--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/third_party/libuv/docs/src/udp.rst	Wed Jan 14 19:39:52 2026 -0800
@@ -0,0 +1,501 @@
+
+.. _udp:
+
+:c:type:`uv_udp_t` --- UDP handle
+=================================
+
+UDP handles encapsulate UDP communication for both clients and servers.
+
+
+Data types
+----------
+
+.. c:type:: uv_udp_t
+
+    UDP handle type.
+
+.. c:type:: uv_udp_send_t
+
+    UDP send request type.
+
+.. c:enum:: uv_udp_flags
+
+    Flags used in :c:func:`uv_udp_bind` and :c:type:`uv_udp_recv_cb`..
+
+    ::
+
+        enum uv_udp_flags {
+            /* Disables dual stack mode. */
+            UV_UDP_IPV6ONLY = 1,
+            /*
+             * Indicates message was truncated because read buffer was too small. The
+             * remainder was discarded by the OS. Used in uv_udp_recv_cb.
+             */
+            UV_UDP_PARTIAL = 2,
+            /*
+             * Indicates if SO_REUSEADDR will be set when binding the handle.
+             * This sets the SO_REUSEPORT socket flag on the BSDs (except for
+             * DragonFlyBSD), OS X, and other platforms where SO_REUSEPORTs don't
+             * have the capability of load balancing, as the opposite of what
+             * UV_UDP_REUSEPORT would do. On other Unix platforms, it sets the
+             * SO_REUSEADDR flag. What that means is that multiple threads or
+             * processes can bind to the same address without error (provided
+             * they all set the flag) but only the last one to bind will receive
+             * any traffic, in effect "stealing" the port from the previous listener.
+             */
+            UV_UDP_REUSEADDR = 4,
+            /*
+             * Indicates that the message was received by recvmmsg, so the buffer provided
+             * must not be freed by the recv_cb callback.
+             */
+            UV_UDP_MMSG_CHUNK = 8,
+            /*
+             * Indicates that the buffer provided has been fully utilized by recvmmsg and
+             * that it should now be freed by the recv_cb callback. When this flag is set
+             * in uv_udp_recv_cb, nread will always be 0 and addr will always be NULL.
+             */
+            UV_UDP_MMSG_FREE = 16,
+            /*
+             * Indicates if IP_RECVERR/IPV6_RECVERR will be set when binding the handle.
+             * This sets IP_RECVERR for IPv4 and IPV6_RECVERR for IPv6 UDP sockets on
+             * Linux. This stops the Linux kernel from suppressing some ICMP error messages
+             * and enables full ICMP error reporting for faster failover.
+             * This flag is no-op on platforms other than Linux.
+             */
+            UV_UDP_LINUX_RECVERR = 32,
+            /*
+             * Indicates if SO_REUSEPORT will be set when binding the handle.
+             * This sets the SO_REUSEPORT socket option on supported platforms.
+             * Unlike UV_UDP_REUSEADDR, this flag will make multiple threads or
+             * processes that are binding to the same address and port "share"
+             * the port, which means incoming datagrams are distributed across
+             * the receiving sockets among threads or processes.
+             *
+             * This flag is available only on Linux 3.9+, DragonFlyBSD 3.6+,
+             * FreeBSD 12.0+, Solaris 11.4, and AIX 7.2.5+ for now.
+             */
+            UV_UDP_REUSEPORT = 64,
+            /*
+             * Indicates that recvmmsg should be used, if available.
+             */
+            UV_UDP_RECVMMSG = 256
+        };
+
+.. c:type:: void (*uv_udp_send_cb)(uv_udp_send_t* req, int status)
+
+    Type definition for callback passed to :c:func:`uv_udp_send`, which is
+    called after the data was sent.
+
+.. c:type:: void (*uv_udp_recv_cb)(uv_udp_t* handle, ssize_t nread, const uv_buf_t* buf, const struct sockaddr* addr, unsigned flags)
+
+    Type definition for callback passed to :c:func:`uv_udp_recv_start`, which
+    is called when the endpoint receives data.
+
+    * `handle`: UDP handle
+    * `nread`:  Number of bytes that have been received.
+      0 if there is no more data to read. Note that 0 may also mean that an
+      empty datagram was received (in this case `addr` is not NULL). < 0 if
+      a transmission error was detected; if using :man:`recvmmsg(2)` no more
+      chunks will be received and the buffer can be freed safely.
+    * `buf`: :c:type:`uv_buf_t` with the received data.
+    * `addr`: ``struct sockaddr*`` containing the address of the sender.
+      Can be NULL. Valid for the duration of the callback only.
+    * `flags`: One or more or'ed UV_UDP_* constants.
+
+    The callee is responsible for freeing the buffer, libuv does not reuse it.
+    The buffer may be a null buffer (where `buf->base` == NULL and `buf->len` == 0)
+    on error.
+
+    When using :man:`recvmmsg(2)`, chunks will have the `UV_UDP_MMSG_CHUNK` flag set,
+    those must not be freed. If no errors occur, there will be a final callback with
+    `nread` set to 0, `addr` set to NULL and the buffer pointing at the initially
+    allocated data with the `UV_UDP_MMSG_CHUNK` flag cleared and the `UV_UDP_MMSG_FREE`
+    flag set. If a UDP socket error occurs, `nread` will be < 0. In either scenario,
+    the callee can now safely free the provided buffer.
+
+    .. versionchanged:: 1.40.0 added the `UV_UDP_MMSG_FREE` flag.
+
+    .. note::
+        The receive callback will be called with `nread` == 0 and `addr` == NULL when there is
+        nothing to read, and with `nread` == 0 and `addr` != NULL when an empty UDP packet is
+        received.
+
+.. c:enum:: uv_membership
+
+    Membership type for a multicast address.
+
+    ::
+
+        typedef enum {
+            UV_LEAVE_GROUP = 0,
+            UV_JOIN_GROUP
+        } uv_membership;
+
+
+Public members
+^^^^^^^^^^^^^^
+
+.. c:member:: size_t uv_udp_t.send_queue_size
+
+    Number of bytes queued for sending. This field strictly shows how much
+    information is currently queued.
+
+.. c:member:: size_t uv_udp_t.send_queue_count
+
+    Number of send requests currently in the queue awaiting to be processed.
+
+.. c:member:: uv_udp_t* uv_udp_send_t.handle
+
+    UDP handle where this send request is taking place.
+
+.. seealso:: The :c:type:`uv_handle_t` members also apply.
+
+
+API
+---
+
+.. c:function:: int uv_udp_init(uv_loop_t* loop, uv_udp_t* handle)
+
+    Initialize a new UDP handle. The actual socket is created lazily.
+    Returns 0 on success.
+
+.. c:function:: int uv_udp_init_ex(uv_loop_t* loop, uv_udp_t* handle, unsigned int flags)
+
+    Initialize the handle with the specified flags. The lower 8 bits of the `flags`
+    parameter are used as the socket domain. A socket will be created for the given domain.
+    If the specified domain is ``AF_UNSPEC`` no socket is created, just like :c:func:`uv_udp_init`.
+
+    The remaining bits can be used to set one of these flags:
+
+    * `UV_UDP_RECVMMSG`: if set, and the platform supports it, :man:`recvmmsg(2)` will
+      be used.
+
+    .. versionadded:: 1.7.0
+    .. versionchanged:: 1.37.0 added the `UV_UDP_RECVMMSG` flag.
+
+.. c:function:: int uv_udp_open(uv_udp_t* handle, uv_os_sock_t sock)
+
+    Opens an existing file descriptor or Windows SOCKET as a UDP handle.
+
+    Unix only:
+    The only requirement of the `sock` argument is that it follows the datagram
+    contract (works in unconnected mode, supports sendmsg()/recvmsg(), etc).
+    In other words, other datagram-type sockets like raw sockets or netlink
+    sockets can also be passed to this function.
+
+    .. versionchanged:: 1.2.1 the file descriptor is set to non-blocking mode.
+
+    .. note::
+        The passed file descriptor or SOCKET is not checked for its type, but
+        it's required that it represents a valid datagram socket.
+
+.. c:function:: int uv_udp_bind(uv_udp_t* handle, const struct sockaddr* addr, unsigned int flags)
+
+    Bind the UDP handle to an IP address and port.
+
+    :param handle: UDP handle. Should have been initialized with
+        :c:func:`uv_udp_init`.
+
+    :param addr: `struct sockaddr_in` or `struct sockaddr_in6`
+        with the address and port to bind to.
+
+    :param flags: Indicate how the socket will be bound,
+        ``UV_UDP_IPV6ONLY``, ``UV_UDP_REUSEADDR``, ``UV_UDP_REUSEPORT``,
+        and ``UV_UDP_RECVERR`` are supported.
+
+    :returns: 0 on success, or an error code < 0 on failure.
+
+    .. versionchanged:: 1.49.0 added the ``UV_UDP_REUSEPORT`` flag.
+
+    .. note::
+        ``UV_UDP_REUSEPORT`` flag is available only on Linux 3.9+, DragonFlyBSD 3.6+,
+        FreeBSD 12.0+, Solaris 11.4, and AIX 7.2.5+ at the moment. On other platforms
+        this function will return an UV_ENOTSUP error.
+        For platforms where `SO_REUSEPORT`s have the capability of load balancing,
+        specifying both ``UV_UDP_REUSEADDR`` and ``UV_UDP_REUSEPORT`` in flags is allowed
+        and `SO_REUSEPORT` will always override the behavior of `SO_REUSEADDR`.
+        For platforms where `SO_REUSEPORT`s don't have the capability of load balancing,
+        specifying both ``UV_UDP_REUSEADDR`` and ``UV_UDP_REUSEPORT`` in flags will fail,
+        returning an UV_ENOTSUP error.
+
+.. c:function:: int uv_udp_connect(uv_udp_t* handle, const struct sockaddr* addr)
+
+    Associate the UDP handle to a remote address and port, so every
+    message sent by this handle is automatically sent to that destination.
+    Calling this function with a `NULL` `addr` disconnects the handle.
+    Trying to call `uv_udp_connect()` on an already connected handle will result
+    in an `UV_EISCONN` error. Trying to disconnect a handle that is not
+    connected will return an `UV_ENOTCONN` error.
+
+    :param handle: UDP handle. Should have been initialized with
+        :c:func:`uv_udp_init`.
+
+    :param addr: `struct sockaddr_in` or `struct sockaddr_in6`
+        with the address and port to associate to.
+
+    :returns: 0 on success, or an error code < 0 on failure.
+
+    .. versionadded:: 1.27.0
+
+.. c:function:: int uv_udp_getpeername(const uv_udp_t* handle, struct sockaddr* name, int* namelen)
+
+    Get the remote IP and port of the UDP handle on connected UDP handles.
+    On unconnected handles, it returns `UV_ENOTCONN`.
+
+    :param handle: UDP handle. Should have been initialized with
+        :c:func:`uv_udp_init` and bound.
+
+    :param name: Pointer to the structure to be filled with the address data.
+        In order to support IPv4 and IPv6 `struct sockaddr_storage` should be
+        used.
+
+    :param namelen: On input it indicates the data of the `name` field. On
+        output it indicates how much of it was filled.
+
+    :returns: 0 on success, or an error code < 0 on failure
+
+    .. versionadded:: 1.27.0
+
+.. c:function:: int uv_udp_getsockname(const uv_udp_t* handle, struct sockaddr* name, int* namelen)
+
+    Get the local IP and port of the UDP handle.
+
+    :param handle: UDP handle. Should have been initialized with
+        :c:func:`uv_udp_init` and bound.
+
+    :param name: Pointer to the structure to be filled with the address data.
+        In order to support IPv4 and IPv6 `struct sockaddr_storage` should be
+        used.
+
+    :param namelen: On input it indicates the data of the `name` field. On
+        output it indicates how much of it was filled.
+
+    :returns: 0 on success, or an error code < 0 on failure.
+
+.. c:function:: int uv_udp_set_membership(uv_udp_t* handle, const char* multicast_addr, const char* interface_addr, uv_membership membership)
+
+    Set membership for a multicast address
+
+    :param handle: UDP handle. Should have been initialized with
+        :c:func:`uv_udp_init`.
+
+    :param multicast_addr: Multicast address to set membership for.
+
+    :param interface_addr: Interface address.
+
+    :param membership: Should be ``UV_JOIN_GROUP`` or ``UV_LEAVE_GROUP``.
+
+    :returns: 0 on success, or an error code < 0 on failure.
+
+.. c:function:: int uv_udp_set_source_membership(uv_udp_t* handle, const char* multicast_addr, const char* interface_addr, const char* source_addr, uv_membership membership)
+
+    Set membership for a source-specific multicast group.
+
+    :param handle: UDP handle. Should have been initialized with
+        :c:func:`uv_udp_init`.
+
+    :param multicast_addr: Multicast address to set membership for.
+
+    :param interface_addr: Interface address.
+
+    :param source_addr: Source address.
+
+    :param membership: Should be ``UV_JOIN_GROUP`` or ``UV_LEAVE_GROUP``.
+
+    :returns: 0 on success, or an error code < 0 on failure.
+
+    .. versionadded:: 1.32.0
+
+.. c:function:: int uv_udp_set_multicast_loop(uv_udp_t* handle, int on)
+
+    Set IP multicast loop flag. Makes multicast packets loop back to
+    local sockets.
