Re: [PATCH 03/12] udp: Polish udp_vu_sock_info() and remove from vu specific code

[Stefano Brivio <sbrivio@redhat.com>]

On Fri,  4 Apr 2025 21:15:33 +1100
David Gibson <david@gibson.dropbear.id.au> wrote:

> udp_vu_sock_info() uses MSG_PEEK to look ahead at the next datagram to be
> received and gets its source address.  Currently we only use it in the
> vhost-user path, but there's nothing inherently vhost-user specific about
> it.  We have upcoming uses for it elsewhere so rename and move to udp.c.
> 
> While we're there, polish its error reporting a litle.
> 
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> ---
>  udp.c          | 25 +++++++++++++++++++++++++
>  udp_internal.h |  1 +
>  udp_vu.c       | 19 +------------------
>  3 files changed, 27 insertions(+), 18 deletions(-)
> 
> diff --git a/udp.c b/udp.c
> index 8125cfcb..6b72c30f 100644
> --- a/udp.c
> +++ b/udp.c
> @@ -629,6 +629,31 @@ static int udp_sock_errs(const struct ctx *c, union epoll_ref ref)
>  	return n_err;
>  }
>  
> +/**
> + * udp_peek_addr() - Get source address for next packet
> + * @s:		Socket to get information from
> + * @src:	Socket address (output)
> + *
> + * Return: 0 on success, -1 otherwise
> + */
> +int udp_peek_addr(int s, union sockaddr_inany *src)
> +{
> +	struct msghdr msg = {
> +		.msg_name = src,
> +		.msg_namelen = sizeof(*src),
> +	};
> +	int rc;
> +
> +	rc = recvmsg(s, &msg, MSG_PEEK | MSG_DONTWAIT);
> +	if (rc < 0) {
> +		if (errno != EAGAIN && errno != EWOULDBLOCK)
> +			warn_perror("Error peeking at socket address");
> +		return rc;
> +	}
> +	return 0;
> +}
> +
> +
>  /**

Excess newline. Fixed on merge.

>   * udp_sock_recv() - Receive datagrams from a socket
>   * @c:		Execution context

-- 
Stefano