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

[David Gibson <david@gibson.dropbear.id.au>]

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On Thu, Aug 03, 2023 at 12:47:59AM +0200, Stefano Brivio wrote:
> 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);

Done.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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