[Core] Enable IPv6 with vllm.utils.make_zmq_socket()

This code did not previously support IPv6 addresses for a TCP
zmq socket. This fixes that, including some test cases.

I spotted this while reading #15977.

Signed-off-by: Russell Bryant <rbryant@redhat.com>

Author: russellb

tests/test_utils.py

@@ -10,14 +10,15 @@
 
 import pytest
 import torch
+import zmq
 from vllm_test_utils.monitor import monitor
 
 from vllm.config import ParallelConfig, VllmConfig, set_current_vllm_config
 from vllm.utils import (CacheInfo, FlexibleArgumentParser, LRUCache,
                         MemorySnapshot, PlaceholderModule, StoreBoolean,
                         bind_kv_cache, deprecate_kwargs, get_open_port,
                         memory_profiling, merge_async_iterators, sha256,
-                        supports_kw, swap_dict_values)
+                        split_zmq_path, supports_kw, swap_dict_values)
 
 from .utils import create_new_process_for_each_test, error_on_warning
 
@@ -662,3 +663,46 @@ def test_sha256(input: tuple, output: int):
 
     # hashing different input, returns different value
     assert hash != sha256(input + (1, ))
+
+
+@pytest.mark.parametrize(
+    "path,expected",
+    [
+        ("ipc://some_path", ("ipc", "some_path", "")),
+        ("tcp://127.0.0.1:5555", ("tcp", "127.0.0.1", "5555")),
+        ("tcp://[::1]:5555", ("tcp", "::1", "5555")),  # IPv6 address
+        ("inproc://some_identifier", ("inproc", "some_identifier", "")),
+    ]
+)
+def test_split_zmq_path(path, expected):
+    assert split_zmq_path(path) == expected
+
+
+@pytest.mark.parametrize(
+    "invalid_path",
+    [
+        "invalid_path",  # Missing scheme
+        "tcp://127.0.0.1",  # Missing port
+        "tcp://[::1]",  # Missing port for IPv6
+        "tcp://:5555",  # Missing host
+    ]
+)
+def test_split_zmq_path_invalid(invalid_path):
+    with pytest.raises(ValueError):
+        split_zmq_path(invalid_path)
+
+
+def test_make_zmq_socket_ipv6():
+    ctx = zmq.Context()
+    ipv6_path = "tcp://[::1]:5555"  # IPv6 loopback address
+    socket_type = zmq.REP  # Example socket type
+
+    # Create the socket
+    socket = make_zmq_socket(ctx, ipv6_path, socket_type)
+
+    # Verify that the IPV6 option is set
+    assert socket.getsockopt(zmq.IPV6) == 1, "IPV6 option should be enabled for IPv6 addresses"
+
+    # Clean up
+    socket.close()
+    ctx.term()

vllm/utils.py

@@ -43,6 +43,7 @@
 from types import MappingProxyType
 from typing import (TYPE_CHECKING, Any, Callable, Generic, Literal, NamedTuple,
                     Optional, Tuple, Type, TypeVar, Union, cast, overload)
+from urllib.parse import urlparse
 from uuid import uuid4
 
 import cachetools
@@ -2250,6 +2251,27 @@ def get_exception_traceback():
     return err_str
 
 
+def split_zmq_path(path: str) -> Tuple[str, str, str]:
+    """Split a zmq path into its parts."""
+    parsed = urlparse(path)
+    if not parsed.scheme:
+        raise ValueError(f"Invalid zmq path: {path}")
+
+    scheme = parsed.scheme
+    host = parsed.hostname or ""
+    port = str(parsed.port or "")
+
+    if scheme == "tcp" and not all((host, port)):
+        # The host and port fields are required for tcp
+        raise ValueError(f"Invalid zmq path: {path}")
+
+    if scheme != "tcp" and port:
+        # port only makes sense with tcp
+        raise ValueError(f"Invalid zmq path: {path}")
+
+    return scheme, host, port
+
+
 # Adapted from: https://github.com/sgl-project/sglang/blob/v0.4.1/python/sglang/srt/utils.py#L783 # noqa: E501
 def make_zmq_socket(
     ctx: Union[zmq.asyncio.Context, zmq.Context],  # type: ignore[name-defined]
@@ -2289,6 +2311,12 @@ def make_zmq_socket(
     if identity is not None:
         socket.setsockopt(zmq.IDENTITY, identity)
 
+    # Determine if the path is a TCP socket with an IPv6 address.
+    # Enable IPv6 on the zmq socket if so.
+    scheme, host, _ = split_zmq_path(path)
+    if scheme == "tcp" and is_valid_ipv6_address(host):
+        socket.setsockopt(zmq.IPV6, 1)
+
     if bind:
         socket.bind(path)
     else: