netdev - Re: [PATCH net-next v4] net: ip6mr: add RTM

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Date:   Wed, 6 Jul 2022 13:38:27 +0300
From:   Nikolay Aleksandrov <razor@...ckwall.org>
To:     David Lamparter <equinox@...c24.net>, netdev@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        David Ahern <dsahern@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH net-next v4] net: ip6mr: add RTM_GETROUTE netlink op

On 06/07/2022 13:00, David Lamparter wrote:
> The IPv6 multicast routing code previously implemented only the dump
> variant of RTM_GETROUTE.  Implement single MFC item retrieval by copying
> and adapting the respective IPv4 code.
> 
> Tested against FRRouting's IPv6 PIM stack.
> 
> Signed-off-by: David Lamparter <equinox@...c24.net>
> Cc: David Ahern <dsahern@...nel.org>
> Cc: Nikolay Aleksandrov <razor@...ckwall.org>
> ---
> 
> v4: rename policy to indicate it is dedicated for getroute, remove
> extra validation loop to reject attrs, and add missing "static".
> 
> v3: reorder/remove some redundant bits, fix style.  Thanks Nikolay for
> pointing them out.  The "extra" validation loop is still there for the
> time being;  happy to drop it if that's the consensus.
> 
> v2: changeover to strict netlink attribute parsing.  Doing so actually
> exposed a bunch of other issues, first and foremost that rtm_ipv6_policy
> does not have RTA_SRC or RTA_DST.  This made reusing that policy rather
> pointless so I changed it to use a separate rtm_ipv6_mr_policy.
> 
> Thanks again dsahern@ for the feedback on the previous version!
> 
> ---
>  net/ipv6/ip6mr.c | 102 ++++++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 101 insertions(+), 1 deletion(-)
> 

Patch looks good to me overall, one minor nit below in case there's a next version.
Thanks,
Reviewed-by: Nikolay Aleksandrov <razor@...ckwall.org>

> diff --git a/net/ipv6/ip6mr.c b/net/ipv6/ip6mr.c
> index ec6e1509fc7c..f567c055dba4 100644
> --- a/net/ipv6/ip6mr.c
> +++ b/net/ipv6/ip6mr.c
[snip]
> +static int ip6mr_rtm_getroute(struct sk_buff *in_skb, struct nlmsghdr *nlh,
> +			      struct netlink_ext_ack *extack)
> +{
> +	struct net *net = sock_net(in_skb->sk);
> +	struct in6_addr src = {}, grp = {};
> +	struct nlattr *tb[RTA_MAX + 1];
> +	struct sk_buff *skb = NULL;
> +	struct mfc6_cache *cache;
> +	struct mr_table *mrt;
> +	u32 tableid;
> +	int err;
> +
> +	err = ip6mr_rtm_valid_getroute_req(in_skb, nlh, tb, extack);
> +	if (err < 0)
> +		goto errout;
> +
> +	if (tb[RTA_SRC])
> +		src = nla_get_in6_addr(tb[RTA_SRC]);
> +	if (tb[RTA_DST])
> +		grp = nla_get_in6_addr(tb[RTA_DST]);
> +	tableid = tb[RTA_TABLE] ? nla_get_u32(tb[RTA_TABLE]) : 0;
> +
> +	mrt = ip6mr_get_table(net, tableid ? tableid : RT_TABLE_DEFAULT);
> +	if (!mrt) {
> +		NL_SET_ERR_MSG_MOD(extack, "ipv6 MR table does not exist");

minor nit: some errors have ":" after "ipv6", in this function's errors it's missing

> +		err = -ENOENT;
> +		goto errout_free;
> +	}
> +
> +	/* entries are added/deleted only under RTNL */
> +	rcu_read_lock();
> +	cache = ip6mr_cache_find(mrt, &src, &grp);
> +	rcu_read_unlock();
> +	if (!cache) {
> +		NL_SET_ERR_MSG_MOD(extack, "ipv6 MR cache entry not found");

ditto

> +		err = -ENOENT;
> +		goto errout_free;
> +	}
> +
> +	skb = nlmsg_new(mr6_msgsize(false, mrt->maxvif), GFP_KERNEL);
> +	if (!skb) {
> +		err = -ENOBUFS;
> +		goto errout_free;
> +	}
> +
> +	err = ip6mr_fill_mroute(mrt, skb, NETLINK_CB(in_skb).portid,
> +				nlh->nlmsg_seq, cache, RTM_NEWROUTE, 0);
> +	if (err < 0)
> +		goto errout_free;
> +
> +	err = rtnl_unicast(skb, net, NETLINK_CB(in_skb).portid);
> +
> +errout:
> +	return err;
> +
> +errout_free:
> +	kfree_skb(skb);
> +	goto errout;
> +}
> +
>  static int ip6mr_rtm_dumproute(struct sk_buff *skb, struct netlink_callback *cb)
>  {
>  	const struct nlmsghdr *nlh = cb->nlh;