Merge bitcoin/bitcoin#27480: doc: Improve documentation of rpcallowip

c8e0664 doc: Improve documentation of rpcallowip rpchelp (willcl-ark)

Pull request description:

  Closes #21070

  v21.0 introduced a behaviour changed noted in #21070 where using a config value `rpcallowip=::0` no longer also permitted ipv4 ip addresses.

  The rpc_bind.py functional test covers this new behaviour already by checking that the list of bind addresses exactly matches what is expected so this commit only updates the documentation.

ACKs for top commit:
  achow101:
    ACK c8e0664
  pinheadmz:
    ACK c8e0664
  jonatack:
    ACK c8e0664

Tree-SHA512: 332060cf0df0427c6637a9fd1e0783ce0b0940abdb41b0df13f03bfbdc28af067cec8f0b1bbc4e47b3d54fa1b2f110418442b05b39d5e7c7e0b96744ddd7c003

Author: achow101

src/init.cpp

@@ -610,7 +610,7 @@ void SetupServerArgs(ArgsManager& argsman)
     argsman.AddArg("-blockversion=<n>", "Override block version to test forking scenarios", ArgsManager::ALLOW_ANY | ArgsManager::DEBUG_ONLY, OptionsCategory::BLOCK_CREATION);
 
     argsman.AddArg("-rest", strprintf("Accept public REST requests (default: %u)", DEFAULT_REST_ENABLE), ArgsManager::ALLOW_ANY, OptionsCategory::RPC);
-    argsman.AddArg("-rpcallowip=<ip>", "Allow JSON-RPC connections from specified source. Valid for <ip> are a single IP (e.g. 1.2.3.4), a network/netmask (e.g. 1.2.3.4/255.255.255.0) or a network/CIDR (e.g. 1.2.3.4/24). This option can be specified multiple times", ArgsManager::ALLOW_ANY, OptionsCategory::RPC);
+    argsman.AddArg("-rpcallowip=<ip>", "Allow JSON-RPC connections from specified source. Valid values for <ip> are a single IP (e.g. 1.2.3.4), a network/netmask (e.g. 1.2.3.4/255.255.255.0), a network/CIDR (e.g. 1.2.3.4/24), all ipv4 (0.0.0.0/0), or all ipv6 (::/0). This option can be specified multiple times", ArgsManager::ALLOW_ANY, OptionsCategory::RPC);
     argsman.AddArg("-rpcauth=<userpw>", "Username and HMAC-SHA-256 hashed password for JSON-RPC connections. The field <userpw> comes in the format: <USERNAME>:<SALT>$<HASH>. A canonical python script is included in share/rpcauth. The client then connects normally using the rpcuser=<USERNAME>/rpcpassword=<PASSWORD> pair of arguments. This option can be specified multiple times", ArgsManager::ALLOW_ANY | ArgsManager::SENSITIVE, OptionsCategory::RPC);
     argsman.AddArg("-rpcbind=<addr>[:port]", "Bind to given address to listen for JSON-RPC connections. Do not expose the RPC server to untrusted networks such as the public internet! This option is ignored unless -rpcallowip is also passed. Port is optional and overrides -rpcport. Use [host]:port notation for IPv6. This option can be specified multiple times (default: 127.0.0.1 and ::1 i.e., localhost)", ArgsManager::ALLOW_ANY | ArgsManager::NETWORK_ONLY, OptionsCategory::RPC);
     argsman.AddArg("-rpcdoccheck", strprintf("Throw a non-fatal error at runtime if the documentation for an RPC is incorrect (default: %u)", DEFAULT_RPC_DOC_CHECK), ArgsManager::ALLOW_ANY | ArgsManager::DEBUG_ONLY, OptionsCategory::RPC);