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Date: Thu, 4 Jun 2009 15:16:34 +0400
From: Dmitry Eremin-Solenikov <dbaryshkov@...il.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
linux-wireless@...r.kernel.org, slapin@...fans.org,
maxim.osipov@...mens.com, dmitry.baryshkov@...mens.com,
oliver.fendt@...mens.com
Subject: Re: [PATCH 03/10] net: add IEEE 802.15.4 socket family
implementation
On Wed, Jun 03, 2009 at 05:32:14PM -0700, Andrew Morton wrote:
> On Mon, 1 Jun 2009 18:54:44 +0400
> Dmitry Eremin-Solenikov <dbaryshkov@...il.com> wrote:
>
> > Add support for communication over IEEE 802.15.4 networks. This implementation
> > is neither certified nor complete, but aims to that goal. This commit contains
> > only the socket interface for communication over IEEE 802.15.4 networks.
> > One can either send RAW datagrams or use SOCK_DGRAM to encapsulate data
> > inside normal IEEE 802.15.4 packets.
> >
> > Configuration interface, drivers and software MAC 802.15.4 implementation will
> > follow.
> >
> > Initial implementation was done by Maxim Gorbachyov, Maxim Osipov and Pavel
> > Smolensky as a research project at Siemens AG. Later the stack was heavily
> > reworked to better suit the linux networking model, and is now maitained
> > as an open project partially sponsored by Siemens.
> >
>
> Some drive-by nitpicking, and I saw a bug...
>
> > + switch (addr->addr_type) {
> > + case IEEE802154_ADDR_LONG:
> > + rtnl_lock();
> > + dev = dev_getbyhwaddr(net, ARPHRD_IEEE802154, addr->hwaddr);
> > + if (dev)
> > + dev_hold(dev);
> > + rtnl_unlock();
> > + break;
> > + case IEEE802154_ADDR_SHORT:
> > + if (addr->pan_id != 0xffff && addr->short_addr != IEEE802154_ADDR_UNDEF && addr->short_addr != 0xffff) {
> > + struct net_device *tmp;
> > +
> > + rtnl_lock();
> > +
> > + for_each_netdev(net, tmp) {
> > + if (tmp->type == ARPHRD_IEEE802154) {
> > + if (IEEE802154_MLME_OPS(tmp)->get_pan_id(tmp) == addr->pan_id
> > + && IEEE802154_MLME_OPS(tmp)->get_short_addr(tmp) == addr->short_addr) {
>
> You must use very wide xterms :(
~120 chars in width :) We prefer to have a single code line split between
several screen lines, rather than split it manually in some weird places
just to justify width of 80 chars.
>
> > + dev = tmp;
> > + dev_hold(dev);
> > + break;
> > + }
> > + }
> > + }
> > +
> > + rtnl_unlock();
> > + }
> > + break;
> > + default:
> > + pr_warning("Unsupported ieee802154 address type: %d\n", addr->addr_type);
> > + break;
> > + }
> > +
> > + return dev;
> > +}
> > +
> >
> > ...
> >
> > +static int ieee802154_create(struct net *net, struct socket *sock, int protocol)
> > +{
> > + struct sock *sk;
> > + int rc;
> > + struct proto *proto;
> > + const struct proto_ops *ops;
> > +
> > + /* FIXME: init_net */
> > + if (net != &init_net)
> > + return -EAFNOSUPPORT;
>
> yeah, I was going to ask about that. What's the problem here?
The FIXME was dedicated to the fact that I didn't understand what is
this. The code fragment is c&p from lots of examples of similar code
(check can, appletalk, etc. for example)
> > + switch (sock->type) {
> > + case SOCK_RAW:
> > + proto = &ieee802154_raw_prot;
> > + ops = &ieee802154_raw_ops;
> > + break;
> > + case SOCK_DGRAM:
> > + proto = &ieee802154_dgram_prot;
> > + ops = &ieee802154_dgram_ops;
> > + break;
> > + default:
> > + rc = -ESOCKTNOSUPPORT;
> > + goto out;
> > + }
> > +
> > + rc = -ENOMEM;
> > + sk = sk_alloc(net, PF_IEEE802154, GFP_KERNEL, proto);
> > + if (!sk)
> > + goto out;
> > + rc = 0;
> > +
> > + sock->ops = ops;
> > +
> > + sock_init_data(sock, sk);
> > + /* FIXME: sk->sk_destruct */
>
> ?
Oh... I nearly forgot about this. When writing this code, I examined
several existing address families. Usually (but not always) the sk_destruct
callback will purge sk_receive_queue and sk_write_queue. However I
didn't understand why and in which case should these queues (or others)
be purged. Could please one clarify this?
> > ...
> >
> > +static void af_ieee802154_remove(void)
>
> Could be __exit, althugh __exit doesn't do much (it used to be
> implemented on UML and might still be).
Added. BTW: I thought, that __exit functions aren't added to (or are
stripped from) the final vmlinux image. Am I wrong?
> >
> > +static inline struct dgram_sock *dgram_sk(const struct sock *sk)
> > +{
> > + return (struct dgram_sock *)sk;
>
> Better to use container_of() - it's clearer and doesn't assume that
> dgram_sock.sk is the first member.
Fixed.
> > +}
> >
> > ...
> >
> > +static int dgram_bind(struct sock *sk, struct sockaddr *uaddr, int len)
> > +{
> > + struct sockaddr_ieee802154 *addr = (struct sockaddr_ieee802154 *)uaddr;
>
> sigh, more casting. Often these things can be done in ways which are
> nicer to the C type system.
Unfortunately sockaddr things can't be done in a more clean way IMO.
> > + struct dgram_sock *ro = dgram_sk(sk);
> > + int err = 0;
> > + struct net_device *dev;
> > +
> > + ro->bound = 0;
> > +
> > ...
> >
> > +struct proto ieee802154_dgram_prot = {
>
> I suspect this could/should be const.
No. proto_register changes the passed protocol struct during
registration.
>
> > + .name = "IEEE-802.15.4-MAC",
> > + .owner = THIS_MODULE,
> > + .obj_size = sizeof(struct dgram_sock),
> > + .init = dgram_init,
> > + .close = dgram_close,
> > + .bind = dgram_bind,
> > + .sendmsg = dgram_sendmsg,
> > + .recvmsg = dgram_recvmsg,
> > + .hash = dgram_hash,
> > + .unhash = dgram_unhash,
> > + .connect = dgram_connect,
> > + .disconnect = dgram_disconnect,
> > + .ioctl = dgram_ioctl,
> > +};
> > +
--
With best wishes
Dmitry
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