netdev - Re: [PATCH iproute2 2/2] lib/libnetlink: update rtnl

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Date:   Fri, 8 Sep 2017 21:26:16 +0800
From:   Hangbin Liu <liuhangbin@...il.com>
To:     Phil Sutter <phil@....cc>, netdev@...r.kernel.org,
        Stephen Hemminger <stephen@...workplumber.org>,
        Michal Kubecek <mkubecek@...e.cz>
Subject: Re: [PATCH iproute2 2/2] lib/libnetlink: update rtnl_talk to support
 malloc buff at run time

On Fri, Sep 08, 2017 at 01:06:52PM +0200, Phil Sutter wrote:
> Hi Hangbin,
> 
> On Fri, Sep 08, 2017 at 06:14:57PM +0800, Hangbin Liu wrote:
> [...]
> > diff --git a/genl/ctrl.c b/genl/ctrl.c
> > index 448988e..699657b 100644
> > --- a/genl/ctrl.c
> > +++ b/genl/ctrl.c
> > @@ -55,6 +55,7 @@ int genl_ctrl_resolve_family(const char *family)
> >  	};
> >  	struct nlmsghdr *nlh = &req.n;
> >  	struct genlmsghdr *ghdr = &req.g;
> > +	struct nlmsghdr *answer = NULL;
> 
> I don't think it's necessary to assign NULL here or in any of the other
> cases.

OK
> 
> >  	if (rtnl_open_byproto(&rth, 0, NETLINK_GENERIC) < 0) {
> >  		fprintf(stderr, "Cannot open generic netlink socket\n");
> > @@ -63,19 +64,19 @@ int genl_ctrl_resolve_family(const char *family)
> >  
> >  	addattr_l(nlh, 128, CTRL_ATTR_FAMILY_NAME, family, strlen(family) + 1);
> >  
> > -	if (rtnl_talk(&rth, nlh, nlh, sizeof(req)) < 0) {
> > +	if (rtnl_talk(&rth, nlh, &answer) < 0) {
> 
> I didn't check, but it's likely that at least in some cases 'nlh'
> contains some buffer space to hold the answer (if it will be larger than
> the input). If so, this could be dropped since the buffer is no longer
> reused.

Yes, I will remove the buffer.

Thanks
Hangbin