netdev - Re: [PATCH net v4 1/8] ipv4/fib_frontend: Rename ip_valid_fib_dump

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Date:   Mon, 17 Jun 2019 07:38:54 -0600
From:   David Ahern <dsahern@...il.com>
To:     Stefano Brivio <sbrivio@...hat.com>
Cc:     David Miller <davem@...emloft.net>,
        Martin KaFai Lau <kafai@...com>,
        Jianlin Shi <jishi@...hat.com>, Wei Wang <weiwan@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Matti Vaittinen <matti.vaittinen@...rohmeurope.com>,
        netdev@...r.kernel.org
Subject: Re: [PATCH net v4 1/8] ipv4/fib_frontend: Rename
 ip_valid_fib_dump_req, provide non-strict version

On 6/16/19 2:04 PM, Stefano Brivio wrote:
> We could do this:
> 
> - strict checking enabled (iproute2 >= 5.0.0):
>   - in inet{,6}_dump_fib(): if NLM_F_MATCH is set, set
>     filter->filter_set in any case
> 
>   - in fn_trie_dump_leaf() and rt6_dump_route(): use filter->filter_set
>     to decide if we want to filter depending on RTM_F_CLONED being
>     set/unset. If other filters (rt_type, dev, protocol) are not set,
>     they are still wildcards (existing implementation)
> 
> - no strict checking (iproute2 < 5.0.0):
>   - we can't filter consistently, so apply no filters at all: dump all
>     the routes (filter->filter_set not set), cached and uncached. That
>     means more netlink messages, but no spam as iproute2 filters them
>     anyway, and list/flush cache commands work again.
> 
> I would drop 1/8, turn 2/8 and 6/8 into a straightforward:
> 
>  	if (cb->strict_check) {
>  		err = ip_valid_fib_dump_req(net, nlh, &filter, cb);
>  		if (err < 0)
>  			return err;
> +		if (nlh->nlmsg_flags & NLM_F_MATCH)
> +			filter.filter_set = 1;
>  	} else if (nlmsg_len(nlh) >= sizeof(struct rtmsg)) {
>  		struct rtmsg *rtm = nlmsg_data(nlh);
> 
> and other patches remain the same.
> 
> What do you think?
> 

With strict checking (5.0 and forward):
- RTM_F_CLONED NOT set means dump only FIB entries
- RTM_F_CLONED set means dump only exceptions

Without strict checking (old iproute2 on any kernel):
- dump all, userspace has to sort

Kernel side this can be handled with new field, dump_exceptions, in the
filter that defaults to true and then is reset in the strict path if the
flag is not set.