start_node(0)
 
+    def test_asmap_with_absolute_path(self):
+        self.log.info('Test bitcoind -asmap=<absolute path>')
+        self.stop_node(0)
+        filename = os.path.join(self.datadir, 'my-map-file.map')
+        shutil.copyfile(self.asmap_raw, filename)
+        with self.node.assert_debug_log(expected_messages(filename)):
+            self.start_node(0, ['-asmap={}'.format(filename)])
+        os.remove(filename)
+
     def test_asmap_with_relative_path(self):
         self.log.info('Test bitcoind -asmap=<relative path>')
         self.stop_node(0)
@@ -74,6 +85,7 @@ def run_test(self):
         self.asmap_raw = os.path.join(os.path.dirname(os.path.realpath(__file__)), ASMAP)
 
         self.test_without_asmap_arg()
+        self.test_asmap_with_absolute_path()
         self.test_asmap_with_relative_path()
         self.test_default_asmap()
         #self.test_default_asmap_with_missing_file() // fixme