netdev - Re: [PATCH net-next 3/5] ipv4: support sport, dport and ip protocol in RTM

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Date:   Tue, 17 Apr 2018 11:10:52 +0300
From:   Ido Schimmel <idosch@...sch.org>
To:     Roopa Prabhu <roopa@...ulusnetworks.com>
Cc:     davem@...emloft.net, netdev@...r.kernel.org,
        dsa@...ulusnetworks.com
Subject: Re: [PATCH net-next 3/5] ipv4: support sport, dport and ip protocol
 in RTM_GETROUTE

On Mon, Apr 16, 2018 at 01:41:36PM -0700, Roopa Prabhu wrote:
> @@ -2757,6 +2796,12 @@ static int inet_rtm_getroute(struct sk_buff *in_skb, struct nlmsghdr *nlh,
>  	fl4.flowi4_oif = tb[RTA_OIF] ? nla_get_u32(tb[RTA_OIF]) : 0;
>  	fl4.flowi4_mark = mark;
>  	fl4.flowi4_uid = uid;
> +	if (sport)
> +		fl4.fl4_sport = sport;
> +	if (dport)
> +		fl4.fl4_dport = dport;
> +	if (ip_proto)
> +		fl4.flowi4_proto = ip_proto;

Hi Roopa,

This info isn't set in the synthesized skb, but only in the flow info
and therefore not used for input routes. I see you added a test case,
but it's only for output routes. I believe an input route test case will
fail.

Also, note that the skb as synthesized now is invalid - iph->ihl is 0
for example - so the flow dissector will spit it out. It effectively
means that route get is broken when L4 hashing is used. It also affects
output routes because since commit 3765d35ed8b9 ("net: ipv4: Convert
inet_rtm_getroute to rcu versions of route lookup") the skb is used to
calculate the multipath hash.