netdev - Re: [PATCH net-next, v4] netlink: support dumping IPv4 multicast addresses

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Message-ID: <CADXeF1F7eXj5K+rvLmRCVbi7ZoqxE8Y0b_Baqawe5P-dF8eCdw@mail.gmail.com>
Date: Fri, 10 Jan 2025 00:52:33 +0900
From: Yuyang Huang <yuyanghuang@...gle.com>
To: David Ahern <dsahern@...nel.org>
Cc: "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, 
	roopa@...ulusnetworks.com, jiri@...nulli.us, stephen@...workplumber.org, 
	jimictw@...gle.com, prohr@...gle.com, liuhangbin@...il.com, 
	nicolas.dichtel@...nd.com, andrew@...n.ch, netdev@...r.kernel.org, 
	Maciej Żenczykowski <maze@...gle.com>, 
	Lorenzo Colitti <lorenzo@...gle.com>
Subject: Re: [PATCH net-next, v4] netlink: support dumping IPv4 multicast addresses

>my comment meant that this `type` should be removed and the wrappers
>below just call the intended function. No need for the extra layers.

Sorry, I still do not fully understand the suggestions.

In the current inet_dump_ifaddr() function, there are two places where
in_dev_dump_addr() is called.

For example, we have the following code snippet.

>if (!in_dev)
>goto done;
>err = in_dev_dump_addr(in_dev, skb, cb, &ctx->ip_idx,
>       &fillargs);
>goto done;
>}

Do you suggest we do the following way?

> If (type == UNICAST_ADDR)
>    err = in_dev_dump_ifaddr(in_dev, skb, cb, &ctx->ip_idx,
>                                             &fillargs);
> else if (type == MULTICAST_ADDR)
>    in_dev_dump_ifmcaddr(in_dev, skb, cb, s_ip_idx,
>                                         &fillargs);

The current functional call stack is as follows:

inet_dump_ifaddr()/inet_dump_ifmcaddr() -> inet_dump_addr() ->
in_dev_dump_ifaddr()/in_dev_dump_ifmcaddr().

The ifaddr and ifmcaddr dump code paths share common logic inside
inet_dump_addr(). If we don't do the dispatching in
in_dev_dump_addr(), we have to do the dispatching in inet_dump_addr()
instead, and the dispatching logic will be duplicated twice. I don't
think this will simplify the code.

Or do you suggest I should pass a function pointer for
in_dev_dump_ifaddr()/in_dev_dump_ifmcaddr() into inet_dump_addr()?

Thanks,

Yuyang

On Fri, Jan 10, 2025 at 12:33 AM David Ahern <dsahern@...nel.org> wrote:
>
> On 1/9/25 12:22 AM, Yuyang Huang wrote:
> > @@ -1889,15 +1935,16 @@ static u32 inet_base_seq(const struct net *net)
> >       return res;
> >  }
> >
> > -static int inet_dump_ifaddr(struct sk_buff *skb, struct netlink_callback *cb)
> > +static int inet_dump_addr(struct sk_buff *skb, struct netlink_callback *cb,
> > +                       enum addr_type_t type)
> >  {
> >       const struct nlmsghdr *nlh = cb->nlh;
> >       struct inet_fill_args fillargs = {
> >               .portid = NETLINK_CB(cb->skb).portid,
> >               .seq = nlh->nlmsg_seq,
> > -             .event = RTM_NEWADDR,
> >               .flags = NLM_F_MULTI,
> >               .netnsid = -1,
> > +             .type = type,
>
> my comment meant that this `type` should be removed and the wrappers
> below just call the intended function. No need for the extra layers.
>
> >       };
> >       struct net *net = sock_net(skb->sk);
> >       struct net *tgt_net = net;
> > @@ -1949,6 +1996,20 @@ static int inet_dump_ifaddr(struct sk_buff *skb, struct netlink_callback *cb)
> >       return err;
> >  }
> >
> > +static int inet_dump_ifaddr(struct sk_buff *skb, struct netlink_callback *cb)
> > +{
> > +     enum addr_type_t type = UNICAST_ADDR;
> > +
> > +     return inet_dump_addr(skb, cb, type);
> > +}
> > +
> > +static int inet_dump_ifmcaddr(struct sk_buff *skb, struct netlink_callback *cb)
> > +{
> > +     enum addr_type_t type = MULTICAST_ADDR;
> > +
> > +     return inet_dump_addr(skb, cb, type);
> > +}
> > +
> >  static void rtmsg_ifa(int event, struct in_ifaddr *ifa, struct nlmsghdr *nlh,
> >                     u32 portid)
> >  {
>