server : add --host-family to control HTTP bind address family

[fanyang89]

Introduce a new server option, --host-family (ipv4 | ipv6 | auto), to avoid relying on OS-dependent default address-family behavior.

[Copilot]

Pull request overview

Adds a new --host-family (ipv4|ipv6|auto) server option to make TCP bind address-family selection explicit and consistent across OSes.

Changes:

• Introduce common_host_family + --host-family CLI/env parsing.
• Plumb the chosen host family into the HTTP server binding logic (with a UNIX-socket ignore warning).
• Extend server test harness and add a unit test covering --host-family.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
tools/server/tests/utils.py	Adds server_host_family to test server process and forwards it to CLI args.
tools/server/tests/unit/test_basic.py	Adds a unit test that starts the server with --host-family.
tools/server/server-http.h	Stores host-family in the HTTP server context.
tools/server/server-http.cpp	Applies address-family selection (AF_INET/AF_INET6/AF_UNSPEC) before binding.
tools/server/README.md	Documents new --host-family option.
common/common.h	Adds common_host_family enum and new host_family param field.
common/arg.cpp	Parses --host-family and maps to internal enum.

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[Copilot]

This test mutates the global server instance but never resets server.server_host_family, which can make later tests order-dependent (they may unexpectedly keep running with --host-family ipv4). Reset the field back to None in a finally block (or use a fresh server instance/fixture per test) to avoid shared-state leakage.

Suggested change

	server.server_host_family = "ipv4"
	server.start()
	res = server.make_request("GET", "/health")
	assert res.status_code == 200
	original_host_family = server.server_host_family
	try:
	server.server_host_family = "ipv4"
	server.start()
	res = server.make_request("GET", "/health")
	assert res.status_code == 200
	finally:
	server.server_host_family = original_host_family

[Copilot]

Storing host_family as a plain int loses type-safety now that common_host_family exists. Prefer using common_host_family host_family here (and keep conversions to AF_INET/AF_INET6/AF_UNSPEC localized to the binding logic) to prevent accidental invalid values and make intent clearer.

[Copilot]

A new data member was added to server_http_context; ensure it is explicitly initialized in server_http_context() (or via an in-class initializer) so it can’t be read uninitialized if start() is ever called before init() (or if future code paths change).

Suggested change

	int host_family;
	int host_family = 0;

[Copilot]

server_args.extend([\"--offline\"]) is functionally correct but unusual for a single element and makes the intent less clear than server_args.append(\"--offline\"). Consider switching back to append for readability/consistency with common list-building patterns.

Suggested change

	server_args.extend(["--offline"])
	server_args.append("--offline")

[Copilot]

The implementation warns that --host-family is ignored when binding to a UNIX socket (*.sock). Consider noting this behavior in the option description (even briefly) so users aren’t surprised when it has no effect for .sock hosts.

Suggested change

	| `--host-family FAMILY` | address family for TCP listen sockets: ipv4, ipv6, or auto (default: auto)<br/>(env: LLAMA_ARG_HOST_FAMILY) |
	| `--host-family FAMILY` | address family for TCP listen sockets: ipv4, ipv6, or auto (default: auto). Ignored when \`--host\` is a .sock UNIX socket.<br/>(env: LLAMA_ARG_HOST_FAMILY) |