linux-kernel - Re: [PATCH net-next v9 19/19] net: WireGuard secure network tunnel

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Date:   Mon, 25 Mar 2019 11:13:59 +0100
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     David Miller <davem@...emloft.net>
Cc:     Linux Crypto Mailing List <linux-crypto@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Netdev <netdev@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH net-next v9 19/19] net: WireGuard secure network tunnel

Hey Dave,

Thanks for the comments.

On Mon, Mar 25, 2019 at 1:03 AM David Miller <davem@...emloft.net> wrote:
> Said another way: "The code isn't optimal with my compiler on my computer
> unless I force inline this" is not a valid reason to use __always_inline

Hah, that was my rationale exactly. Okay, no problem, I'll remove
those. And if I can't find a way to make the compiler to do the right
thing without it, and nothing looks overly insane, then I'll fix gcc
bugs separately.

> > +             ((u64 *)dst)[0] = be64_to_cpu(((const __be64 *)src)[0]);
> > +             ((u64 *)dst)[1] = be64_to_cpu(((const __be64 *)src)[1]);
>
> Are 'dst' and 'src' both 64-bit aligned?  If not you'll get traps on some cpus.

Yes, they are.

>
> > +     __skb_queue_head_init(&packets);
> > +     if (!skb_is_gso(skb)) {
> > +             skb->next = NULL;
>
> Why?  Direct ->next and ->prev pointer accesses should never be used,
> along with anything that assumes what the implentation of skb lists
> looks like.
>
> Always use the helpers instead.

Ack, will do.

> > --- /dev/null
> > +++ b/drivers/net/wireguard/hashtables.c
>
> No way.
>
> Do not invent your own hashtables, we have several generic versions in
> tree and in particular rhashtable.
>
> If the generic kernel facilities have a weakness, fix that instead of
> rolling an entire new hashtable implementation.

That file might be poorly named; I'm certainly not implementing my own
hashtable, but rather using <linux/hashtable.h>. The file simply has
the various accessors for it that does the proper locking and
reference counting associated with the things inserted into the
vanilla <linux/hashtable.h> hashtable. I'll rename the file to
something more descriptive.

Jason