+
+    :param handle: UDP handle. Should have been initialized with
+        :c:func:`uv_udp_init_ex` as either ``AF_INET`` or ``AF_INET6``, or have
+        been bound to an address explicitly with :c:func:`uv_udp_bind`, or
+        implicitly with :c:func:`uv_udp_send()` or :c:func:`uv_udp_recv_start`.
+
+    :param on: 1 for on, 0 for off.
+
+    :returns: 0 on success, or an error code < 0 on failure.
+
+.. c:function:: int uv_udp_set_multicast_ttl(uv_udp_t* handle, int ttl)
+
+    Set the multicast ttl.
+
+    :param handle: UDP handle. Should have been initialized with
+        :c:func:`uv_udp_init_ex` as either ``AF_INET`` or ``AF_INET6``, or have
+        been bound to an address explicitly with :c:func:`uv_udp_bind`, or
+        implicitly with :c:func:`uv_udp_send()` or :c:func:`uv_udp_recv_start`.
+
+    :param ttl: 1 through 255.
+
+    :returns: 0 on success, or an error code < 0 on failure.
+
+.. c:function:: int uv_udp_set_multicast_interface(uv_udp_t* handle, const char* interface_addr)
+
+    Set the multicast interface to send or receive data on.
+
+    :param handle: UDP handle. Should have been initialized with
+        :c:func:`uv_udp_init_ex` as either ``AF_INET`` or ``AF_INET6``, or have
+        been bound to an address explicitly with :c:func:`uv_udp_bind`, or
+        implicitly with :c:func:`uv_udp_send()` or :c:func:`uv_udp_recv_start`.
+
+    :param interface_addr: interface address.
+
+    :returns: 0 on success, or an error code < 0 on failure.
+
+.. c:function:: int uv_udp_set_broadcast(uv_udp_t* handle, int on)
+
+    Set broadcast on or off.
+
+    :param handle: UDP handle. Should have been initialized with
+        :c:func:`uv_udp_init_ex` as either ``AF_INET`` or ``AF_INET6``, or have
+        been bound to an address explicitly with :c:func:`uv_udp_bind`, or
+        implicitly with :c:func:`uv_udp_send()` or :c:func:`uv_udp_recv_start`.
+
+    :param on: 1 for on, 0 for off.
+
+    :returns: 0 on success, or an error code < 0 on failure.
+
+.. c:function:: int uv_udp_set_ttl(uv_udp_t* handle, int ttl)
+
+    Set the time to live.
+
+    :param handle: UDP handle. Should have been initialized with
+        :c:func:`uv_udp_init_ex` as either ``AF_INET`` or ``AF_INET6``, or have
+        been bound to an address explicitly with :c:func:`uv_udp_bind`, or
+        implicitly with :c:func:`uv_udp_send()` or :c:func:`uv_udp_recv_start`.
+
+    :param ttl: 1 through 255.
+
+    :returns: 0 on success, or an error code < 0 on failure.
+
+.. c:function:: int uv_udp_send(uv_udp_send_t* req, uv_udp_t* handle, const uv_buf_t bufs[], unsigned int nbufs, const struct sockaddr* addr, uv_udp_send_cb send_cb)
+
+    Send data over the UDP socket. If the socket has not previously been bound
+    with :c:func:`uv_udp_bind` it will be bound to 0.0.0.0
+    (the "all interfaces" IPv4 address) and a random port number.
+
+    On Windows if the `addr` is initialized to point to an unspecified address
+    (``0.0.0.0`` or ``::``) it will be changed to point to ``localhost``.
+    This is done to match the behavior of Linux systems.
+
+    For connected UDP handles, `addr` must be set to `NULL`, otherwise it will
+    return `UV_EISCONN` error.
+
+    For connectionless UDP handles, `addr` cannot be `NULL`, otherwise it will
+    return `UV_EDESTADDRREQ` error.
+
+    :param req: UDP request handle. Need not be initialized.
+
+    :param handle: UDP handle. Should have been initialized with
+        :c:func:`uv_udp_init`.
+
+    :param bufs: List of buffers to send.
+
+    :param nbufs: Number of buffers in `bufs`.
+
+    :param addr: `struct sockaddr_in` or `struct sockaddr_in6` with the
+        address and port of the remote peer.
+
+    :param send_cb: Callback to invoke when the data has been sent out.
+
+    :returns: 0 on success, or an error code < 0 on failure.
