Re: [PATCH 08/17] netlink: Treat send() or recv() errors as fatal

[Stefano Brivio <sbrivio@redhat.com>]

On Mon, 24 Jul 2023 16:09:27 +1000
David Gibson <david@gibson.dropbear.id.au> wrote:

> Errors on send() or recv() calls on a netlink socket don't indicate errors
> with the netlink operations we're attempting, but rather that something's
> gone wrong with the mechanics of netlink itself.  We don't really expect
> this to ever happen, and if it does, it's not clear what we could to to
> recover.
> 
> So, treat errors from these calls as fatal, rather than returning the error
> up the stack.  This makes handling failures in the callers of nl_req()
> simpler.
> 
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> ---
>  netlink.c | 36 +++++++++++++++++-------------------
>  1 file changed, 17 insertions(+), 19 deletions(-)
> 
> diff --git a/netlink.c b/netlink.c
> index 3620fd6..826c926 100644
> --- a/netlink.c
> +++ b/netlink.c
> @@ -103,9 +103,9 @@ fail:
>   * @req:	Request with netlink header
>   * @len:	Request length
>   *
> - * Return: received length on success, negative error code on failure
> + * Return: received length on success, terminates on error
>   */
> -static int nl_req(int s, char *buf, const void *req, ssize_t len)
> +static ssize_t nl_req(int s, char *buf, const void *req, ssize_t len)
>  {
>  	char flush[NLBUFSIZ];
>  	int done = 0;
> @@ -124,11 +124,17 @@ static int nl_req(int s, char *buf, const void *req, ssize_t len)
>  		}
>  	}
>  
> -	if ((send(s, req, len, 0) < len) ||
> -	    (len = recv(s, buf, NLBUFSIZ, 0)) < 0)
> -		return -errno;
> +	n = send(s, req, len, 0);
> +	if (n < 0)
> +		die("netlink: Failed to send(): %s", strerror(errno));
> +	else if (n < len)
> +		die("netlink: Short send");

If you respin, probably worth doing:

		die("netlink: Short send (%li out of %li bytes)", n, len);

-- 
Stefano