+
+    .. versionchanged:: 1.19.0 added ``0.0.0.0`` and ``::`` to ``localhost``
+        mapping
+
+    .. versionchanged:: 1.27.0 added support for connected sockets
+
+.. c:function:: int uv_udp_try_send(uv_udp_t* handle, const uv_buf_t bufs[], unsigned int nbufs, const struct sockaddr* addr)
+
+    Same as :c:func:`uv_udp_send`, but won't queue a send request if it can't
+    be completed immediately.
+
+    For connected UDP handles, `addr` must be set to `NULL`, otherwise it will
+    return `UV_EISCONN` error.
+
+    For connectionless UDP handles, `addr` cannot be `NULL`, otherwise it will
+    return `UV_EDESTADDRREQ` error.
+
+    :returns: >= 0: number of bytes sent (it matches the given buffer size).
+        < 0: negative error code (``UV_EAGAIN`` is returned when the message
+        can't be sent immediately).
+
+    .. versionchanged:: 1.27.0 added support for connected sockets
+
+.. c:function:: int uv_udp_try_send2(uv_udp_t* handle, unsigned int count, uv_buf_t* bufs[/*count*/], unsigned int nbufs[/*count*/], struct sockaddr* addrs[/*count*/], unsigned int flags)
+
+    Like :c:func:`uv_udp_try_send`, but can send multiple datagrams.
+    Lightweight abstraction around :man:`sendmmsg(2)`, with a :man:`sendmsg(2)`
+    fallback loop for platforms that do not support the former. The handle must
+    be fully initialized; call c:func:`uv_udp_bind` first.
+
+    :returns: >= 0: number of datagrams sent. Zero only if `count` was zero.
+        < 0: negative error code. Only if sending the first datagram fails,
+        otherwise returns a positive send count. ``UV_EAGAIN`` when datagrams
+        cannot be sent right now; fall back to :c:func:`uv_udp_send`.
+
+    .. versionadded:: 1.50.0
+
+.. c:function:: int uv_udp_recv_start(uv_udp_t* handle, uv_alloc_cb alloc_cb, uv_udp_recv_cb recv_cb)
+
+    Prepare for receiving data. If the socket has not previously been bound
+    with :c:func:`uv_udp_bind` it is bound to 0.0.0.0 (the "all interfaces"
+    IPv4 address) and a random port number.
+
+    :param handle: UDP handle. Should have been initialized with
+        :c:func:`uv_udp_init`.
+
+    :param alloc_cb: Callback to invoke when temporary storage is needed.
+
+    :param recv_cb: Callback to invoke with received data.
+
+    :returns: 0 on success, or an error code < 0 on failure.
+
+    .. note::
+        When using :man:`recvmmsg(2)`, the number of messages received at a time is limited
+        by the number of max size dgrams that will fit into the buffer allocated in `alloc_cb`, and
+        `suggested_size` in `alloc_cb` for udp_recv is always set to the size of 1 max size dgram.
+
+    .. versionchanged:: 1.35.0 added support for :man:`recvmmsg(2)` on supported platforms).
+                        The use of this feature requires a buffer larger than
+                        2 * 64KB to be passed to `alloc_cb`.
+    .. versionchanged:: 1.37.0 :man:`recvmmsg(2)` support is no longer enabled implicitly,
+                        it must be explicitly requested by passing the `UV_UDP_RECVMMSG` flag to
+                        :c:func:`uv_udp_init_ex`.
+    .. versionchanged:: 1.39.0 :c:func:`uv_udp_using_recvmmsg` can be used in `alloc_cb` to
+                        determine if a buffer sized for use with :man:`recvmmsg(2)` should be
+                        allocated for the current handle/platform.
+
+.. c:function:: int uv_udp_using_recvmmsg(uv_udp_t* handle)
+
+    Returns 1 if the UDP handle was created with the `UV_UDP_RECVMMSG` flag
+    and the platform supports :man:`recvmmsg(2)`, 0 otherwise.
+
+    .. versionadded:: 1.39.0
+
+.. c:function:: int uv_udp_recv_stop(uv_udp_t* handle)
+
+    Stop listening for incoming datagrams.
+
+    :param handle: UDP handle. Should have been initialized with
+        :c:func:`uv_udp_init`.
+
+    :returns: 0 on success, or an error code < 0 on failure.
+
+.. c:function:: size_t uv_udp_get_send_queue_size(const uv_udp_t* handle)
+
+    Returns `handle->send_queue_size`.
+
+    .. versionadded:: 1.19.0
+
+.. c:function:: size_t uv_udp_get_send_queue_count(const uv_udp_t* handle)
+
+    Returns `handle->send_queue_count`.
+
+    .. versionadded:: 1.19.0
+
+.. seealso:: The :c:type:`uv_handle_t` API functions also apply.